Clock Repair
& Horology

1.1 A Brief History of Timekeeping

Time is the most fundamental measurement in human civilisation, and the instruments we have devised to track it reveal, as much as any technology, the ingenuity and ambition of the people who built them. To repair a clock is to hold that history in your hands — to engage directly with the accumulated skill of countless craftsmen spanning seven centuries.

Ancient Timekeeping

The earliest timekeepers relied on observable natural phenomena. The sundial — attested as early as 3500 BCE in Egypt and Babylon — cast a shadow across a calibrated surface. The water clock (clepsydra) overcame limitations of the sundial by allowing continuous time measurement through controlled water flow. Other early devices included fire clocks, sand-glasses, and incense clocks used in China and Japan.

The Birth of the Mechanical Clock

The mechanical clock emerged in medieval Europe around 1300 with the invention of the escapement — a device releasing a gear train in controlled increments. The Salisbury Cathedral clock, built around 1386, is one of the oldest surviving mechanical clocks in working order. Early tower clocks were large, heavy, and inaccurate — gaining or losing fifteen minutes per day was considered acceptable.

The Pendulum Revolution

Everything changed in 1656 when Christiaan Huygens applied the isochronous properties of the pendulum to clockwork. The fundamental formula governing pendulum motion is:

Where T is the period in seconds, L is the effective length in metres, and g is gravitational acceleration (9.81 m/s²). For a seconds pendulum, the required length is approximately 994 mm. The pendulum transformed accuracy from minutes per day to seconds per day almost overnight.

Graham, Harrison, and the Longitude Problem

The deadbeat escapement (George Graham, c. 1715) eliminated recoil characteristic of the anchor escapement. John Harrison's marine chronometer H4 (completed 1759) achieved less than two minutes' error over a 156-day voyage, establishing the lever escapement as the gold standard for portable timekeepers — a position it has never surrendered.

The Industrial Revolution and Mass Production

The nineteenth century brought mass production to clockmaking. In America, Waltham, Elgin, and Hamilton industrialised pocket watch production with interchangeable parts. In Germany, the Black Forest became synonymous with cuckoo clocks. The Swiss industry produced at every price level and developed extraordinary diversity in calibres and complications.

The Quartz Revolution

In 1969, Seiko launched the Astron — the world's first commercial quartz wristwatch, accurate to within five seconds per month. Quartz movements are now ubiquitous. From the repairer's perspective, they are largely modular — when the movement fails, replacement is usually the correct response.

1.2 How to Use This Handbook

This handbook is designed to be used at the workbench. Read through an entire procedure before you begin, gather all the tools and materials listed, then work through the steps with the book open beside you. Do not skip steps on the assumption that you know what comes next.

For complete beginners: Read Chapters 1–3 first, then acquire a simple German mantel clock and follow the disassembly, cleaning, and reassembly procedures. For experienced repairers: use the index and table of contents as your primary navigation — Chapter 14 and the appendices are designed for those encountering less familiar movement types.

1.3 Overview of Clock Categories

Weight-Driven Mechanical Clocks

Use gravitational potential energy of hanging weights. Provide superior rate consistency due to constant torque. Types include: longcase (grandfather) clocks, Vienna regulators, cuckoo clocks, Black Forest wall clocks, and turret clocks.

Spring-Driven Mechanical Clocks

Store energy in a coiled mainspring. The principal disadvantage: torque decreases as the spring runs down. Various devices — the fusee, going barrel, remontoire — equalise output. Types include bracket and mantel clocks, carriage clocks, pocket watches, and wristwatches.

Electric and Quartz Clocks

Derive motive power from electrical sources. AC synchronous motor clocks derive accuracy from mains frequency. Quartz movements use crystal oscillation (typically at 32,768 Hz) divided electronically to drive a stepping motor.

The quality of a clock repair is inseparable from the quality of the tools used. Working with incorrect or poorly made tools leads to damaged screw heads, bent pivots, contaminated parts, and frustrated repairers.

2.1 Essential Hand Tools

Screwdrivers

The watchmaker's flat-blade screwdriver is nothing like its hardware-store counterpart. The blade must be ground to a precise width and thickness to fit the specific screw slot. A basic clock repair set requires blade widths of approximately 0.5, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, and 3.0 mm. Recommended brands: Bergeon 6899, Horotec, Vessel (Japanese).

Tweezers

Required patterns include: No. 2 — straight, fine point (general purpose); No. 3 — straight, medium point (larger parts); No. 5 — angled, fine point (confined spaces); No. 7 — cross-locking self-closing (both hands occupied); Anti-magnetic brass tweezers (near magnetised parts). Recommended: Bergeon, Dumont, Horotec.

Pliers

Clockmaker's pliers must be smooth-jawed (no serrations) to avoid marring components. Required types: flat-nose parallel-jaw, round-nose, snipe-nose (needle-nose), bow-opening spring pliers, pin-vice pliers (parallel-action).

Additional Essential Tools

• Files: Set of needle files in various profiles; flat file in cut 0 or 1; riffler files and burnishing file for pivot work.
• Hammers and Punches: Small cross-peen hammer (~100g), brass or nylon mallet, steel punches in 0.5–4 mm steps.
• Pin Vice: Small one for drills down to 0.3 mm; larger for arbors up to ~4 mm.
• Eyepiece / Loupe: 7× for clock work, 10× for watch work. Bausch & Lomb Hastings triplet or Zeiss 7× are professional standards.
• Movement Holder: Grips plates without applying pressure to arbors or wheels.
• Mainspring Clamp: Prevents spring from unwinding violently. Never remove a click spring without one fitted.
• Hand Remover: Two flat prongs that slide under the hand; never lever hands off with a screwdriver.
• Peg Wood: Orange wood or boxwood rod, 3–4 mm diameter. Used to clean pivot holes — use a fresh piece for each hole.

2.2 Specialist Tools

Mainspring Winder

Safely winds a mainspring into its barrel without damaging coils. The Bergeon 5537 and similar sets cover barrel sizes from pocket-watch diameter upward.

Bushing Tool

K&D-style sets use interchangeable fluted cutters that drill and countersink the worn hole simultaneously. The professional standard is a cam-operated bushing machine (Presto) allowing microscope-aided centering.

Staking Set

A collection of steel stakes and punches used for: driving out and replacing pins; tightening wheel collets; setting staff shoulders; flattening bent plates; fitting cannon pinions and driving hands onto collets.

Lathe

A watchmaker's lathe (Boley, Schaublin, 8–10 mm WW standard) opens up pivot turning, wheel arbor repair, and operations impossible without one. A significant investment (quality used lathes: ~£200–500) but the single tool that most expands what a repairer can accomplish.

Timing Machine

Measures beat rate and displays rate, beat error, and amplitude. Professional machines: Witschi, Elma, Greiner. Free smartphone applications (Atomic Clock Sync, Watch Timing) are sufficient for most clock work.

Cleaning Machine

Rotates parts through successive jars of cleaning fluid and rinse. The L&R 111 is the standard two-jar machine widely used in British workshops. Brands include L&R (American), Elma (Swiss), and various German makers.

