Re: AC Speed Controller for Lathe: Meat or Accident?

This thread is off topic so expect it to be banned or bring it back
on topic.

That said,

if you plan on CNC'ing the lathe, you will want to have the spindle
speed monitored and/or controlled.

Speed sensor on the spindle and then that would feed back to your
software for reading.

About the speed controller part, what is needed is to maintain a
volts to hertz ratio. slightly more complicated than just a few
chips.

Check E-Bay or one of the motor sites for both a motor AND Variable
speed drive. you should be able to get a combination for less than
$500.00

http://www.dealerselectric.com/

Also, I would imagine your lathe is geared with the motor pulley for
the low speed needed for lathes. so look for a 1,200/1,700 RPM
motor, not a 3,400 one.

Dave







--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Abby Katt" <abbylynx@y...>
wrote:

> Swarfer-breatheren,
>
> I seemed to have (accidentally) bought myself a massive big old

lathe

> at an auction. When I picked it up however, I found that the motor
> was some horrid 3-phase electical fire with a rats nest in it, so I
> dropped this and decided to just buy a new one of ebay. However: as
> I'm now missing the belt-drive and motor assembly I'll have to make
> this up.
>
> I thought this would be the best place to ask this: I'm thinking
> about building my own AC motor speed controller (with some
> thyristors) and just leaving the motor belted on one setting or the
> other. I was wondering what advice people would have on this? I'd
> have asked this on another forum, but as you all are so terribly
> nice, and experienced with this type of thing I thought I'd ask

here

> (and hey! I'll probably convert the lathe to CNC in the future
> anyway. :) )
>
> So what's the deal? Is this good science, or bad science? Will the
> lower voltage mean the motor will turn really slow, but also have

no

> torque what-so-ever? Should I use some other kind of circuit? Or is
> this is all just a terrible idea that's going to wreak havoc on the
> electrical grid for blocks around as I throw rude-pulses at a 2KW
> motor? Should I use a DC motor instead? (I want to do this on the
> cheap, really)
>
> BTW> This is a BIG old lathe! 5foot long and weighs.. well.. the
> tailstock weighs about a third of my weight. :P
>
> Thanks for your advice!