# Please help me choose a motor & VFD for a vintage Rivett lathe



## cazclocker (Jun 26, 2014)

I'm buying a vintage Rivett 715 plain-turning lathe (no screwcutting capability) from a friend in the next couple of months. I have a fair idea what I'll do for a bench, but I obviously need to choose a motor. Right now, I'm in the process of narrowing down my choices of an AC motor from Surplus Center.

I will also need to choose a VFD - I watched the videos by TubalCain with great interest on how he installed a VFD on his drill press. Do I need to wait until I pick a motor to choose a VFD? Or can I start choosing now? My electrical source will be a 220VAC dryer outlet in my shop.

Thanks in advance...
...Doug


----------



## JimDawson (Jun 26, 2014)

Before you choose a VFD, you will need the motor horsepower.  You will be choosing a 3 Phase, 230/460 volt motor.  And connecting it for 230V.  That's all there is to it.


----------



## CluelessNewB (Jun 26, 2014)

Make sure you read the fine print on the Surplus Center motors.   Make sure it is "Continuous Duty".  When selecting a VFD typically the horsepower rating will get you the right one but you should also check the current rating.  The VFD should be rated for at minimum the rated amperage of the motor.  For example on a 230/460 volt motor you may see amperage 2.8/1.4, the higher number (2.8) is the current at 230 volts and is what you would use to select a VFD.  You will want a "sensor-less vector" type of VFD for a lathe (so skip the Teco FM50).   I have used Teco N3 and Teco 7300 both work well.  If I was buying today I would look at one of the Teco JNEV VFD's.  Hitachi has a good reputation also.   I have one eBay cheapo but I would recommend spending a few extra bucks.


----------



## cazclocker (Jun 26, 2014)

JimDawson said:


> Before you choose a VFD, you will need the motor horsepower.  You will be choosing a 3 Phase, 230/460 volt motor.  And connecting it for 230V.  That's all there is to it.



Thanks, Jim! With the parameters you mentioned, my choices just got cheaper - that's a good thing. I need at least 1 horsepower. So Surplus Center offers a *1 HP motor* and I'm also looking at a *1.5 HP motor*.

So how do I now choose a VFD? I'd like to stick with Surplus Center - no particular loyalty here, I've had good experiences with them in the past and I'd rather order the motor and VFD from one place unless there's a compelling reason not to. Their line of VFD's can be seen *HERE*.

Thanks,
...Doug


----------



## cazclocker (Jun 26, 2014)

CluelessNewB said:


> Make sure you read the fine print on the Surplus Center motors.   Make sure it is "Continuous Duty".  When selecting a VFD typically the horsepower rating will get you the right one but you should also check the current rating.  The VFD should be rated for at minimum the rated amperage of the motor.  For example on a 230/460 volt motor you may see amperage 2.8/1.4, the higher number (2.8) is the current at 230 volts and is what you would use to select a VFD.  You will want a "sensor-less vector" type of VFD for a lathe (so skip the Teco FM50).   I have used Teco N3 and Teco 7300 both work well.  If I was buying today I would look at one of the Teco JNEV VFD's.  Hitachi has a good reputation also.   I have one eBay cheapo but I would recommend spending a few extra bucks.



Clueless, sorry I didn't see your post! On the *1.5 HP motor* from Surplus Center I don't see the word "continuous" anywhere, but I do see a pair of amp ratings (4/2 amps). So I see that this motor will run at 4 amps at 230 volts.

If it was you, where would you shop for motors?


----------



## Ulma Doctor (Jun 26, 2014)

just a fyi ...
you can over-rate the VFD,  that is to say, if you are running a 1 hp motor, it doesn't hurt if the VFD is rated for 2 hp.
if the price is right and you have the ability i would go a little larger if possible.

but that's just my 2 cents, but, i get paid to repair other's mistakes.

as far as where to get a motor many surplus companies have them pretty cheap
baldor is a good name
sew eurodrive also is top notch
the dayton motors can be used with sucess
but any 3 phase air compressor duty motor around 1740 rpm will work fine but you'll have to watch out for using the motor at low speeds for too long a period of time.
an inverter duty would be optimum but they can be expensive
 i hope the info helps out


----------



## rdean (Jun 26, 2014)

I agree with Ulma Doctor on sizing up.  I have used Woods, Allen Bradley, Lenze, and Siemens VFDs over the years and I always up one size when installing.  All drive manufactures I am familiar with have cheapened their drives to save money and be competitive.  Some even tell you they are not for continuous full load amps.   
Go one size larger and it will be well worth the price.

Ray


----------



## JimDawson (Jun 26, 2014)

Doug, I just took a look at the motor you linked to.  I think it has sleeve bearings, not what you want.