2.3 Cleaning Equipment and Solutions

2.4 Lubrication Reference

2.5 Workspace Setup

An ideal bench is 750–850 mm high with a smooth, hard-wearing surface — traditionally linoleum, or fine-grained leather or black rubber mat. Lighting should be daylight-balanced LED at 5000–6500 K, positioned at 45° to the work surface. A white sheet of blotter paper beneath the movement catches small parts and makes them visible. Never work over carpet or upholstered seating — a fallen part will disappear.

2.6 Budget vs Professional Recommendations

Do not economise on: screwdrivers, tweezers, and cleaning fluids. Can economise on: movement holders, parts trays, peg wood. Defer until needed: mainspring winder, staking set, lathe, timing machine, bushing machine. A realistic starting toolkit costs approximately £150–250 from quality second-hand sources or £250–400 new.

3.1 The Frame: Plates and Pillars

The frame of a mechanical clock consists of two flat plates — the front plate (dial plate) and the back plate — held apart by a set of pillars. Construction types include: posted-frame (grandfather and Vienna regulators — open structure, wheels visible from sides); plate-frame (mantel and bracket clocks — solid flat brass plates with train sandwiched between); and bridge/pillar-plate construction (common in American pocket watches — lower pillar plate with individual bridges above).

3.2 Arbors, Pivots, and Wheels

An arbor is the shaft on which a wheel or drum rotates. Each arbor has a body, two or more pivots (fine reduced-diameter ends running in pivot holes), and a collet to which the wheel is fixed. Pivot diameters in clocks range from ~0.5 mm (fine carriage clock) to ~2.5 mm (longcase great wheel). In watches: ~0.07 mm (balance staff) to ~0.5 mm (barrel arbor).

Wheels are toothed brass discs with cycloidal tooth profiles (minimising friction, self-releasing). Pinions are small-toothed steel gears — their teeth are called leaves. Lantern pinions (cylindrical pin-cage design, common in cuckoo clocks) vs solid pinions (universal in fine clockwork).

3.3 The Going Train

3.4 Train Calculations and Gear Ratios

The train value is the total beats per hour the escapement must produce. For a seconds-beating clock: 3,600 bph. For a pocket watch beating at 5 beats/second: 18,000 bph. To verify a known train, multiply all wheel tooth counts and divide by all pinion leaf counts, then multiply by escape wheel teeth × 2 (each tooth produces two beats).

3.5 The Striking Train

A separate train powered by its own mainspring or weight, consisting of: Great Wheel (Striking); Pin Wheel (pins lift the hammer); Count Wheel or Rack (controls blows struck); Fly (air-brake governor controlling striking speed — two-bladed vane).

3.6 The Chiming Train

A third train in chiming clocks, featuring a pin barrel (rotating cylinder with pins in a programmed pattern) that lifts a series of hammers to play a melody. Westminster, Whittington, and St Michael are the commonest chime sequences. The chime train releases four times per hour — at each quarter.

3.7 Power Sources

The Mainspring

A long, thin strip of hardened and tempered steel, coiled into a flat spiral within a cylindrical brass barrel. Specified by: width (height in barrel), thickness (determines torque), and length (determines power reserve). The outer hook attaches to the barrel wall; the inner hook to the barrel arbor.

Weights

Provide constant driving torque: mass × g × drum radius. Longcase weights typically 3–8 kg. The constant torque advantage over springs makes weight-driven clocks preferred for precision regulators.

3.8 Escapement Types

Verge Escapement (c. 1275)

The oldest mechanical escapement — a crown wheel with a vertical arbor carrying two pallets. Used until late 17th century. Highly susceptible to changes in driving force; incompatible with long pendulums.

Anchor (Recoil) Escapement (c. 1670)

The most common escapement in weight-driven longcase and wall clocks. Named for the anchor-shaped pallet frame. Characteristic brief backward movement (recoil) of the escape wheel between beats. Key parameters: lock, drop, and impulse angles. Escape wheel typically has 30 teeth (for seconds-beating clock: 3,600 beats/hour). Compatible with long, slow-swinging pendulums.

Deadbeat Escapement (George Graham, c. 1715)

Eliminates recoil by making locking faces concentric with the pallet arbor — the wheel is "dead" on the locking face between beats. Preferred for precision longcase regulators and astronomical clocks. Slightly more susceptible to wear on locking faces than the recoil escapement.

Cylinder Escapement (early 18th century)

Used extensively in flat pocket watches. The balance staff is hollow (a cylinder); escape wheel teeth engage alternately with inside and outside of the cylinder. A frictional escapement — requires clean, correctly oiled cylinder surfaces. Very sensitive to contamination.

Lever Escapement

The dominant escapement in virtually all mechanical watches from the mid-19th century to present. Features a safety action — guard pin on the roller table and safety dart on the lever — preventing accidental unlocking. Key parameters: lock (~0.05–0.10 mm), draw (~12–15°), drop (0.5–1.5°), and run.

Platform Escapements

Self-contained lever escapement modules used in carriage clocks and portable spring-driven clocks. Driven by the clock going train via a contrate wheel. Available in lever platform (Swiss lever) and cylinder platform (older) types.

3.9 The Motion Work

Converts hourly rotation of the centre wheel to 12:1 ratio for the hour hand: Cannon Pinion (friction fit to centre arbor, minute hand attached) → Minute Wheel (36–40 teeth) → Minute Wheel Pinion (8–12 leaves) → Hour Wheel (~90 teeth, one revolution per 12 hours).

3.10 Click Work

The click is a spring-loaded pawl engaging the winding ratchet to prevent the mainspring from uncoiling during winding. The click spring holds the click in engagement — a common failure point after many years of service. The click is what you depress (or circumvent with a mainspring clamp) to let down the mainspring before disassembly.

4.1 General Principles of Safe Disassembly

Photograph Everything

Before touching any fastener, take systematic photographs of the movement from every angle — front, back, both sides, and overhead. Pay particular attention to: hand positions, position of striking/chiming detents at rest, winding positions, all adjustable components, and any unusual features. It is almost impossible to over-photograph a movement at this stage.

Label and Organise Parts

Use a divided parts tray with sections clearly labelled. A suggested organisation for a plate-frame clock: (1) Screws; (2) Springs; (3) Going train wheels; (4) Striking train wheels; (5) Chiming train; (6) Levers and detents; (7) Motion work; (8) Pendulum and crutch; (9) Mainspring barrels; (10) Miscellaneous.

Use the Correct Tool for Every Fastener

Every screw deserves a screwdriver blade that exactly matches its slot. Taper pins are driven out from their narrow end toward the larger end — the opposite will jam them. Taper pins are reused during reassembly.

4.2 Letting Down the Mainspring

Procedure:

1. Secure movement in holder, dial-side facing you.
2. Identify the click and click spring on the back plate.
3. Apply a mainspring clamp to the barrel — insert through click hole, tighten gently against coils.
4. Turn the winding arbor slightly in the winding direction to relieve click tooth pressure.
5. Depress the click clear of the ratchet with thumb or fine screwdriver. Allow the key to turn back slowly in increments of no more than 15°, replacing the click on the ratchet between each increment.
6. Continue until all tension is removed. Verify no spring-back when ratchet wheel is released. Remove mainspring clamp.
7. For two-train or three-train movements: repeat for each train separately.

