Key takeaways: a watchmaker’s screwdriver differs from a classic screwdriver in three ways: a very fine blade (approx. 0.5 to 2 mm) shaped to fit watch screw slots exactly, a rotating head that allows you to apply pressure with your index finger while turning with your thumb and middle finger, and precision hardened steel, often with interchangeable blades. A standard screwdriver, even a “precision” one, slips on these screws and scratches polished parts.
Changing a screw-in strap, tightening a caseback screw, or dismantling a movement: as soon as you touch a watch, you are handling screws with heads that sometimes measure less than a millimeter. This is where the tool makes all the difference between a clean intervention and a damaged screw or a scratched mainplate.
A blade shaped for tiny screws
A DIY screwdriver has a 3 to 8 mm blade, designed to transmit force. A watchmaker’s screwdriver goes down to 0.5 mm, and each size corresponds to a precise slot width.
- The width must match the slot: a blade that is too narrow will turn inside the slot and damage it, while a blade that is too wide will overlap and scratch the bridge or mainplate.
- The tip is flat and square: it rests along the entire length of the slot, whereas a beveled blade tends to lift and slip.
- The steel is hardened: the tip does not bend or dull at the first sign of effort, even on a screw that has been tightened for years.
This is also why slotted screws are found almost exclusively in watches: a straight slot and a well-fitted blade transmit torque without marking the head, which is often polished or blued.
A rotating head for a stable gesture
The watchmaker’s screwdriver has a head that rotates freely at the top of the handle. You press it with your index finger to keep the blade in the slot, while your thumb and middle finger turn the handle. The pressure remains constant and vertical: the blade does not slip out of the slot. With a standard screwdriver, the same hand must both press and turn, increasing the risk of slipping, especially under a loupe.
Interchangeable or fixed blades?
Quality watchmaker’s screwdrivers often have interchangeable blades, held by a small screw or a collet in the handle. When a tip wears out or breaks, you replace the blade rather than the entire tool. Sets are generally identified by a color or a number on the handle, indicating the blade width.
Anti-magnetic screwdriver: useful or superfluous?
The hairspring, the very fine spring that regulates the rate of a mechanical watch, is sensitive to magnetism: if magnetized, its coils can stick together and the watch will run very fast. A magnetized tool passing near the balance wheel can be enough to cause this. For a strap change or a caseback screw, this point is secondary; it becomes important as soon as you work on the movement.
Standard vs. watchmaker’s screwdriver: what changes
- Blade width: 3 to 8 mm for a standard screwdriver, approx. 0.5 to 2 mm for a watchmaker’s screwdriver.
- Head: fixed on one side, rotating with index finger support on the other.
- Tip: often beveled on one side; flat, square, and fitted to the slot on the other.
- Usage: DIY and force on one side; strap, caseback, and movement screws on the other.
Which screwdrivers for which use?
- Changing or shortening a strap: a screwdriver around 1.6 mm is usually sufficient. Our BERGEON strap change kit includes a 1.6 mm screwdriver, the 7767-S fork tool for spring bars, and a microfiber cloth.
- Maintaining and dismantling a movement: several blade sizes are required. The OH Selection expert tool kit includes seven precision screwdrivers with interchangeable blades, tweezers, a movement holder, a case opener, and two loupes.
- Seeing what you are doing clearly: a watchmaker’s loupe with 5x to 10x magnification allows you to check that the blade is properly seated before turning.
Maintaining your watchmaker’s screwdrivers
- Store them upright or in a pouch so the tips do not knock against each other.
- Check the tip with a loupe: it must remain flat and square.
- Sharpen or replace the blade as soon as it becomes dull.
- Clean them with a clean cloth to avoid carrying oil or dust into the movement.
Find all our tools in the watchmaking tools category.
FAQ
It is not recommended. Screwdriver sets for electronics often have beveled blades and softer steel, which slip and mark watch screws. A watchmaker’s screwdriver of the correct width prevents damage to the screw head and polished surfaces.
For metal bracelet link screws, a 1.4 to 1.8 mm blade is suitable in most cases, with 1.6 mm being the most common size. Choose the blade that fills the entire width of the slot without overlapping.
It allows you to apply continuous pressure with your index finger while your thumb and middle finger turn the handle. The blade remains pressed into the slot, preventing it from slipping and scratching the watch.
For working on the movement, it is preferable: a magnetized tool can magnetize the hairspring and significantly disrupt the watch’s timekeeping. For a strap change, this point is less critical.
Look at it through a loupe: a tip in good condition is flat, sharp, and square. If it is rounded, chipped, or bent, it will slip: replace the blade or have it reground.