Tap and Die Kit

[margolisd]

Hi. I have a watch movement with stripped threads in a very tiny 0.4 mm screw hole. Is it best to fix this with a tap? Or at this miniature level is there another tool that would be more suitable? I've never used taps or dies but willing to invest in a kit. Can anyone recommend something not too expensive? I was also wondering if there was such a thing as a tap accessory for a jeweling tool or staking set. (Sorry if that's a stupid question, just that would seem to make sense in my head!) New to this so any advice appreciated

[oldhippy]

You could just use the tap with a pin vice. Here are a couple of links for the sets. Not only do you have mm size but the old types of thread will probably come in BA size.

https://www.cousinsuk.com/category/tap-die-sets

https://www.esslinger.com/tap-and-die-1/

[margolisd]

Thanks for this. I'll give it a try.

[measuretwice]

thats not a bad idea, something for the staking set that holds the tap - it would help with small tap breakage where not keeping it straight is the major cause.  Its very common with larger, but still small and breakable, size tapping jobs to use a tapping stand to avoid breaking them

As for tapping, that's a very small tap.   How do tap a stripped hole the same tap size - do you close it in or bush it, or go a size bigger and make a new screw?  .....as in if it is really stripped there won't anything left to tap....it maybe its just slightly damaged and needs to be chased/cleaned up?

 

 

Edited October 10, 2018 by measuretwice

[praezis]

Quote

I was also wondering if there was such a thing as a tap accessory for a jeweling tool or staking set. (Sorry if that's a stupid question, just that would seem to make sense in my head!) New to this so any advice appreciated 

Bergeon sold 4.7 mm punches with a set of collets. There are also collet holding arbors for Seitz jewelling tools, I have one in the big Seitz set.

Frank

[margolisd]

35 minutes ago, measuretwice said:

As for tapping, that's a very small tap.   How do tap a stripped hole the same tap size - do you close it in or bush it, or go a size bigger and make a new screw?

I think a bigger screw is the way to go. If you closed it in I guess the wall of the screw hole would go from being strait to being curved in so less thread would make contact with the screw.

[oldhippy]

The proper way, this will depend on your skill is to plug the hole, drill and tap. So you have the correct screw size.

[margolisd]

Would you plug it with solder? What kind of solder would you use?

[oldhippy]

Just a standard soft solder and flux. You don’t need anything out of the ordinary.

[measuretwice]

19 minutes ago, oldhippy said:

Just a standard soft solder and flux. You don’t need anything out of the ordinary.

 

to clarify, you're saying to soft solder ta plug of brass in, then drill and tap....not just fill the hole with solder.

Edited October 10, 2018 by measuretwice

[oldhippy]

That is right, plug drill and tap.

[measuretwice]

that's what I figure, it looked like Margolisd's response that he might be thinking plug with solder which would make for a very weak thread

[margolisd]

Ah, I see. I thought that might have been quite weak! That makes more sense.Thanks for all the advice.

[rodabod]

For brass main plates with stripped holes, I usually try a screw which is around 0.1mm larger and try to self-tap with the new screw itself. Just add a little oil and screw/unscrew repeatedly while removing any swarf. 

If you do buy a tap/die set, avoid the (possibly Indian) set in carbon steel which may be sold by Anchor as it’s awful (poorly made, not accurately cut and break easily). Get the HSS set which is possibly Chinese and made by Toolzone or similar for £30 - £40. It’s excellent. 

[StuartBaker104]

I repaired a Longines 23m a few years back with a 0.3mm hairspring stud screw that had a stripped thread in the balance cock.

Cousins had a selection of stud screws and I found one ever so sligthly larger, held it in a pin vice and worked it in and out with some oil.

[margolisd]

Thanks. I got a few Bergeon taps and some beeswax. And it worked perfectly. Screw hole back in action