Small machine motor smokes at start-up, why?

I have a bunch of Cameron Drill presses, These were made in CA. starting in the 1960s and stayed nearly unchanged for 50 years. The motors they originally used were built for them and I understand they have run out of them and the parts. They were a 110 volt motor with brushes kind of like a sewing machine motor. I have one that when I take it apart everything looks fine but when I turn it on it starts off slow and blows a lot of smoke out of it and then it seems to run smooth and at speed after a minute or so. It also stops blowing smoke. I do not think there is too much tension on the belt or any other source of resistance in the spindle or motor bearings.

So what should I be looking for as a cause to this problem?

Thanks

material that smokes when it gets hot - like oil, or wire insulation,.

rivett608 said:

They were a 110 volt motor with brushes kind of like a sewing machine motor.

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It sounds like contaminants such as dust and/or oil on the commutator or a worn (uneven wear) commutator.

Rob

I have a drill-driver that sometimes smokes from the brush area when starting or under heavy load. It's not new, but is in nearly new condition, since it was an unused backup unit for 12 years or maybe more, and I recently started using it as well as the old one. May be an initial brush wear-in issue that will go away.

Look at the windings of your motor, and if they are OK, not burnt, the brushes may have an issue. I would expect that is the answer, since the smoking at start-up sounds as if it happens before anything like windings could credibly have heated up to the smoke point.

Brush may not be making good contact due to needing to be replaced, so it heats up in a spot from the high start current.

Rubber belts can also cause much smoke ,with a small pulley slipping in the rubber ,until the belt gets up a bit of velocity to carry it over the worn spots.