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The spindle crank. The arm is made of two pieces of 1/8" drill rod soldered to the 3/8" shaft. Details are in the text.

Two different places to use cranks to allow enhanced control. The motor crank is balanced so that it does not cause vibration in the motor at high speed.

The setup on the left was used to cut left-hand threads on 3/16" diameter brass rod for a demo at a model engineering show. I believe the setup is for 32 TPI making the rod screw into some #10-32TPI Left Hand nuts I used for the demo. Note the threading tool and the inverted cutoff tool both mounted on the carriage. The setup on the right shows the "built-up" crank mounted in the spindle position.

For work to be "parted" from a long piece of stock running through the spindle, the spindle crank cannot be used but the balanced crank on the motor pulley can be used. For this smaller diameter threading, the full torque from the spindle crank is probably not necessary so this works out just fine. For some really heavy torque, a spindle crank even larger than the one on the right can be made.

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