Unscrewing a Rolex, Omega or Seiko case-back without leaving a mark is neither luck nor a matter of an expensive key. It is a precise technique that the watchmakers of rue du Rhône in Geneva call "the 4 pawls". This page details it for the first time in English.
Why 80% of unscrewed case-backs are scratched
Scratches on a case-back come from:
- Bit slips mid-rotation (loses engagement in the notch)
- Imprecise initial centering: the wrench is placed by eye, not under a loupe
- Lateral force applied to "help" rotation
- Only one fork bears instead of the 3 expected
- Metal bit on polished 316L steel back
The "4 pawls" method
The idea: instead of turning with one large 90° motion, unscrew through successive quarter-turns (4 mini-rotations of 22.5°), recentering the wrench between each pawl.
- Pawl 1 — engagement at zero: place the wrench, verify under 10x loupe that all THREE forks are equally engaged. Turn gently 22°, until you feel the first mechanical "click" of torque.
- Pawl 2 — release, recenter: remove the wrench, observe the residual engagement (did each pin move equally?). Reposition. Another 22°.
- Pawl 3 — half-way: at mid-rotation, friction drops suddenly (the thread begins releasing the gasket). Relax axial pressure, 22° by hand.
- Pawl 4 — bare-hand finish: the last 22° can be done by grabbing the back directly with a chamois cloth or a nitrile glove, no wrench.
Total: 90° in 4 stages instead of one continuous motion. Benefits: (a) the wrench stays centred 100% of the time, (b) you feel the instant the gasket gives, (c) no slipping possible.
Preparing the bench
Before touching the wrench, prepare:
- Case holder block in high-density foam or rubber, diameter matched to middle case
- 10x binocular loupe or head loupe
- Jaxa wrench with new forks (check them)
- Chamois or clean microfibre cloth (never cotton, fibres = dust)
- Ultrasonic bath ready for gasket cleaning (water + 2% neutral watchmaker soap)
- New replacement O-ring (identical inner Ø + section)
- Tube of Moebius 8200 silicone grease or equivalent
Place the watch on the holder, back UP, glass in a protected cavity. Verify it cannot rotate (the critical instant of final unscrewing).
Hard cases: seized back, water-logged back
Seized back (resists 1.2 Nm)
Probably corroded thread. Before forcing:
- Spray WD-40 or Liqui Moly Servo at the back/middle case joint.
- Wait 20 minutes (solvent migrates into the thread by capillarity).
- Retry the "4 pawls" method.
- Still stuck: gentle heating with a hair dryer at 60-70°C max (steel expands more than the titanium/gold case). DO NOT exceed 80°C (risk for movement and sapphire glass).
Water-logged back (water entry, visible oxidation)
Do NOTHING before 48 h of drying in a controlled environment (dry rice or silica gel). Forcing a water-logged back = movement lost. Once dry, normal method.
After opening: systematic checks
Once the back is open:
- Inspect the gasket under 20x loupe: look for radial cracks, crushing marks (flattened zone that does not return to round in 30 seconds), black streaks (nitrile oxidation).
- Clean the gasket groove with an isopropyl alcohol swab (never acetone, which attacks internal nylons).
- Inspect the thread under loupe: look for burrs, metal chips (sign of previous over-torque).
- Check the movement: dust, debris, humidity traces?
- Replace the gasket systematically, even if it looks OK.
- Grease with Moebius 8200 in a thin coat on the new gasket BEFORE reassembly.
"A back opened without a replaced gasket is a watch that will take water on the next subway ride."
FAQ
Which wrench for my Seamaster 2531.80 without scratching?
Bergeon 5700-Z wrench with POM or Teflon forks. NEVER the generic metal Jaxa wrench.
My Rolex Submariner back refuses to open, should I force it?
No. Either the crown is not unscrewed (yes, that prevents opening on certain models with stem-coupled back+crown), or the gasket is fused. When in doubt, authorised workshop.
How much for a pro wrench to open 10 different brands?
Bergeon 5700-Z + 6789 torque: 280-450 €. Recoupable in 5 independent service jobs.
Any magnetic risk when opening a case-back?
Yes if your tools are magnetised. Demagnetise screwdrivers and tweezers systematically before working (Elma demagnetiser €100 or DIY coil).