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I have a 48 key Lachenal English (no 53716) which I am attempting to restore. 3 of the end bolts have sheared off at end box level, leaving the thread bits inside, with nothing to get hold of, to try & twist them out. Has anyone any idea how to remove the female socket, without causing damage to the end boxes, or is it a case of complete new bolts & new holes in the rosewood ends, & filling/laquering the old holes.  Bazza12.

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It will be interesting to see what advice you receive....

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Posted (edited)

Usually there is a little brass plate held in by two tiny wood screws, the centre of which is threaded for the end bolt. 

 

If you lift up the chamois around the hole for the end bolt then you should be able to access this plate and, if the wood screws are not too rusty, remove it.  If the screws are rusty then be very careful not to break those off as well or you will be truly screwed (pun intended).  I know that we are not supposed to use lubricants in a concertina but I think that in this case i would consider a drop or two of penetrating fluid applied with a toothpick to free the heads of these screws.

 

Making and fitting a replacement is a whole other story.  I have done it but I had to use a modern standard threaded bolt so that I could use a tap (tap and die) of the same size.  You can get modern cheese head bolts that are a reasonable aesthetic match for the old bolts.  In order to prevent confusion sometime in the future, I replaced all of the plates and screws at the same time.

Edited by Don Taylor

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I had to do this recently, also on a Lachenal, and used a similar method to Don's. The plate retaining screws were rusted in and I removed these by applying a hot soldering iron to the slots in the screws and heating them up. The important point is that you need a screwdriver that fills the slot to remove the screws cleanly - by giving the screws a sharp tightening "nip" before loosening them.

Once out I clamped each plate flush with the tops of a vice and used a scriber to unscrew the sheared bolts. I used a few drops of Plus Gas to free the threads, with a sharp tap from a small hammer before gently chasing out the tapped bolt remains. The advantage with this method is that it retains all the original thread in the plate and you may be able to source used bolts to replace them. If not then you can tap them 2.5 mm and get some brass filister/cheesehead bolts to replace them.

 

Mike

 

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48 minutes ago, Mike Hulme said:

I had to do this recently, also on a Lachenal, and used a similar method to Don's. The plate retaining screws were rusted in and I removed these by applying a hot soldering iron to the slots in the screws and heating them up. The important point is that you need a screwdriver that fills the slot to remove the screws cleanly - by giving the screws a sharp tightening "nip" before loosening them.

Once out I clamped each plate flush with the tops of a vice and used a scriber to unscrew the sheared bolts. I used a few drops of Plus Gas to free the threads, with a sharp tap from a small hammer before gently chasing out the tapped bolt remains. The advantage with this method is that it retains all the original thread in the plate and you may be able to source used bolts to replace them. If not then you can tap them 2.5 mm and get some brass filister/cheesehead bolts to replace them.

 

Mike

 

 

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Hi all. Many thanks for your replies. I will try to follow the advice given. If I don't succeed, then that's another story.

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If you do end up replacing one bolt with another with a non-standard thread there is some merit in making the bolt head look different to the others as it is a clue to anyone reassembling the concertina at a later point to be careful which hole the non-standard one goes into. 

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Posted (edited)

I've had similar issues with concertinas I've restored and have replaced the bolts and receiver plates with modern threads - I felt that rather the replace just a few bolts it's better to replace them all for consistency.

One tip, on reassembling put a bit of graphite on the threads - don't however use a liquid based graphite lubricant.

Edited by SteveS

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5 hours ago, Mike Hulme said:

The plate retaining screws were rusted in and I removed these by applying a hot soldering iron to the slots in the screws and heating them up. The important point is that you need a screwdriver that fills the slot to remove the screws cleanly - by giving the screws a sharp tightening "nip" before loosening them.

That sounds like a better method than using penetrating fluid.

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Thanks again everyone for your responses. They will give me food for thought when I can get round to doing something about the bolts. Bazhow.

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