What's new
What's new

Heavy 10L with 3/4hp 1ph 110 VAC to 2hp 3ph 220 VAC conversion? Why not?

adam9274

Plastic
Joined
Dec 20, 2018
It seems most Heavy 10L's were delivered with a single phase 3/4 hp. I'm thinking of converting to a 2 hp, 3 phase motor, that uses a VFD for speed control.

Now, most of the time, I would anticipate running the VFD at 60 Hz (Nominal), and basically using the VFD as a phase converter. 110 or 220 VAC 1ph in, and 220 VAC 3 ph out. The only advantage in this "configuration" would be extra power. i.e. 3/4hp to 2hp

Sometimes, when cutting a difficult material, or cutting a difficult geometry or using a form tool or something, I can visualize using the speed control pot to "trim" the speed through the VFD to obtain an optimal cutting speed. But I feel like I would try to change the speed through mechanical means first, rather than just relying on the VFD. I mean, "get as close" to the optimal cutting speed through gears and pulleys first, then make small trim adjustments through the VFD. That's the idea.

So, I understand that the lathe would have been engineered to use 3/4hp. But are there any inherently "weak links" in the drive trains of the 10L that I should be concerned about? I mean, the headstocks are pretty beefy. We're talking about belts and pulleys mostly there. The quick change gear box, is definitely not as simple/beefy/robust, but looks pretty damn tough? I can't imagine it couldn't take some extra power?

I know if I made a really bad mistake, extra power wouldn't be my friend. But for the sake of this discussion, I am assuming I won't do that, and/or I could leave the tension a bit looser when I think something "hairy" could happen...

Also assume there is no cost penalty for this. I already have the components.

My Question is: Why WOULDN'T I want to up the horsepower? Surely others have done this. Wouldn't it just mean I could take heavier cuts if desired, and the smaller cuts, would be that much easier? Has anyone ever broke their lathe because they over-powered it?

Or is 3/4 hp already LOTS of power? And the mechanical speed ranges available are plenty?

Opinions?

Adam
 
My 10l came with a 1hp 3phase from South Bend. I use a KB Electronics vfd that has a remote trim pot I mounted on the factory Cutler Hammer switch. Plenty of torque for cutting steel with carbide, plus having the remote pot is very handy. The only limit is the old belt which I will soon replace with a serpentine belt.

Looking back through an old South Bend catalog from Steve Wells website, you could get a Heavy 10 with a 2hp 3phase motor from the factory. Honestly the lathe is rigid enough to handle a 2hp motor.

Using the 3phase is preferable over single phase since the torque delivered is more even than single phase and gives a better finish on the part. The KB Electronics vfd I chose is very simple to set up and is a sensorless vector drive. Instead of confusing digital inputs and a 200 page manual, the drive uses simple header pins and jumpers as well as wire terminal blocks. Very user friendly you do not have to be a certified industrial electrician to set it up! I had the drive mounted and wired in about 2 hours. I did use a Siemens power switch with 25 amp fuses as the power cut off.
 
f9021524eb89e80d2f812de70df87356.jpg


Pic of the lathe when I first brought it home. I will post a couple pics of the switch, vfd and pot mount when I get home from work tonight.


Sent from my iPhone using Tapatalk
 
My 10l came with a 1hp 3phase from South Bend. I use a KB Electronics vfd that has a remote trim pot I mounted on the factory Cutler Hammer switch. Plenty of torque for cutting steel with carbide, plus having the remote pot is very handy. The only limit is the old belt which I will soon replace with a serpentine belt.

Looking back through an old South Bend catalog from Steve Wells website, you could get a Heavy 10 with a 2hp 3phase motor from the factory. Honestly the lathe is rigid enough to handle a 2hp motor.

Using the 3phase is preferable over single phase since the torque delivered is more even than single phase and gives a better finish on the part. The KB Electronics vfd I chose is very simple to set up and is a sensorless vector drive. Instead of confusing digital inputs and a 200 page manual, the drive uses simple header pins and jumpers as well as wire terminal blocks. Very user friendly you do not have to be a certified industrial electrician to set it up! I had the drive mounted and wired in about 2 hours. I did use a Siemens power switch with 25 amp fuses as the power cut off.

:o I have a KB KBMD-240D old stock new unopened in the box...likely never use...marked $125.. guess $65 plus postage a fair price.

