Re:Lathe threading

Andrew wrote:
<snip>spindle encoding very simply- just attaching a small magnet to
the spindle head, with a reader to register it as it flew by. That
done, a fairly simple circuit can control the speed of the toolpost.
He's getting ready to sell kits for between $100-$200. I couldn't
get him to subscribe to this list, but if someone's looking for a way
to do this, they might contact
him- he's Jim Lewis jimlewis@m.... ]
Andrew Werby

Andrew, the way you describe this he has created a ONE SLOT encoder.
Although you could monitor the spindle speed from the magnet, and
calculate the speed necessary for the toolpost(at this spindle speed)
and then issue a start toolpost moving, stop toolpost command with
this setup, I imagine it could get pretty dicey, pretty fast. A lot
of variables to creep in. I'd like to know how repeatable he has been?

Maybe an air cylinder to move the tool slide in and out quickly,
could be an add-on?

Adding magnets improves the situation, but pretty soon you'd be
better off just using an encoder.

Just doing threading on a lathe does not require a PC for control,
and he's taken an interesting approach. I might suggest using a real
encoder and some simple divider circuitry or s/w (this IS a PIC type
project). One encoder for the spindle, one stepper for the carriage,
and a hand calculator size "black box" to set TPI.
(metric/TPmm??;Hey! you guys across the pond, how do you write
this?).

Sherline is already most(if not all)the way to this already.
But it could make an interesting product???

Ballendo