Need small screw drilled out

[jboger]

I'm sure this topic has come up before, but a search did not find it. I have an Exhibition soundbox, the early type with ferruled tension nuts and round-head screws. The three screws on the back that hold the two halves together are NOT the flat-head type but the slightly rounded ones that are countersunk. Two of them came out rather easily. The third screw head was already damaged when I got the sound box and I probably opened the slot a bit more. At this point, I think the screw is not going to come out with the use of a screwdriver.

What are my options? Can it be drilled out with no damage to the internal threads? I certainly don't mind sacrificing the screw; it's pretty much buggered up already. What about a watchmaker? I have a lathe but don't have the chuck plate and don't intend in investing in one for just this repair. This soundbox is not a rare item, and from a cost perspective it probably makes no sense to have this done. Still, how much would it cost to have that last screw drilled out?

Anyone have any experience with this? Thanks in advance for any thoughts.

[mattrx]

John Nagy at phongraphs.org has drilled out a thumbscrew for me before. Shipping there, back, and the repair was all less than $20 a few years ago. Later, Steve Medved told me he would've done it, but I know he has a bit of a back log of work to do at the moment.

Matt

[jboger]

John Nagy, yes, he had done a nice job on a Concert reproducer for me a few months ago.I've tried about everything else. There is still some slot left on the screw, but I know that the iron head is softer than the force required to break the screw loose. If the original internal threads can be saved so I can put a replacement screw from another sound box on this one, well, I'd be a happy camper. If anyone has any other suggestions I'd be glad to hear. In the meantime, I'll contact John N.

Thanks!

[alang]

I had the same problem once and pretty much only drilled out as much until the head of the screw came off. Once the back plate was off I was able to grad the stump of the screw with locking pliers and screw it out. While the threads were not hurt at all it slipped a few times and marred the brass back plate a little.

Andreas

[EarlH]

I've had some luck by soaking something like that in a mixture of 1 to 1 acetone and automatic transmission fluid, and then heating the end of the screw with a soldering iron. It might have to soak a few days, but that will often times get in around the threads and loosen it up enough to give up it's grip. The heat will help break it loose, and sometimes when it's hot if you cool it off with an ice cube that will break the bond. Good luck with it now.

[jboger]

Andreas: I will check the other holes. If the holes in the back plate are not threaded, this then sounds like a good idea.

I've soaked it with rust remover, oil, and heated it with a hot iron (not all at the same time)--no luck. I did not try to chill it down. Interesting idea.

[EarlH]

The acetone/transmission fluid mixture will work MUCH better than anything you can buy off the shelf. I had an old car mechanic tell me that a long time ago, and he was right on that one. But ice on something that's quite hot will break a lot of rusty bolts loose. You can't really heat that up red hot like you could a bolt on an old car, but you can get it pretty hot with a soldering iron or a pencil torch if you have one. Those screws can be frustrating, but if you are patient and pester it enough it will probably come loose. It didn't lock up overnight! (At least that's what my Dad would have told me) Too bad they didn't have anti-seize compound back then....

[toysbyroy]

I've taken several Exhibitions to a local jeweler to remove broken screws; so far have been successful each time.

[jboger]

After two days of working on it, I got the screw out. I filed the screw head down as flat as I safely could but left it raised above the back plate. I eventually took a round needle file that comes to a point and managed to bore out a small hole pretty near dead center. Next I took a watchmaker's vise and chucked up a Dremel drill. This drill has a rather small bulbous head. I was afraid to actually use my Dremel because these run at high speeds and I was afraid it might slip. Anyway, with this particular drill bit and my little vise, I managed to remove most of the screw head. Because two back screws were already out, I separated the plates, and a little ring of the remaining screw head broke free and the plates came apart. The stump of the screw was then easy to remove. Not a lot of fun. I'd provide a picture but not a lot to see: (1) my camera is not working and (2) most of us have seen Exhibition sound boxes before.