Calulating Torque on a nut

[albmopar]

I am designing a pnuematic clamp device to hold a nut while a bolt is threaded through a plate and into the nut. How do I calculate the torque on the nut to properly design the clamp mechanism. I am using a M10 X 1.0 bolt and nut.

 

[KENAT]

faq725-536 should help

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[hydtools]

How much torque will be applied to the bolt? You have to exceed that.

Ted

 

[albmopar]

I am torquing the bolt to 70Nm through a 12mm plate.

 

[desertfox]

Hi albmopar

Have a look at this site it will show you how to calculate the clamping force from the torque:-

http://www.roymech.co.uk/Useful_Tables/Screws/Preloading.html

Failing that for a rough estimate of the clamping force use this formula:-

F= 0.2*T/(d)

where F=clamping force
T= Torque
d= bolt dia
0.2 = friction factor (dry)

desertfox

 

[MRSSPOCK]

The lubrication used or not used has a huge influence.
In my reference book, supposedly as used by Airbus manufacturing, (ISBN 3-8085-1910-X), M10 x 1.0 can have a torque value ranging from 36Nm to 51Nm, depending on the friction, i.e. they quote µ from 0.08 to 0.14 If you then consider bolt grades, the range goes from 36Nm to 88Nm, the 36Nm value being applicable to 0.08µ with a bolt Grade 8.8 and the 88Nm value applying to 0.14µ with a bolt Grade 12.9
It seems so easy to pull the head off a bolt by simply having it lubricated, if the torque value recommended was for an unlubricated condition. It's always a dilemma for me when quoting a recommended torque, as I try to cater for the operator not having the correct lubrication. It's pretty difficult to cover every eventuality, while still ensuring the joint is as secure as it was intended in it's design.

 

[albmopar]

I am trying to figure out what the max torque will be on the nut when I thread the bolt in. Theoretically, the nut won't see any torque until the bolt and nut seat against the faces of the plate, at which point the friction should absorb some of the torque.

 

[hydtools]

Select the value of the torque you expect to apply to the bolt, 70Nm. This would be an adequate to conservative value. Any friction under the nut will reduce that resistance necessary for the clamp to provide to prevent nut rotation.

If you want to feel 20% better, plan on the clamp resisting 120% of the applied torque or 84Nm.

How do you propose to prevent cross-threading when the bolt contacts the nut?

Are you wanting to calculate the clamp force necessary to cause enough friction force resistance under the nut to resist rotation of the nut? Use 1/2 the average diameter of the nut face for the radius through which the friction force acts. Use the clamp force x a friction factor to calculate the friction force. The friction factor will depend on lubrication or dry friction conditions under the nut. Friction force x 1/2 average diameter = torque resistance.

Ted

 

[TBone216]

Bolt Loading Calculator

http://www.riverhawk.com/boltloading.php

 

[dicer]

And for a clamping force equation why would there be no mention of the threads per inch, meaning a helix angle?

 

[hydtools]

In my answer I was presuming the clamp force is that force pushing against the nut to hold it against the twisting torque applied to the bolt. The force required to hold the nut against the plate. No thread per inch needed for the calculation. Just how hard to push against the nut to prevent rotation while the bolt is tightened.

Ted