Replacing Screws

[KoboldShinies]

Hello,

 

I bought a concertina years ago and back when I first got it I kept having a button stick so took it back to the music store for a repair. They opened it, couldn't find an issue, and after they put it back together it was perfectly fine. Forward to now after the instrument has been sitting for a few years, I started to finally learn how to play. Unfortunately, the issue came back on a different key. I went to open it to see if that would fix it, but a couple of the heads got messed up. I know I used the right screwdriver since I went to a hardware store to find the right one and I also know I didn't use too much force since I have a disability in my arms (a large part of why I wasn't able to learn over the last few years) so can't produce enough force to damage a regular screw. Any way, I now have 2 ruined screws and want to replace all 12 to be sure this doesn't happen again.

 

The screws are 1 x 1 3/4 oval head chrome brass screws for a Musician's Gear 20 button Concertina. If you google "red concertina" then you're almost certainly looking at the model I have. Due to the shape of the screws I haven't had luck at hardware stores, the music store I bought it from, or finding out how to contact the company directly for replacements so signed up to see if anyone here knows where to get them. Please let me know if you do or if you have a theory about my original problem.

 

Thank you for reading and any help this can lead to!

[David Barnert]

Not sure what "1 x 1 3/4” means in this context, but I googled "oval head chrome brass screws” and came up with dozens of suppliers, for instance, this. If you can express the size screw you want as a #, as listed on the site, you should be able to find what you need.

[Tryintolearn]

The screws used in old concertinas were put together before screw threads were standardised, I have two EC’s that use very long thin screws that appear to use a thread pitch of 42.5 threads per inch. You wont buy these new. Try Mark Aday at Concertinaspares.com (in Wales, UK) he has used parts.

[David Barnert]

The kind of concertina he’s talking about:

 

is not one of the “old concertinas” you’re referring to.

[KoboldShinies]

Thank you both for the recommendations! I'll get in touch with TN Fasteners ASAP.

[RogerT]

I was going to ask about the threads on 19C made concertinas. In fact thread standardisation came in earlier than when many concertinas were made. So…did makers just have their own thread taps and dies …which didn’t conform to any standard (like, say, BA)? Other than buying old bolts, which may or may not have a viable thread, has anyone ever tried making bolts, with a small lathe and suitable die? 

[alex_holden]

37 minutes ago, RogerT said:

I was going to ask about the threads on 19C made concertinas. In fact thread standardisation came in earlier than when many concertinas were made. So…did makers just have their own thread taps and dies …which didn’t conform to any standard (like, say, BA)? Other than buying old bolts, which may or may not have a viable thread, has anyone ever tried making bolts, with a small lathe and suitable die? 

 

They seem to have used custom taps and dies that were coarser than modern threads. The major diameter is almost the same as 8BA, and indeed that is what I use on my new instruments, but 8BA is significantly finer pitch than the old bolts. If you have a screw cutting lathe with the right gear ratio, it should be possible albeit time-consuming to turn new bolts that match the old thread. Making a working tap that small is theoretically possible but outside my ability (I attempted it a couple of years ago). I also looked into having a custom tap professionally made and the cost was eye-watering. I believe Adrian Brown managed to make a tap that cuts the Jeffries thread.

[Clive Thorne]

On the occasion that I had a problem with end screws I retapped the plates to M2.5 and used stainless Allen Heads.

[d.elliott]

Each manufacturer had their own screw form, so Lachenal screws will not fit Wheatstone etc, etc. Also remember that the screw heads were Fillister pattern, if you can find them.

[Tryintolearn]

I have successfully made screws for a lachenal, the originals seem to be 42 to 43. Tpi my 1940 lathe could manage 44 which is close enough as thin as the “nut” plates are. You need to make a tool that supports the thin shaft as you turn it, otherwise it bends and you get a conical screw!

the similar fixture with a vee tool holds it while you cut the thread.

you need to cut the thread in one pass.

I had to round the tool just a little, the sharp vee was just too much of a stress concentrator, and the first ones broke too easily, looking at the originals Lachenal made the same discovery the bottom of his threads are rounded.