A solid shaft of 65mm outside diameter and a hollow shaft of 85mm outside diameter are connected by 6 bolts with the mean pitch of thread being 155mm. The shear stress due to the torque on the shafts is equal to the shear stress on the bolts.

Question

a) Find the diameter of the bolts.

b) Find the inside diameter of the hollow shaft.
Where do I start?

Note: Solid shafts and hollow shafts system are used in low stress,low RPM applications, like a large air fan. The solid shaft comes from the motor and the hollow shaft will be used on the fan.Because of the lighter hollow shaft a smaller driving motor can be used.They are usually connected by a flange welded over the smaller diameter solid shaft. The flange outside diameter is equal to the hollow shaft outside diameter.The shafts are then secured together by bolts.

Answer 1

For the shear stress (in terms of the torque) use
http://www.engineeringtoolbox.com/torsion-shafts-d_947.html
Then use that stress for the diameter of the bolts. Assume the torque is distributed evenly over the bolt cross sectional areas. I don't see what the thread pitch has to do with it.

Answer 2

Thanks... I couldn't figure out why there's is a thread pitch either!!!