Allen bolt removal

[RJH]

5 of 8 allen bolts fixing 2 metal sheets on my car have stripped the hex key. They are/were 4mm, and I think stainless steel. I've tried drilling one out to 5 and 5.5, but the spirally tool in this pic:

can't generate enough purchase. It grips a little, but slips. I don't know what that other bit is in the photo - memory suggests it's a screw extraction tool I got from Aldi. There isn't enough head on the bolt to use mole grips.

I'm not sure if I'm using the extractor incorrectly, or it's just not very effective. Thinking now about cutting a slot in the head and trying a flat blade screwdriver. I don't think they're outrageously tight. I can access the other side - but I don't want to damage the thread in the sheet the bolt screws into.

Suggestions appreciated.

[T i m]

Is this amour plating or something? ;-)

It looks very 'stubby' compared with what I have which are longer and with a finer taper?

You can get fairly fine 'Mole' style grips with a curved jaw that might?

It doesn't look like it would be (but I've not seen one like that before).

Yup, a Dremel with a cutting disk or if it doesn't matter if you nick the top plate they are fixing, tapping the rim round on that 'Button head' (?) screw (as you are getting new anyway) with a fine cold chisel and toffee hammer might do it?

If you grip them with some small Mole grips and some lolly stick to make 'soft jaws' and don't go mad, that might be worth a try?

I'm assuming you have already dosed them with some Plus Gas or equiv?

Cheers, T i m

[Andy Burns]

big rubber band wedged in what's left of the head to let an allen key, or the extractor get a bit more bite?

[RobH]

A tap extractor might be better, if you can't do it any other way.

[Clive Arthur]

If there's room, put a nut on the back, and use mole grips on the thread. Once loose, grind the thread down to the nut and remove the nut.

[GB]

If there's lots of room, put two nuts on the back and lock them together. Then turn that lot.

[Clive Arthur]

Good idea.

[Martin Brown]

My suggestion would be drill a slightly deeper hole about in the middle of the allen socket and then use a conventional extractor tool sized for the hole. It is a close thing because you can't afford to make the hole too big or you will just snap the head off the bolt and then be forced to drill the entire thing out and retap it to oversize.

[John Rumm]

Drop a hex nut over the end of the screw, and fill the nut with weld while joining it to the screw, then remove with a spanner.

[RJH]

Thanks everyone - plenty to go on.

There really isn't enough to grip with mole grips etc.; penetrating oil - good plan (although the ones that did come out were more stiff than tight); weld a nut - good plan but no gear; rubber band - intriguing/odd, I'll try it tomorrow; tap extractor - close to last resort; nut on the other end - bolt flush the other side.

I'm going to try the slot/screwdriver/hammer/chisel tomorrow. The heads are very soft - the multitool cuts a slot in a few seconds.

(it's removing a wheelchair ramp - but I want the removal reversible)

[Andy Burns]

Might not work for allen, but does for phillips, worth a go

[alan_m]

Hex or Torx? Even with a rounded hex there still may be enough grip using a torx bit.

Cold it have been a hex security bolt requiring a hex bit with a hole in the centre of the bit to get it deep enough to grip?

[alan_m]

Irish screwdriver? Try inserting the hex bit and tapping with a hammer which may shock any tight bond loose before attempting to undo.

Amn impact driver may also work - it hammers the bit in at the same time as turning.

[Fredxx]

Most of these bolts in the past 10-20 years are Torx and not true Allen bolts.

Last bugger I got out I use a MIG welder to attach a bolt to the hex bolt.

Only other suggestion is use a impact driver with a tapered hex key.

[newshound]

Remarkably effective technique, but 4mm is a bit small IMHO.

[Roger Mills]

Could you file some flats on the thin flange of the head, and then use an open-ended spanner on it?

[alan_m]

Not so small for tor this type of impact driver

rather than

can be a lot more brutal.

[Dave Plowman (News]

A suitable sized Torx bit hammered in often works.

[RJH]

Yes, I'll give that a go. The panel is a not that firm so getting a decent 'thump' may be tricky.

I've got a 14V ID - the few that came out came out using that.