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Minute arbor screw thread

StuartG

New Member
Aug 23, 2020
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49
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I am working on repairing a Waterbury Winchester chime mantel clock. The minute hand is held on by a nut but the threads on the end of the arbor are rather messed up (see photo) and I want to clean them up. The OD of the chewed up threads is 0.090" and the best match to my thread gauge is 50 TPI. The closest match I can find to this is a Whitworth #95 instrument thread (Whitworth Instrument Thread) but this seems to be long obsolete. Was this thread even used on American clocks?

Is there anything I can do to clean this up? I think part of the reason the threads are so chewed is that a previous owner has tried jamming a 4-40 nut on them to hold the hands in place. Would I be able to rethread the end with e.g. a 3-48 die, or would I have to drill out and replace the end as in a re-pivoting operation? This operation would have to wait a while since I don't have a lathe yet but plan to get one soon.

Any advice appreciated.

Minute arbor.jpg
 

Jerry Kieffer

NAWCC Member
May 31, 2005
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wisconsin
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I am working on repairing a Waterbury Winchester chime mantel clock. The minute hand is held on by a nut but the threads on the end of the arbor are rather messed up (see photo) and I want to clean them up. The OD of the chewed up threads is 0.090" and the best match to my thread gauge is 50 TPI. The closest match I can find to this is a Whitworth #95 instrument thread (Whitworth Instrument Thread) but this seems to be long obsolete. Was this thread even used on American clocks?

Is there anything I can do to clean this up? I think part of the reason the threads are so chewed is that a previous owner has tried jamming a 4-40 nut on them to hold the hands in place. Would I be able to rethread the end with e.g. a 3-48 die, or would I have to drill out and replace the end as in a re-pivoting operation? This operation would have to wait a while since I don't have a lathe yet but plan to get one soon.

Any advice appreciated.


View attachment 629797
Stuart

First, welcome to the message board.

At .090" OD, a 3-48 nut would fit rather loose. Given that the strength required is minimal, I would suggest a common 2-56 thread utilizing a USA made die.
If purchasing a die, I would suggest that you purchase one that is threaded all the way to the end of the die on the exit side such as the one on the left in the photo. The one on the right is short of the rear die surface.
This allows you to thread from the front of the die to start and then turn over and finish up close to the shoulder.

Jerry Kieffer

fullsizeoutput_7af.jpeg
 

StuartG

New Member
Aug 23, 2020
2
0
1
49
Country
Thank you. I will try that.

Stuart
 

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