mini lathe with vs speeds

[Bob Hampton]

ok I have a question for the electricians in the group....
i have a mini lathe w/electronic vs and min speed is like 500rpm...now just out of curiousity could this be slowed down by changing components on the circuit board somehow?
Reason im curious is because i have a scroll saw that is also electronic vs and the low speed on it is much slower then on the mini...thats what made me curious if a person could do this
just a point to ponder...now lets see what the guru's think
thanks
Bob

[Allen Neighbors]

Goood Post, Bob. I'm interested, too!

[Paul Engle]

One way would be to change out either the motor pulley to a smaller one, or change out the spindle pulley to a larger one ( best bet ) then you would be stuck with lower high rpm . The factory has set the trim pot on the circut board to a minimum voltage feed back to the rehostate used for the VS and that should not be adjusted with out the electionic devices to read the tp out put. It the motor is AC ( llike a VS corded drill) then it was set for min to keep from burning out the motor, if it is DC then it should go to dead slow and again the factory has set the tp for minimum voltage and I would not excede that setting. I'd look to change one or the other pulleys , they will be proprietary and the shaft sizes will most likely not be standard, you will need " blanks" and have a machine shop bore them to the shaft sizes if not standard , get several and do them all at once and you can vary your speed changes the same way I can on my Jet 1236 with VS DC I added and keeping the reeves style drive , dead slow is wonderful for out of round / balance pieces...

[Bob Hampton]

paul
thanks for the reply ...that satisfies my curiosity for sure. I pretty sure from what little i know about motors that its a DC..because it is reversible by just switching the black and white wires...discovered this quite by accident as the vs box went bad the first day i had it ..got a new one and crossed the wires by accident so im assuming its a dc since everyone has told me that only DC motors are reversable.
anyway thanks for all the info ...one of these days i might take it to a good motor shop and see if they can do this adjustment.

[Vern Little]

It would be wrong to asume that only DC motors are reversable. AC motors are reversable as well.
Most electric motors have a fan inside them to keep things cool. If you slow them down too much you are not moving enough air over the windings and armature to keep them cool.

[Jeff Nicol]

I have a steel city mini with a VS and I think that if it were to start out at 0 rpm it would not have the torque to do much good. It would turn the piece but as soon as you tried to put the tool to the wood I think you would stop it. The big lathes with VS use large motors that are most of the time 220v 3 phase with a Vfd to control the speed. This type of set up with a 1-3 hp motor has many times the power at low speeds. So the little 1/2 hp motor on most of the minis are set so the power band is useful at its lowest speed.

I retrofited an cheapy lathe that had a reeves drive on it to a Vfd and 3 phase motor. I have infinite speed control but it has less torque at the 0-150 rpm range. It is a 1hp motor running on 110 single phase using the vfd to up it to 220v 3 phase. I could have gotten a Vfd that used 220v single then boosted it to 220v 3ph but the price was a bit more than I wanted to spend at the time. If I would have gotten that one the tourque at low speeds would almost double.

Electricity is a strange and wonderful thing! Just keep safe and unplug!

Jeff

[robert hainstock]

The easy way to tell if it is a DC motoris to look for rush ports on the sides of the motor towards one end. Paaul is very much tight in advising you to look to mechanical rather than electrical fixes. The Jet 1220 VS has a multi stage pulley to optomize the speed range. :)
Bob