Drilling out sheared off bolts.

[Chris Bacon]

Good Lord, are they *really* case-hardened? I am surprised.

[Rob Morley]

This is good because the heat helps loosen the bolt. If there's a bit of the broken thread protruding I usually try to weld a nut to it.

Even if you only manage to clear the first few threads you can often use a plug tap of the appropriate size to clean out the rest (but don't try it if you can't get it started cleanly).

But beware of punching through the bottom of the hole.

I'd rather use an oversize bolt if possible - helicoils have an annoying habit of coming out when you undo the bolt.

[Funfly3]

I have used these on a Exhaust stud on a car and it was so easy apart from drilling the hole

[Dave Plowman (News)]

hardened steel out. If buying easy outs go to a good quality tool shop or engineer's suppliers. And pay for the best.

[Dave Plowman (News)]

And then snap off. ;-)

The parallel sided ones are much better.

[Matt]

Yes

No, with the notable exception of one supplier (Tracy Tools) I can honestly say that I've NEVER seen a single left handed tap or die, let alone a set of them for sale in any secondhand tool shop (and I have frequented many over the years)

[Matt]

Can't agree with that! unless they "snag" during drilling all they do is drill out the hole and exert no force in line with the thread helix. They are usually just an expensive waste of time - I've got quite a few but they hardly ever get used!

[The3rd Earl Of Derby]

You must be unlucky then (Willdridges second hand shop, west derby road, Liverpool, merseyside).

If you want new try RS components.

-- Sir Benjamin Middlethwaite

[Duncanwood]

Left handed drill bits are fairly common & achieve the same result.

[Duncanwood]

Start with a centre drill, then continue with left hand spiral drill bits

[Guy King]

The message from Chris Bacon contains these words:

Properly done, case hardening would be ideal for this application. Leave the metal tough enough not to snap but with a very hard skin so there's plenty of bite into the victim.

[Matt]

Not been over that way for years, but if I'm in the area again I'll go just for the hell of it!

Thanks but I have plenty of sources for new - RS would be the last place I would go (unless it was post 5pm desperate need for the next day) I would suspect they would only do Metric coarse anyway - most of my left hand requirements would be for UNF or Metric Fine. For the bolt I would turn from scratch and screwcut in a few minutes rather than even contemplate using a die.

But back to the original problem - left handed tapping and using a left handed bolt is a crazy idea!

[Matt]

But even the "best" break :-)

[dojj]

is the cast iron removable from where it is fixed? if so get it to an engineering shop and get them to do it

[Chris Bacon]

Hm, not sure about that, I think that these things are generally hardened and tempered - the materials for these processes are generally different, low carbon steel being used for case hardened things. Very long time since I did any metallurgy, which I haven't looked at since!

[Dave]

When they do, just drill them out. You will need a solid tungsten carbide twist drill though. Local engineers supplier will have one.

Dave

[Dave]

What size are the sheared studs?

It makes a big difference to the tactics that you can use.

Dave

[ChasesDragons]

Ok, these are my methods, you may like em or not. Most of this is practiced on motorbikes and have all worked at one time or other, saving me a buyndle on heli-coiling and whatnot.

Before you do any of these, allways heat the bolts and then spray chilled water on em, I think it breaks any bonds that the threads have made with the each other. then:

1: use a hacksaw blade or one of those dinky little dremel jobbies to cut a "slot" on the stub that is left over. If the stub is flush with the rest of the metal, I'd cut the slot anyway, and then repair the "colateral damage" on the surrounding area (solder, metal-epox, whatever), after the stud is extracted. When you have a slot, heat again and turn with a flat blade SD- heating is not advisable if the stud expands faster than the hole, for obvious reasons. I tend to use impact with a hammer as I turn, to give it the best chance of unscrewing.

2: If the bolt is large (10mm+) you could go through all the superheat/chill mallarkey and then turn the stub with some well placed tangential blows with a punch and hammer.

3: Use the Snap-On stud extractor bit (which by the way was stolen from me, and I swear by the almighty that if I find the dirty weazel I will feed his swingers into my bike's chain), good stuff anyway.

Hope this helps.

[Andrew Mawson]

If the stud is sheared off flush with a surface, place a nut over it and mig weld the stud end until the blob of metal is big enough to fuse to the nut. When it cools remove with a spanner. Obviously not applicable to flamable objects, but in iron, steel and aluminium the heat of the welding expands the stud, when it cools it will be freer than it was and now you have something the grab!

AWEM

[mrcheerful]

8mm