Hobbs…not sure I underestand what you mean by ‘polish the flat
laps’. Do you mean ‘slabs’? Do you intend to polish flat surfaces?
Cabs? If so, what size are they?
The answer to each question will determine what you need to do the
job. I think the 8" trim saw would be a better bet but, there is a
great deal more cost than for a 6". Why not go for the difference and
purchase a 7" tile saw? The original tile blade will have a wide kerf
but you can always replace it with a lapidary blade later. You can
pick up a tile saw at the local Lowes or Home Depot for around $60.
the lapidary saw will run $250 to 500.
Wrong, much polishing is still done by hand. I cut and polish
hundreds (thousands?) of cabs, including domes and flats all by hand
on my combo unit…thats as with round wheels. There are techniques
to do so that produce flat (for the puriests out there… no, they
are not optically flat but) polished surfaces.
Some combo units are not that difficult to change wheels. The
Caberet and Genie are quite simple and have shafts that easily hold 6
wheels so you can go from 100 grit through 14K without changing
wheels or machines. Bearings on these machines commonly last 10 years
Donivan was correct that long shafts can cause problems. Not only
with the bearings but if you are using 2.5 or 3" expanding drums,
which are very heavy, you will get run-out also known as whipping at
the shaft ends. Most modern combo units use 1.5" wide wheels and they
are keep about 1" apart to reduce such conditions. Again, it depends
on your requirement. If you are doing large slabs and need wide
wheels you should use shorter arbors that would hold perhaps only 2
or 4 of the wide wheels spaced 3-4" apart. Lortone makes such arbors.
If you are doing smaller slabs, the 6-1.5" arbors are great.
I currently use a forerunner to the Caberet, it is nearly 9 years
old and the bearings are still strong. The motor is just beginning to
give me a little trouble but that can be replaced for around $80-90.
I normally only need to change the wheels every 2 years or so and I
cut loooots of agate, jasper, wood, jade etc, etc.
I hope that explains it a bit. Cheers, Don in SOFL