Re: [CR] Snapped ajustment screw

(Example: Framebuilders:Mario Confente)

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Date: Mon, 15 Mar 2010 23:28:44 -0700 (PDT)
From: <minneman@onomy.com>
To: "John D Proch" <johnprochss@yahoo.com>
Cc: classicrendezvous@bikelist.org
Subject: Re: [CR] Snapped ajustment screw


John,

I'm not sure exactly what you're saying. My note was reporting that, having used extreme care and caution and years of experience (I'm a mechanical engineer who is very comfortable in a machine shop and I've done this kind of "drill it out" process with some regularity over the years), it's doable and it's not that hard. In particular, I have removed broken adjuster screws from bike frames more than once, without damage to any of the frames I've done it to.

I agree that if you're in a situation where you simply *cannot* mess up a frame, then there might be a professional you'd want to turn to...that's why I was asking Jack for more details. I'd certainly want to *know* that the professional was going to use at least as much care as I would, and I'd want to know they were more skilled at the sort of operation being considered than I am.

Furthermore, some of the techniques being bandied about here are simply not sensible for anything but the most valuable frames. Wire EDM doesn't really make a whole lot of sense for this kind of problem, and plunge/sinker EDM will work, if you want to pay for it. EDM requires that the part be submerged in an insulating fluid (like oil), and the rigging needed to get the tail end of a frame aligned with the business axis of an EDM machine (and submerged) isn't pretty. Those techniques make sense for removing taps or drills (very hardened materials) in a situation where the value of the thing it broke in makes the cost worthwhile.

I keep a good machinist in the background, too. This is simply not an instance where I'd trot him out, unless it was a frame where the slim chance of damage is simply unthinkable.

Ok. Loads of disclaimers and all of that, again. If the chance of damage, for you, isn't slim, and you're likely to mess up the frame...don't try it!

I'm also the sort who might decide that *building* an EDM rig from scratch for such a purpose might be a fun distraction.

There are a bunch of frame builders and restorers on this list. Speak up, please -- how do you approach this? I can pretty much guarantee that few of you have an EDM rig in their shop.

Cheers,

Scott

Scott Minneman San Francisco, CA, USA
> Hi Scott,
>
> I trust my skills and abilities so much that if it is critical I keep a
> reputable machine shop in the background.
> Many years of experience with mechanical and restoration have kept me
> humble to know that the guy who does it all day 50 hours a week is better.
> Just a suggestion. If you have a friend that works in one that you trust.
>
> Best Regards,
> John Proch
> La Grange, Texas
> ________________________________
> From: Scott L. Minneman <minneman@onomy.com>
> To: Mark Bulgier <Mark@bulgier.net>; Jack Gabus <jgabus@gmail.com>; CR
> <classicrendezvous@bikelist.org>
> Sent: Mon, March 15, 2010 6:34:39 PM
> Subject: Re: [CR] Snapped ajustment screw
>
> 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