Hello all,

If this is the wrong section of this forum, I apologize.

I am currently building a lathe using 18" x 7.5" I beams.  The shaft is probably going to be 1 7/16" with a 8 TPI 1" thread.

I have been looking at various pulley combinations and leaning towards a 3HP Baldor motor that spins at 1725 RPM.   

So my question is this, is there a relatively in expensive way to put a variable speed controller on a 3HP single phase 220 V AC motor or am I stuck with trying to use step pulleys?

I would like to be able to run the RPM all the way down to 50-100 RPM  if possible.  Anyone converted a motor like this to a variable speed?  I don't know alot about electric motors but I believe that if a slow a single phase AC motor down, it will probably hinder it's ability to self cool correct?

Anyway, I am stuck with 110  or a 220 volt set up with single phase, so if anyone has any ideas how to get a 3HP motor (or so) that I can get a variable speed set up on it without breaking the bank, please let me know. 

Thanks in advance.

Brent

Brent

You are a candidate for a variable frequency drive.   That will allow you to drive a 3phase  220 volt motor from 220 volt single phase for a reasonable cost.

Constant torque drives are on the market but are costly.  Use of step shelves for 2 or 3 speed/torque adjustments is a common design choice.

Why not the 1 1/4 by 8 head stock thread?  Lots of heavy duty gear available and the  shaft is stronger.

Thanks for the tips guys.  I actually ended up picking up a 1.5 HP Baldor motor 110v for $75 in good working order.  So the motor problem is solved for now.  If I end up needing bigger I will swap it out. 

To start out with I'm going to use a 4 step pully on the motor shaft and two different wheels sizes on the spindle.  I calculated out all of the possible RPM combinations and I can get down to about 180 RPM and up to 1200 RPM or so.

Finally, I think I am going to go with a 2" spindle and put a 1.5" 8TPI thread on the end. I have found adapters that will go from 1.5" to 1", as well as a couple of  1.5" to 1.25" 8 TPI.  Might give me more flexiblity to use different chucks?  I have one 1" 8TPI chuck already.  Just wanting a little more beefy spindle that I can reduce to various chuck sizes.

You don't tell us what you'd like to turn on your lathe nor what centre height you're planning, but 1200 top speed is rather low if you want to turn pens, for example. The other way around, if you're planning 20" centre height and turning big bowls, 180 low speed is too high...

Worries about self-cooling motors at low speeds have never materialized for me on a lathe - the motor never runs at 100% power for a long time, you always start a new cut, sharpen your gouge, fiddle with the toolrest, stand back to look at the profile you're turning etc. so the motor never runs a long time at full power.

1 1/2x8 is the spindle size for many of the smaller metal lathes like South Bend, Logan, etc. Easy to find chucks and faceplates that will fit on ebay, Enco, or Grizzly.

Please tell us what you plan to turn, and where you are located.

Well, as a bowl turner, a couple of suggestions...

First the 1 1/2 hp Baldor is a good motor. However, you should run it on 220, especially if you are putting heavy loads on it, as you will do in bowl turning. Every book I read on setting up a wood shop said that any motor over 1 hp should run on 220. They just work better. Turning 30 inch pieces will put a strain on that small of a motor, no matter what your gearing is. If you plan on being a serious bowl turner, you will want  a 3 hp and 3 phase motor with the phase converter, so plan for being able to up grade in the future if it isn't in the budget for now.

As far as spindle size, 1 1/4 by 8 is the standard for bowl turning. If you want to reduce vibration, you can turn the larger headstock spindle down from heavier stock, like 2 inch or bigger. Bearing mounts on the spindle are every bit as important as spindle size. Over kill is recommended. Possible double bearings on the front. A longer spindle also makes for less vibration.

The farther away from the headstock the mount is, the more vibration you will have. Simply, a shorter lever will have less vibration, the longer ones will have more vibration. Adding thread adapters makes the lever longer, so it adds to vibration. One lever is the height of the spindle mount. Another is the width and length of the headstock. Having a properly made sliding headstock compared to a fixed headstock makes a difference too.

I don't believe that motor is set up for any real variable speed set ups without risking motor problems. For speed ranges, I would want down to 100 minimum, and up to 2000 or more for 6 inch bowls.

Are you going for a short bed lathe or a long bed lathe. For a dedicated short bed lathe, I wouldn't go for more than 2 foot long bed, so maybe a 1 foot long space for the motor mounting, and 2 feet of bed for the rest of the lathe to have your banjo and tool rests on. Tailstock really comes in handy for larger pieces and a more stable mount for unbalanced and large pieces. You may need a floor mount for your tool rest and banjo set up.

Look up the VB36 lathe. Monster bowl turning lathe...

robo hippy