Bolt torque to prevent slipping

[MEjmr]

I am trying to figure out bolt torque requirements to prevent slipping. I have a bracket with 1.5" oversized holes to allow for alignment, and a clamping plate with .5" bolts. I am trying to figure out torque requirements for the bolts to keep the bracket in place once aligned. The bolts go into a steel threaded plate in the floor. Any ideas where to start?

 

[MintJulep]

Quantify the loads.

 

[byrdj]

just take the bolts to 60Kpsi and that will give about 22k clamping. with a steel/steel CF of 0.8 , it would take 18k to slip.

but you asked for a torque, not a bolt loading. so what thread, threads lubed or dry, bolt face diameter. 75 ft/lbs would be a good start

 

[MEjmr]

well to be clear, its a mounting frame for an actuator. The actuator is mounted to the frame. I am only concerned with the frame bolted to the ground as described previously. It is located at the center of the frame and produces 4425 in-lb of torque. The bolts are located 10.875" away from center line and 3.5" spacing of the two bolts.

 

[MEjmr]

using ASTM A193 Gr class 2
1/2-13unc-2a x 1-3/4L

 

[chicopee]

Machinist Handbook (MH) has equations for similar situation. Obviously you know the coefficient of friction and the force F. You have friction on both sides of the lower plate which must be equal to or greater then F. You then calculate the normal force N which is the tensile load on the bolts. Then use the MH equation to calculate torque.