Torqueing of bolts....any bolts
 

I note with interest a lot of posts on both this site and others, where kind people mention torque settings for bolts...but we have to ask outselves a couple of things...

1. Is this value for dry, unlubricated bolts?

2. What happens when we torque a bolt...what does it do to the bolt ?

3. Stainless bolts...can we torque them to the same value as steel ones ?

4. what if we replace a fastener with a different grade ?

5. when we use a torque wrench...where do you hold it to achieve the correct setting ?

answers please from the pupils, then Ill give the correct ones

1. Yep, always dry unless stated otherwise.
2. Torque is just a turning force so hopefully the value given is lower than that which will snap the bolt but enough to stop it undoing itself. It'll be where the bolt just starts to stretch but before it breaks.
3. No, they will be different.
4. See above
5. Hold it on the grip. Torque is force multiplied by distance so if you change the distance you alter the torque.

1. Ditto.
2.Depends on the bolt, it's specific use and the material it's made from.
3.Ditto.
4.Ditto.
5. Surely it doesn't matter where it's held it's the settings within the wrench that determine the torque figure applied to a component. Holding it at the grip or as far from the pivot point would only make it easier on the user to apply the necessary force.

Hello

would stainless steel bolts need a higher torque setting then? or lower and if so by how much either way as a rule.

regards

TopiToo

[Edited on 15-07-1968 by TopiToo]

http://www.inoxbolt.co.uk/faqs.htm#tighten

Darren

1. Is this value for dry, unlubricated bolts?
Dry

2. What happens when we torque a bolt...what does it do to the bolt ?
Very complicated - it depends on the Modulus of Elasticity "E" of the bolt compared to the components that are being clamped.Basically the bolt stretches and the components are compressed a certain amount so that the forces are in equilibrium. The stretch vs compression clamps the two parts together.

3. Stainless bolts...can we torque them to the same value as steel ones ?
It depends on the "E" value - if they are the same then yes. If different then no.

4. what if we replace a fastener with a different grade ?
See above
5. when we use a torque wrench...where do you hold it to achieve the correct setting ?
Hold on the grip and apply force perpendicular to the shaft axis. Some pointer type wrenches have a hinge grip which results in the force being applied at a known distance from the bolt/nut.

Errrr...why do you ask?

RX

some excellent answers from you all..

1. yes, generally dry, but some manufacturers even state values with certain lubricants, like copperslip, which brings the torque value down. But remember that approx 60% of the torquieng effort is used in friction, ie you have to overcome this to obtain the correct value.
Correction factors are also applied in torque tables for dry bolts, generally 90% of lubed bolts.

2. Thats right, you are actually stretching the bolt within its elastic range, going too far causes it shear (actually waisting occurs around the head of the bolt, before it gives way)

3. Stainless bolts require a lower value than carbon / steel fasteners, otherwise they will become damaged / sheared. As a matter of interest, if you look at the head of a stainless bolt you may see A2 or A4, these relating to the quality of the fastener...A4 being a better grade

4. Different grade fasteners require different values to bring them into an equivalent elastic area on the youngs modulus of elasticity graph...ie to obtain the required clamping force as you rightly say.

5. Generally you must hold the wrench on the hand grip, in order to achieve the correct radial distance from the centre of the fastener...Ive seen people hold it half way down and sweat their bollox off trying to get the wrench to 'click'.

Take a look at some good quality fasteners, and you'll see a number of marking on the head...these relate to the grade of bolt, say 8.8 for high tensile. There may even be 3 'slashes' or 6 'slashes', which signifys an SAE grade bolt (society of automotive engineers).

What does amaze me is hearing people in bike shops asking for anodised bolts for their brake calipers !

Don't forget when mixing bolts from standard the effect of differing metals in close contact - in a salt water mix (Spring, Autumn and Winter in the UK)!

Ok then, what would the torque values be for 12 sided titanium nuts for the wheel & sprocket side on a 748 be please.


Chris.:burn:

Are you referring to the Corse mag swingarm, Chris?

If so those large 55mm 12-sided nuts aren't made of Ti. They are hard anodized Al-nuts. The eccentric pinch bolts and the cush drive nuts are made of Ti, however.

The torque values are as follows:

- Lefthand sprocket carrier nut: 235 Nm.
- Righthand wheel nut (L/H tread): 295 Nm.

The reason the torque values are significantly higher than the stock ones are due to the much coarser thread on the Corse nuts.

Good luck!