Newbie lathe speed question

[Ray Phillips]

High guys, I am a newbie when it comes to turning wood. I have a question concerning lathe speed. I have turned several pens but I have not turned any bowls and I am in the process of watching videos and reading especially the threads on this forum to learn to turn bowls. I have a Jet mini lathe that tells me the speeds in the different belt positions. I had the oppurtunity awhile back to buy an old Delta Rockwell 46-200 12x36 lathe.for $75.00. It had no motor. I found a used motor for $35.00 and it seems to do fine. The pully is a four step pully and my question is does anyone know the approximate speeds of the lathe in the different belt positions? I have looked on the OWWM site but I could find nothing about the different speeds. Thanks in advance for any help.

[Scott Conners]

A little info and a little math will get us the answers.
First, we need to know the speed of the motor. It should be on the motor plate, and it should be either 1725 rpm or 3145 rpm, or rounded similarly.
Then you need to measure the diameter of the pulleys. Typically you'd have a step pulley on both drive shaft and spindle, giving you four widely ranged speeds. Remember, you want your belt to track as straight as possible. Misalignment will lead to premature wear on the belt and pulley.
Then, using the formula D1/D2 = S2/S1, where
D1 = diameter of the pulley on the drive shaft
D2 = the diameter of the pulley on the spindle
S1 = the drive speed
S2 = the spindle speed
we can find the spindle speed when using any given two pulleys.

Solving for S2 gives us an equation to put numbers into: S2=(D1*S1)/D2.

That means if we have a 1" drive pulley, a 3" spindle pulley, and a motor that spins at 1725 rpm, we'd use (1*1725)/3=575 rpm.

I hope that's clear enough, if you need help just get the motor speed and measurements and we'll give you the speeds =)

[Ray Phillips]

Thank you Scott. I will get that information when I get home from work. Work always gets in my way. Guess I should be thankful for work in these economic hard times.

[Dave Ogren]

Ray,

The dia. of the pulleys to get the correct number, are the pitch dia. not the outside dia. The pitch is about in the center of where the belt rides. Best of luck and happy turning.

Dave Ogren

[hank dekeyser]

Do a google search for "pulley speed calculator" Thers many available that allow you to input the motor speed and pulley diameters. Some allow you to input the desired speed and calculate the pulley size needed to achieve it.

[Cliff Rohrabacher]

I just go as fast as I dare.
It's usually a sense of feel that I get from the cut the balance and the weight of the thing being turned.

Faster speeds give me better cuts. Too fast gives me objects flying around the shop.

[Ray Phillips]

I now have obtained the numbers to fill in the formula. The speeds on my lathe is 493,1006,1821 and 3450 according to my calculations of the formula provided by Scott. Again, thank you Scott.

[Scott Conners]

You're most welcome Ray.
That's a good useable range for that lathe, it should work just fine!

[Bob Hallowell]

I used this calculator to figure out the size of pulley I needed on my lathe

http://www.gizmology.net/pulleysbelts.htm

[Ray Phillips]

Thanks to all who responded to my question. This is the reason I contribute to the Creek. Everyone seems to enjoy giving advice and good information to those who are woodworking challeged. Anyone ever feel like a 62 year old first grader like me. I have learned a lot from lurking on the forum and one of these days I will pass to the second grade. One has to start some where. I look forward to learning more and becoming a wood turner. I have a lathe and wood and now I need to get some learnon. Again thanks guys for the help.