The advantages of Sherline's DC motor and electronic speed control
Sherline's 90 volt DC motor is very smooth and powerful, particularly at low RPM. The specially designed electronics package also provides some unique advantages in addition to smooth speed control with a usable speed range of 70 to 2800 RPM. A special circuit compensates for load, helping to keep RPM constant. The machines can also be used on any current world wide from 100 VAC to 240 VAC, 50 or 60 Hz without any further adjustment other than seeing that the proper wall plug is used. The control reads the incoming current and automatically adjusts to the proper settings.
We offer the motor and speed control along with the headstock and spindle as a package to builders of special machinery at a very reasonable price. They are especially popular for custom tooling in small industrial applications because of the large number of Sherline accessories that fit the spindle. We use them in our own production facility for a number of operations.
CAUTION—Motor is thermally protected
Thermal protection means there is a built-in circuit breaker that will shut down the motor if it gets too hot. This keeps the motor from burning out. The breaker will automatically reset as soon as the motor cools and you can go back to cutting, but you should be aware of how it works and what to do if the machine suddenly shuts itself down. If your motor is shutting down from overheating on a regular basis, it means you are taking too heavy a cut or operating at too high an RPM for long periods. Slow your speed down, reduce your cut or feed rate and you should have no further problems.
Due to the nature of miniature machining, overloading the machine is a common problem. It is often tempting to try to speed up the process by working faster. Keep in mind this is a small machine and work with patience and precision-don't be in a hurry. Your parts will come out better and your machine will last much longer if it is not overstressed.
What to do if the motor shuts down
If your thermal protection circuit shuts down the motor while work is in progress, immediately shut off the power switch and then back the tool out of the work. It should only take 10 seconds or less for the circuit breaker to reset, then you can turn the motor on and start the cut again, this time putting a little less stress on the motor. If you leave the tool engaged in the part and the power on, when the circuit breaker kicks back on, the motor must start under load. This can be very hard on your motor.
Remember that the circuit breaker turns the speed control off which turns off the motor. If power were to be applied to the speed control with the motor disconnected, it could damage the speed control.