In the same price range, they also have some 1.5 HP Chinese motors, that are ball bearing, continuous duty, and are 230V only.  The down side is that (1) they are Chinese, and (2) they have a 22mm shaft rather than a 7/8.  It is a standard metric size, so you can get pulleys for it, or use a 0.005 shim wrapped around the shaft to use a 7/8 pulley, and modify the (6mm?) key to fit.

I agree with Ulma Doctor that upsizing the VFD can't hurt.)


----------



## CluelessNewB (Jun 27, 2014)

Also do you really want a motor that runs that fast?  Typically on a lathe you would want an approximately 1800 rpm motor not a 3600 rpm motor.  Note the 1hp motor link you shared has a very weird oddball shaft and a duty of only 2 minutes (not continuous).  

The Surplus center VFD's are all TECO FM50's (not ideal for a lathe) except 11-3424 which is a Teco JNEV 101-H1 which would work well but it is 115V input (might even be preferable).  Just remember when you go with a 115V input VFD the currrent draw on the 115V line will be high so you probably can't share that circuit with much else.  As others have said oversizing a VFD isn't a bad idea. 

If I was buying a new motor I would look for a TEFC (totally enclosed fan cooled).  For a small lathe like that 3/4 or 1hp should be plenty.   


Surplus Center has some cool stuff but make sure you check shipping prices, they can be a deal breaker.

I have bought VFD's but not motors from http://dealerselectric.com/ they also sell VFD/Motor combined packages that look attractive.


----------



## cazclocker (Jun 27, 2014)

Yes, I am positive that I need a motor rated at 3600 RPM or thereabouts. The lathe is a vintage precision bench lathe that was originally designed to run at a maximum of 3500 RPM. The lathe spindle runs a pair of size-matched V-belts which pass through a hole in the bench straight down under a headstock cover. I just found out that my friend who is selling the lathe to me will supply the SAME SIZE pulleys for mounting onto the motor shaft, so the drive ratio will be 1:1.

So far I now know that I want a 230/460 VAC motor, 1hp - 1.5hp, 3600 RPM (+/- a few RPM's) and (for reasons I don't understand) I don't want sleeve bearings.

Why are sleeve bearings not desireable?

I have yet to pick a VFD - thanks for suggesting dealerselectric.com.

...Doug


----------



## CluelessNewB (Jun 27, 2014)

cazclocker said:


> Yes, I am positive that I need a motor rated at 3600 RPM or thereabouts. The lathe is a vintage precision bench lathe that was originally designed to run at a maximum of 3500 RPM. The lathe spindle runs a pair of size-matched V-belts which pass through a hole in the bench straight down under a headstock cover. I just found out that my friend who is selling the lathe to me will supply the SAME SIZE pulleys for mounting onto the motor shaft, so the drive ratio will be 1:1.
> 
> So far I now know that I want a 230/460 VAC motor, 1hp - 1.5hp, 3600 RPM (+/- a few RPM's) and (for reasons I don't understand) I don't want sleeve bearings.
> 
> ...



But didn't that machine lathe have belt reduction to give a wide range of speed?  (See link below).   It says 150-3500 rpm.  You will NOT get near that range with only a VFD for speed control.  You are limited with a VFD at the low speed end by two things.  #1 Motor cooling, the motor must run at a speed fast enough for the internal fan to cool it.  #2 Power, at slow speed.   You can go to a more powerful motor to help #2 but there isn't much you can do about #1.  Personally I don't run any of my VFD driven motors below about 1/2 rated speed and no more than 1.5x rated speed.  Using those seat of the pants numbers and a 1:1 belt ration with an 1800 rpm number you could go from 900 - 2700 rpm.   Using a 3600 rpm and 1:1 it would be 1800-5400 rpm.  With a different belt ratio you can move this speed range around but you will always have a limited range unless you provide for a way to change the belt ratio.  I also like slower motors because are quieter and run smoother.  

FWIW my Logan has it's original 1945 1800 rpm sleeve bearing 3 phase motor, I did put new bearings in it when I got it.  

http://www.lathes.co.uk/rivett/page7.html


----------



## Ulma Doctor (Jun 27, 2014)

sleeve bearings are not as precise as roller bearings and can't hold up to high speeds.


as far as what you need for a motor given your specs is
230volt 3 phase, if you get a dual voltage 230/460 that's great but a single voltage motor(230 v 3 phase or even a 200v 3 phase motor) would suffice
1-5 hp, 3600 rpm 

a 56 frame motor has a 5/8" keyed shaft with 1 exception the 56HZ which has a 7/8"(keyed 2" long) shaft
a 145t motor frame has a 7/8" shaft
a 182t has a 1 1/8" shaft
a 213t has a 1 3/8" shaft
a 215t has a 1 3/8" shaft

i hope the info helps


----------



## JimDawson (Jun 27, 2014)

cazclocker said:


> Yes, I am positive that I need a motor rated at 3600 RPM or thereabouts. The lathe is a vintage precision bench lathe that was originally designed to run at a maximum of 3500 RPM. The lathe spindle runs a pair of size-matched V-belts which pass through a hole in the bench straight down under a headstock cover. I just found out that my friend who is selling the lathe to me will supply the SAME SIZE pulleys for mounting onto the motor shaft, so the drive ratio will be 1:1.
> 
> So far I now know that I want a 230/460 VAC motor, 1hp - 1.5hp, 3600 RPM (+/- a few RPM's) and (for reasons I don't understand) I don't want sleeve bearings.
> 
> ...