4.3 Disassembly: Spring-Driven Plate-Frame Clock

Applies to German and French mantel clock movements and most English bracket clock movements. Key steps in sequence:

1. Remove hands with hand remover (not a screwdriver).
2. Remove dial (held by feet through corresponding holes in front plate, secured by taper pins or screws).
3. Lay movement on its back (back plate uppermost). Let down all mainsprings.
4. Remove pendulum or platform escapement.
5. Remove any external levers or detents passing through the plates.
6. Remove all back plate screws.
7. Carefully lift the back plate exactly horizontally — pivots must exit their holes cleanly. Do not tilt.
8. Observe general condition before removing further parts.
9. Remove motion work, then going train wheels (escape to great wheel), then striking train wheels, then mainspring barrels, then remaining levers and springs.

4.4 Disassembly: Longcase Clock

Requires removal from case first — a two-person operation for larger movements. Lower and remove weights, detach pendulum (wrap in cloth), remove hood, remove hands and dial, then lift movement and seat board clear of the case. Proceed as for the general plate-frame procedure. See Chapter 14A for full detail.

4.5 Disassembly: Carriage Clock

Remove platform escapement first (two screws) before letting down the mainspring. Note how the platform pinion meshes with the contrate wheel for correct reassembly. Strip main movement plates as per the general procedure. See Chapter 14C for full detail.

4.6 Disassembly: Cuckoo Clock

Wooden plate construction with lantern pinions. Lower and unhook weights. Remove cuckoo/bellows mechanism from top of housing. Release movement from case. Pivot holes are drilled directly into wood — arbors may require gentle upward persuasion. See Chapter 14D for full detail.

4.7 Disassembly: Pocket Watch

Work at a clean bench with excellent lighting, fine eyepiece, and a movement holder. Remove from case via stem release lever. Let down mainspring using the click (very small — use fine pointed screwdriver). Remove dial via dial foot screws, then hands with watch hand remover. Remove keyless works, balance and cock, pallets, then train wheels in order. See Chapter 14E for full detail.

4.8 Disassembly: Wristwatch

Pocket watch work on a smaller scale plus case complexity. Use correct case-opening tools (case knife for snap-back, case wrench for screw-back — never a screwdriver as a case knife). Remove crown before extracting movement. See Chapter 14F for full detail.

4.9 Disassembly: Electric & Quartz Clocks

Remove battery first. Remove hands, then the movement module from its case. Quartz modules are rarely repaired at component level — the service strategy is diagnosis then module replacement if faulty. See Chapter 14G.

5.1 The Diagnostic Protocol

Step 1: Take a History

Record on your job card: When did the clock last run correctly? What changed when it stopped? Has it been repaired before, and by whom? Is the fault consistent or intermittent? Does it strike correctly? The answers are clues — a clock that stopped after being moved was probably knocked out of beat; one that has run increasingly slowly for months likely has an accumulated oil problem.

Step 2: External Inspection

Before removing the movement from its case, check: Is the pendulum engaged in the crutch? Are weights correctly hung at the right height? Are hands binding against the dial or each other? Is the clock level (use a spirit level)? Are there any obviously broken external components?

Step 3: Wind the Clock and Observe

Carefully wind and observe: Does it start when given an impulse? Continue running, or stop after a few beats? Is the beat even? Does amplitude increase to a stable level or decline? Are there irregular sounds? Does it stop at the same point in its cycle (indicating a localised fault) or randomly?

Step 4: Movement-Level Preliminary Inspection

With the back plate accessible (movement removed but not disassembled), inspect: Pivot holes — hold to light; a round hole with bright circle = good; oval hole = worn; dark edges = old oil. Pivots — perfectly cylindrical, mirror-polished, free of flat spots. Springs — check for breakage, fatigue, displacement. Main wheels — broken teeth. Rust or corrosion — pitting indicates moisture exposure. Evidence of previous work — marked screw heads, off-centre bushes, wrong screws, improvised springs.

5.2 Common Faults by Clock Type

5.3 Assessing Wear

Pivot Holes

Hold the cleaned plate up to a bright light source. Examine each hole. Signs of wear: oval elongation in the direction of load; black oil residue in and around the hole; bevelled edge where the pivot has been riding up; score marks radiating from the hole. Acceptable clearance: ~0.01–0.02 mm. When oval elongation exceeds ~0.1 mm, the hole should be bushed.

Pivots

Under a 10× loupe, a good pivot surface is mirror-polished and perfectly cylindrical — edges appear as sharp parallel lines. Warning signs: longitudinal grooves (dry running); taper (pivot riding on hole edge); flat spots (complete pivot hole failure); corrosion pitting.

Pallet Stones and Escape Wheel

Inspect pallet stones for: wear on locking faces (polished flat visible under loupe); chipping of impulse face (requires replacement); loss of draw angle (stone has been moved by previous repairer). Check escape wheel for broken or bent teeth.

5.4 Reading Signs of Previous Amateur Repairs

• Mangled screw heads — wrong screwdriver used; badly damaged screws must be drilled out and replaced
• Wrong-size or wrong-type screws — will strip on removal
• Off-centre bushes — most common error of amateur bushing work; misaligns wheel mesh
• Wrong oil in wrong places — grease in pivot holes; no oil on pallet stones; excessive oil on dial
• Springs replaced with inappropriate materials — strip of tin can or bent nail where click spring should be
• Components from different movements — wrong tooth count wheels; wrong barrel arbor diameter

5.5 When to Repair vs Replace

• Replace without hesitation: Any mainspring (small cost relative to labour); any cracked click spring; any balance staff with worn pivots or loose roller jewel; any gasket or seal.
• Repair where possible: Pivot that can be polished without lathe; click that can be reshaped; rack tail that can be re-bent; suspension spring replaceable with standard material.
• Do not attempt to repair: Cracked plate (in critical area); severely corroded pivot (economically assess lathe turning); broken escape wheel tooth in precision movement (replacement is almost always correct).

Old, degraded oil is the primary cause of a serviced clock failing prematurely. When oil breaks down — typically after 5–10 years in a clock, 2–5 years in a watch — it becomes thick, gummy, and abrasive. Fresh lubrication applied over old oil is not a service. Every movement that is fully stripped must be completely cleaned before reassembly.

6.1 Hand-Cleaning Methods

Prepare three containers: (1) clock cleaning fluid; (2) rinse (IPA or petroleum-based rinse); (3) final rinse (clean IPA or lint-free cloth wipe with dry solvent). Place plates in cleaning fluid and brush gently with a soft brass-bristle brush — never steel on brass. Rinse immediately — do not allow cleaning fluid to dry on the surface. Peg each pivot hole individually — twist a sharpened peg wood stick inside the hole until it emerges clean and dry. Rinse with final rinse and dry with warm (not hot) air.

6.2 Ultrasonic Cleaning

Fill tank with ultrasonic concentrate diluted per manufacturer instructions (typically 1:9 to 1:19). Heat to 40–60°C for best results. Place parts in mesh basket, ensuring parts are not touching. Run 5–10 minutes for typical built-up oil. Transfer immediately to rinse. Dry immediately and thoroughly — rust on steel parts begins within minutes of water-based solution exposure.

