Omega f300 Cone Case Graining

Omega f300 Seamaster Steel (198.0018)

The Omega f300 Seamaster “Cone” case is one of the more common f300 styles but many of them have lost their vertical graining around the outside of the case. Some have even been highly polished.

Although places like Swiss Time Services and Omega, Bienne, have the sophisticated machinery for re-graining stainless steel cases, it is not cheap to have it done. So, with some advice from a watch friend in Belfast, I decided to set out and have a go myself. I’ll describe each step in the series of photographs below.

Please note: this was an experiment and, although I was pleased with the outcome, I no longer use this method for the graining of Cone cases.

: On the left is a NOS Cone case showing perfect vertical gaining from bottom to top. To the right are two used cases; one has been polished while the other has been hand grained. Before starting, the cases need to be completely dismantled: glass and gasket removed as well as the stem tube.

: On the left is a NOS Cone case showing perfect vertical gaining from bottom to top. To the right are two used cases; one has been polished while the other has been hand grained.

: Step 1: turn down some Acetal rod that will be used to hold the case as well as supporting a ball race in the centre.

: Step 2: Acetal rod now turned to correct inside and outside diameter and ball race mounted in the centre. Acetal holder was parted off from main rod.

: Step 3a: Acetal holder, cases, washers, nuts and holding bar ready.

: Step 3b: Acetal holder, cases, washers, nuts and holding bar ready.

: Step 4: Acetal holder and case mounted on the steel arm. Case can now be spun freely due to bearing mounted in the holder.

: Step 5: Steel arm etc now mounted in the surface belt grinding machine.

: Step 6: Setting up the correct angle on the belt grinder.

: Step 7: Setting up the correct clearance on the belt grinder. The hammer is a precision instrument!

: Step 8: We’re already to start the belt grinder; using 240 grit belt.

: Step 9: Belt is now running and the case is turned by hand.

: Step 10: Looks pretty good alongside the one that hasn’t been done. Note: the stem tube has to be removed from the case before you start graining!