CluelessNewB is correct.  You will not have the speed range you need with the motor direct coupled to the spindle.  I have never seen a belt drive lathe that didn't have step pulleys (or variable speed pulleys) for changing the speed ranges, even when using a VFD.

It is very unusual to have a lathe motor run the spindle directly at a 1:1 ratio.  The exception would modern CNC equipment with big AC servos running the spindle.  

The motor HP is a function of Torque x RPM, therefore, a 3600 RPM, 1.5 hp motor develops 0.75 HP at 1800 RPM.  Also a 1.5 HP, 3600 RPM motor has 1/2 the torque of a 1.5 HP, 1800 RPM motor.

If I were going to run that lathe direct drive, I would be looking at about a 3 KW AC servo drive, and gear it down to about 1.5:1.  This would give you the wide speed range, with reasonable torque throughout the speed range.

Sleeve bearings (bushings) are not good for side (radial) loading on the motor shaft, like a belt drive.  If the motor is driving a load with no or very light radial load, like a fan, they have a reasonable service life.  Ball bearings will hold up to the heavy radial loads for continuous belt drive duty.


----------



## cazclocker (Jun 27, 2014)

CluelessNewB said:


> But didn't that machine lathe have belt reduction to give a wide range of speed?  (See link below).   It says 150-3500 rpm.  You will NOT get near that range with only a VFD for speed control.  You are limited with a VFD at the low speed end by two things.  #1 Motor cooling, the motor must run at a speed fast enough for the internal fan to cool it.  #2 Power, at slow speed.   You can go to a more powerful motor to help #2 but there isn't much you can do about #1.  Personally I don't run any of my VFD driven motors below about 1/2 rated speed and no more than 1.5x rated speed.  Using those seat of the pants numbers and a 1:1 belt ration with an 1800 rpm number you could go from 900 - 2700 rpm.   Using a 3600 rpm and 1:1 it would be 1800-5400 rpm.  With a different belt ratio you can move this speed range around but you will always have a limited range unless you provide for a way to change the belt ratio.  I also like slower motors because are quieter and run smoother.
> 
> FWIW my Logan has it's original 1945 1800 rpm sleeve bearing 3 phase motor, I did put new bearings in it when I got it.
> 
> http://www.lathes.co.uk/rivett/page7.html



Clueless, you're right - the Rivett 715 came stock with a motor of  unknown-to-me specs, and an intermediate countershaft between the motor  and the lathe's spindle. Hence the 150 - 3500 RPM's both forward and  backward.

OK, I'm starting to see that this is more involved than  I was hoping for. I think I need to slow down and find out what the  heck I need!



Ulma Doctor said:


> sleeve bearings are not as precise as roller bearings and can't hold up to high speeds.
> 
> 
> as far as what you need for a motor given your specs is
> ...



Thanks that's very useful.



JimDawson said:


> CluelessNewB is correct.  You will not have the speed range you need with the motor direct coupled to the spindle.  I have never seen a belt drive lathe that didn't have step pulleys (or variable speed pulleys) for changing the speed ranges, even when using a VFD.
> 
> It is very unusual to have a lathe motor run the spindle directly at a 1:1 ratio.  The exception would modern CNC equipment with big AC servos running the spindle.
> 
> ...



Thanks for that - I may have to change my goals - maybe I need to build a countershaft like the OEM had.
...Doug


----------



## cazclocker (Jul 15, 2014)

I'm still trying to decide on a motor - I'll choose a VFD once I've settled on the motor for my soon-arriving Rivett 715 bench lathe. I've decided against the motors from Surplus Center. Instead, I've decided to choose a better quality motor. Can anyone here help me decide if the one I'm looking at is a wise choice or not? I'm looking at *THIS ONE* from MSC. I've been trying to study up on AC motors and I think I've learned a bit, but maybe not enough to make an informed decision. A few days ago I received the first box of bits & bobs from the seller (30 4C collets were included!), and the motor pulley was one of the items included. The pulley has a 5/8" keyed shaft opening, so right there it narrows down my motor frame search to the 56 series...am I correct in that?

