Homebrew PCBs

In a message dated 7/25/2006 3:42:54 P.M. Central Daylight Time,  
stefan_trethan@... writes:

What  sort of grinder do the diamond wheels need?



ST:  I can't answer your question by specifying a "usual  grinder-motor" 
which would be suitable, except to say it'd have to be one with  very good 
bearings, well balanced, so smooth-running, and I'd want at least 6000  RPM.
 
I made an arbor with a 12.7 mm dia. shank, which accepts 100  mm dia. X 3 mm 
thick diamond-rim wheels (3 mm of O.D. is diamond-compound) and I  use that in 
my vertical mill ("Bridgeport" type mill).  This makes it  possible to do 
relatively precision grinding by holding the bit being ground in  a collet 
fixture or vise on the mill-table, which can be moved with 0.0005 inch  precision 
fairly well in the X & Y directions.  But I can get this  spindle on up to about 
3500 RPM before I am afraid to take it higher, lest the  machine  vaporize!   
         Jan  Rowland


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