Use a torque wrench to turn the x-translation stage's knob to a suitable value.

Note that the larger the wear track radius, the lower the RPM required (RPM should never exceed 3000). However, a lower wear track radius would also increase the wear of the disk counterface.

Recall from the hardware guide that:

For pin specimen, Wear track radius = X + 25 - (S - 4.5)cos45

Where X is value read from x-translation stage and S is sample size in mm.