On Sat, 16 Sep 2006 08:40:00 -0700, in rec.crafts.jewelry "Too_Many_Tools"
wrote:

Hi,

I have an used Rock Rascal that I wish to use to section rocks and
minerals.

It does not currently have a motor.

From reading supply websites, it would seem that a 1/3 hp 1725 motor is
sold for it.

Is there any advantage to using a more powerful or faster motor?


yes, to the sellers of the more powerful and faster motors, since they'll be
able to make more money from you, selling you the bigger motor. To you, there's
no advantage other than not having that pesky extra money around. A quarter to
third horsepower motor at 1725 rpm is just fine for your small saw. Remember in
use, you don't really want lots of extra pressure on the blade. It will cut
best with just modest feed pressure. More than that will wear out the blade
more quickly, not cut all that much faster, and will give you a less uniform
cut. Be sure to use a proper lubricant for the type of blade you've got and the
material being cut. Often it's just water with an additive to improve wetting
and impede corrosion. Some materials though, cut better with cutting oils.

Is there any advantage of using a variable speed motor?

No. the saw blades have an optimum speed of operation. Find that from the
manufacturer of your particular blade, or from a manufacturer of a similar type
of blade. If you need to adjust the speed of the blade, this is normally done
not with motor speed, but by choosing the appropriate pulley on the motor, since
almost all these machines are belt driven. The blade speed depends on the
pulley combination used on the machine and motor. The motors themselves can be
very generic standard "washing machine" type motors. Used to be, you could pick
them up for five or ten bucks as used motors at salvation army or similar
stores, or yard sales. Anything more sophisticated than that is overkill for
the saw.

Now, for some combined lapidary units, it may be useful to have a dual speed
motor, if you're running not just a saw, but several different types or sizes of
sanding or buffing wheels too, since sometimes a slower or faster speed can be
handy, especially when working with softer or more fragile materials. But just
for sawing, that's not usually useful. Precision grinding machines like
faceting machines often do have variable speed motors, and for that type of
very picky grinding and polishing, it's quite useful, even essential sometimes.
But those machines are a whole different ballpark than a rock raskal...

Thanks for any advice you might have to offer.

TMT