servo vs. treadmill motor

I was planning to do the same, but tripped over what looks like a
suitable servo on ebay
seller kolakow; starting price of 35.00, he has a few.

20 volts, 10 amps, 20 amps with air cooling, in other words,
about 1/3 to 2/3 HP, and a real servo.

The advantage will be the brush arrangement. In the treadmill
motors (I assume the enclosed DC ones, not the open frame GE ones)
the brushes are sort of sloppy in their guides, and when they run in
one direction, the commutator wears an offset pattern in them. This
gives the trailing edge a sharper shape, and when you reverse the motor,
this can grab a groove in the commutator. This is a real phenomenon,
as Marcus (frequent and valued contributor to this group) knows for
a fact, as his Sherline lathe motor suffered when a piece of a brush
broke off, lodged itself where it shouldn't have, and caused a bit of
a meltdown of a brush holder / spring.

I had asked earlier about using the treadmill motor, got mixed
responses, and decided on a "real" servomotor.

The G320 looks like a winner for this application! Thank you,
Mariss, for making our CNC adventures more rewarding!

By the way, mine is going on the SPINDLE of my little 5-inch
EMCO lathe, probably use a toothed belt / sprocket arrangement to
increase the number of rotary encoder steps per spindle rotation.

There is, by the way, an index wheel / optical sensor on the EMCO,
one indexing hole extends to the edge of the wheel. As the sensor
has only 3 wires, I'm assuming that if it's used for position
feedback, rather than just as a tach, the original EMCO logic had
to sense the "slot" and count the holes, to determine both position
and speed - I assume no reversing during program execution, at
least without suitable pauses.. Don't think I'd want to try
making a program that would thread using the original....

/mark

/mark