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Snapped off end bolts


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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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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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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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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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  • 1 year later...

I have the same problem - three sheared end bolts on one end of https://pghardy.net/concertina/lachenal_32801/lachenal_32801.html. 

Bazza12, can you describe what you achieved?

 

Anyone else got an excess of spare end bolts? I would have gone to Concertina-Spares, but I'm unsure as to whether Mark has recovered back to full service - anybody know?

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One common work around, particularly if the plate nuts have stripped and a replacement 'good' thread will not engage any more. 6BA set screws, and tap the nut out in situ. You usually end up changing the full set both ends, for cosmetic reasons. You can try and get a replacement bolt with it's nut complete, and then modify the bellows frame to suit, hopefully without spoiling the leather work. I have done both, the benefit of the 6BA is that it is inherently stronger, and you can have commercially available setscrews or bolts, remember to specify a fillister head, not a standard cap head. 

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Regarding Lachenal tutor models-

On snapped off end bolts I have used the jaws of a small Keyless drill chuck to grip on the shaft then screw it out. It doesn’t always work as the bolt can be firmly seized into every wooden part it passes through. This can be sorted but it involves major surgery. I haven’t had such problems with brass bolts, only the steel ones which rust and tend to lock into the woodwork rather than the holding plate.

If steel bolts are rusted solid into holding plates that are located inside the bellows frames then again it needs major surgery.  On the other hand the plates that are located on top of the bellows frames are easy to work on and replace.
If the threads in the plate are damaged I make new brass 8ba bolts and plates. If the plates are ok but the bolts are nasty then I tap out the plates to m2.5 and make new brass bolts. The downside of this is that the holes through the end plates are around 2.3mm diameter and need to be slightly enlarged to pass the bolts.

After working on several Lachenals  with steel end bolts I wouldn’t buy one without checking the bolts first.

 

 

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