6.3 Rotary Machine Cleaning

The professional standard four-jar L&R process: (1) L&R Clock Cleaning Solution — 3–5 minutes; (2) Rinse No. 1 — 2 minutes; (3) Rinse No. 3 / dry rinse — 2 minutes; (4) Warm air drying — 5 minutes. After the machine cycle, peg each pivot hole individually — the machine does not replace pegging. Replace solutions when they become noticeably dirty (typically after 20–50 full cycles).

6.4 Cleaning Specific Materials

Brass Parts

Any cleaning method above. For bright finish: 30-second wash in 5% ammonia solution, rinse immediately. Do not exceed 30–60 seconds — over-exposure coarsens the surface. Lacquered brass: petroleum-based cleaning fluid and soft brush only — no ammonia.

Steel Parts

Use petroleum-based fluid or IPA only. Dry immediately and apply a very thin film of clock oil to exposed steel surfaces immediately after cleaning. Do not use WD-40 as protection — it is not a stable long-term lubricant and attracts dust.

Painted Dials

Never immerse in any cleaning solution. Remove loose dust with a very soft brush (make-up brush). For oil or grease smears: tiny amount of IPA on a cotton stick, dab — do not rub. For general soiling: very slightly dampened soft cloth, followed immediately by drying. Do not attempt to restore missing numbers.

Silvered Dials

Tarnish to a warm grey patina — usually best left as found. If cleaning is desired, use a proprietary silver cleaning cloth applied very gently. Never use liquid silver cleaner — it runs into chapter ring engraving and is very difficult to remove.

Worn pivot holes are the most common mechanical fault in mechanical clock movements. Once a pivot hole becomes oval, the affected wheel sits off-centre, increasing friction, reducing power delivery to the escapement, and ultimately causing the movement to stop.

7.1 Why Worn Pivot Holes Matter

A new pivot hole is drilled to a precise diameter with a clearance of approximately 0.01–0.02 mm. Consequences of wear: increased friction from pivot pressing against the hole side; altered gear geometry (even 0.1 mm shift changes tooth engagement); poor oil retention; and ultimately train stopping as the pivot rides out of its hole entirely.

7.2 How to Bush a Pivot Hole — Step-by-Step

Finding the True Centre of the Worn Hole

The bush must be centred on the original pivot hole centre — not the worn oval's geometric centre. Find it by: holding the plate to strong light and identifying the circular portion of the oval (the unworn end, closest to the original centre); or measuring from the hole in the opposite plate (which may have worn less). On a bench-mounted bushing machine, position the unworn edge at the crosshair centre, then offset by half the original hole diameter in the direction of wear.

Selecting the Correct Bush Size

Measure the pivot diameter with a micrometer. The bush inner hole should be 0.01–0.02 mm larger than the pivot (0.5–1 thou). Select the smallest bush with the correct inner hole. The bush should require light thumb pressure to insert — not fall in freely, and not require hammer force.

Reaming, Installing, and Finishing

1. Mount the plate securely. Select the cutter matching the chosen bush outer diameter.
2. Position the cutter over the original hole centre. Apply light downward pressure and rotate clockwise, cutting only 1.0–1.5 mm depth. Clear swarf frequently.
3. Test-fit frequently. Stop when the bush can be pushed in with light thumb resistance.
4. Press the bush into the reamed hole using the press arbor. Seat flush with or slightly below the plate surface.
5. Peen the bush into the plate: strike lightly around the edge with a flat-faced punch to expand the outer diameter into the plate material. Peen both sides.
6. Create a slight chamfer (45°, ~0.1 mm wide) on both faces of the hole — this acts as an oil sink.
7. Polish inner surface with a tapered peg of hardwood twisted inside the hole.
8. Test-fit the pivot: smooth entry, free rotation, minimal side play, no roughness.

7.3 Burnishing Pivots

A pivot that is scored but not pitted or tapered can be restored by burnishing — compressing and smoothing the surface using a very hard, smooth steel burnisher. Burnishing does not remove metal; it displaces the surface layer, filling fine scratches by plastic deformation.

Procedure: Hold the arbor in a pin vice or lathe collet. Apply the burnisher with moderate pressure while the arbor rotates, moving along the pivot length. Apply a small amount of oil to the burnisher. Examine under the loupe after each pass. Clean with IPA after burnishing to remove displaced metal particles.

8.1 Safe Removal from Barrel

1. Verify the mainspring has been let down through the click mechanism. Even fully let-down springs retain set tension from inner coils.
2. Place the barrel on the bench mat. Identify the barrel lid.
3. For friction-fit lid: use a barrel opening tool (flat-bladed lever) with a rotating, pressing motion. Do not lever directly across the centre — this bows the lid.
4. Have a thumb ready above the lid — spring tension may push it off once the rim releases.
5. With lid removed, disengage the outer coil hook from the barrel wall using flat-nose pliers. Allow the spring to slowly uncoil into a wide loop on the bench mat — do not hold it tightly coiled.
6. Remove the barrel arbor (press fit, held by a small C-clip or friction) to access the inner hook.

8.2 Mainspring Sizing

Rule of six: Spring length should be approximately 6 times the internal circumference of the barrel. The spring should fill approximately two-thirds of the barrel area when fully coiled inside.

8.3 Checking the Old Spring for Faults

• Set: Spring has taken a permanent coiled form — cannot develop full torque. When uncoiled, remains nearly as tightly coiled as when in the barrel. Always replace.
• Cracks and fractures: Flex the spring gently and look under a loupe for lines that open and close with bending. A cracked spring will break in service — replace.
• Rust and corrosion: Surface rust can be cleaned in an emergency; pitting creates stress concentrations — replace pitted springs.
• Broken outer hook: Spring can be fitted but has a reduced effective length — common cause of "not running for the full power reserve." Replace.
• Kinked inner coils: Create a weak point — usually from incorrect previous removal. Replace.

8.4 Using a Mainspring Winder

1. Select the arbor matching the barrel arbor diameter.
2. Attach the spring's inner end to the winder arbor hook in the correct orientation (spring winds in the correct direction).
3. Hold the outer end against the winder housing rim.
4. Turn the winder arbor to coil the spring progressively into the housing — work steadily.
5. Slide the winder housing over the open barrel, aligning the arbor pivot hole.
6. Gradually release the housing, allowing the spring to expand into the barrel from outside inward.
7. Insert the barrel arbor, engaging the arbor hook with the spring's inner hook.
8. Fit the barrel lid, pressing evenly into its groove. Test by turning in the winding direction.

8.5 Mainspring Lubrication

The correct lubricant is a medium-to-heavy mainspring grease (Moebius 8301, Molykote EM-30L, or equivalent). Do not use: light oil (expelled from coils within hours); petroleum jelly/Vaseline (hardens, attracts dust); excessive grease (migrates into the train). Application: before inserting into the winder, uncoil the spring fully on the bench and apply a thin smear to the full length of one face (the inner face when coiled). A slight sheen — barely visible. For watch mainsprings use Moebius 8201 or Fixodrop — lighter formulations appropriate for smaller clearances.

9.1 The Anchor (Recoil) Escapement

Key Parameters

• Lock: Depth at which the escape wheel tooth rests on the pallet locking face. Too little = unreliable; too much = excess energy lost.
• Drop: Angle the escape wheel rotates freely after one tooth escapes and before the next tooth lands. Represents wasted motion — minimum practical drop ~0.5°, typical ~1–2°.
• Impulse: Angle through which the tooth pushes the pallet during impulse. More = more energy transferred but more arc required.

