Guides / Industries

Watch and Clock Parts on Swiss Lathes: Pinions, Winding Stems and Screws

October 28, 2026

The Swiss-type lathe started in watchmaking. Pinions and staffs, the thin steel parts that carry gears inside a movement, were too slender to turn on an ordinary lathe because the work bent away from the tool. The sliding headstock fixed that, by moving the bar through a guide bushing next to the cutter. Two centuries later, the principle still holds, and watch and clock parts remain a demanding use of the machine.

This guide covers the parts, the features that make them hard, the tolerances involved, the materials and the finishing steps that follow turning. It treats the machine type as a machine type: where a part is made has nothing to do with the name.

The parts

A mechanical movement contains dozens of turned parts, most of them very small.

Part	What it does	Typical size	Notes
Pinion	Small gear that meshes with a wheel	0.8 to 4 mm	Leaves cut into a turned arbor
Arbor and staff	Axle carrying a wheel or the balance	0.5 to 3 mm	Pivots at each end
Winding stem	Connects crown to movement	1 to 3 mm	Square or threaded end, grooves
Crown tube and case tube	Seals the stem through the case	2 to 6 mm	Thin wall, polished or threaded
Screws	Hold plates and parts together	0.5 to 1.5 mm	Fine thread, slotted head
Pillar and post	Spaces plates	1 to 5 mm	Tight length tolerance
Setting lever parts	Switch between winding and setting	0.5 to 2 mm	Small pins and screws
Clock parts	Larger pinions, arbors and pivots	2 to 10 mm	Similar methods at a bigger scale

Clock parts are larger, and the same methods apply. Alarm clocks, wall clocks and mechanisms for instruments use arbors, pinions and screws that a Swiss-type lathe makes in volume.

What makes a pinion

A pinion is the most characteristic watch part. It is a small gear, usually with six to twelve teeth called leaves, cut directly into a turned arbor, with pivots at both ends and sometimes a shoulder for pressing on a wheel.

The Swiss-type lathe turns the arbor to its diameters and cuts the pivots. The leaves are then formed by one of three methods.

Hobbing. A hob, a gear-shaped cutter that rotates in step with the part, cuts the leaves in one pass. Some machines carry a hobbing attachment for this.

Milling. A small cutter forms each leaf in turn. Slower and more flexible.

Broaching. A shaped tool pushed along the arbor forms the profile.

Pinions are generally heat treated for wear resistance, then ground or polished, with the pivots finished last. The leaf profile has to match the wheel that meshes with it, so the profile is part of the drawing, not an afterthought.

Pivots

A pivot is the small, hardened tip of an arbor that turns in a jewel or bearing. Pivot diameters can be well under half a millimeter, and the surface has to be smooth and round to reduce friction and wear.

After turning, pivots are usually burnished or rolled, a process that presses a hard, polished tool against the surface to compact it and give a mirror finish. This is a secondary operation on dedicated equipment, and it determines how a movement runs.

The turned pivot must arrive within a tolerance of a couple of microns and a round, clean shape for burnishing to work. A pivot with chatter marks or taper cannot be rescued by burnishing. The surface finish guide and the tolerance guide explain how such requirements are stated.

Screws

Watch screws are among the smallest threaded parts in common production. Diameters of 0.5 to 1.5 mm, a slotted head and a fine thread are typical. They are made by turning a head and a shank, cutting or rolling the thread and cutting the slot with a live tool or a slitting saw.

Considerations:

Thread form. Watch threads follow their own standards, such as those of the watch industry’s standards body, not ISO metric coarse. Name the standard on the drawing.

Thread formation. Rolling gives a stronger, smoother thread than cutting, though it needs the right core diameter. For very small sizes, rolling is common. The fasteners guide covers how threads and heads are chosen.

Head and slot. A slot with a clean edge and an exact depth, so a screwdriver seats. Burrs on the slot make a screw hard to turn and mark the screwdriver.

Finish. Screws are polished, blued by heat or plated, depending on the movement. Heat bluing is a controlled temper that gives a color and a slight hardening.

Winding stems and tubes

A winding stem links the crown to the movement. It has a square or threaded end for the movement, grooves for the setting lever and a thread for the crown. The shaft is slender and the features are cut by a combination of turning, thread rolling and live tooling.

Tubes are thin-walled and the walls are the issue. A crown tube with a wall of a tenth of a millimeter must stay round and finish well, since it seals the case. The thread whirling guide covers slender threaded parts, and the thin-wall issues resemble those of the pogo pin barrel.

Clock parts and larger mechanisms

Clock and instrument mechanisms use the same part types at a larger scale. Arbors run 2 to 10 mm, pinions have fewer and coarser leaves and screws are standard small sizes. Tolerances are looser than for wristwatch work, typically a few hundredths of a millimeter on most features, and tight only at pivots and fits.

This makes clock work friendlier to price. Brass is the usual material, the features are easy to turn and finishing steps are fewer. Volumes can be large, as in alarm clocks, timers and appliance mechanisms, and the same shop that makes a clock pinion may make a motor shaft or a gear pin for another product. If your part is closer to a clock than a wristwatch, say so in the request, because it changes which shops will quote and at what price.

