pulley size, variable speed

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tmesker12
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Joined: Tue Jan 16, 2018 1:43 pm

pulley size, variable speed

Post by tmesker12 » Wed Jan 17, 2018 3:51 pm

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.

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GlennW
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Re: pulley size, variable speed

Post by GlennW » Wed Jan 17, 2018 4:24 pm

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!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

tmesker12
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Joined: Tue Jan 16, 2018 1:43 pm

Re: pulley size, variable speed

Post by tmesker12 » Wed Jan 17, 2018 6:19 pm

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
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Re: pulley size, variable speed

Post by John Hasler » Wed Jan 17, 2018 8:58 pm

> 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
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Re: pulley size, variable speed

Post by Inspector » Thu Jan 18, 2018 12:44 pm

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
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Joined: Tue Jan 16, 2018 1:43 pm

Re: pulley size, variable speed

Post by tmesker12 » Fri Jan 19, 2018 7:15 am

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.
Attachments
pulley.jpg

tmesker12
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Joined: Tue Jan 16, 2018 1:43 pm

Re: pulley size, variable speed

Post by tmesker12 » Fri Jan 19, 2018 7:21 am

And here is lathe
Attachments
20180117_131910.jpg

RMinMN
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Joined: Tue Jan 02, 2018 8:50 am

Re: pulley size, variable speed

Post by RMinMN » Fri Jan 19, 2018 7:34 am

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
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Re: pulley size, variable speed

Post by Russ Hanscom » Fri Jan 19, 2018 1:33 pm

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
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Joined: Tue Jan 16, 2018 1:43 pm

Re: pulley size, variable speed

Post by tmesker12 » Mon Jan 22, 2018 8:43 am

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

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