Spindle Motor & its Mount
Caution: Only use a motor that is either non-thermally protected or has a thermal overload circuit that requires a manual reset. If the motor automatically shuts down due to excessive heat, it then has the potential (upon cooling) to unexpectedly start-up again while you are touching/changing sharp end mills, saw blades, pulleys or other rotating parts.
Sealed, GE H120, ¼ hp, continuous duty, 1725 RPM, split-phase, ball bearing motor, mounted onto a plate, in-turn held by a large, galvanized door hinge. Generally, these hinges are loose so it was drilled out and a close-fitting bolt with nut was installed.
The motor is externally cooled by a fan. Note the height-adjustable rubber stop. This stop allows belt tension to be set for optimal performance i.e., good traction, minimized vibration & compensation for any minor belt stretching. It uses a ¼ -20 bolt passing through the work surface & then screws into a flush nut on a small block of pressure-treated wood. The hard rubber stop has washers on both sides to increase rigidity & a star lock washer is used under the nut. I enlarged the clearance hole & installed shims on the wooden block. The adjustment screw is set at an angle perpendicular to the motor mounting plate bottom. The entire rubber stop face is in contact with the motor mounting plate. There is a spacer plate under the hinge. The power cord is protected from abrasion that could occur from repeatedly pivoting the motor over time.
The sealed motor is impervious to metal debris. ¼ hp is considered by Taig to be the maximum size. By comparison, this ¼ hp motor is 50% stronger than a 1/6 hp motor & 250% stronger than a 1/10 hp motor. Mounted to the left (CCW rotation) provides additional work space.
The relatively high motor weight (~13 lbs.) & low belt angle give good tension for turning small parts. The motor is solid mounted, not in a rubber bushing which causes too much wobble under high torque. This set up also works well when using the spindle riser block. The ON/OFF switch is a standard, 20A, wall switch mounted in an outdoor metal switchbox with a stainless steel cover plate. I have the switchbox mounted high on the bench leg making it difficult to bump it ON (switch down) but if I do accidentally bump it with my knee, it turns the motor OFF (switch up). Make sure to properly ground the circuit.
For low belt tension, the motor plate rests on its stop. Higher belt tension places the plate about one or two mm's above the stop. Vibration against the stop can occur. When I upgraded the mill motor, I noted the high V-belt traction due to its locking mounting plate arrangement. This suggested the addition of the hold down action clamp. In order to eliminate vibration & increase belt tension, install a vertical hold down action clamp from Enco. Mount it at the same angle as the motor mounting plate. It quickly opens & closes using the lever. When closed, the motor mounting plate is then captured between the upper & lower adjustable rubber-ended stops. Belt tension can now be increased when turning larger pieces. Runs very smoothly & with high V-belt traction.
Under the bench power switch arrangement. Note the (blue) lathe mount reinforcement plate.
The DC variable-speed motor controller has since been removed.
Motor-reversing switch shown.
Switch is down for normal, CCW rotation & up for reverse, CW rotation.
Wiring schematic is on the motor ID plate.
WARNING:
Spindle accessories must be wrench
tightened
before using in
forward or reverse operations to prevent them from spinning off.
The 3-jaw chuck jaws can loosen & fly off the chuck if spun-up without being clamped onto a part.