Sheared off bolthead on bottom front of sump! Argh!

[Colonel Nikolai]

Previous owner apparently had either cross-threaded or tightened a blot too tight that's needed to correctly mount the Thunderbike bars I got. The head of the bolt is broken off.

I've had bad luck with extractors in the past (actually broke one off!) can someone walk me through getting this out and maybe repairing the threads?

[Bixxer Bob]

Col Nick, did the head come off as a result of being seized in place (or cross threaded) or because it had been over tightened?  If it was overtightened it would either shear in use or as soon as you put a little pressure on it to undo it.  If it was seized or x'ed it would take a fair effort to shear it.  If it was over tightened it'll come out easy enough, if it was seized then you need to use extractors.  The key to getting a result with an extractor is to drill the hole exactly in the middle of the bolt as big as you can without actually touching the threads then using the biggest extractor you can get in there.


Getting the middle of the bolt while on the bike can be tricky so, if there's any thread left proud, make yourself a guide by drilling a piece of bar and tapping it the right size and then drilling a giude hole up the centre.  you can then screw it in place and use the guide hole to position your drill.

If you can't make one yourself,  have you a friendly machinist, or do they have a metal shop at your local school even?

Heat is also helpful, but probably not in this case.

[iansoady]

I've never had success with easy-outs. It could be because I've only ever used the cheap ones which are super-hard but break as soon as you put any pressure on them.

I'd go with Bob as far as the drilling part  but would either fit a helicoil or retap the hole to the next size up. If you do break an extractor in the hole they're virtually impossible to remove other than with spark erosion.

[Nick Calne]

I've had some similar experiences with shearing bolts on an old yamaha tenere I used to own.  The extractors are very brittle and a sod to remove if they break.  And as the gents mention, they certainly do!  Using the biggest one you can certainly is good advice.  Go careful chap!

[Colonel Nikolai]

You guys scared me off trying to do it myself. I think I'll try a machinist.

[Bixxer Bob]

I've never had success with easy-outs. It could be because I've only ever used the cheap ones which are super-hard but break as soon as you put any pressure on them.

I'd go with Bob as far as the drilling part  but would either fit a helicoil or retap the hole to the next size up. If you do break an extractor in the hole they're virtually impossible to remove other than with spark erosion.

Spot on.  Stands to reason that if the original bolt sheared, the extractor is probably going to as well.  That's why you must use the biggest possible.  What I should have said is the drill - as well as being on centre - should be just under the root diameter of the thread, effectively taking the bolt out and leaving just the thread.  

I used to get a lot of extraction jobs in my shop floor days as I had a bit more "feel" than some of my stronger peers.  Harrier tail plane spigots were a speciality.... [exits left with a glazed, those were the days, look...]

[Colonel Nikolai]

Harrier tail plane spigots were a speciality....

:shock:

Yeah you've left the stratosphere in experience and skill compared to me on that one. Wish I had your skill!

[Bixxer Bob]

It was a long time ago, when I was young and oh so sure of myself.... :?

To quote someone wiser than me, "The older I get the less I know".... :lol:

[nightrunner]

I have to question this claim of using the largest drill possible for an easy-out.  The extractor has to bite into the body of the bolt enough to turn it.  That bite means outward pressure.  If the hole is nearly as big as the threads, then the threads will expand a bit and make the bolt tighter against the female threads as you rotate the extractor.  Of course too small of an extractor will just snap off.  There has to be a happy medium there somewhere.

[BruKen]

I have never had success with an easy out...ever... unless the bolt hadn't seized and it was just the head that had sheared off from over tightenning. I would bet that the bolt has probably corroded itself in. If the bolt is an M6 say, drill it with a 2mm then 3mm etc to 5.5mm drill and tap in a 12 spline (think torx) bit so that the splines cut into the residual bolt and undo. If it still fails to extract you should go for the helicoil option.

[Bixxer Bob]

I have to question this claim of using the largest drill possible for an easy-out.  The extractor has to bite into the body of the bolt enough to turn it.  That bite means outward pressure.  If the hole is nearly as big as the threads, then the threads will expand a bit and make the bolt tighter against the female threads as you rotate the extractor.  Of course too small of an extractor will just snap off.  There has to be a happy medium there somewhere.

It's sometimes difficult to be clear.  "... just under the root dia of the thread... " leaves enough to bite but not enough to keep the integrity of the bolt and allows the extractor to bite.  To minimise the risk of snapping the extractor, the hole should allow it to bite just before the shank thus using the widest, strongest part.  If you use a size too big and start half way down the extractor, you're doomed.

Ken, that's an interesting approach; I've got some old torx bits so I'll give that a go next time I'm stuck, as long as it's in a place where using a hammer is not going to do make things worse  :lol:

[BruKen]

Ken, that's an interesting approach; I've got some old torx bits so I'll give that a go next time I'm stuck, as long as it's in a place where using a hammer is not going to do make things worse  :lol:

Not a standard Torx bit Bob. They have six splines which are rather too thick. You get a 12 spline bit. The splines are thinner and will cut easier without using as much force

see the cross section

[JetdocX]

Everyone needs a set of these.  They don't break off.  Period.



Done my fair share of screw removal, too.

[Bixxer Bob]

They're similar to the extractors we used in my shop floor days but I've never seen them for sale - who makes them?

[JetdocX]

I got mine off the Snap-On truck.  And before anyone bitches about how expensive they are, I say these are worth every penny.