Common problems

Burrs on leaves and slots. A burr on a pinion leaf damages the wheel that meshes with it, and a burr in a screw slot ruins a screwdriver. Cleaning and inspection under magnification are normal for these parts.

Distortion in hardening. A slender arbor with leaves bends in the furnace. Shops straighten after hardening and leave grinding stock on the pivots, but the arbor must be designed with an even section where possible.

Pivot damage in handling. A pivot is a fine tip, and parts that touch in a bin bend or nick them. Individual trays or separators are standard for finished arbors. The packaging guide covers the options.

Thread tearing in soft metals. Brass and nickel silver screws tear if the tool is dull. Tool changes by count keep it clean.

Magnetization. Steel parts that become magnetic attract dust and swarf, and in a watch they can affect timekeeping. Demagnetizing is a normal step on steel parts.

Typical tolerances

Feature	Typical tolerance	Notes
Pivot diameter	about ±0.002 mm	Burnished after turning
Arbor diameter at a fit	about ±0.003 to ±0.005 mm	Often ground or lapped
Screw head and shank	about ±0.005 mm	Fine tolerance on small sizes
Length of pillars and posts	about ±0.01 mm	Spacing of plates
Concentricity of pivots	about 0.003 to 0.005 mm	Both ends from one setup where possible
Roundness	a few microns	Measured with a roundness gauge

All are typical and some sit at the limit of turning. Temperature affects measurements at this scale, since a steel pin changes length with a degree or two of temperature. Shops that hold these tolerances measure in a controlled room and keep parts there before checking. Confirm what the supplier can hold for your part.

Materials

Material	Typical use	Notes
Free machining carbon steels made for watch work	Pinions, staffs, stems	Hardened after turning
303 and 316L stainless	Stems, screws, tubes	Corrosion resistance, wearer contact
Brass	Pillars, plates, clock parts	Easy to machine
Nickel silver	Decorative parts, plates	Silver color
Phosphor bronze	Bearings, bushings	Wear surface
Gold and silver alloys	Crowns, cases	Precious, yield matters
Titanium	Cases, crowns	Light, hard to machine

Stainless is often a good compromise, and the stainless guide and the brass guide cover the common materials. Precious metals bring the issue of scrap value, and the bar remnant article explains yield, which matters a great deal when the metal is gold.

Finishing after the lathe

Much of what makes a watch part a watch part happens after turning.

Hardening. Steel pinions and staffs are heat treated for wear resistance.

Grinding and lapping. Fits and pivots reach their final size and finish.

Burnishing. Pivots are rolled to a mirror finish.

Polishing. Visible parts, such as screw heads and crowns, are polished or finished with a satin pattern.

Plating or coloring. Gold, rhodium, black coatings or heat bluing.

Cleaning. Ultrasonic cleaning removes oil and particles, which matter in a mechanism that runs on a drop of lubricant.

The secondary operations guide lists how these steps sit around turning and what they add to lead time.

What drives cost

Driver	Effect
Tolerance	Every micron needs slower cuts and more checks
Material	Precious metals and stainless cost more than brass
Hobbing and special tools	Tooling per profile
Secondary processes	Hardening, grinding, burnishing, polishing
Inspection	Optical and roundness measurements per lot
Volume	Watch parts run in large lots, which spreads setup

The cost guide shows how these combine. For watch parts the secondary steps often outweigh the turning, so a change in finish can cost more than any change in the turned shape.

A worked example

Take a steel pinion arbor: 1.2 mm at the leaf section with six leaves, pivots of 0.2 mm at each end, total length 6 mm. The drawing asks for hardened leaves, pivots ground to a micron tolerance and a burnished surface.

The shop turns the arbor from a free machining watch steel, cuts the leaves by hobbing, turns the pivots slightly oversize and parts off the piece. The parts go to hardening, then to grinding for the pivots, then to burnishing. Inspection uses optical measurement for the leaves and a roundness check for the pivots.

The lathe does perhaps a third of the work. The drawing should name the pivot size after burnishing, the leaf profile and the hardness, and leave the stock allowances to the shop, which knows what its grinder and burnisher need.

What to put on the drawing

1. Material and condition, including the standard for watch steels
2. Leaf profile or gear data for pinions
3. Pivot dimensions after finishing, with tolerance and finish
4. Thread standard and form for screws
5. Critical fits and concentricity, with the datum scheme
6. Heat treatment and hardness
7. Finish and plating
8. Cleaning and packaging
9. Yearly volume

Getting watch and clock parts quoted

Send the drawing and STEP file through the RFQ form. State the material, the critical features and finishes, and the yearly volume. We match the part with up to three shops that run Swiss-type lathes and reply within 24 business hours.

Say which finishing steps you expect the shop to arrange and which you will do yourself. A quote that includes hardening and burnishing and a quote that does not are different jobs, and stating the scope makes the quotes comparable.

Frequently asked questions

Keep reading

• Valve Spools on Swiss Lathes: Fits, Roundness and Finish
• Surgical Instrument Components on Swiss-Type Lathes: Pins, Shafts, Screws and Tips