On 09/12/2013 07:03 AM, Robert Nichols wrote:
No. The action of the set screw pulls the opposite side of the part
against the shaft, and that is where most of the torque resistance comes
from, not from the screw itself. Two screws at 90 degrees assist each
other in pulling the part against the shaft. But, two opposing set
screws will fight each other. The part is not pulled against the shaft
anywhere, and the tiny tips of the screws are doing all the work.

Opposing sharp point set screws digging into a soft shaft might behave
the way you expected, but that's not what you have.

Afterthought: As a low-tech solution, put a little valve grinding
compound in the joint and use just one set screw.



--
Bob Nichols AT comcast.net I am "RNichols42"