Thread repair question.

[GlennB]

Hello all-
I have a size 16 OF model 1888 (5,000,000 series) that has the tap for the setting lever screw stripped-out. Can this be repaired by heli-coil (do they make them that small?), or should I just plug the plate with brass and re-tap?
If I were to re-tap the plate, where would I purchase a tap set that small? Did watchmakers at that point in history use standard thread sizes?
Thanks in advance for any information anyone can give me.
Regards,
Glenn

[GlennB]

Hello all-
I have a size 16 OF model 1888 (5,000,000 series) that has the tap for the setting lever screw stripped-out. Can this be repaired by heli-coil (do they make them that small?), or should I just plug the plate with brass and re-tap?
If I were to re-tap the plate, where would I purchase a tap set that small? Did watchmakers at that point in history use standard thread sizes?
Thanks in advance for any information anyone can give me.
Regards,
Glenn

[doug sinclair]

Glenn,

The thread pitch that was used by the American manufacturers was quite a bit finer than what the Swiss used. You'll need a suitable larger tap. I would suggest that an American screw of suitable larger size could possibly machined to the dimensions of the stand-off screw you need for that application. One that is just a bit oversized which may pick up what might be left of the original thread. This would likely be the simplest and best way.

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[GlennB]

Yes, that's also a good idea.
I'm just going to have trouble making the special shoulder that mates with the set lever inside diameter.
I'll look to see if maybe I can "rework" a #0 or #00 stock screw.
Glenn

[jim88]

Glenn, one of H. Fried's books describes a way to remove screws broken off in a plate. He drilled two holes next to the broken screw right thru the plate 180 degrees apart. He then put a jewelers frame saw blade thru one hole and attached the frame to the blade and sawed thru the screw. If the blade fine enough there will still be enough threads on each side to do the job of holding a screw in place. Jim.

[Julian Smith]

Glenn,
The 1958 Waltham material book lists all the screw and tap sizes for all Waltham screws.This list might help you find a tap of a proper size to repair your watch.
See pages 24-26
J Smith

[GlennB]

Thanks Julian.
Maybe someone will list the thread size for this particular hole.
I have already been able to get the broken screw out, and I was able to find a parts movement from Tom at Dash-2.
Glenn

[Julian Smith]

Glenn,
the 1888 set lever screw tap is
Thread diam. 1.20
tap required # 3
the screw # is 156
Tap #3 is 110 tpi,
1.20 mm dia
45 deg sharp
Drill dia. 1.02 mm
These are English threads.
The English dia. is .047 approx.
Hope this helps.
J Smith

[jim88]

Chuck, thanks for that clarification.

Glenn, so tell us, how did you get the screw out? Jim.

[GlennB]

Julian-
Thank you VERY much for this information. I'm going to look around to see if I can find a manufacturer who sells a tap like this. Worst comes to worst, I can make one that will probably last one shot in brass.

Jim88-
I was able to just turn the screw out using my smallest jewelers screwdriver. There was a slight lip protruding from the broken end, and I was able to just turn the screw a little at a time until it was out far enough to grab with tweezers. It probably helped that the tap was already partially stripped-out, this made the fit very sloppy so the screw came right out.

What's the deal with the setting lever on these 1888 movements? They seem VERY hard to pull the crown out to set the watch. It's like you have almost no mechanical advantage looking at the way the setting lever is proportioned. Have any other owners that have these models experienced this?
Thanks
Glenn