Hi all

What is it that dictates a torque setting - is it the type of bolt or what it's securing ?

For instance is the torqued tightness (is that even a proper way of describing it !!) of a steel M10 bolt the same whether its used in say suspension or the engine ? Or does the same steel m10 bolt need to be torqued tighter dependent on where its beng used ?

Also read that if you use anti-seize lubricant or locking compound you need to adjust the torque - is this true and if so how do you know what to adjust it by ?

thanks in advance

Paul

there is tables to be found on the internet that list the torque by the diameter of the bolt.
however, not sure if the meterial its bolted to makes a difference.

if your putting a steel bolt, into ali, then the force you need will be quite small, as it will easily strip the threads!

i think its size and mterials, sometimes wet and dry settings are given

Had this one for years, hope it can be of some help.

Excellent - thanks to everyone.

One question re the table - are 8.8, 10.2 and 12 different grade/strengths ?

Presumably you therefore use a higher grade when you need a tighter fitting ?

Tensile Strength the higher the number the stronger the bolt

Depends also on how much the bolt is designed/intended to stretch?
I suspect there will be a significant difference in applied Tq to achive a given clamping force between a, say, 1" full-thread bolt (which won't/can't stretch) and a 5" long cylinder head bolt with 4" shank and 1" of thread.
John.

Its the strength of the metal of the bolt that you're fitting, to put it to perspective. Most 'normal' bolts are 8.8, 10.2 are used for example in exhaust manifolds and suspension components should all be 12 or above.

Ok - great. Think that's cleared my thinking.

Thanks all.

The torque dictates the clamping force available.

The max torque for a given grade of bolt into a HT nut will take the bolt to 70% of its UTS, this is when the max clamping force is available. Obviously in different materials, ther eis a limit to what torque can be use without stripping the threads, and as such the clamping force is reduced as well.

Take for example a pair of driven flanges bolted together. It is not the bolts which take the load when the falnges are rotated, rather the friction generated between the faces by the clamping force of the bolts.

David

STOP STOP STOP - read Engineer to Win or Prepare to Win by Carol Shelby or read all the info on the ARP website. If it really matters - do it right.