Setting the Beat

For correct operation, each tick must equal each tock — equal time on each side of centre. Out-of-beat clocks produce TICK...tock TICK...tock rather than tick...tock tick...tock. To correct:

1. Mount movement on a level surface. Use a spirit level for pendulum clocks.
2. Hang the pendulum and give it a gentle push. Listen carefully to the rhythm.
3. For an uneven beat: adjust the crutch position. Most clocks require the crutch to be gently bent on its arbor — bend in the direction of the shorter interval. Better quality movements have a beat-setting mechanism (small adjustable collar with a locking screw) — always preferable to bending, which can fatigue the metal.
4. Iterate — small adjustments and careful listening. Target: beat error less than 0.5 ms (under 1 ms acceptable for household clocks).

9.2 The Deadbeat Escapement

The locking faces must be true concentric arcs from the pallet arbor centre — any deviation causes either recoil or excessive friction. The draw angle (slightly inside the concentric arc, typically 1–2°) holds the pallet securely against the banking pin. Worn locking faces must be reground on a pallet stone grinder.

9.3 The Lever Escapement (Watch)

Key Parameters

Overbanking

Occurs when the balance swings with excessive amplitude — the impulse pin passes through the lever notch and strikes the opposite banking pin from the wrong side. Symptoms: the watch "gallops" briefly then stops; balance reverses sharply. Caused by excessive amplitude, insufficient draw, or an improperly positioned guard pin. Correct by identifying the root cause — do not simply reduce amplitude.

9.4 The Cylinder Escapement

Critical adjustments: Cylinder height (must engage escape wheel teeth at correct depth); Endshake (~0.03–0.05 mm axial play to prevent grip as temperature changes); Lubrication (a very small quantity of Moebius 9010 on the cylinder surfaces — the most sensitive lubrication point in a cylinder watch; too much migrates and stops the watch within hours).

9.5 Platform Escapements

Service the platform as a complete unit. Remove from the movement (two screws). Inspect balance amplitude — should be ~270–310° when properly wound. Test by flicking balance with peg wood: should oscillate freely for several seconds. Service (clean, relubricate) then replace to movement. After refitting, verify contrate wheel drives platform pinion smoothly.

9.6 Detecting and Correcting Worn Pallets

Pallet stone wear detection: Visual — polished flat on locking face under 10× loupe; Depth test — advance escape wheel by hand and observe if lock is becoming insufficient; Chipping — inspect impulse faces for chips; any chipped stones must be replaced. For anchor escapement pallet stones set in shellac: remove by heating pallet arm over spirit lamp (~90°C, shellac softens), slide out old stone, fit new with fresh shellac at the correct angle.

10.1 Count-Wheel (Locking-Plate) Striking

The count wheel is a brass disc with slots cut around its periphery. The slots represent pause positions between hours. Angular slot spacing is proportional to the cumulative number of blows in each hour — not evenly spaced. The hoop wheel (a wheel with a gap in its outer rim) carries the count detent: as the striking train runs, the continuous rim holds the detent clear of the count wheel; as one blow completes, the gap comes around and the detent falls toward the count wheel. If it falls into a slot, striking stops; if it falls on the raised surface, striking continues.

10.2 Rack and Snail Striking

Invented by Edward Barlow in 1676 — the critical advantage: the number of blows is determined afresh at each hour by the current hour hand position, making it immune to synchronisation errors when the clock is set. The rack is a curved toothed component (typically 12–13 teeth) with a rack tail that rests against the snail — a twelve-stepped cam coupled to the hour wheel. When striking begins, the rack falls until the rack tail rests on the current snail step. How far the rack falls determines how many rack teeth are exposed. The gathering pallet gathers one rack tooth per blow. When all fallen teeth are gathered back, the rack hook stops the striking train.

10.3 Common Striking Faults

10.4 Chiming Trains

The pin barrel — a rotating cylinder with pins in a programmed pattern — lifts a series of hammers to play the melody. The melody depends entirely on the pin positions. Westminster chime uses four bells on five notes of the scale. The barrel makes one-quarter revolution per quarter hour, with the complete four-quarter pattern arranged sequentially around its circumference.

10.5 Synchronising Strike and Chime with the Going Train

After reassembly: (1) Set going train so minute hand is at 12 o'clock. (2) Set the snail (rack striking) to its 12 o'clock step under the rack tail. (3) For chiming movements, position chiming barrel at "four quarters complete" position. (4) Set the warning pin position — advance going train slowly until the minute hand reaches ~57–58 minutes; the warning pin should engage the warning detent at this point. (5) Continue to exactly 12 — the warning should release. If release is early or late, adjust the warning pin or motion-work trigger pin. (6) Check synchronisation through several quarter hours before closing the movement.

Work in the reverse order of disassembly. Your photographs and job card are your reassembly guide. Before beginning: all parts must be clean and inspected; any necessary repairs must be completed; all pivot holes must be bushed and chamfered; mainsprings must be in their barrels, lubricated, and the barrels closed; all levers and detents should be laid out in order; oiler set and correct oils must be ready — lubrication is applied during assembly, not after.

11.2 Reassembling a Plate-Frame Clock

1. Place all going train wheels into their front-plate pivot holes in order (great wheel barrel first, then centre, third, fourth, escape wheel).
2. Apply one drop of correct clock oil to each lower pivot hole before fitting the back plate.
3. Place striking train wheels the same manner.
4. Install all levers, detents, and springs to the front plate. Check rack moves freely and rack hook engages correctly.
5. Lower the back plate exactly horizontally: hold just above assembly, check all pivots are centred under their holes, lower until pivots enter their holes — do not tilt. Work progressively, easing down a millimetre at a time. When the plate is nearly seated, check pillars are entering their locating holes.
6. Fit plate screws finger-tight, then tighten evenly — all screws progressively, not one fully then the next.
7. Check movement runs freely: rotate great wheel arbor in the let-down direction. The train should turn smoothly without binding at any position.
8. Oil all upper pivot holes, then oil the pallet stones with pallet grease.
9. Refit motion work, oil pivot and post pivots.
10. Wind slightly (3–4 turns) and start the pendulum or balance. Observe for several minutes before proceeding to case fitting.

11.3 Pre-Wind Checks

• Beat check: Listen with stethoscope or smartphone app. Correct if beat error exceeds 1 ms.
• Striking synchronisation: Advance hands slowly through several hours. Should warn and strike correctly with correct number of blows.
• Power reserve check: Allow to run down over 2–3 days, confirming correct duration for the movement type.
• Case fit: Verify movement is held correctly without pressure on any moving parts.

Correct lubrication is the single most important factor in the longevity of a serviced clock or watch. Over-lubrication attracts dust and debris, forming a grinding compound in the pivot holes and destroying them far faster than dry running. Under-lubrication causes rapid wear. The wrong oil in the right place can be as damaging as no oil at all.

12.1 Why Correct Lubrication Is Critical

Clock oil degrades through oxidation, evaporation of lighter fractions, polymerisation (becoming gummy), and contamination with wear debris. Mineral oils typically last 5–7 years; synthetic oils last 10–15 years in a clean, enclosed movement. Watch oils degrade more rapidly due to smaller quantities, higher operating temperatures, and greater air exposure when the case back is open.

