Technical Another sheared bolt...

[spleenharvester]

Me again! There's a good reason I've been methodically replacing every bolt I remove with a brand new one when I work on this car...

This time it's the one of the two M6 (or maybe M8?) bolts on my 1.2 8v holding the coil pack in place, this one (pic not mine):

Head sheared off after recent work with next to no force. It's far too deep to weld anything to, and hammering a torx in failed - can't go any larger without destroying the thread. What's the next step here, just drill a bigger hole in the remaining bolt/thread and helicoil?

For once it isn't the most important bolt in existance as I can just replace the rocker cover if it comes to it, just a bit of a wind up!

Cheers!

 

[steveras57]

Hi i would drill it out then tap the hole and fit a blind hole time-sert to original size!

 

[GettinBetter]

Head sheared off after recent work with next to no force

Were you undoing it, or doing it up when it broke?

 

[spleenharvester]

Were you undoing it, or doing it up when it broke?

Tightening, it sheared as soon as it hit resistance. I have a proper Milwaukee socket set and the bolt is the original one so I think it was just fatigued.

 

[The Panda Nut]

These things really only need a few fingers of tightening, Wrist power is too much. At least its a soft bolt. You can get stud extarctors and reverse thread screw extarctors on line.

 

[GettinBetter]

Tightening, it sheared as soon as it hit resistance. I have a proper Milwaukee socket set and the bolt is the original one so I think it was just fatigued.

That my friend, is why we have torque wrenches. Not because we're too stupid to tighten a bolt, but because we've all broken a few bolts.

Get a torque wrench for the small stuff for now, any thing up to 12mm, learn the feel for 6 - 8 & 10Nm etc, you'll be surprised how little effort you need, and many of the lower torque settings will feel lose, but you can always add a bit of nutlock if you're not happy. Don't use a larger torque wrench for the lower settings, they have no 'feel' to them.

It'll save you a ton of heartache with broken bolts.

 

[steveras57]

That my friend, is why we have torque wrenches. Not because we're too stupid to tighten a bolt, but because we've all broken a few bolts.

Get a torque wrench for the small stuff for now, any thing up to 12mm, learn the feel for 6 - 8 & 10Nm etc, you'll be surprised how little effort you need, and many of the lower torque settings will feel lose, but you can always add a bit of nutlock if you're not happy. Don't use a larger torque wrench for the lower settings, they have no 'feel' to them.

It'll save you a ton of heartache with broken bolts.

Or put em in loose with a dab of threadlock on em wont snap or fallout!!!

 

[GettinBetter]

Or put em in loose with a dab of threadlock on em wont snap or fallout!!!

Mmm.. but the last thing you'd want is a rattle

 

[steveras57]

Mmm.. but the last thing you'd want is a rattle

One more probably wont make that much difference!!!

 

[GettinBetter]

Argh, I'm obsessed with rattles can't abide them. You can't hear if anything is on it's way out.

 

[steveras57]

Argh, I'm obsessed with rattles can't abide them. You can't hear if anything is on it's way out.

I like living on the edge! (its better for me to have loads of little "tinkles" so i cant concentrate on any one of em! )then try and fix it and bust something else!!!

 

[GettinBetter]

I like living on the edge! (its better for me to have loads of little "tinkles" so i cant concentrate on any one of em! )then try and fix it and bust something else!!!

I thought that was what the radio is for, drowning out all the noises.

c'mon then what have you broken?

 

[steveras57]

I thought that was what the radio is for, drowning out all the noises.

c'mon then what have you broken?

A) i am not very musical and never drive with the radio on unless i am on a longer journey and need the traffic info!
B) pick something!(anything!) door card clips, obd port cover, handbrake handle! and about half a million other odds and sods!

 

[Cornish Ian]

That my friend, is why we have torque wrenches. Not because we're too stupid to tighten a bolt, but because we've all broken a few bolts.

Get a torque wrench for the small stuff for now, any thing up to 12mm, learn the feel for 6 - 8 & 10Nm etc, you'll be surprised how little effort you need, and many of the lower torque settings will feel lose, but you can always add a bit of nutlock if you're not happy. Don't use a larger torque wrench for the lower settings, they have no 'feel' to them.

It'll save you a ton of heartache with broken bolts.

I’m not disagreeing with using a torque wrench but unfortunately if a bolt has been previously over tightened, specifically past its ultimate tensile strength then even applying the correct torque could still cause it to fail.
Put another way when the bolt material has reached its ultimate tensile strength it will continue to stretch with less and less applied load until it fails.
I suspect the OPs problem is that someone big and hairy has previously has overtightened many of his bolts close to their failure point so replacement is his only real safe option.

 

[GettinBetter]

.... has reached its ultimate tensile strength it will continue to stretch with less and less applied load until it fails.

Agreed, but maybe the OP is big & hairy, but just needs to calibrate his muscles somewhat (as we all have) .

Caveat: I could be wrong, I've been wrong before.

 

[Cornish Ian]

Agreed, but maybe the OP is big & hairy, but just needs to calibrate his muscles somewhat (as we all have) .

Caveat: I could be wrong, I've been wrong before.

That’s certainly the other possibility.
I was going by the “sheared as soon as it hit resistance” but yes calibrated muscles is something that normally comes with experience and small bolts, especially any made from low strength steel will snap very easily.

 

[spleenharvester]

I'm already using a torque wrench - was set to 5 Nm in this case and didn't reach the clicky!

And nope I am not big and hairy lol I think it was just already stressed

 

[Cornish Ian]

I'm already using a torque wrench - was set to 5 Nm in this case and didn't reach the clicky!

And nope I am not big and hairy lol I think it was just already stressed

I can’t see the bolt head clearly enough to tell what material it is made from but if it was 8.8 then that torque should have been fine. 4.6 or no markings then not so much.

 

[GettinBetter]

And nope I am not big and hairy..

 

[Jockstrap]

Just having a read and thinking ... Yup .

My wee 2008 motor had been 'serviced' annually. ******** . Every which way some or has been involved.

Muppets! No feel for the material or stress. Plastic squeezed to break, nuts ripping threads, get the impact wrench and 'uck the panel'.

No worries, paying punters ' no see'.

When's the last time a torque wrench was calibrated?

As a young pup (long ago), I was stocktaking (not nicking) at a sweety manufacturer. The jelly beans being polished and the foreman (old name) put his hand in the polishing drum and said the weight. Young pup auditor, not ok with this! Long story but subsequently weighed 3 drums and foreman was spot on .

Nothing like a good feel .