Sherline 5000 Mill Assembly Instructions

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6. Place the drive belt over the spindle pulley and insert
two 10-32 x 3/4" socket head screws (with 2 washers on
each) through the motor mount slot and into holes in the
ends of the motor standoffs. (These standoff ends should
be exposed through locating holes in the outer belt guard.)
NOTE: The normal operating position for the drive belt is
on the large diameter groove on the motor pulley and the
small diameter groove on the spindle pulley. Use of the
other (low RPM) position is discussed in the instructions
on page 10.
7. Tighten the motor mount screws, tilt the speed control
unit out of the way and check the alignment of the drive
belt. It should be perpendicular to the drive pulleys. If it is
not, loosen the set screw on the motor pulley and adjust it
in or out on its shaft until the drive belt is square with the
motor.
8. Pull the desired tension into the drive belt by sliding the
motor unit outward in the bracket slot. Tighten the mounting
screws to hold the motor and control unit in place.
NOTE: Do not over-tension the drive belt. Just make sure
it has enough tension to drive the spindle pulley without
slipping under normal load. By not overtightening the belt
you will not only extend its life, but will also provide a margin
of safety for belt slippage should a tool jam in a part or an
accident occur. The belt must be a little tighter when used
in the low speed range because small diameter pulleys are
not as efficient.
9. Set the mounting plate into the top of the belt guard
housing so it rests on the rails molded onto the inside
surfaces of the housing. (The pressed-in nut goes down
and to the outside.) Slide the plate toward the outside (toward
the spindle pulley) until it stops. NOTE: The mounting plate
was designed to be easily removable so it is out of the way
when changing the drive belt position.
10. Rotate the speed control unit down into place and insert
the single 10-32 x 3/8" socket head screw through the hole
in the speed control housing and into the nut in the mounting
plate. Tighten enough to hold it in place. Do not overtighten.
NOTE: If you machine a lot of wood or brass, you may
want to purchase and install a switch cover (P/N 3015) to
keep the fine dust out of the power switch. The wood dust
can gum up the switch causing intermittent operation. Brass
dust can short out the switch or cause a risk of electric
shock to the operator.
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 worldwide 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.
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 cuts that are too heavy 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 SUDDENLY 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.
Thermal protection is built into your motor to insure it is not
damaged by overloading. Use good common sense when
operating the motor for years of trouble-free operation.
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FIGURE 6—DC motor and speed control assembly