Decided to fit stepper motor onto bull wheel of lathe to create a dividing head via a worm.
Reasoning that the stepper had a ball bearing embedded in an aluminium casing at one end, that there was no need for a separate bearing at that end of the worm and that the worm could be mounted directly onto the stepper shaft with just one bearing at the other end.
Would I get away with it?
All seemed OK until I created the supporting frame and tightened everything up.
Then the stepper, instead of turning (by hand) with a slight purring, was cogging sharply and became difficult to turn by hand.
Diagnosis... had I damaged the motor by tightening up too much?
Dismantle everything, check the motor now moves freely, yes it does.
Slowly reassemble, checking at each stage to see if cogging has returned.
No, all OK.
Mount assemblage back onto lathe bed and tighten up. Cogging has returned. NOT POSSIBLE! because fixing bolts not near to stepper configuration.
Puzzlement reigns.
Then one of those "Condor" moments. (That must date me, wasn't the advertising campaign sometime in the early 70s?)
When the assemblage was bolted onto the lathe, the connecting wires were dangling any old how (electronic controller not yet fabricated) and were shorting together on the lathe bed.
Just like any dynamo or DC electric motor, they become difficult to turn by hand if shorted together. Similar to field telephones if too many on the circuit, the magneto becomes coggy when trying to ring the other phones.
Separate the wires, it turns freely. Re-short them together, the cogging returns.
Moral? Stick to mechanical contrivances in the future!