12.2 Full Lubrication Map

• Going and striking train pivot holes: One drop of medium clock oil (9020) per hole. Drop applied from a 0.8–1.0 mm oiler held vertically until a small sphere contacts the pivot. Do not overflow.
• Barrel arbor pivot: Medium clock oil. Barrel arbor at its contact with the barrel cap: thin smear of grease.
• Pallet stones (clock anchor): Thin smear of pallet grease (D5) on impulse face and locking face of each stone. Almost invisible — a thin, even film. Escape wheel teeth themselves: do NOT oil.
• Pallet stones (watch lever): Tiny drop of D5 on impulse face only. Do not oil the locking face — this reduces draw and increases unlocking risk.
• Click and click spring: Small drop of medium oil or light grease on the click face. Tiny amount of grease under the click spring where it bears on the click body.
• Rack and snail: Thin smear of light grease on the rack tail where it contacts the snail. Oil the rack pivot.
• Suspension spring: Do NOT oil — oil stiffens the spring and distorts the pendulum's rate.
• Balance staff cap jewels (watch): Single drop of 9010 from a 0.3 mm oiler to each cap jewel. Over-oiling causes oil to migrate onto the hairspring — catastrophic effect on rate.

12.3 How Much Lubrication

The correct quantity fills the oil sink (chamfer or oil cup around the bearing) but does not overflow. After applying oil, look at the hole under the loupe — you should see a slightly convex meniscus around the pivot. If oil spreads in a thin film across the plate surface, too much was applied: remove excess with fine pegwood, then reapply a smaller drop.

13.1 Functional Testing

Run the movement for at least 24 hours on the bench before returning it to the customer or case. Listen for irregular sounds at regular intervals (suggesting a bent tooth); periodic hesitation (suggesting a missed worn pivot hole); rattling (loose screw or detent). Observe pendulum amplitude every few hours — it should remain constant. Check striking through at least three hours. Check the power reserve.

13.2 Rate Testing and Regulation

Note the exact time and a reliable reference (GPS-disciplined clock). Allow the clock to run for at least 24 hours — preferably 48–72 hours — before the next comparison. Compare and express the difference in seconds per day.

Adjusting Rate — Pendulum Clocks

The rate is determined by the effective pendulum length. To make the clock run faster: raise the bob (turn the rating nut clockwise as viewed from front). To make it run slower: lower the bob. The general formula for rate change ΔR (seconds/day) from a length change ΔL (mm):

For a seconds pendulum (L ≈ 994 mm), 1 mm rise ≈ 43 seconds/day gain. A tolerance of ±30 seconds/day is acceptable for a household clock; ±5 seconds/day is a good practical target for a well-adjusted movement.

Adjusting Rate — Watches

Watch movements regulate using the regulator lever — two index pins (curb pins) that embrace the outer hairspring coil. Moving toward + (advance) shortens effective hairspring length, increasing beat frequency and making the watch run faster. Moving toward − (retard) does the opposite. One full graduation typically changes rate by ~30–60 seconds/day.

13.3 Using a Timing Machine

A timegrapher connects to a microphone and analyses tick timing. From the trace: Rate — slope of the trace (level = perfect, upward = gaining, downward = losing); Beat error — unequal spacing between successive dot pairs; Amplitude — arc of balance oscillation (should be 270–300° for a watch in good condition; below 230° indicates a fault). Free smartphone apps (Lepsi, Timegrapher, Tick: Timegrapher) use the phone microphone and are reliable for clock work and adequate for most watch work.

The longcase clock — known colloquially as the grandfather clock since the late nineteenth century — is the dominant form of domestic precision timekeeping from the late seventeenth century to the early twentieth. At its best it is among the most accurate mechanical instruments ever made.

Key Characteristics

• Weight-driven going and striking trains (8-day movements run 8 days; 30-hour require daily winding)
• Anchor (recoil) or deadbeat escapement with long seconds pendulum (~994 mm effective length)
• Rack-and-snail or count-wheel striking (English 8-day: usually rack-and-snail; 30-hour and Continental: usually count wheel)
• Posted frame construction: long pillars (150–200 mm) connecting two large plates

Removing the Movement from the Case

A two-person operation. Lower weights to the bottom of the case by allowing lines to unwind under control — never simply let weights drop. Unhook weights. Detach pendulum (lower the bob first, then lift rod from crutch slot, wrap in cloth). Remove hood (usually slides upward off runners). Have a second person support the hood as it comes free. Remove hands and dial. With a second person supporting the movement, unscrew any screws attaching the seat board to the case, or lift the seat board free from its locating shoulders. The complete movement and seat board then lift straight upward out of the case.

The Weight Lines and Gut Line

Traditional longcase movements use gut line (dried twisted catgut) or twisted steel cable. Gut line should be inspected at every service and replaced if there is any sign of fraying, brittleness, dryness, or uneven diameter. The correct diameter for most English 8-day movements: 0.8–1.2 mm. Length: sufficient to allow the weight to descend from fully wound position to the bottom of the case (typically 1.1–1.3 metres).

Common Faults Specific to Longcase Clocks

• Pendulum stopping: First check whether pendulum has been displaced by careless door opening. Also check weights not touching pendulum rod or each other.
• Worn teeth on count or hoop wheel (30-hour): The rope drive uses a single rope for both trains. When the rope wears through, both trains stop. Replacement rope or chain available from suppliers.
• Click spring failure: The most common cause of a longcase failing to maintain its winding. A broken click spring allows the ratchet to reverse when the winding key is removed. Replacement springs available in assorted lengths.
• Worn pallet faces: Most common cause of losing time progressively until stopping. Inspect pallets under loupe after removing movement.

Anchor Escapement — Setting Up in the Case

1. Install movement, fit dial, hang pendulum without replacing the hood.
2. Hang weights, giving each train two or three turns — sufficient power without full wind.
3. Level the case with a spirit level. Shim feet as necessary.
4. Start the pendulum. Listen to the beat rhythm. Adjust crutch position if uneven beat.
5. Check pendulum swings freely throughout its arc without touching the case sides, seat board, or pendulum aperture.
6. Allow 24 hours before making rate adjustment.

French Mantel Clock Movements

The French eight-day pendulum movement is the most widely encountered mantel clock in Britain. Characteristics: two-train going and striking (both spring-driven), rack-and-snail striking, Brocot or anchor escapement. The Brocot escapement (designed by Achille Brocot) has its pallets and escape wheel mounted on the front plate — visible through or over the dial, and adjustable from the front without removing the movement from the case. Uses silk suspension — a short ribbon rather than a metal spring — which is fragile and almost always requires replacement at service.

Silk Suspension Replacement

1. Measure the length of the old suspension silk (from top clamping bar to bottom clamping bar) — this determines effective pendulum length and hence rate. Note the measurement before discarding the old silk.
2. Cut new silk suspension material to the correct length plus ~3 mm at each end for clamping.
3. Thread through the slots in upper and lower suspension bars and clamp tightly. The silk must be taut — not slack.
4. If rate changes after fitting a new suspension (it can stretch or the clamping position may differ), adjust the pendulum bob with the rating nut.

