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New to me South Bend

Cad1220

Plastic
Joined
Jan 27, 2024
Location
United States
Hi to all:
I just purchase a new to me 14.5 x 6' bed South Bend lathe. It was made in the early 50's I think. Serial number is 135072. It has a 1.5 HP 3 phase motor and like most I don't have 3 phase. Would like to know what is the best way to change. A phase converter, a rotatory phase converter or just change out the motor? It has a Wagner Electric motor that has a RPM of 1450. This is the only machine that I currently have, but would like to add a Bridgeport Mill some day. Thanks to all that will give there expert advise.
 

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Your machine was made in 1943, during WW2. Looks like you have a war production tag by the legs of tail stock end also, very nice. Steve's serial data base, scroll about a 3rd of the way down for your serial range:

You should buy the serial card, get it here:

After you get it, post a copy of it and relevant info here, and yours will be added to that data base:

I like an RPC for the win. Suggest a 5hp tp 7.5hp. Pick and buy your own idler motor, then buy the control cabinet from whomever you like. I like this brand myself:

 
Not sure but need to ask. Do I have to buy the converter and then another motor beside the motor that I have in the lathe?
 
From a money perpective it's about a wash, between a VFD, a new single phase motor, or a rotary converter. If you plan on that bridgeport, that leans you to a rotary converter, of the sizes mentioned above. If you really like variable speed capacity then the VFD's the way to go. I run my 10L on a rotary because I like to plug-reverse it now and then.

Targets of opportunity: if you find the 1.5 hp single phase motor or cheap (new those will be $$$) or an inexpensive 5 or 7.5 hp 3 ph motor inexpensively, surplus.
 
Not sure but need to ask. Do I have to buy the converter and then another motor beside the motor that I have in the lathe?
The 1450 rpm you mentiond is odd, though not impossible, i suppose. But most motors using 60hz or cycles will fall into 1200, 1800, or 3600 rpm ranges. I don't see location on your bio, but I'm assuming USA, we use 60hz here. Its a math problem, x number of poles in motor by 60hz equals speed... I'd like to see a pic of motor and also its data tag. If you get that serial card, it'll tell you what motor was original.

It seems to me that the quality of single phase motors these days is total garbage. I would not choose single phase. Same with the idler motors offered by the rpc manufacturers. They are running a business, they need to operate cost effectively. Their control cabinets are nice, but idler motors are trash. You can get excellent 3 phase motors all day, everyday on ebay, Craigslist, fb whatever for very reasonable prices. And use for your idler, and IF you need a motor for your lathe, that way too, but i think you may be fine with that motor, lets see those pics though.

Get measurements of your motor's pulley diameter, plus the pulley above it as well. We'll make sure you're making rated speed.
 
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I'd go with a VFD. Couple hundred bucks, relatively quiet, variable speed and reversing (handy for metric threads).
I'm sure you know, and didn't complete your thoughts, but those who don't, a vfd is not giving you metric capability if the math on end gears and qcgb dont support metric numbers.

Like anything, vfd's have positives and negatives. With those, you'll buy one per machine. With an rpc it can be the sole power source for many machines.
 
Thanks for the reply's. My shaft on the motor is .75 dia. with a 2.50 pulley. The top drive is 12.00". See the attached photo of the motor tag. It also states that it is 50 cycle. Not sure why.
 

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Do yourself a favor and just get an American Rotary phase converter especially if there is any chance at all you'll add another 3 phase machine, like a Bridgeport mill. One RPC runs all your 3 phase equipment assuming it is sized appropriately. I have a 10HP RPC and it'll run anything up to a 5HP motor. Vintage motors are NOT designed for VFDs and you can actually damage the motor by using one.
 
I'm sure you know, and didn't complete your thoughts, but those who don't, a vfd is not giving you metric capability if the math on end gears and qcgb dont support metric numbers.

Like anything, vfd's have positives and negatives. With those, you'll buy one per machine. With an rpc it can be the sole power source for many machines.
nope, I was very complete in my thoughts - reversing is handy for cutting metric threads as you can keep the half nuts engaged and reverse the spindle to get the carriage back to the start of the threads.

How anybody would jump to the conclusion that changing the way electricity is supplied to a motor would somehow enable metric threads to be cut when other criteria are not met is beyond me.
 
This topic has been beat to death many times here. Different people like different 3 phase power solutions.

My thoughts:
Rotary phase converters---On the plus side you can make your own from a three phase motor which can often be found cheaply and you can run multiple machines from one. On the down side they are the most noisy solution and you can't change their frequency to control your machine's speed.

Static converter--Quiet but again no frequency control. Can run multiple machines. On very rare occasions, when the capacitors get old, possible fire danger (see Wheelieking's thread where his house and shop were almost lost.

VFD--- Quiet. You can adjust frequency output to slow down or speed up your machine which to me is a big plus. Downside is you really need one for each machine. Small (1-5 hp) are reasonably priced but big ones can get expensive.

I own three vfd's and love to be able to adjust the speed of my machines with the turn of a dial. If I had a big machine with a 10+ hp motor I would probably set up a rotary phase converter for it.
 
Static converter--Quiet but again no frequency control. Can run multiple machines. On very rare occasions, when the capacitors get old, possible fire danger (see Wheelieking's thread where his house and shop were almost lost.
You forgot to mention that these downrate your motor by 1/3 horsepower since it's only supplying power to 2 of the 3 legs once it starts spinning.
 
