I am enjoying the discussions regarding the usage of a knife edge pivot 
point.  If I understand correctly two points that were made were (1) that it 
is the hardness of the material and (2) a more rounded edge rather than 
sharp edge that is important.

This leads me to a question.  What would be the difference between using a 
hard "rounded" edge and using a hard ball bearing?  (Size of curved surface 
is obvious.)  Is it the groove that the edge fits into?  Ted, told me about 
a method that he has used: two parallel roller bars and a ball fitting 
between them.  Orientation of the bars would dictate whether horizontal of 
vertical movement of the arm.

Regards to all,
Jerry 







I am enjoying the discussions regarding the usage of a knife edge =
pivot=20
point.  If I understand correctly two points that were made were =
(1) that=20
it is the hardness of the material and (2) a more rounded edge rather =
than sharp=20
edge that is important.  
 
This leads me to a question.  What would be the difference =
between=20
using a hard "rounded" edge and using a hard ball bearing?  (Size =
of curved=20
surface is obvious.)  Is it the groove that the edge fits =
into?  Ted,=20
told me about a method that he has used: two parallel roller bars and a=20
ball fitting between them.  Orientation of the bars would =
dictate=20
whether horizontal of vertical movement of the arm.
 
Regards to all,
Jerry