set screws and flats on shafts

[joe]

After working on an old pedal steel guitar for somebody, I ended up with some questions about set screws and required size of flats on round shafts.
One of the problems with this particular old guitar was that whoever did the machine work on it originally didn't do much more that make a small flat on the round shaft for a set screw to land against. I made a bigger flat by milling across the full length of the shaft partly so I could mount a bell crank in any position. I noticed that the 8-32 set screws did not want to hold very well on these 5/16" shafts and that has led me to wonder whether cup points on the end of set screws are a good idea in this application. They seemed to dig into the steel shaft pretty well but would allow the bell crank or lever to move a bit with useage. Was this the set screws fault or the softness of the steel (unknown alloy)?
I haven't tried to look up standard practice for flats for set screws, but I increased the set screw size to 10-32 and ground the cup point flat and they seemed to work better. I realize round shafts are not the best solution but they were used in a lot of older steel guitars.
Opinions or suggestions?

[Bent]

Opinion: The setscrew is weak in that it holds on to a very small area of the cross shaft. It invites loosening and dead play after a few hours operation. The best of this evil would be a cup set screw (larger holding surface than a point). Use stainless steel ones you can reef them tighter than black steel ones.

[joe]

Thanks for the tip about stainless set screws. I'll try some. Set screws are a PITA but a lot of the older guitars I work on use them extensively.
Joe