pulley size, variable speed

[tmesker12]

I am hoping for some info, or to be pushed in the right direction, to find a helpful topic I could not find by searching. I have an old Elgin (Hardinge) lathe, with a 1 hp, 115 volt motor, with step pulleys (6',7',8') connected via a counter shaft. I have been wanting to add a variable speed controller, but one of the step pulleys broke before I even did that. Seems pulleys this size are not readily available, so I am looking to modify my pulley set up and then run the lathe with the speed control. With the upper pulley still intact, what size pulley should be attached to the motor, I am assuming smaller so that my speed control gets the lathe to maximum rpm's when needed, but i am surely missing something..... I am a novice, know just enough to know nothing, but believe the variable speed control will allow me to learn how different metals and tools cut to help me learn. Looking for any and all comments, thanks.

[GlennW]

You will need to post the diameters of both step pulleys, the motor rpm, and the rpm range of the spindle in order to get any usable info.

Welcome to the group!

[tmesker12]

The motor pulley has 2" 6',7' and 8", the upper has 10,8,7,6. the motor rpm is 1725, not sure of the rpm range on spindle, will post pic when i figure that out.

[John Hasler]

> The motor pulley has 2" 6',7' and 8", the upper has 10,8,7,6.

This is not clear. Normally the motor would have a single small pulley driving a single large pulley on the counter shaft. The counter shaft would then have three pulleys opposite three complementary pulleys on the spindle. If you can give us the pitch diameters of all the pulleys we can compute the spindle speeds. Does the lathe have a back gear? If so what is the gear ratio?


We also need to know the maximum and minimum speeds that your new variable speed motor will be capable of.

[Inspector]

Is your motor a 3 phase motor? Or are you planing on replacing the existing motor with a 3 phase to go with the VFD (Variable Frequency Drive).

[tmesker12]

Good morning, let me back up a bit. After one of my step pulleys broke I had this idea of variable speed control, but its way over my pay grade just yet. My motor, mounted below the head, has a step pulley on it (that one is broken), it connects above to the counter shaft, to another step pulley. The sizes listed above are correct, the counter shaft has a 3" pulley that connects to the spindle. No back gear. The lathe worked great like this till the pulley broke, so my goal now is to simple get it back together like it was, variable speed control is not necessary yet. So to switch gears, can anyone help me source a step pulley of this size, I had no luck online or reaching out to manufacturers. 5/8 arbor, 2",6',7',8' pulleys, with 2" closet to motor. You guys are an invaluable resource, thanks for your input.

[tmesker12]

And here is lathe

[RMinMN]

Those step pulleys are available in several places if you use the correct search term. Try a Google search with the term "step sheave 5/8 bore" and you will get several choices for them.

[Russ Hanscom]

Also look at hubless pulleys - it is possible to stack several single groove pulleys to make a custom stepped one, or use a three grove for the large part and add the smaller single groove to make what you want.

Of course, that is all much easier with a working lathe!

[tmesker12]

Words are important! Sheave got me a lot closer to where I need to be, thanks!