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Help finding specs on an electric motor for my lathe

Tom75

Plastic
Joined
Jun 23, 2023
Hi, I have an enterprise 1330 lathe from the early 80’s that I’m restoring. My problem is that I’m trying to find the motors RPM rating for this lathe, I know from the factory it used a 3hp 3 phase electric motor but it doesn’t state the RPM’s.. the lathe came with the wrong motor ( think it’s a furnace motor… ). So I would like to use a 3hp- 5 hp single phase 220v motor for it.
I know that originally the lathe didn’t have a dual speed motor on it. What would be the best suited size of electric motor and rpm for this size of lathe???
 
From online pix, lathe looks like a medium duty 1000+# or so machine that a 3hp motor would be more than adequate for and almost certainly ~1800 rpm. One site suggests a weight of around 700# but that seems light, so probably another lathe.
 
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Tom, I'm assuming this is the manual you are looking at, it shows the standard motor as 3Hp 4P, the 4P indicates 4 pole, which would be a 1750 rpm motor. It also shows Optional 5Hp 2P / 2.5Hp 4P, I'm honestly not sure if that indicates 2 optional motors, or if its an optional 2 speed motor, 2P would indicate a 2 pole motor which would be a 3450 rpm motor. What was the rpm of the motor you removed?
https://cdme.osu.edu/sites/default/...h_speed_precission_lathe-operation-manual.pdf
 
Tom, I'm assuming this is the manual you are looking at, it shows the standard motor as 3Hp 4P, the 4P indicates 4 pole, which would be a 1750 rpm motor. It also shows Optional 5Hp 2P / 2.5Hp 4P, I'm honestly not sure if that indicates 2 optional motors, or if its an optional 2 speed motor, 2P would indicate a 2 pole motor which would be a 3450 rpm motor. What was the rpm of the motor you removed?
https://cdme.osu.edu/sites/default/...h_speed_precission_lathe-operation-manual.pdf
Hi,
Yes I was looking in the manual which came with the lathe. The motor that came with it was a 3/4 hp motor with a 1/2” shaft ( it was only bolted in place and not hooked up ). Not sure on the rpm’s but I’m thinking it was around 2200 but that said it looks like a motor off a furnace. I have the lathes pulley for the motor side and it would have to have a shaft of 1 1/8” dia. In which the motor doesn’t have.
 
Tom, I'm assuming this is the manual you are looking at, it shows the standard motor as 3Hp 4P, the 4P indicates 4 pole, which would be a 1750 rpm motor. It also shows Optional 5Hp 2P / 2.5Hp 4P, I'm honestly not sure if that indicates 2 optional motors, or if its an optional 2 speed motor, 2P would indicate a 2 pole motor which would be a 3450 rpm motor. What was the rpm of the motor you removed?
https://cdme.osu.edu/sites/default/...h_speed_precission_lathe-operation-manual.pdf
It was fairly common to use three phase two-speed motors in mills and lathes before VFD's became popular. Of course, the two-speed motor cost more, so they were mostly found in better quality machines. Hardinge used 3/4 HP 1750 RPM/3/8 HP 875 RPM motors in their lathes and mills as early as 1935 and was still using them decades later. At some point, possibly 1960, they went to higher HP two-speed motors in the lathes.

My Clausing 12 x 36 lathe was built with a three phase 2 HP 1750 RPM single speed motor, but I saw they had an optional two-speed RPM dial for the variable speed control. By then, I had come to appreciate my Hardinge machines' two-speed motors, so I replaced the original motor with a new Baldor 2 HP 1750 RPM/1 HP 875 HP and bought the two-speed dial.

Looking at the manual cited above, I see the belt ratio between the motor and headstock is different for the single speed and two-speed motor option in that lathe, so the two-speed has a lower minimum and higher maximum spindle speed.

Larry
 
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Hi,
Yes I was looking in the manual which came with the lathe. The motor that came with it was a 3/4 hp motor with a 1/2” shaft ( it was only bolted in place and not hooked up ). Not sure on the rpm’s but I’m thinking it was around 2200 but that said it looks like a motor off a furnace. I have the lathes pulley for the motor side and it would have to have a shaft of 1 1/8” dia. In which the motor doesn’t have.
I was just thinking someone might have done some pulley swapping already, and you might have to correct it, sounds like you are probably ok.
 
These question often arise. My suggestion is calculate motor speed by working backward. Engage the highest headstock spindle speed and by turning the headstock input pulley say 20 revs count the spindle revs. That gives you a ratio you can calculate motor RPM from the spindle RPM.

As stated by many others, it's most likely 1750.

The 3 phase motor and VFD is a fine suggestion. You get continuously variable spindle speeds, controlled accel and decel, much better finishes from the lack of single phase motor vibration. And as Vanice pointed out, there may not be a significant difference between a motor/VFD bundle and a new single phase motor.
 
These question often arise. My suggestion is calculate motor speed by working backward. Engage the highest headstock spindle speed and by turning the headstock input pulley say 20 revs count the spindle revs. That gives you a ratio you can calculate motor RPM from the spindle RPM.

As stated by many others, it's most likely 1750....
After you find the headstock gear ratio for the maximum spindle speed (probably 1:1), you then need to know the ratio between the motor and headstock pulleys to calculate the designed motor speed.

Larry
 
Hi,
Okay sounds good, I will take your advice on the motor.
THANK YOU ALL, for helping me answer my questions, this is a truly great forum! 😎
I run a VFD on my milling machine and love it but I’m on a budget and was trying to save a few dollars by running it 220v 1 phase motor. Otherwise I agree the VFD would be my best option.
 
Hi,
Okay sounds good, I will take your advice on the motor.
THANK YOU ALL, for helping me answer my questions, this is a truly great forum! 😎
I run a VFD on my milling machine and love it but I’m on a budget and was trying to save a few dollars by running it 220v 1 phase motor. Otherwise I agree the VFD would be my best option.
My comment about cost was based on my experience years ago when I was actively looking for three phase motors after the price of VFD's got reasonable. I bought several new three phase motors on eBay for $1 because I was the only bidder, though the shipping added quite a bit to the total cost. At the time, I also got some cheap motors locally, partly because people thought three phase motors were worthless. I have not looked for a motor on eBay lately, but I know shipping cost is pretty high now.

I also bought quite a few new VFD's on eBay for low prices.

Larry
 
I checked out the price on a 3 HP single phase on the Tractor Supply website a while back. It was very close to one grand! OMG! I can buy a surplus 3 HP 3 phase motor and a TECO VFD for under $400. I have two TECO VFD's on two lathes in my shop, wouldn't trade it for a single phase motor ever!
 








 
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