Lathe VFD Motor selection

[lucsimoneau]

Hi all - looking for some insight for my manual lathe.
It's a CT-1440B King Canada Back Gear lathe and I'm thinking about installing a VFD so Ì don't have to fiddle around with belt changes and back gears to get spindle speeds.

Current motor is a single phase 1-1/2HP 220V motor running at 1720 RPM with a 3/4" keyed shaft.


The motor I have on hand is a Weg 2HP 3Phase 220V running at 3450 RPM. Shaft size is 5/8".



The question I have is the following: with double the motor speed, will this cause any problems in obtaining low speeds for threading and other slow speed type applications? I will not get rid of the back gears and pulleys so they could be used if needed.

Has anyone else gone this route to change their main motor?

Thanks!

 

[TorontoBuilder]

Personally I'd not use that motor... it would be great for a 2x72 belt grinder, but the rpm is too high if you want to be able to get low speeds on your lathe...These motors are a dime a dozen, get one with 1745 rpm as it will be much better suited and be less prone to overheating at 50hz or less

 

[phaxtris]

Used 3hp 3ph 17xx rpm motors are pretty cheap, that's the way I would go, save that motor for a grinder like @TorontoBuilder suggested

 

[TorontoBuilder]

OH and would you not want to add some oomph while you are at it? I'd have thought 3 ph better suited to 1440 lathe

 

[TorontoBuilder]

Used 3hp 3ph 17xx rpm motors are pretty cheap, that's the way I would go, save that motor for a grinder like @TorontoBuilder suggested

You just beat me with the 3 hp.

At first I missed the model being 1440.

 

[phaxtris]

You just beat me with the 3 hp.

At first I missed the model being 1440.

Ha yea, all good, 3hp just seems to be a real easy size motor to get for dirt cheap around here, I believe they use that size for a lot of HVAC roof fans, just happens to be a good size for a 1440!

 

[PeterT]

Watching with interest. I have a 1440 lathe too with 1.5HP, 220v single phase. Not that I'm planning motor conversion anytime soon, but.....
I'm not sure if @John Conroy documented his VFD/3p motor swap on his 14" Modern lathe, but would be great reference. Beyond the motor/VFD selection, where I get conversion apprehension syndrome is all the other obligatory wiring involved with a typical lathe: the E-stop button, the jog button, the brake (e or mechanical if it has), the forward/off/reverse (carriage handle control) switches all somehow feeding control inputs to VFD. Obviously it can be done, I've seen finished projects that make me green with envy. But electrons are not my forte so personally I would need clear, dummy proof instructions.

 

[TorontoBuilder]

Watching with interest. I have a 1440 lathe too with 1.5HP, 220v single phase. Not that I'm planning motor conversion anytime soon, but.....
I'm not sure if @John Conroy documented his VFD/3p motor swap on his 14" Modern lathe, but would be great reference. Beyond the motor/VFD selection, where I get conversion apprehension syndrome is all the other obligatory wiring involved with a typical lathe: the E-stop button, the jog button, the brake (e or mechanical if it has), the forward/off/reverse (carriage handle control) switches all somehow feeding control inputs to VFD. Obviously it can be done, I've seen finished projects that make me green with envy. But electrons are not my forte so personally I would need clear, dummy proof instructions.

I did my belt drive 12x37 lathe within the past year... gutted the inferior busybee controls and started from scratch. I should have documented the process better and blogged it but I did not.

I'll likely be planning the same for a new 1440 that this tme I'll do complete documentation of. But that said I thought @John Conroy's was one of the conversions I relied on for guidance.... at least I seem to recall some videos I thought were his.

 

[PeterT]

I thinkClough42 did one on his channel, but different/smaller lathe from a control inputs standpoint?
Hobby Machinist forum has some bigger/14" type conversion projects including bedway positionable e-stop switches & some braking resistor stuff. I had a list of links but seem to be MIA.

 

[lucsimoneau]

Thanks for all the input - greatly appreciated. I was looking at a budget of approx $500 since I already had a 2HP 3PH motor. Looking a bit on the web and a 3HP 3PH motor goes for around my total budget. For @PeterT, if I do get to install the VFD I'll post a detailed description of the route taken. This is my King Canada CT-1440B lathe before installing a Mitutoyo DRO and a backsplash:

I would probably used the existing panel cover to place the relative switches, mainly the speed control, forward/reverse keeping the E-Stop. Don't have coolant on this machine so the position could be used for the potentiometer.



Was watching the Clough42 conversion of his Grizzly lathe and it seems very simple to do.
Regards,

 

[PeterT]

For @PeterT, if I do get to install the VFD I'll post a detailed description of the route taken. This is my King Canada CT-1440B lathe before installing a Mitutoyo DRO and a backsplash:
I would probably used the existing panel cover to place the relative switches, mainly the speed control, forward/reverse keeping the E-Stop. Don't have coolant on this machine so the position could be used for the potentiometer.

