Reostat on polisher?

Jewelry Discussion
1

Hi, folks,

I know virtually nothing about motors, so I’m looking for help: Can
a standard buffing machine have a reostat added to it to control the
speed? I just tried one that has that feature, and I really liked
it.

If I can do this, is there a special kind I should use? I have a
rotary switch I plug a soldering iron into to control heat for wax
work-- it would be just too easy if I could plug my buffer into that
or something like it. Will I damage my motor if I do that?

Thanks!!
Noel

2

Noel,

I have rheostats on many motorized things in my studio, they work
well, except at the lower speeds, the motor may stall or not have
any torque. I like DC motors for these things and a electronic
control system, but I still go back to the old AC motor and put
rheostats on them.

Jerry

3

A motor needs to be a universal type or series wound motor to use a
rheostat.

The motor will have brushes and can run on AC or DC. This is the
type found on standard Dremils, Foredoms and the Foredom polisher.

DC motors can usual have various types of speed controls- Ac only
motors generally not.

The bigger motor polishers are induction type and and are AC only
have a fixed speed and will not work on a rheostat.

There are ways to change speeds on some types of AC motors but this
is not a common thing you can do.

jesse

4

Hi Noel,

Most buffing motors are AC induction motors and will not work with a
speed control. The AC/DC motors where the field is in series with
the armature will work with a speed control. These motors are used
with flex shaft systems and some small polishing machines like the
Foredom BL1.

John Cranor
The Jewelry Equipment Dr.

5

Hi Noel,

I know virtually nothing about motors, so I’m looking for help: Can
a standard buffing machine have a rheostat added to it to control the
speed? I just tried one that has that feature, and I really liked
it.

Without seeing the buffer motor the answer is no.

Generally speaking, only universal or motors using brushes can have
their speed controller with a rheostat. The typical buffer/grinder
motor is not a motor of this type.

Dave

6

You should be able to do that without too much trouble… Just
make sure whatever you use can handle the current you need to run
your machine. A simple ceiling fan dimmer would probably work
nicely. Or you can buy speed controllers used for woodworking
equipment(mainly routers and shapers) and use that. Just look at
what your motor draws and find something that can handle at least
that much current… something that can handle a lot more current
is ok too, but if you go too small you will have trouble.

Mike

7

Noel,

It probably won’t work. A soldering iron is a resistive load and
motors are inductive loads. It would by similar to trying to use a
standard dimmer switch on a flourescent light.

Tim