Lathe/VFD Conversion

[JG Owens]

I'd like to change out my Delta 1460 lathe from the jack shaft to a 3-Phase VFD setup. When I go to sites like Grizzly and look at the specs for the lathe motors they're rated at 1725 rpm. No doubt this is a silly question but how do they achieve a top end spindle rpm of 3200?

 

[Mgdoug3]

Usually there's a set of gears or pulleys you change to change speeds and I'm assuming lathes with factory VFD have at least a high and low range. To change the speed within a given gear or pulley you adjust the frequency/hertz. Increase frequency, spindle speed also increases. On VFD rated motors you have a wide range of hertz without any heating issues. On motors no rated for VFD you can still use VFD but the motor won't cool as well because it wasn't designed to run at lower rpm and might need be able to move enough air to cool off.

 

[PoorUB]

You can also overdrive the motor with a VFD.

On my drill press I have the max hertz set to 120 so the 1725 RPM motor will run at 3450 RPM.

With your lathe, I believe it come with a four step pulley. I would ditch the jack shaft and keep the four step pulleys. Add the 3 phase motor and VFD then play with the belt speeds and you probably will find one belt setting that covers 90% of your use.

 

[strantor]

You can also overdrive the motor with a VFD.

On my drill press I have the max hertz set to 120 so the 1725 RPM motor will run at 3450 RPM.

With your lathe, I believe it come with a four step pulley. I would ditch the jack shaft and keep the four step pulleys. Add the 3 phase motor and VFD then play with the belt speeds and you probably will find one belt setting that covers 90% of your use.

+1 and I would suggest choosing your final belt ratio somewhere in the lower end of the range of ratios you have now. You get the speed back by going >60hz with the vfd. But if you choose a high ratio then you'll be starved for torque at lower speeds.

 

[JG Owens]

Very helpful everyone....thanks!!

 

[Showkey]

I did this VFD conversion years back on wood lathe. Used a 1.5 HP three phase motor.
I found no loss of power or torque at 10 to 200 hz.

I had step pulley but very very rarely used the steps. VFD allowed quick and precise rpm.
I turned items from 1/2” to 48” diameter so slow rim speed was important on 48”.
Roughing 24” bowl blank slow speeds are important.