Closing a snap-on case-back without a dedicated hammer is a recipe for dented bezels and broken crystals. This watchmaker's hammer features a soft nylon head that delivers controlled impact, evenly seating the case-back and compressing the gasket without damaging the case finish.
Product overview
The hammer combines a hardwood handle with a replaceable nylon head, the standard of professional ateliers. Its weight and balance allow the user to apply a measured tap on the case-back, ensuring the O-ring is properly compressed and the watch reaches its rated water resistance.
Technical specifications
- Head: replaceable nylon, white or natural
- Handle: hardwood, varnished
- Total length: 220 mm
- Weight: 110 g
- Head diameter: 22 mm
- Use: closing snap-on case-backs
- Compatible with all watch case sizes
When to use it
Use the hammer to close a snap-on case-back after a service. Place a wooden block or a leather pad between the hammer and the case to distribute the force. A press is preferable for thin or precious cases.
How to install / how to use
Verify that the gasket is properly seated and lightly greased with Moebius 8217 before closing.
- Place the watch face down on a soft cushion or a leather pad.
- Position the case-back square on its seat.
- Cover the case-back with a piece of leather or a wooden block.
- Tap gently on the centre of the block with the nylon head.
- Move around the case-back, tapping evenly to seat the gasket.
- Check the rim: the case-back should be flush with the case.
- Test water resistance if the watch is rated for diving.
Materials and compatibility
Watch gaskets exist in several elastomer families, each with its own properties. NBR (nitrile butadiene rubber) is the most common and offers good resistance to oils and ageing. FKM (also marketed as Viton) withstands higher temperatures and aggressive solvents, and is the preferred choice for professional dive watches. EPDM resists ozone and weathering and is often found on sport models. Hytrel, a thermoplastic elastomer, is used on certain Rolex and Omega references. This tool is fully compatible with all four families, provided the gasket is lubricated with a silicone grease such as Moebius 8217.
It can be safely used on Swiss makes (Rolex Submariner, Omega Seamaster, Tissot PRX, Longines HydroConquest), Japanese makes (Seiko 5, Seiko Prospex, Citizen Promaster) and German makes (Sinn, Junghans) as long as the case-back type matches the tool's purpose. For watches rated above 10 ATM, always pressure-test after every gasket service.
Maintenance and storage
Keep the tool dry, in a clean drawer or its original sleeve. Wipe the metallic parts with a soft cloth after each use; if you have worked near solvents, dry the steel parts immediately to prevent corrosion. Inspect the working surface (tip, head or die) for marks or burrs every few months; small irregularities can be polished gently with a fine-grit abrasive cloth, but heavier damage requires replacement.
Avoid contact with strong acids, chlorinated cleaners and rubbing alcohol on plastic handles. Heat above 60 °C can soften polymer grips and reduce dimensional accuracy on precision blades — never leave the tool in direct sunlight or near a soldering iron.
Common mistakes to avoid
Three errors account for the majority of damage observed in workshops: applying excessive torque (which strips the case-back notches), using the wrong tip diameter (which slips and scratches the bezel), and forgetting to replace a hardened gasket after service (which compromises water resistance even with a fresh O-ring of the wrong size). Always work under a loupe, double-check the gasket reference before ordering a replacement, and verify the seating of the case-back before closing the watch.
A final tip from the workshop: never combine a new gasket with an old, dried-out one on a multi-seal case. If the case-back gasket is replaced, also inspect the crown gasket and the crystal gasket — they age at the same rate and a single tired O-ring will let humidity in.
Quality and origin
The replaceable nylon heads guarantee long service life. Heads are sold separately for refurbishment.
Frequently asked questions
Can I use a metal hammer instead?
No, a metal hammer will dent the case. Always use a nylon or wood head.
How do I replace the head?
Unscrew the metal collar, slide out the worn head and insert a new one.
Is a press better than a hammer?
For precious cases and high water-resistance ratings, a press provides more uniform pressure.
