American PW SCREWY ELGIN

viclip

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Jul 20, 2018
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Two of the three threaded holes for the dial foot screws in the main plate of my current project pocket watch, are stripped. It's a 16s Elgin Model 7 of Grade 340 (manufactured circa 1908).

According to the 1915 Elgin watch material catalog, there were only 3 sizes of dial foot screws used:

~ for all 18s watches, tap diameter of 0.0368" with 140 tpi
~ for all 16s thru 3/0s watches, tap diameter of 0.0248" with 220 tpi
~ for 5/0s & 10/0s watches, 0.0208" tap diameter with 220 tpi

So it's occurred to me that I could re-tap the screw holes to the larger 18s dimension & simply use 18s screws to secure the dial feet in my 16s watch.

Where can I source a tap of diameter 0.0368" with 140 threads per inch?
 

4thdimension

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Oct 18, 2001
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I may be wrong but I doubt that tap is a modern made off the shelf item anywhere and custom made taps cost a small fortune. Many would simply use a near size screws and ease them in but since you are trying to do the right thing and tap the hole first here are two options. Go with a ready made tap of a standard thread that you can find screws for. Make your own tap using a longer steel screw. Groove it and harden it. I would probably find a near matching screw and work it in and out until the threads are formed. Brass is malleable enough I think you could get acceptable results. I'd be happy to learn ideas others have.-Cort
 

viclip

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Thanks for your thoughts 4thdimension.

Of course wth my luck, the movement is nickel rather than brass.
 

viclip

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I've been thinking.

Do metallized epoxies have a role in watch repair? Such as J-B weld which can be drilled & tapped & is robust enought for automotive fastener applications, at least non-critical ones.

Properly applied, dial foot screws should be torqued next to nil, they should just barely hold the feet in place without flexing them & causing the hard enamel to "pop off". How someone managed to strip the hole threads in my project watch is beyond my utter comprehension.

Anyways the epoxy route would enable me to re-use the correct factory screws, assuming that I locate the correct tap.
 

kevin h

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Apr 9, 2015
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It just so happens ..... I was in your shoes last month . I have some taps , but if the hole is stripped out , you need to go bigger or plug and drill , or are you trying to chase them ? The pictured set goes to 038-140 , I have other taps also

s-l1600.jpg
 

viclip

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Jul 20, 2018
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It just so happens ..... I was in your shoes last month . I have some taps , but if the hole is stripped out , you need to go bigger or plug and drill , or are you trying to chase them ? The pictured set goes to 038-140 , I have other taps also

View attachment 489040
Hi kevin h, I'm heading in the direction of plug/drill/tap so that I could re-use the factory screws. The two holes in question are so badly stripped that the screws can be pushed all the way in without even turning them.

This would call for a tap diameter of 0.0248" with 220 tpi.

Can you provide?
 

mooredan

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Jan 23, 2022
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I have a similar problem: An Elgin 12s with a stripped out thread in the main plate for one of the dial foot screws. Tap size: 0.0248", 220 tpi

My first thought was to drill and tap for the next size up dial screw 0.0368", 140 tpi I got some of the larger dial foot screws, and I guess I got lucky and found the $2.00 Elgin tap set on ebay. The set is "complete", but several taps are broken including the 0.0368", 140 tpi Yes, it is difficult to find one. Can anyone provide a source? I see another tap set on ebay as part of a larger set of tools, but its hard to see if the needed one is there or intact.

Now I'm thinking to fill the hole with JB Weld, and drilling and tapping for the original screw. Besides, the next size up dial foot screw is about 50% larger and will take a bigger bite out of the main plate's edge, possibly leaving a very thin-walled hole. So is the JB Weld route a viable option?

For completeness, I found a some further data on the Elgin tap set:

ElginTapSet-1.jpg

ElginTapSet-2.jpg
 

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