Thanks for the reply's. My shaft on the motor is .75 dia. with a 2.50 pulley. The top drive is 12.00". See the attached photo of the motor tag. It also states that it is 50 cycle. Not sure why.
You're fine to use that motor. That motor is capaple of running at 50hz, if by chance it ended up in a foreign county that used 50hz electricity. However here in the US our electricity is delivered at 60hz, hence here it will run at 1750, that 1800-ish rpm i mentioned.

Note the voltage says 220 or 440. If you know where this lathe was last hooked up, ask which voltage they were using, it matters, a lot. If 220, you are golden, with whatever rpc or such. However, if they were running 440-480v you need to change the connections in the motor's little box for low voltage. If in doubt, dont guess, open that box and check how its wired.

I was guessing a 12" pulley for upper the same as a 16" South Bend. With a 2.5" pulley on motor that'll equate to a slower top speed of spindle, than its rated for. I'm thinking you'll want a 3" or 3.25" at motor to make rated speed. I'll link more about that in a bit.
 
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Thanks, I read the tag wrong on the first post. Would I not just be better to get a single phase motor?
You certainly can. The previous owner of my 1942 13" SBL did just that and it runs fine. However, I have 4 other machines that are all 3 phase and I am not about to change all those motors. LOL. It was easier for me to just get a rotary and power them all with one.
 
Thanks, I read the tag wrong on the first post. Would I not just be better to get a single phase motor?
You're free to do however you like, there are lots of solutions to the same problems. Single phase can provide sort of a quick fix if you are a little leery of messing with electrical stuff if its not a comfortable zone for you. I say sort of, because changing that motor that's mounted upside down, and a little bit heavy is a good time, trying to work through those openings :D.

I don't like single phase motors, but that's me. I'm finding most these days are not real good quality. Amp draw is higher, which uses more electricity. Noise, vibration, whatever. Could be my luck, but i'm always finding issues with single phase. Plus they have caps needed to run. Wiring for reverse is a maybe, and more complicated if so.

It might seem complicated, but 3 phase motors are actually easier. 3 hot wires, thats it. Reversing the motor is as easy is swapping any two, of the 3 hot wires, which is done by itself in that 3 position drum switch you got mounted, fwd-off-rev. Amp draw is nice. The nature of the poles in 3 phase make them smoother during operation as well.

Now consider, you mentioned a Bridgeport. . .certainly not single phase. Then as that machine disease creeps deeper into you. . . you'll begin to notice more machines that run on 3 phase. That cool old pedestal grinder with its own base, hmm only 3 phase, some drill presses, tool grinders. . . Or your air compressor motor craps out, hey you can replace it with a 3 phase. . . Ultimately you can work around it and avoid it, or give in to the dark side now.
 
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nope, I was very complete in my thoughts - reversing is handy for cutting metric threads as you can keep the half nuts engaged and reverse the spindle to get the carriage back to the start of the threads.

How anybody would jump to the conclusion that changing the way electricity is supplied to a motor would somehow enable metric threads to be cut when other criteria are not met is beyond me.
Come on man, what's wrong ? :D

You specifically mentioned metric threading, not threading in general, on a USA 1943 WW2 lathe. That lathe doesn't have a commie metric bone in its body. Threading chart in inches. Electric reversing is not unique to vfd's, all 3 phase can reverse. The unique characteristic of a vfd is the ability of variable speed. To those not familiar with the machine or set up, they might have inferred variable speed might somehow give them the ability cut metric threads. It does not.

Reversing is nice for threading period, regardless if standard or metric threads.
 
For the op's motor pulley size, spindle speed chart.

The chart shows high and low speeds. That was for two speed motors. Yours is not two speed, nor will any replacement you buy, unless you specifically try to buy one. That 50 and 60hz readings don't count, regardless you have a single speed motor. And that speed is "high" according to the chart. So you have the 8 speeds listed next the "high". The slowest four speeds are with back gear engaged, and bull gear un-pinned. The higher speeds are with back gear disengaged, and bull gear pinned. Four each, as noted that you have a four cone pulley in headstock. Looking at the headstock, the smallest section of those four is the highest speed, and the largest of the four is the slowest, whether engaged at back gear, or bull gear.
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Take note, the top speed is listed as 875rpm. In doing the math to determine pulley size for motor, that top speed number is the one to know. That top speed number will be 2 x the speed of that 12" pulley you measured for me. So if set up correctly, where spindle spins at 875rpm, that 12" vee pulley should be spinning at 437.5rpm. However, doing the math, I can tell you that the current set up is well under speed. Current top speed is only 729rpm !

Input the numbers we know into this calculator. 1750rpm of small pulley(motor pulley), motor pulley diameter 2.5", large pulley 12". Hit the "calculate" button. Now multiply the rpm of large pulley by 2. And you'll get 729.

Now on that calculator, change the small pulley to 3". Note the large pulley rpm change to 437.5rpm. Multiplied by 2 equals 875rpm, the machines rated speed.

I don't think I'd run more than 1000rpm with this machine's style of spindle bearings. But 875 is a little slow for South Bends. Most average 950rpm. I would not be scared to use a 3.25" pulley on motor to give me 950 at spindle. Either way, you should go to at least a 3" pulley.

I went through a bunch of this with more details starting at the top of page 2, post# 21-27 here:
 








 
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