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Wheatstone broken end bolt removal


Fanie
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One of the end bolts are broken of, so I opened the chamois cover and then found that it does not have a threaded nut plate on the edge of the bellows frame, but it has a plate inserted from the side of the frame about 10mm from the edge.

Any advice on how to remove this broken bolt?

Thank you

 

 

End bolt.jpg

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Assuming (in your case) the plate is inserted through a slot on the inside of the frame…which is how it works on a Lachenal….I peeled back the chamois on the inside and cut a channel down to the plate and beyond, to where the bolt ends, just wide enough to extract the bolt, with the plate attached, but leaving the rest of the frame in place. I then reinserted the plate and screwed in a new bolt and patched the slot with epoxy putty, making sure to turn the bolt to stop it adhering to the putty. A Dremel was the key tool…I used an engraving bit to machine the slot (the same diameter as the bolt). I smoothed the putty (Miliput) after it had set with some other Dremel bit. My aim was to remove the minimum amount of frame, so that the slot for the screw plate still functioned. Once the chamois is replaced the repair is invisible.

Edited by RogerT
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53 minutes ago, Fanie said:

Thank you guys, I appreciate your help.

I will first try to grip it with pliers, but there is so little protruding that I don't think it will work.

Roger, in this case the plate is inserted from the outside. 

Thanks

If you have a fretsaw with a fine blade you may be able to cut a slot in the top of the broken bolt and turn it out with a small screwdriver.

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Apply a hot soldering iron to the end of the bolt before trying to turn it.   The heat will tend to loosen the the screw and make it easier to remove.  Hold the soldering iron in place for long enough for the heat to travel along the bolt.  Maybe 30 seconds, or a minute.  You can also try a few taps with a light hammer on the end of the bolt.  If you can get any turning movement it's also worth turning it back and forward an 1/8th of a turn a few times before attempting to fully unscrew it.  All these suggestions are well known engineers tricks for removing stuck bolts and should mean you can avoid having to weaken the woodwork in an area that is already highly stressed.  

 

If you do have to cut a slot through the wood then a better repair method is to cut a shallow trench that extends either side of the bolt for something like 1/2 an inch each side and glue on a patch of wood with the grain running the same way as the bellows frame.  That will give you back most of the strength of the original.  You can use a thicker piece of wood and sand it flat after the glue has dried,

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“the plate is inserted from the outside”.

oh, that’s a nuisance. If the bolt won’t come out I’d probably still dig it out as described. If I was going to rebind the bellows I'd just work a channel on the outside and repair. But you could still get it out from the inside of the frame as well. I had a Lachenal where the bolts wouldn’t come out…and I had to cut them to get the end off anyway. This was how I tackled the issue. The main thing is to avoid damaging the flat edge of the frame, because obvs this has to be perfectly flat to seal with the action casing, and if you start drilling or cutting with a hacksaw blade or grabbing with pincers, you may easily wreck the edge/top of the frame. Anyway, that’s how I would tackle it. If it won’t come out your choices are limited. And the amount of wood I removed was tiny.

I should also add …these screws shear off really easily…so even if you do get to turn it,,it may shear off lower down (been there…done that..).

 

Edited by RogerT
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You can get special screw extraction pliers, I find that they help. Oil is not a good idea for the reason stated above, but a shot of heat can help free things. Personally I think that you can do more harm by pussyfooting about. If the pliers and/ heat don't work then plan the surgery and cut out the minimum necessary to release the plate nut. Replace wood with wood, fillers and epoxies are OK, until another bolt shears off. it is worth checking to see if the bolt was bottoming in it's blind hole before, or just as it started to clamp onto the action box. Certainly check after the repairs are completed.

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Ok, I got it out. 

I first heated it with a soldering bolt, then cut a slot in the end with one of those small dremmel blades and then tried with a small screwdriver, but it did not work. Then I cut it open on the side and got it out. Now I must find a screw that will fit and cut threads for it and then cover the slot with epoxy.

Fortunately I am busy building new bellows, so I did not have to destroy anything in the process.

Thanks for all your help. 

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