×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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!
  • Students Click Here

*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

Jobs

Plastic Screws Recommended Torque
2

Plastic Screws Recommended Torque

Plastic Screws Recommended Torque

(OP)
I am looking for standards or recommendations for maximum allowed torque for plastic screws, specifically for size 4-40 x ½ screw made of "peek" material (http://www.berry-is.com/PEEK%20overview.html). Do these standards or recommendations exist?
I would appreciate if someone could share with this information.
 

RE: Plastic Screws Recommended Torque

Many times the maufacture of the screw will specify this in their documentation. This max. torque is also highly dependent on the size of the pilot hole.

Typically though #4-40 is a thread pitch for metal and #4-17 is for plastics,etc..

I would look into plastic thread forming screws like the hi-lo types or Plastite 45 from Reminc as they will allow a higher torque because thats what they are made for.

Here we torque a #4-17 screw into ABS using 7 in-lbs.
 

RE: Plastic Screws Recommended Torque

mcgyvr,

   I think minchanin is asking for the torque required to drive a plastic machine screw into a previously tapped hole.  The standard torque equation should answer this question.  You can get the proof stress by reading up on the material.

   T = KDF...

   ...where T is torque in inch pounds, D is major diameter in inches, and F is clamping force in pounds.  The stress area of a 4-40UNC screw is 0.00604sq.in.  

   Does anyone know the friction factor K would be?  I have all sorts of literature on metal bolts and screws, with and without lubrication.  I have seen nothing on plastic.

                          JHG

RE: Plastic Screws Recommended Torque

Unreinforced (and without PTFE filler) PEEK against another part should have μ ~ 0.15.

Regards,

Cory

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Plastic Screws Recommended Torque

Sorry I missed the "made of PEEK" and assumed going into PEEK..

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!


Resources