German Mantel Clock Movements

The most commonly encountered mantel clock in general repair work. Produced by Junghans, Gustav Becker, HAC, and others from ~1870 to 1940. Characteristics: two-train or three-train; pendulum escapement (recoil anchor or modified deadbeat); stampings visible on back plate (maker's name, movement number, grade). Often wound from the front by a key through the dial. Some versions have wooden plates (older Black Forest movements); later movements have brass or German silver plates.

English Bracket Clock Movements (Fusee)

English bracket clocks use a fusee movement — a cone-shaped pulley over which the mainspring chain runs, progressively increasing mechanical advantage as the spring runs down, equalising torque output. Key service points:

• Fusee chain: Inspect for damaged or swaged links before reassembly — one damaged link will cause jamming.
• Let-down: On a fusee movement, the click is on the fusee wheel, not the barrel. Depress the fusee click to allow the chain to wind from fusee back onto barrel.
• Maintaining power: Many English bracket clocks include a maintaining power mechanism — keeps the going train powered during winding. When the winding key is inserted, a small reserve spring activates.
• All-or-nothing piece: Prevents the rack from falling unless the warning is at precisely the correct position — prevents incorrect striking if the rack is disturbed mid-cycle.

The carriage clock — "pendule de voyage" — is a compact, robust, spring-driven clock in a distinctive brass-and-glass case, designed to be portable and accurate while being moved. The great majority of antique carriage clocks were produced in France, primarily in Paris, from approximately 1830 to 1914.

Platform Escapement — Service Procedure

Removal: Let down the mainspring completely before removing the platform. The platform is held by two small screws (~1.2–1.5 mm, slotted pillar heads). Before lifting, note carefully how the platform pinion meshes with the contrate wheel. Lift the platform straight upward, keeping it horizontal.

Service: Inspect balance wheel — flick with pegwood, should oscillate freely for several seconds. Remove balance cock (one screw), lift balance by gripping rim only (never touch the hairspring). Remove pallet bridge and fork. Clean all platform parts in petroleum-based fluid or IPA. Peg each pivot hole carefully. Reassemble in reverse — when replacing the balance, the impulse pin must correctly enter the lever notch (check under loupe — the most common error in platform reassembly). Lubricate: one drop of 9010 on each balance staff pivot cap jewel; D5 pallet grease on impulse face of each pallet stone only.

Test off the movement: Hold platform flat and flick the balance — should oscillate freely for 30 seconds or more at correct amplitude.

Refitting: Lower onto the movement with the platform pinion engaging the contrate wheel. Check mesh from the side using a loupe before the platform sits flat. Fit the two retaining screws gently — do not over-tighten.

Cylinder vs Lever Platforms

Early carriage clocks (pre-1860) and some quality plain-case movements use a cylinder escapement platform — identified by a balance wheel without a pallet fork, no banking pins, and a softer characteristic sound. Cylinder platforms are more delicate — the cylinder is easily cracked if the balance is removed incorrectly. Lubrication must be precisely applied: a single tiny drop of 9010 on the cylinder entry slot using a 0.3 mm oiler only.

Common Faults Specific to Carriage Clocks

• Platform running erratically: Nearly always oil degradation on the platform. Service interval: 3–5 years.
• Mainspring broken: Small mainsprings (0.20–0.30 mm thick) prone to cracking if over-wound repeatedly. Always replace with correct dimensions.
• Contrate wheel tooth bent or broken: Caused by forcing the platform pinion into mesh at the wrong position, or removing the platform without first letting down the mainspring.

The cuckoo clock originates from the Black Forest region of Germany. Its plates are made of linden (lime) wood, its going train is weight-driven by pine-cone shaped weights on a chain, and it incorporates a pair of bellows that produce the characteristic "cuck-oo" call by forcing air through two small flue pipes of different pitches.

The Bellows and Bird Mechanism

Two bellows — small conical or rectangular pouches of leather and cardboard — are each connected to a thin wooden pipe of a different length. The bellows are compressed alternately by levers driven by the striking train. When compressed, each bellows forces air through its pipe: the lower note ("cuck") from the longer pipe, the upper note ("oo") from the shorter.

Bellows Service

Old bellows leather dries out, cracks, or loses sealing properties. A dried bellows produces a weak, airy call. Service: carefully remove bellows from the cuckoo mechanism. If leather is dried but not cracked, apply a small amount of neatsfoot oil to the external leather surface, allow to absorb for 24 hours. If cracked or holed: replace with new leather cut using the old piece as a template, using bookbinder's PVA or appropriate contact adhesive. Replace faulty flap valves inside the bellows (small squares of thin, supple leather). After refitting, test the call by compressing each bellows manually — both notes should be clear and loud.

Wooden Pivot Holes — Repair

Worn wooden pivot holes can be repaired by installing a brass bush (the preferred method) or by very slightly reaming and treating with a hardener (thin shellac or cyanoacrylate). For the brass bush method: enlarge the worn hole with a drill bit of the correct size. Press the brass bush into the enlarged hole — a light interference fit — and apply a tiny amount of cyanoacrylate adhesive around the outside before pressing in. Allow to cure completely before running the movement.

Lubrication of Cuckoo Clocks

• Wooden pivot holes: Traditionally lubricated with natural pine resin or a small drop of light clock oil — re-lubrication every 5 years is necessary
• Steel arbors and pivots: Lightly oil where they run in the wooden holes
• Lantern pinion arbors: Oil the bearing pins where they run in their holes
• Bellows leather: Neatsfoot oil at service
• Cuckoo mechanism pivot and door hinges: Small drop of light oil to prevent squeaking

Common Faults

Plate Construction Styles

• Full-plate: Single large plate covers entire train with individual cocks for barrel and balance. Dominant style in English pocket watches to ~1850. Robust but poor train access.
• Three-quarter plate (¾ plate): Large bridge covering three-quarters of the movement. Most common in quality Swiss movements from 1870s onward; characteristic of Glashütte German movements. Good balance access.
• Bridge (pillar plate): Lower pillar plate supports all wheel arbors; individual bridges cover each component. Dominant style in American pocket watches (Waltham, Elgin, Hamilton). Excellent individual component access.

Common American Calibres

American Watch Sizes

Size is given in the American "sizes" unit: 18 size ≈ 46 mm diameter; 16 size ≈ 43 mm; 12 size ≈ 39 mm; 6 size ≈ 35 mm.

Jewelling

7 jewels: Minimum for a quality lever watch (balance staff, pallet stones, impulse jewel). 15 jewels: Adds jewelled bearings at escape, pallet, third, and fourth wheel pivots. 17 jewels: Standard for railroad-grade; adds centre wheel and barrel arbor. 21–23 jewels: Additional jewels at keyless works and setting lever pivot.

Timing and Adjustment — Position Testing

Fine pocket watch movements are tested and adjusted in multiple positions: dial up, dial down, crown up, crown down, crown left, crown right. The standard for American railroad watches (per American Railroad Watch Standards) is a maximum of 30 seconds per day rate variation between any two positions. Large positional errors indicate: incorrectly poised balance wheel; hairspring not perfectly flat; or worn balance staff pivots.

