Corroded End Bolts

[Paul Read]

I have an old 20-button Lachenal that needs repair. The end bolts on one end have badly corroded and the ends sheared off when trying to unscrew them. Does anybody have suggestions for how to remove the end without damaging the instrument?

[Frank Edgley]

Paul,

These are probably steel end bolts which were sometimes used on certain Lachenals. These are sometimes badly rusted. It's doubtful that you can get enough of one of those release liquids down to the threaded plate, which is most likely inset deeper within the bellows frame as opposed to screwed down under the chamois gasket. Using a screwdriver may not wotk either as it may likely slip and damage the ends, or distort the screw head. I know it sounds extreme, but a small vice grip will hold the screw head more securely, if the vice grip is applied to the screw head from the end rather than from the side. Make sure the vice grip does not touch the wood and turn very slowly. It wiil probably come out if you take it slowly. It may also break. In this case you will have to replace the screw. There are plenty of these available. If you get stuck ask one of the makers/resorers, or you can contact me as I have a few. Once out, clean the shafts of the screws with steel wool and some WD-40. You may have to use very fine sandpaper on the shaft only (not the threads). Any broken screws (end bolts) will have to be removed. This may be possible now that the ends have been removed as you may now have enough of the shaft to grip with the vice grip. If not, carefully peel back the chamois gasket. If the threaded plate is screwed down to the bellows frame, it is fairly easy to remove it. The whole thing (broken end bolt and threaded plate) can be soaked in WD-40. If the threaded plate is slotted into the bellows frame, you may have to cut out a small slot of wood (from the inside of the bellows frame) so that the broken screw and threaded plate can be removed and soaked. This can be replaced and the cut out slot repaired using thin veneer. After all this you will have to put everything back as it was.

[Paul Read]

Thanks for the excellent advice Frank. The heads were sheared as discussed in our follow-up telephone conversation. I did manage to get it apart, with minor damage, but it's back together and seems fine now.