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We get several watches in where the mushroom pin has broken off the bracelet clasp. Usually it is possible to replace the whole clasp, but not always. So I was really pleased to find an assorted box of mushroom pins in the Cousins catalogue.

In my ignorance, I assumed that they were two piece affairs that you pushed together though the hole in the clasp, and then whacked with a hammer to secure. I was wrong.  It seems that you just put the bottom end through the clasp and then use a punch to knurl it over.

Have any of you fitted these before? And if so can you advise the best way if holding everything in place.  

Thanks, Valerie

mushroom pin.jpg

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  • 4 years later...

I did get some, and wanted to use them for mending catches on watch bracelets when the original one has dropped off. The only problem is that I cannot work out how to get them to stay in place. I had imagined that they were in two pieces that you pressed together but they're not, so presumably the bottom end needs to be flattened somehow. Just haven't managed to achieve that yet. 

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Although I'm no expert (you probably want to speak to a watch/clock maker), I believe what you have are press fit parts, therefore the hole that you press them into needs to be slightly smaller than the diameter of the part you are pushing into the hole (interference fit).

For an interference fit using a hand press for parts of that size I believe the holes need to be about 10um or 0.01mm smaller than the pin.

So for the pin where the D section (on the first image you posted) is 1.25 mm in diameter you will need a hole of 1.24mm.

You would need to ream out the hole to the appropriate diameter and then using a hand press push the pin into the hole.

Another option would be to ream the hole out to a larger size and again with an interference fit insert a bushing using a hand press, then press a pin of the original size into the bushing.

Best Regards


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