One spec on the above-referenced motor is the frequency Hz....it says 60/50. What does that mean? Again, my power source will be the 220VAC dryer outlet in my workshop.

By the way, I was also looking at part #6136K77 from McMaster Carr, but I have a long history with MSC.
Thanks,
...Doug


----------



## JimDawson (Jul 15, 2014)

50/60 Hertz means it will run on either USA or European power at rated HP.  It will run fine on your dryer outlet.  In the North America our power is 60 Hz.

The price looks good, and the brand is well known.  With a 5/8 pulley, you will want a 56 frame motor.


----------



## cazclocker (Jul 15, 2014)

JimDawson said:


> 50/60 Hertz means it will run on either USA or European power at rated HP.  It will run fine on your dryer outlet.  In the North America our power is 60 Hz.
> 
> The price looks good, and the brand is well known.  With a 5/8 pulley, you will want a 56 frame motor.



Jim, do you really think the price ($303.10) is a good price? My friend who's selling the lathe to me that it's outlandishly expensive; I can do better elsewhere.
...Doug


----------



## JimDawson (Jul 15, 2014)

Here is an alternative.  

About 1/3 the price, and a good vendor.  Doesn't have the external cooling fins, and is not inverter duty, but I have used this motor with VFDs without problems.  Extended running at low RPM might require an external cooling fan.


----------



## cazclocker (Jul 16, 2014)

JimDawson said:


> Here is an alternative.
> 
> About 1/3 the price, and a good vendor.  Doesn't have the external cooling fins, and is not inverter duty, but I have used this motor with VFDs without problems.  Extended running at low RPM might require an external cooling fan.



Jim, thanks so much for that recommendation. At $101.00, it appears to be an unbeatable deal and for $13.00 more I can step up one notch *to a 1.5HP motor*. I especially appreciate the fact that you seem to have had personal experience with the 1HP version.

OK....now to pick out a VFD.
...Doug


----------



## JimDawson (Jul 16, 2014)

Glad I could help.  I buy a lot of stuff from those guys.

Take a look at the same vendor under Drives


----------



## master53yoda (Jul 16, 2014)

*The below paragraph is from the Lathes UK site  it gives some information about the dirve and pulley setup that was with that lathe originally.    It speaks of a 900/1800 rpm 2 speed motor driveing a gear box with  8 speeds for 150 to 3500.    without the gearbox it appears likely that you would need to setup something like the under bench Atlas lathes us.   I run my 12" atls with a 2 HP treadmill motor without any issues and get excellent speed control form about 60 rpm to 3000   The treadmill motor is 2 hp at 4000  so it would be = to about a 3/4 hp normal AC motor at 1800.

I think you will need to address the gearbox issue in some form as direct driving the lathe isn't going to work very well

Art B

*
*http://www.lathes.co.uk/rivett/page7.html**

Stands and Drive System
*A  choice of two stands was offered: a compact 45" x 24" all-welded heavy  steel-plate cabinet with a collet and tool drawer and locking storage  cupboard, or a traditional open-type with cast-iron legs braced by steel  tie rods and a large, 60" x 26" by 2.25-inch thick 5-ply laminated  wooden top with side and backboards. The open stand was intended for  laboratory and toolroom use - where it was necessary to mount the  auxiliary motor unit and "overhead" to power high-speed grinding and  milling spindles, or if space was needed for tools, small parts and  sub-assembles to be laid out and a trail fit of components made. 
Both  stands used an identical drive system with a 2-speed 900/1800 r.p.m.  motor (though some single-speed fittings have also been found) fitted  with a 2-step V-pulley that drove to a matching pulley mounted on the  rear of two shafts that extended from a simple clutch-gearbox unit  bolted to the underside of the bench. Fitted to the output side of the  rear shaft were high and low-speed pulleys that drove pulleys on the  front shaft that were free to turn until locked by a sliding dog clutch.  Final drive to the spindle was by twin V-belts, assembled as a  specially-matched pair. In order to allow a quick release of belt  tension for speed changes the motor was mounted on a hinged plate  controlled by a lever hinged on a bracket bolted to the front face of  the stand's lower shelf. By this (relatively complex) means the operator  could juggle belt and clutch lever positions to give eight spindle  speeds that spanned a very useful 150 to 3500 r.p.m.  To promote smooth,  vibration-free running, all rotating parts were dynamically balanced  and ran in self-aligning ball races. Usefully, in addition to individual  screw adjustment for each belt's tension, all could be changed without  any dismantling being necessary.  
Electrical control was simplified  to a single switch and pilot light (to indicate current on or off)  mounted low down on the front face of the headstock.The lever was turned  to the right for high and low forward speeds and to the left for low  and high in reverse - with, in each case, intermediate stop positions  between every setting. Sensibly, the makers constructed the switch  handle if the form of a large T, so enabling an oily hand to obtain a  secure


----------

