At 01:36 PM 9/23/2011, craig cowan wrote:
>Should I try a stack of washers to use a different section of thread to hold
>the tension? (Stack of washers right under the nut).

Yes.  If you don't have a good section of thread to work with you'll
have to  cut the stud off and drill and tap for M6x0.75.

>I put aluminum foil on the splines as well, hoping to hold things in place.

I think that will make things worse and not better.  The splines are
quite small and have to engage the splines that you've cut into the
soft metal of the arm.  Anything between them would interfere with
the engagement.

Yours,
David