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10" Sheldon lathe motor recommendation

challenger

Stainless
Joined
Mar 6, 2003
Location
Hampstead, NC-S.E. Coast
I purchased a VFD and would like to use it on my Sheldon EXL lathe. The motor on it is a single phase without a data plate. The original motor is a 3-pH by is in storage. I have a 3/4hp 3ph at my shop that is new but I don't know if I can drive the lathe with it. Any suggestion? Thanks
Howard
 
3/4 will work fine.

Just be sure it is the proper rpm. I would guess ~1740 rpm.

I don't think Sheldon used 3480 rpm motors on their lathes.

That and the VFD, will make for a nice setup
 
I disagree with most of the others. I have a 13" Sheldon with a factory 2HP motor. These lathes can take cuts that will slow even that thing down. You'll not be able to fully utilize your machine with less than 1 1/2 to 2HP.
 
Yes, Bill. Chips will be made, and with small diameter stock you might be able to take a fairly good cut. While some might not think the ability to take a significant cut very important, it dramatically reduces the time required for many projects. If one needs to cut or face a 6 or 8" piece of steel, 3/4HP is going to reduce the DOC to ten or fifteen thousandths. Then there's carbide tooling. Besides DOC you need a certain speed to get the best results, and that lathe, properly powered, is quite capable of giving great results using carbide. Short story: if you power it like an Atlas/Craftsman lathe it will perform like one. If the OEM motor is not too hard to get to, I still highly recommend it.
 
Yes I can get the original motor without much hassle. I'll be doing this soon.
One thing stuck me however:
Why will I need to change the belt placement on the three groove pulleys if I am using a VFD?
I have read here & other places that the VFD takes away all that manipulation plus, of course, gives total RPM control?
Now I'm worried about what I am missing.
Thanks
Howard
 
The belt placement will be determined after you're up and running with the VFD. There are limits to how slow and how fast you can directly drive the motor, so by experimenting you'll find the pulley step that works well for most of what you do. There could still be times when you want to change the pulley ratio, but they'll likely be quite infrequent.
 
3/4hp at the spindle is what that lathe wants; a 1720-1800 rpm motor. Even a true 1/2 hp motor wouldn't be out of place. However, if you intend to use the VFD over a somewhat wide range (say, down to 20 Hz), 1 hp would be my recommendation. Larger than that and you risk having greater ambitions for your cuts than the lathe was really designed to handle.
 
I have a copy of the factory brochure. It recommends 3/4 hp 1725rpm for the L and XL drives and 1 to 1 1/2 hp for the E and U drives. I have a 1943 11"x56 with the E drive and it has a single phase 1hp Westinghouse motor. While I don't know if it is original, it seems to do just fine.

bedwards
 
I have a copy of the factory brochure. It recommends 3/4 hp 1725rpm for the L and XL drives and 1 to 1 1/2 hp for the E and U drives. I have a 1943 11"x56 with the E drive and it has a single phase 1hp Westinghouse motor. While I don't know if it is original, it seems to do just fine.

bedwards

Ouch! I am busted. I also have a copy of the brochure but wanted to hang back and not admit that I knew what was recommended.
I am strictly a hobby metal hack and will never get close to maxing out this lathe with what I do. I almost never use carbide because I am afraid of the speed required to use it. I normally lean toward excessiveness in just about everything I do-not a good character trait. When I work the machines I have I am 180* opposite and I try to be extremely cautious. I feel any machine that cuts material harder than bone deserves the utmost respect and an untrained hand is bound to be untrained in the safety required to operate these machines so I try and compensate my lack of formal training by using extreme caution and, "common sense". Is that phrase still alive or has our society made it an absurdity?
I'll retrieve the original motor today and wire it to my RPC to make sure it works. It worked when I purchased a he lathe about 12 years ago so I hope the years of sitting didn't make it ornery. Maybe some lube and sweet talk will do the trick.
Thanks
Howard
 
I'm just a hobby guy too, and I don't do production work. My material budget is severly limited and I buy or am given whatever is available at the right price. Sometimes I need to make a half-inch diameter shaft out of inch thick stock, or turn down most of a length leaving a hub at one end. I just can't afford to go buy the closest size for the job every time. With your Sheldon and the appropriate motor, you can do in an hour what would otherwise take all day, and projects that wouldn't fit your available time are now doable. Carbide is awesome! You can whittle stuff down in no time without stopping to sharpen the bit every few minutes. If there's a downside it's that the chips fly off hotter than hell. I use carbide for 80% of my work.
 
I'd like to start using carbide tools one day. Maybe the VFD will create the motivation.
I am thinking the original motor would not be inverter duty.
How would I know what designation specifies a motor as inverter duty?
Thanks
 
OK I have actually run EXL Sheldons.

3/4hp is fine..

A 10 in IS NOT a 13 in lathe... A Sheldon R series, is a serious lathe.. Not a light school/homeshop lathe like the smaller Sheldons..

As to VFD rated motors... If motor is in good condition, and made from say early 50's on.. It will handle a VFD just fine..

I would not put a VFD, on an old cotton wire insulated motor.

VFD rated means.. Good insulation. And ability to run at very low rpm for a very long time.. It can handle the extra heat build up..

