# Max torque on a couple to cause slip

1. Jan 15, 2014

### CaptainofIron

So I've been spinning my wheels (I guess I should say slipping, haha) on this problem we've been having

We have a coupling intended to transfer torque:

One side of the coupling is a smaller insert that slides inside of a larger nut. The insert has male threads on one side and the nut has female threads on the other side.

The insert has 2 friction surfaces that will carry the torque, 1 is a flat ring, the other is a conical section inclined at 37 degrees

I need to calculate the maximum torque the joint will carry until the insert will slip inside of the nut.

Here is a sketch of both friction surfaces
Case 1:

Case 2:

So I solved the first one, the flat ring, hoping that it would provide enough frictional resistance so that we could properly torque the male threads on the insert, but its close. Now Im looking at the conical section in case 2 trying to figure that out, but its been a WHILE since I have done this.

for case 1 I got T=(2*μ*(F/(Ro^2-Ri^2))*((Ro^3-Ri^3)/3)

Thanks