Wristwatch work shares all fundamental principles of pocket watch work but is smaller in every dimension, adding specific challenges: pivots may be as fine as 0.06–0.08 mm; components are lighter and more easily deformed; the ergonomics require higher magnification and finer tools. A well-designed and correctly serviced wristwatch should run reliably for 3–5 years between services.

Case Entry

• Snap-back case: Open with a case knife inserted in the notch at 6 o'clock. Twist gently — never lever with the full blade or the case back deforms.
• Screw-back case: Use a case-back wrench with the correct diameter and number of pins. Never improvise with a screwdriver.
• Four-screw case back: Remove all four screws, retaining them in a parts tray.

Automatic Winding Mechanism

Automatic movements add a rotor — a semi-circular weighted segment that rotates in response to wrist motion. The rotor drives the mainspring via a reversing mechanism (pawl clicks or ball-bearing reversing device) that converts bidirectional rotor rotation into unidirectional winding. Common automatic winding faults:

• Rotor not spinning freely: Rotor bearing worn or dirty — clean and relubricate with a very small amount of 9020
• Manual wind works but auto does not: Pawl clicks for the reversing mechanism broken or springs failed
• Mainspring unwinding when moving wrist: Winding click on the ratchet wheel has failed

Waterproofing — Critical Post-Service Step

After any service involving case opening, waterproofing must be re-established. Three critical gaskets: case back gasket (O-ring or die-cut gasket — always replace at service); crown gasket (O-ring around the crown tube — replace at every service); crystal gasket (if present). All gaskets harden and lose resilience over time. Gasket material: nitrile rubber (NBR) for most; silicone for some higher-specification watches. Use only the correct diameter and cross-section — an incorrectly sized gasket will leak.

Battery-Powered Quartz Movements

A quartz movement contains: a quartz crystal oscillator resonating at 32,768 Hz (2¹⁵, chosen to be divided down to 1 Hz by a 15-stage binary divider); an integrated circuit that buffers the oscillator, divides the frequency, and drives the stepper motor; a stepper motor receiving one pulse per second (each pulse rotates the rotor 180°); and a gear train reducing this to correct hand speeds.

Fault-Finding in Quartz Movements

1. Replace the battery with a fresh cell of the correct specification — even if battery voltage measures 1.4V on a multimeter, it may be unable to deliver sufficient current for the stepper motor. This is the correct first step in any quartz clock diagnosis.
2. If still not running, inspect the battery contacts for oxidation. Clean with a pencil eraser or IPA on a cotton stick. Re-test.
3. If battery and contacts are good, test the stepping motor coil resistance (set multimeter to 2 kΩ or 20 kΩ range). Typical coil resistance: 1.5–10 kΩ. Open circuit or very low resistance indicates a failed motor.
4. If the motor coil is intact but movement still doesn't run, the IC may have failed (rare — more likely if a battery leaked). A failed IC requires complete movement module replacement.
5. If the movement runs (you can hear or feel the tick of the stepper) but hands don't advance, the fault is in the gear train — inspect for broken wheel teeth or debris jamming a wheel.

AC Synchronous Motor Clocks

The AC synchronous clock uses the mains supply frequency (50 Hz in UK/Europe, 60 Hz in North America) as its timekeeping reference. Fault-finding: if a synchronous clock gains or loses time persistently, the motor is not running synchronously — check for mechanical friction in the gear train. If it doesn't run at all, listen for a hum: if it hums but the gear train doesn't advance, the motor rotor may be seized or the gear train is jammed. If it doesn't hum at all, the coil winding has failed — motor replacement required.

UK Suppliers

Finding Parts for Obsolete Movements

• Donor movements: A second movement of the same calibre provides identical parts. Often found on eBay, at horological fairs, through specialist dealers.
• Making from stock: Many simple parts (click springs, detent springs, suspension springs) can be made from flat spring steel stock cut to the required shape.
• Turning on the lathe: Pivot replacement, wheel collet replacement, and other turned components can be made by a capable machinist.
• Specialist horological restorers: For unique or very valuable pieces, contact the British Horological Institute for referrals.

Wood Case Restoration

The primary rule is reversibility — any treatment applied should be capable of being removed in the future without damage. Cleaning: start with the gentlest approach — a soft cloth barely dampened with water for surface dust, then a 50:50 mixture of white spirit and linseed oil (traditional "furniture reviver") for more stubborn grime. French polish repairs: use fresh shellac dissolved in methylated spirits, applied sparingly in the direction of the grain. Veneered cases: lift bubbling veneer with a heated clothes iron through a damp cloth to soften old hide glue, then clamp with fresh hide glue. Do not use modern PVA on antique veneers — it is difficult to reverse.

Brass and Metal Case Polishing

Lacquered brass: Clean with soft cloth and mild soapy water only — no brass polish (abrades the lacquer). If lacquer has become patchy, strip completely with lacquer thinner, polish the brass to a uniform finish, and re-lacquer with purpose-made metal lacquer. Unlacquered brass: Whether to polish or preserve the patina is a matter of judgement. If polishing is desired, use a proprietary brass polish (Brasso, Peek) applied sparingly, then apply Renaissance Wax to retard subsequent tarnishing.

Dial Restoration

Do not attempt to restore a painted or enamelled dial without professional training and experience. An amateur refinishing job on a valuable painted dial can reduce its monetary value by 80–90%. For silvered chapter rings, re-silvering is a specialist service. Enamel dials (genuine fired enamel) should only be cleaned by hand with water and a soft brush — any chips or cracks require a specialist enameller.

Eye and Hand Protection

Always wear safety glasses when: using a staking tool (small parts can fly from the block); releasing a mainspring; working with lathe cutting tools; handling chemical cleaning solutions. The risk of a small steel component striking the eye at velocity is very real — one mainspring accident or one staking set impact can cause permanent eye damage.

Handling Antique and Valuable Pieces

Before accepting a clock or watch for service, inspect it thoroughly with the customer present and record all existing damage on your job card. Both parties should sign acknowledging the pre-existing condition. Handle all pieces with clean, dry hands or cotton gloves — fingerprints on gilded or polished brass surfaces are acidic and etch the surface within days.

Record Keeping

Every clock or watch that passes through your workshop should have a job card recording: owner's name and contact details; description of the piece; fault as reported; your diagnosis; work performed; parts used (with sizes and costs); date received and returned. These records are the basis of invoicing and protection in the event of a dispute.

Appendix A: Mainspring Sizes

Appendix B: Full Lubrication Reference

Appendix C: Recommended Reading

• De Carle, Donald — Practical Clock Repairing. NAG Press. The classic introduction to English clock repair.
• De Carle, Donald — Watch and Clock Encyclopedia. NAG Press. Comprehensive illustrated dictionary of horological terms.
• Britten, F.J. — Britten's Watch and Clockmaker's Handbook, Dictionary and Guide. 16th or later edition. The horologist's standard reference work.
• Daniels, George — Watchmaking. Philip Wilson Publishers. Demanding but invaluable — comprehensive guide to high-quality watchmaking.
• British Horological Institute (bhi.co.uk) — Course notes, examination study guides, and membership resources including their library at Upton.
• Online: ranfft.de — Definitive online database for identifying Swiss watch calibres by photograph and specification.
• Online: cousinsuk.com/information — Free technical resources, identification guides, and calibre data.