Yours looks identical to mine. You should get started.... Like tomorrow! LOL

My manual says 70-1350 (spindle) rpm. I'm not sure what the stock single phase motor nominal rpm is, I should check ID plate. I never really contemplated what would be required from a sheave standpoint if VFD motor was significantly different. Maybe that's what limits, or at least factors into 3p motor selection to begin with. I seem to remember one guy selected a 'higher' RPM 3p motor but I can't recall details like by how much - was it a little or a lot. Maybe he just somehow maximized his RPM output level through the VFD to stay within spindle bearing & chuck max limits? Higher speed might be useful in some cases but maybe pushing things in other respects.

 

[TorontoBuilder]

I thinkClough42 did one on his channel, but different/smaller lathe from a control inputs standpoint?
Hobby Machinist forum has some bigger/14" type conversion projects including bedway positionable e-stop switches & some braking resistor stuff. I had a list of links but seem to be MIA.

Yes James was another resource I relied upon, but his was relatively simple compared to 1440 with more controls that must be kept

 

[TorontoBuilder]

Thanks for all the input - greatly appreciated. I was looking at a budget of approx $500 since I already had a 2HP 3PH motor. Looking a bit on the web and a 3HP 3PH motor goes for around my total budget. For @PeterT, if I do get to install the VFD I'll post a detailed description of the route taken. This is my King Canada CT-1440B lathe before installing a Mitutoyo DRO and a backsplash: View attachment 28751

I would probably used the existing panel cover to place the relative switches, mainly the speed control, forward/reverse keeping the E-Stop. Don't have coolant on this machine so the position could be used for the potentiometer.

View attachment 28752

Was watching the Clough42 conversion of his Grizzly lathe and it seems very simple to do.
Regards,

A goof VFD will eat up that budget.

You really should use a "better" VFD that allows for external braking resister for this class of lathe. That will blow your budget. Unless you don't turn anything heavy at all and dont use a larger motor than 2 HP.

 

[cjmac]

A goof VFD will eat up that budget.

You really should use a "better" VFD that allows for external braking resister for this class of lathe. That will blow your budget. Unless you don't turn anything heavy at all and dont use a larger motor than 2 HP.

I went through this process about 15 years ago. My 12 x 36 lathe had a 1.5 hp motor. My motor supplier recommended using a 1 hp 1200rpm 3 phase motor. This means 6 poles instead of 4. He said the better low speed torque from the 6 poles would make up for the lower horsepower. It works great. I don't think I have used the gears since I installed this.

Chris

 

[PeterT]

The smoothness of 3p motor vs 1p & elimination of 1p start/run capacitors & centrifugal switch are other advantages. I want to dive into this VFD stuff one day, but not really on on my main grocery getter where the downtime would drive me nuts. At least at my amateur level. Smells like one of those 'weekend' jobs that runs a year LOL

 

[TorontoBuilder]

The smoothness of 3p motor vs 1p & elimination of 1p start/run capacitors & centrifugal switch are other advantages. I want to dive into this VFD stuff one day, but not really on on my main grocery getter where the downtime would drive me nuts. At least at my amateur level. Smells like one of those 'weekend' jobs that runs a year LOL

One thing I learned during the process... you need a clear plan and to acquire everything you need before starting. Dont touch anything on the lathe til then if you want to minimize down time.

I made a layout for my electrical controls cabinet in fusion to plan my layout... only mistake was it was kind of tight enclosure that made working inside it tricky rather than easy. I'd have gone with larger one in hindsight

 

[PeterT]

Yes James was another resource I relied upon

Not to tangent this post but James (Clough42) just posted 2 videos on rotary phase converter for his 3p mill. Not so much the RPC itself which was interesting, but more the broader electrical picture - what's coming in from the wall & what needs to go out to motor & where common misconceptions occur. I'm still clueless on this stuff but I gained some incremental understanding.

 

[Dabbler]

A couple of points to consider in your lathe conversions: it is a good practice to use a motor rated at about 1 1/2 times you single phase motor if you use a VFD. You end with better starting torque.

When I use a GE TECO 510, I match the HP rating and the VFD rating, as they have extra electrical and thermal headroom built in to their design. When I use a very inexpensive VFD, (offshore, etc) I run a 1HP motor on a 2HP VFD, to get some thermal buffer. On a 3HP motor, I'd use a 4HP VFD if it were one of the cheap ones.

Putting a VFD on a lathe requires considerable wiring changes - doing it on a mill is a couple of hours at worst. It's like night and day.

 

[YotaBota]

A search for VFD should get you 4+ threads on lathe installs and a couple on mill installs.

I agree with not using the high RPM motor.

eMotorsDirect.ca is a good source for VFD's and motors. The TECO brand VFD is one used often, it's not cheap or inexpensive but has all the options and support.

I think I'd look for an inexpensive used motor but spend the money on a good VFD, or save up a few more $ and buy both new.

I'm using a 2hp TECO VFD with the factory 1.5hp 3ph motor on my lathe and love it.

 

[YYCHM]

Single phase to 3 phase conversion on Modern GH1440W lathe

I've been thinking about doing this since I got the new lathe a little over a year ago but a few things have happened lately to push me toward starting this project. First was the capacitor failure I experienced on the single phase motor that came with the lathe. Second, my wife and I got back...

canadianhobbymetalworkers.com