Since the bed on that 10 in lathe, is somewhat less than say 30 ft.. It will never have much of a continuous full load at low rpm...

A quick check of motor housing temperature with your hand, will tell you if things are getting too hot.

NO need to put a bigger motor on the lathe, You will still have to change belt positions once in a while, AND use backgears...

A direct drive motor to spindle, would require a larger motor to still provide usable torque at low RPM. Not a problem with stock countershaft and backgears...

Carbide is just OK on a light lathe, I would use HSS most of the time, saving carbide for... Abrasive materials, Hard materials.

I do a LOT of low speed threading to a shoulder, Carbide has no advantage over HSS there.. A quick touch up with a stone, keeps the HSS razor sharp...
 
OK I have actually run EXL Sheldons.

3/4hp is fine..

A 10 in IS NOT a 13 in lathe... A Sheldon R series, is a serious lathe.. Not a light school/homeshop lathe like the smaller Sheldons..

As to VFD rated motors... If motor is in good condition, and made from say early 50's on.. It will handle a VFD just fine..

I would not put a VFD, on an old cotton wire insulated motor.

VFD rated means.. Good insulation. And ability to run at very low rpm for a very long time.. It can handle the extra heat build up..

Since the bed on that 10 in lathe, is somewhat less than say 30 ft.. It will never have much of a continuous full load at low rpm...

A quick check of motor housing temperature with your hand, will tell you if things are getting too hot.

NO need to put a bigger motor on the lathe, You will still have to change belt positions once in a while, AND use backgears...

A direct drive motor to spindle, would require a larger motor to still provide usable torque at low RPM. Not a problem with stock countershaft and backgears...

Carbide is just OK on a light lathe, I would use HSS most of the time, saving carbide for... Abrasive materials, Hard materials.

I do a LOT of low speed threading to a shoulder, Carbide has no advantage over HSS there.. A quick touch up with a stone, keeps the HSS razor sharp...

Thanks for the information. I didn't know I would still need to use belt changes AND back gears. I need to decide if this VFD would be better on a mill I plan on restoring or the lathe now???
Howard
 
Why not use the pulley that would give the highest rpm needed for a workpiece diameter or general speed range with the OEM motor? Adjust RPM downward as needed with the VFD to get the most turning torque from the lathe's gearbox/back gears within that range and take advantage of both. (btw: Check out Surplus Center for 3PH motor options.)
 
I have a 10" Sheldon that came with a 3/4 hp single phase Peerless motor from the factory. If you use the pulley system you can certainly use the 3/4 hp. I was dissatisfied with the vibration of the single phase and replaced it with a 1hp 3ph with an automation direct GS-1. The whole conversion delivered with tax was less than $265. I couldn't be happier with it and switching pulleys is no problem. In fact that is also how my Brideport M-head is set up (DC motor and step pulleys).

If you go with a bigger motor, you'll have to go with a bigger VFD. The price goes up geometrically once you get over 1 1/2 hp. For me economy is not just the initial cost but the cost of replacement. When the thing dies in the middle of a job, I would rather shell out $140 than $300-$400.

Best Regards,
Bob
 
I think I'll put the 3/4 HP motor I have, which is not the original, on the lathe and see how I like the VFD/motor combination. I can always go back to how it is now if I need to.
I'll use the new Magnatec motor instead of the original UNLESS I look at the original and see it is 1hp or larger. I still need to get it from storage. I know this old motor won't be inverter duty but as little as I use the machine I don't think I'll fry it.
I've never heard of a 3ph being chosen over single phase for vibration reasons???
Thanks
Howard
 
There's a ton of posts here on PM and elsewhere regarding the subject do a search for '3ph vs 1ph' or 'cogging'

Here's one example by one of the guys here who seems to be well respected:

...To all. Single phase motors have a distinct disadvangate in machinery where sources of vibration has an effecton the work performed. As Jerry pointed out single phase motor delivers mechanical power in 60 Hz surges. This surging are called "cogging" and can be compared to the repetitive lunging action felt in a roller coaster car as its pulled by the chain up the first slope.

Cogging has two components: that transmitted by the rhythmic armature torque and by the tortional vibration of the motor stator. The torque is transmitted to the spindle via the spindle drive mechanism and to the machine structure by the motor stator.

Cogging can affect finishes by relative motions of the machine elements where the tool meets the work.

The effects of cogging is not chatter. Chatter is a self-excited oscillation of the tool with the work where elesticity and mass forms a resonant system and a non-linear interaction of the tool with the work forms the excitation, much like a violin bow on a string.

Cogging in a lathe the tool may leave marks in the finish that look similar to the wavy grooves in a phonograph record and it called "phonographing" (not to be confused but the finish used for certain steam tight gasket surface preparations).

In a milling machine the finish may have a rhythmic interferance in the finish. In face milled finishes it looks something like a "moirre" pattern.

Adding: the machine gearing sometimes has an effect on the finish. This is often seen in spur gear driven shapers and large lathes when the light is right. This appearance is call "Telegraphing". So far as I know there's no finish condition called "Televising" or "Telephoning" but give it time.


[This message has been edited by Forrest Addy (edited 12-29-2003).]

Best Regards,
Bob
 








 
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