Jack,
Is it flush on both ends? No chance of getting some purchase anywhere? How'd it happen? Is there enough visible on one end or the other that a skilled tig welder can tack something on for the removal (this can be done without ruining paint/chrome)? Obviously, if you manage that, you want to *completely* remove material from the other end (see Dremel trickery, below).
I've drilled them out before, without much fuss. The trick is getting a good (centered) start and staying on line. I'm assuming this is an M3 fastener. If it's an M4 (uncommon...very early Campagnolo, for instance), the drill sizes below are wrong, but the job is much easier and less stressful.
Getting a good start is helped by a good divot in the old screw, which you can do with a quality punch or, better, with a tiny carbide or stone bit in a Dremel (think dentist).
After that, drilling isn't really all that difficult. A good quality bit really helps minimize the chances of breakage. Either make yourself a jig and do it in a drill press, use human spotters for when you're off of straight, or make yourself a guide or two so that the desired direction is visually obvious (I've used the first and last of these techniques, and have never messed up a frame). You want a drill bit in the neighborhood of a #45...the bigger you have the nerve to use, the less chance you have of it breaking. If you're happy with where the bit emerges on the far side, you can enlarge that hole even further...up to a #39 or so.
Then, chase the crap out of the threads with a good tap. Again, don't economize on the tool. I use a gun tap on through holes like this, so the chips get pushed out the far side and don't cause the tap to jam.
Needless to say, if any of this isn't making sense to you, or the various places where you should be using loads of cutting fluid aren't obvious, or you don't own the right tools (or know where to get them), then you probably shouldn't try doing it. You can make a mess of things and ruin a frame for good (or, at least, make the job harder/impossible for somebody trying to remediate a botched effort).
Your call. What's the frame this happened to?
Scott Minneman San Francisco, CA USA
-----Original Message----- From: classicrendezvous-bounces@bikelist.org [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of Mark Bulgier Sent: Monday, March 15, 2010 4:01 PM To: Jack Gabus; CR Subject: Re: [CR] Snapped ajustment screw
Jack Gabus wrote:
> I have a snapped adjustment screw on a back drop out. You know
> the bad one where no one can get to it. Any new great ideas on how to
> remove it or am I toast.
You might ask Bill Davidson (of Davidson Cycles / Elliott Bay Bicycles in Seattle). He has taken frames with that problem to a machinist with a wire EDM, which I believe stands for Electron Discharge Machining and is capable of drilling a very accurate hole. After drilling out the body of the screw, the dropout threads can be chased with a tap. Don't know what it costs but it was deemed worth it to save a nice frame.
Davidson's guy isn't the only place to have that done of course -- you may know a local machinist you can take it to.
Most dropouts can be replaced by a framebuilder too, not too expensive usually, but it ruins the paint of course.
Mark Bulgier
Seattle WA USA