Thread: Lapping Plates - Glass or Granite or somthing else?

I have both a glass lapping plate and a granite lapping plate but what is better?

I would have thought glass would wear less but in the wood working shop around Perth they only sell granite plate with a certified accuracy.

I would also like to to say, the granite plate that i have with its certified accuracy of 0.0001" is not that accurate! lol i chucked my certified DMT plate on it and a ruler and it had sections where light was visible. The glass plate is also slightly out (I'm using a 6mm thick glass chopping board) but not my too much

I have now lapped the granite plate with my certified DMT, not as hard of a process as i was expecting but i guess it was only slightly out.

I then chucked a stone and lapped it on the granite plate with a 600 grit powder and it turned out extremely smooth and flat and very quickly! My glass plate would have left scratching in the stone still i think...

So will granite be as hard wearing as glass or is glass longer lasting, is the granite more accurate or would glass be just as good or more accurate. Which would be better for lapping in general?

Thanks!