KBMD-240D - KB Electronics - DC Drives | Galco Industrial Electronics
 
Why WOULDN'T I want to up the horsepower? Surely others have done this. Wouldn't it just mean I could take heavier cuts if desired, and the smaller cuts, would be that much easier? Has anyone ever broke their lathe because they over-powered it?

I'm working with one now that has a Baldor 2hp, 3ph motor and it doesn't seem any different or more capable than the 3/4, and 1hp motors I've used before. You can still bog it down with too deep a cut. It was like that when I bought it so there's no reason for me to switch it, but I wouldn't actively seek one out.

If you do swap motors, make sure you get the exact same shaft size so the 2-step pulley will transfer over.
 
Years ago I bought an unmentionable(here) lathe with a 1/2hp motor, it sucked and struggled with light cuts. Found a 1.75hp that would fit and installed that, world of difference and made it a great machine. Using a vfd to vary speed to avoid chatter I can see, using it to control speed so you don't have to take 30 seconds to change a belt, c'mon, don't be that lazy.
 
If you have a motor already, post what it is....not all are suitable for VFD use and verging speed.

+1 for the KB VFD....a little more money up front but it's a wash IMO for the convenience and because it needs no enclosure.
 
I've got a heavy 10 with a 3 phase 3/4 hp motor. It is running on a static converter so I can't get full power.

I have taken .1 inch deep cuts in mild steel with an advance of .010 inch/rev. HSS bit. Chips were coming off smoking and blue, motor never got close to slowing down.
I don't think you could use a full 1hp even if you tried.
 
I would suggest a 1.5 hp 3phase motor. This leaves a good deal of hp available if you run the VFD at reduced speed.

You might have a bit of trouble fitting a 2 hp motor onto the motor plate in a heavy ten. Check the dimensions
carefully before you buy.
 
So, what I'm reading... is... There are some different opinions about how much power a 10L needs or doesn't need, but overall.. no one seems concerned about failure of any component, or overloading anything?

@jim rozen - That's a good thought.. allowing extra horsepower for reduced speed. Generally you can run any 3-ph motor fairly efficiently between 40 and 80 Hz.. But outside of that band, usually you want an inverter/VFD rated motor, and when you get significantly out of that band you start to lose power. I would try to avoid being that far out of the band... and I'd change "gears" manually and try to keep the motor running at or near 60Hz, but I think the principle is still sound.
 
How would a high quality 1140rpm 1HP metric frame inverter duty rated motor grab you?
that lets you bascially forget the high speed step on the motor pulley and run the VFD up to 90hz to get your full speed range...constant HP above 60hz,albeit with a LITTLE torque loss but none that you'll notice. I like slow anyway though and rarely ran over ~1000rpm.

that how I ran mine, and it was great, loved the kick butt low end it gave.
 
So, what I'm reading... is... There are some different opinions about how much power a 10L needs or doesn't need, but overall.. no one seems concerned about failure of any component, or overloading anything?

@jim rozen - That's a good thought.. allowing extra horsepower for reduced speed. Generally you can run any 3-ph motor fairly efficiently between 40 and 80 Hz.. But outside of that band, usually you want an inverter/VFD rated motor, and when you get significantly out of that band you start to lose power. I would try to avoid being that far out of the band... and I'd change "gears" manually and try to keep the motor running at or near 60Hz, but I think the principle is still sound.

So the deal is, a VFD-driven motor above nameplate speed is constant horsepower. Below nameplate speed it will be constant torque. This is true over just about all speed ranges and
does not depend on the motor having any special inverter rating. (that's a whole 'nother story).

As one data point I am currently running a SB heavy 9 (basically your lathe) with a 1.5 hp motor and a Hitachi VFD run in sensorless vector mode. For the majority of the work
(except maybe threading) there is no need to shift belts or use the back gear. This has nearly full torque down to tick-over speed.

If you go this route be sure to use the auto-tune feature for your motor. In fact I autotuned again once the motor was installed and the spindle actually
belted up and running. The behavior of this system is really nice, so much so I am considering installing a similar drive on my 10L, which is exactly the same machine
you have (probably close in serial number).

The one thing you cannot do (and this is actually the only feature I don't want to give up) is to plug-reverse the motor when it is VFD operated.
 








 
Back
Top