×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

How do I calculate tightening torque???

How do I calculate tightening torque???

How do I calculate tightening torque???

(OP)
This is probably a simple question to some who does it everyday, but I'm struggling....

How do I work out the torque that should be applied to nut to give a specified 'clamping' force on a gasket.

I have a connection comprising of a single nut(female thread!) screwing on to a male threaded connection.  

These when mated together compress a ring gasket.
The threads are 2.5" right hand Whitworth with 5 (five) teeth per inch.  I have 30mm of thread.  The threads are cut from Hastelloy C276.

I assume the torque is a function of thread contact area and friction between the threads.

Any guidance will be greatly appreciated!

Biggy

RE: How do I calculate tightening torque???

Are you sure you have Whitworth threads?  They are disfavored over the 60 degree flank angle thread forms.  Can you switch?  I would recommend the ISO M thread (standard use) or the ISO MJ thread (fatigue applications).

This formula will calculate what torque will generate what preload.  It requires SI units, so you will need to convert.
If you do change to M/MJ threads, the 0.56 factor will need to be changed to 0.58.


M = F/1000 * [(0.16*P) + (0.56*d*mu) + (mu*D/2)]

where

   M = input torque in N m
   F = preload in N
   P = pitch in mm (this is the inverse of threads per inch)
   d = pitch diameter in mm
  mu = friction coefficient
   D = (dout+din)/2
dout = outer nut contact diameter in mm
 din = inner nut contact diameter in mm

Cory
cpadfield@omninmetalslab.com

RE: How do I calculate tightening torque???

I use  Torque = 0.2 * Force * Diameter as a quick, memorable formula for torques for steel bolts. This is not as accurate as Corypad's formula, but close enough for most applications. Note that the friction coefficient will be of the order of 0.15 to 0.20 because the contact pressures on the threads are quite high.

Hasalloy may have a different friction coefficient. Check whether galling is a problem. If it is then apply an anti-galling compound, or simply grease the threads before installation.

Russell Keays

RE: How do I calculate tightening torque???

(OP)
Cory!

Thanks for that it is just what I need, just two things....

Can you please explain to me what the 'dout' and 'din' are.

Regards,

Biggy

RE: How do I calculate tightening torque???

Your nut contacts the piece underneath it in two places - an outer contact diameter (dout) and an inner contact diameter (din).  The outer diameter is the largest diameter of the bearing face, while the inner diameter is usually the hole in the piece underneath that the externally threaded fastener extends through.

As an example, let's assume you are using a hex flange nut with an outer diameter of 5 inches.  This is your dout.  Let's say the piece under your nut has a hole in it of 2.75 inches (to allow a 2.5 inch fastener to easily pass through) - this is your din.

You may contact me directly if you have additional questions.

Cory
cpadfield@omnimetalslab.com

RE: How do I calculate tightening torque???

Sprintcar is on target and you should really avail yourself of the FAQ section of these forums when available.  The site mentioned has been there for some time!!!


Rod

RE: How do I calculate tightening torque???

The calculator at www.futek.com is not particular good (it asks the user for a K factor, which a novice wouldn't know about), and it wouldn't account for Biggy's unusual geometry.  The equation I posted in a previous message (taken from VDI 2230) is vastly superior to anything that uses a K factor, which can introduce significant errors.

RE: How do I calculate tightening torque???

(OP)
And that's enough about my unusual geometry!!!!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close