I'm considering the purchase of a Crystalmaster 8 flat lap machine
and would appreciate any advice or thoughts from those that have
had experience with this piece of equipment or other flat lap
While I do not use the Crystalmaster, I use and old Sapphire
faceting machine for this purpose. My cabbing machine is a Covington
8" Combo unit. You are right in that it is a bugger to polish the
backs on a round wheel, you would think it would be easy.
I made a couple of changes to the sapphire so it would work better
for me. I put cork around the splash lip and I put a bar across the
top of the plate with cork attached to the face. The cork is for when
a stone slips, it may(has)chip, and second as the drag of the stone
is often more than my finger grip on a wet slick stone. The bar works
well for me to retain the stone. To start with I use a 300 diamond
plate and then to a 600 and 1200 and progress to 2500 wet ‘n’ dry, I
dampen the top of the plate to hold wet ‘n’ dry paper and then on top
I have a drip on. I did not have good results using the diamond
films, it was hard for me to hang on to, and the water trick on the
back did not seem to work as well, the film wanted to hydroplane. Not
knowing what your top plate will be, make sure you dry it off, mine
is aluminum and depending on the stone will cause pits if you don’t.
When this happens the only way to clean it and keep your plate flat
is to chuck it up in a lathe and go over the face lightly.
I have had a couple of comments regarding this equipment as hard to
I have not tried to cab with the sapphire, but would suspect it to
be a bugger unless you make a plate that has a foam top to contour
with. A hard surface for me just will not blend the surface well or
to my liking. I just see no way to get optically smooth curves from a
flat hard device.
Hope this helps, it has been my experience to date with cabbing.
P.S. Rotate the stone while on the lap, keeps it from slanting to
bad. At least you won’t notice it as much, there is nothing to be
done to actually keep it from curving a little when laid on a
straight edge, there will always be hydraulic pressure in the middle
you can not over come and I have found it useless to try.