Originally Posted by
Bush65
IMHO, slotting the swivels is better than castor correction radius arms or castor correction bushes. Better still, but more work, is welding the holes and re-drilling.
I'm sorry, but I have known a lot of fitters and machinists, but none that know very much about bolted connections, particularly for connections subjected to cyclic loads that lead to fatigue failure (such as the bolts that hold the swivels to the axle housing).
Slotted holes reduce the fatigue strength of bolts, and in this application, should only be slotted just enough for the castor correction. Fitting a thick washer (say about 4 thick if possible) under the bolt head will help to restore some (if not all) of the fatigue strength).
An excessively long slot, where the bolt is not at one end of the slot may be pushing your luck, and not worth the risk IMHO.
If you want me to explain why the fatigue strength is reduced, I can try, but without diagrams it will not be easy and the concept can be hard to understand. It involves the ratio of the stiffness of the bolt to the stiffness of the joint. The stiffness of the joint depends upon how the compression from the bolt pre-tension is dispersed from the underside of the bolt head/nut (which is adversely affected by slotted or oversize holes).
Edit: Note, I am talking about the fatigue strength of the bolts, not the shear strength.