ahhhhhhh rear axle bolt snapped (again)

[hobbiniho]

ahhh right the fat bit at the top, and its purpose is???

[herbster]

acts like a washer and puts the shear load on the stronger part of the bolt as the metal is formed thicker. When you get your new bolt, try tightening the nut onto the bolt, don't screw a torque bolt into a nut, the torque is on the pull(nut) not the twist(bolt) when a nut is used. Try going in stages, do 20nm, 40nm 50nm then if feels good to go higher try, if that fails again, god knows why though on a 10mm thread, they should take 120nm no probs, get a bolt the same length from a proper supplier with a higher torsion number stamped on it, like 10.8 or 12 instead of 8.8. The size of the head on the bolt only matters if the area it sits is likely to be fouled by something. Hope you sort it!!

[hobbiniho]

sorry to piss on your parade but this is a m12 bolt from the stealers and it is a 10.9 not a sh!tty little 8.8    ok so i was tightning the BOLT could this cause them to snap even with the torque wrench set to 60nm 

[hobbiniho]

hold on am minute when i was putting my front bumper back on i torques the BOLTS up to 82nm and they didnt f**kin well snap so what the f**k is goin on here then 

[herbster]

 
you need to get another torque wrench, a m12 bolt will shear of course,!!!   but it takes some force, I doubt it could be done with a 3/8" ratchet and spanner easily just to give you some idea, try taking the bolt back and and asking them to get it tested, could be a bad batch!

[hobbiniho]

as i said the torque wrench is brand new, and what kind of pressure are we talking to snap said bolt 150nm?? more it just doesnt make sense ok if the torque wrench is f**ked i can understand snapping the bolt with it as its 600mm or so long but not with a normal sized t bar is it possible to exert that amount of force?? 

[dadrathers]

I'm with Herbster on this one. A 10.9 M12 can take around 80 kN ultimate strength in tension. So you could hang 7 or 8 Golfs off one bolt before it actually broke!! Temsile strength is not the same as applying torque of course - if there is too much torque applied then the bolt could break by twisting - shear off. Shear failure looks different to failure in tension. If you break it in tension then it will 'neck' i.e get smaller diameter just where it fails.

It is always better if possible to apply the torque from the nut end but 60Nm is relatively small for an M12 - as aleady said.

I would suspect a bad bolt or batch. I have had problems recently with nuts stripping threads. Could be poor quality imports from India or China.

You could try greasing the threads and also make sure the nut runs freely right up the bolt before you put it on the car.

Good luck.

[herbster]

your right, with a normal t bar your on the verge of severe knucklelitis to snap a m12 bolt especially as its a 10.9 !!!! Put all the pull on the nut, this pulls the bolt through the hole to tighten, worst that should happen is the threads on the nut will go, good luck

[herbster]

Just a tip, only use oil if torque not grease, as the grease gets older it wastes away leaving a void thus potentially loosening! Sorry  But a steel bolt thru an alloy head into a cast case needs no lube just for reference, only oil if the head is cast too!!

[Mew]

Just a tip, only use oil if torque not grease, as the grease gets older it wastes away leaving a void thus potentially loosening! Sorry  But a steel bolt thru an alloy head into a cast case needs no lube just for reference, only oil if the head is cast too!!

Wrong thread by any chance!?