The other night I was bolting my engine back into it's cradle. To speed things up a bit I stupidly decided to use my new Aldi air wrench to run the bolts in most of the way before nipping them up by hand. Anyway I ended up cross threading one of the engine mounting lugs. (Facing the exhaust manifold side it's the one on the top right that takes an M10x1.25 bolt.) I'd managed to chew up quite a bit of thread before I realised it had gone in at an angle. Any suggestions for re-tapping appreciated. I've got a set of taps but they're only standard course thread ones. Is it possible to drill & tap out to M12 or am I going to weaken it too much?
Rule 1: locate nuts & bolts two or three turns with your fingers before using power tools to finish them off...
To be more helpful: is this something that could be taken to a machine shop to have a helicoil fitted? That would be the most sound solution,
engineering-wise.
[Edited on 5/3/11 by David Jenkins]
I would try and tap with the original tap first you may have on damaged a coupl of threads, if you manage to do thid then put thread lock onto the bolt
You may end up with a helicoil but get the correct tap or a thread chaser and try that first.
M10x1.25
Helicoil
...And you dont need a machine shop to insert a helicoil.
Fair enough - I've never had to do it (but I've read the machine shop guides...).
Is it just a case of drilling the correct-sized holes, making a thread with the correct tap, then winding the helicoil in? Is it cheaper to do it
yourself, of better to slip a machine shop a fiver to do it for you (if that can be done)?
quote:
Originally posted by David Jenkins
Fair enough - I've never had to do it (but I've read the machine shop guides...).
Is it just a case of drilling the correct-sized holes, making a thread with the correct tap, then winding the helicoil in? Is it cheaper to do it yourself, of better to slip a machine shop a fiver to do it for you (if that can be done)?
Thanks for the replies. It'll be a real pain in the a**se to take it to a machine shop 'cos it's all plumbed in. So I'm going to try the helicoil. Cheers.
Just don't strip the helicoil - I know someone who's done that!
If possible replace the bolt with stud and secure with Loctite as this will reduce any danger of unscrewing the helicoil next time you take it apart.
quote:
Rule 1: locate nuts & bolts two or three turns with your fingers before using power tools to finish them off...
There used to be a thread on here, but it's long since gone. You certainly wouldn't be the first to tap a 12mm hole.