A large case-back wrench for opening screw-back watches up to large diameters, including divers and chronographs.
Product overview
This watchmaker tool is a heavy-duty case-back opener for screw-back watches. The wide opening accommodates large case-backs found on divers and chronographs, going up to 60 mm. Three or more interchangeable pins lock into the notches of the screw-back and unscrew it cleanly. The robust steel body delivers torque safely without slipping. Owning the proper instruments is the first step toward enjoyable, repeatable watch servicing on the bench at home or in a professional workshop. This watchmaker tool belongs to a broader range of horological accessories trusted by amateur restorers, vintage watch collectors and professional repair benches alike. Every stage of a watch service from case-back removal, gasket inspection, movement cleaning, bracelet sizing to crystal pressing benefits from dedicated, correctly sized instruments. Investing in the right tool prevents costly scratches on polished bezels, broken lugs, sheared screw heads or damaged spring bars. Whether you service a Seiko 5, an Omega Speedmaster, a Rolex Submariner clone or a Bergeon-compatible reference, working with proper hand tools dramatically reduces the risk of damaging your timepiece. Many enthusiasts start with battery changes on quartz watches and gradually move to bracelet adjustments, then case-back openings, before attempting movement work. Each phase needs its own specialised instruments, and assembling a full kit over time is more economical than buying a closed boxed set. Always work on a clean, well-lit bench, ideally on a soft mat that catches small parts, and keep a magnetic tray nearby for screws and pins. Lubricants like Moebius oils, drying papers and a dedicated dust blower complete the typical workshop. Combine this item with a watch holder, a 10x loupe and a fine screwdriver set ranging from 0.6 mm to 2.0 mm for a fully functional repair station. The hardness of working surfaces is calibrated around 55 to 60 HRC on most professional benches, ensuring repeatable results without marking the workpiece. Used carefully and stored away from humidity, this watchmaker tool will support hundreds of services without significant wear, and will pay for itself after only a few interventions on quartz or mechanical calibres.
Technical specifications
- Tool steel body with chrome finish
- Adjustable opening up to 60 mm
- Interchangeable hardened pins
- Total length approx. 18 cm
- Compatible with Seiko, Tissot, Omega and Bergeon-style backs
- Hardness around 58 HRC
When to use it
Use this wrench whenever a screw-back must be removed for battery change, gasket inspection or movement service on a large case watch.
How to use
- Place the watch in a case holder face down
- Select pins that fit the notches of the screw-back
- Adjust the opening to centre the pins in the notches
- Apply downward pressure and rotate anti-clockwise
- Lift the case-back once it spins freely
- Inspect the gasket before reassembly
Quality & origin
Manufactured from hardened tool steel and supplied with multiple pin profiles, this Bergeon-style opener is ready for daily workshop use.
FAQ
Does it fit Rolex screw-backs?
It fits most generic notched backs; for genuine Rolex backs a calibrated key is recommended.
Are spare pins included?
Yes, several spare pin shapes are supplied to cover slotted, round and square notches.
Can it open a snap-back?
No, snap-backs require a case knife. This wrench is dedicated to screw-backs.
