Recommended Torque for Steel- Brass Combo
Recommended Torque for Steel- Brass Combo
(OP)
At our company, we have a standard listing of recommended torque for steel to steel, zinc plate steel and friction modified steel fasteners but nothing on bimetal combination fastener systems.
I have been asked to determine the grade of steel bolt required to assemble a plastic part with threaded brass inserts to a steel flange.
The bolts are 6 and 8 mm diameter and the maximum torque applied will be 15Nm for the 6mm bolt and 35Nm for the 8mm bolt.
If the inserts were steel my references suggest a 10.9 bolt for both. Is this also a suitable bolt grade for brass inserts?
Thanks in advance
GD
I have been asked to determine the grade of steel bolt required to assemble a plastic part with threaded brass inserts to a steel flange.
The bolts are 6 and 8 mm diameter and the maximum torque applied will be 15Nm for the 6mm bolt and 35Nm for the 8mm bolt.
If the inserts were steel my references suggest a 10.9 bolt for both. Is this also a suitable bolt grade for brass inserts?
Thanks in advance
GD





RE: Recommended Torque for Steel- Brass Combo
You seem to have this a little backward. The required property class for a screw is based on what clamping force is required. The applied torque is calculated based on this clampign force. The axial thread engagement (insert length/height) is calculated to resist the maximum possible pretension. In my experience, a plastic component cannot resist the localized stresses (at bearing locations and along the plastic/brass interface) created by a 10.9 property class screw. For a 10.9 to work, the insert length and screw head outer contact diameter need to be enormous.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.