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.
I would appreciate if someone could share with this information.





RE: Plastic Screws Recommended Torque
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
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
Regards,
Cory
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RE: Plastic Screws Recommended Torque