Drill out sheared cage bolt?

[Thaumaturge]

Can anyone recommend somewhere in London for this job? Stripped a frame and one of the cage bolt heads sheared off rather than turn. I tried to extract it by hand with a screwpuller/drillbit but as the head left a metal nipple right in the center the only progress i could make drilling was getting too close to the frame itself. It seems to me that any workshop with a drill press could clamp it up and accurately drill/extract but the well recommended LBS i spoke two wanted to completely drill out the eye and weld a new one in rather than make the attempt. Can anyone recommend somewhere in London that might do this?

 

[MikeyMK]

Have you managed to break the cage away? If it's alloy or plastic it can almost certainly be broken away off the bolt, leaving the bolt head protruding enough for a pair of grips to remove it..?

 

[Thaumaturge]

There's no cage. The head is sheared off the bolt that's why i'm trying to drill it out.

 

[ishaw]

Re:

Have you tried easy-outs? Has worked for me on a few occasions, but you need to be able to drill a pilot hole, though not a deep one.

 

[Thaumaturge]

I bought a screw extractor kit but since the remainder of the bolt has a peak in the center you can't do it manually. With a drill press i would think a slow progression would remove this allowing you to drill on center then remove with the screwpuller. Is easy out a screwpuller/reverse bit?

 

[jonthefish]

Can't recommend anyone but I'd have thought a quick google of machine shops/light engineering might reveal something. When I used to fettle old motorbikes I was amazed how helpful some of the guys could be.

For diy, I suppose you might be able to make fabricate some kind of guide to stop your drill wandering off the bolt. Drill very small hole in guide and fix over annoying bolt to keep you lined up.

 

[kingoffootball]

I've had to drill out sheared bolts that have a point towards the centre before and it is awkward.

I think last time I did it, I used a slightly larger punch to flatten the central point a little and then a very fine punch to create a small depression to guide the drill bit.

Also, bear in mind that because it is a cross-section of a threaded bolt, what looks like the centre is not the centre, if that makes sense.

 

[integerspin]

Best way is often to weld something to the remains of the broken bolt, some times you can just grip the blob of weld and
unscrew the bolt, other times you have to weld an old nut on it and unscrew it. I do this pretty often on motorbike parts.
I do drill some out but stud extractors[easyouts] are not always easy to use and they often break, it's always harder to
remove a broken extractor than the old bolt.

 

[Thaumaturge]

Some good idea's here thanks. I can try and flatten the bolt remainder as suggested for another attempt. Failing that, i like the idea of welding a nut on. Very little tolerance so welding through the middle of a lined up nut could avoid frame damage. That or the drill press will mean a trip to the machine shop.

 

[ishaw]

Re:

My dremel has a grinding tool that would be perfect for removing the bit of metal preventing you from drilling. It's a conical shape. Maybe you have one?