Extremely Fine Thread Damage

armyguber

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Oct 8, 2019
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How can I repair ‘mashed’ threads on a pendulum adjusting screw? The piece is from a French portico mantle clock, circa 1850. The brass adjusting screw works fine up to about 2/3 up the shaft where it hits the damage. I have gone to a local hardware store in search of a steel nut to force the threads, but no one is yet able to match to fine scale, estimated between metric #2 and #3. A razor blade is the only edge I’ve found that fits the thread, but the blade gives little in the way of clearing the thread debris.

BTW the clock runs great, but is just slightly slow, hence the need to fix the thread to speed the beat.
 

armyguber

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Oct 8, 2019
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Roughbarked, a jewelers saw sounds interesting (since the damage are 'mashed' threads I discount the effectiveness of either of the brushes). The saw sounds like a specialized item, so I read your advice as my going to a jeweler. I have contacted two, but both denied doing any clock repair work. I'll keep looking around...
 

roughbarked

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Suppose I was lucky in that I trained under a watchmaker who had done lots of things from starting out making barometers and studying fine jewellery at the London School of Arts before he came to Australia and trained here. His father was a toolmaker/fitter and turner.

Yes, you'll need to get a Jewellers saw frame and seek the finest blades. Not terribly expensive gear but very useful in clockwork as well.
 

Shipsbell

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Get a thread
How can I repair ‘mashed’ threads on a pendulum adjusting screw? The piece is from a French portico mantle clock, circa 1850. The brass adjusting screw works fine up to about 2/3 up the shaft where it hits the damage. I have gone to a local hardware store in search of a steel nut to force the threads, but no one is yet able to match to fine scale, estimated between metric #2 and #3. A razor blade is the only edge I’ve found that fits the thread, but the blade gives little in the way of clearing the thread debris.

BTW the clock runs great, but is just slightly slow, hence the need to fix the thread to speed the beat.
Get a thread Gauge and determine the correct gauge, then measure the thickness of the thread. Then go on line to locate the correct die and buy the correct die to reset the threads. Repeated for emphasis. Patrick
 

FDelGreco

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You need a screwplate that has all the common fine threads, as shown below. Screw the rod into it and it will straighten out the threads. In the meantime, you can cheat. Since you need to raise the pendulum bob a bit to speed up the clock, put a small washer - one or more - between the top of the nut and the bottom of the bob until you get the right tools.

Frank

CIMG5910screwplate.jpg
 

Kenny S.

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Once I knew the pitch, I would use a thread file and dress the threads back down. Knowing most people don't have a thread file, you can take a small triangle file and run this through the flattened portions of the threads to dress them back out. It will take some time and a little finesse but it will work, I promise.
 

JimmyOz

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Feb 21, 2008
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Why don't you just screw off the top hook and extend the thread on the steel post and then cut a bit off so you can then adjust up or down.
 

Ralph

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Frank D, had the correct answer. Buy some screwplates. You probably want the French or Swiss ones for this project.

Bill Bonta from Virginia has developed this aid for using screw plates.


Ralph
 

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Ralph B

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Finding a screw plate that has the thread you want, and it isn't damaged, could be bit of a mission.
Not to mention expensive if that's the only time you use it.
I have some very fine knife edged files for this type of job.
However if I didn't I'd have a go at making something by grinding a knife edge onto the back, ( not the front as that's usually wobbly, and has big teeth !), of an old hacksaw blade.
Then a quick, coarse grind on the bench grinder and you'll have a fine, sharp edged, file.
Good price too !

Ralph B.
 

shutterbug

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I would try real hard to find the proper die for the threads. However, expanding on Frank's idea in post #7, a piece of brass tubing could act as a spacer if you need more than a washer. It would be nearly invisible to the average eye, and completely reversible.
 

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