PDA

View Full Version : Lathe speed

skipd1
08-25-2011, 06:10 PM
I am building an overhead drive system for my 1930 9" lathe. I thought I read somewhere that the proper speed for the countershaft with the step pullys should be around 300 rpm. I have mine setup with a 2 1/2" motor pully driveing a 12" countershaft pully. The motor is 1725rpm reversable capacitor start single phase and should give about 340rpm by my calculations. As I get a little further along I will have some pictures.

Skip

SGW
08-25-2011, 09:34 PM
I thought about doing that at one point, as a way of isolating the motor and countershaft vibration from the lathe. I'll be interested to see your pictures.

skipd1
08-26-2011, 10:46 AM
I am building an overhead drive system for my 1930 9" lathe. I thought I read somewhere that the proper speed for the countershaft with the step pullys should be around 300 rpm. I have mine setup with a 2 1/2" motor pully driveing a 12" countershaft pully. The motor is 1725rpm reversable capacitor start single phase and should give about 340rpm by my calculations. As I get a little further along I will have some pictures.

Skip

Actually I didn't really word my thread correctly as I am asking is this speed is correct??? Or what is the correct speed for the countershaft??

Skip

Scottike
08-26-2011, 11:50 AM
I think your looking at this from the wrong direction.
What is the the lowest and highest speed range you want your lathe to operate at ?
Use that to determine the pulley size & desired rpm of your ceiling mounted countershaft at the lathe end,
And then use that to determine the pulley sizes at the Jackshaft/ motor end.
Machinery's Handbook States that the maximum speed for a flat belt drive to be 6000 fpm, so you need to stay below that, If it were me, I'd shoot for about 1/2 that or less.

SGW
08-26-2011, 11:55 AM
Even more to the point, what is the highest speed the lathe is designed to run at? My 10K with essentially the same bearing technology has a top speed of 1475 rpm.
Lowest speed with backgear etc. is 60 rpm.

RussZHC
08-26-2011, 07:01 PM
Don't know if this info will be of use to you...

I converted my late 1930s 10" Sheldon from horizontal to a home brewed overhead version [sorry, no pics posted yet] and isolated motor from lathe as much as possible. Bronze "shell" bearings.

Stock was 2.5" to 10" pulley (at the counter shaft), with a 1725 rpm motor this yields 431 rpm of the shaft.
When the two cone pulleys are taken into account, the speeds became 819 rpm, 431 rpm, 226 rpm [4.75" and 2.5"; 3.5" and 3.5"; 4.75" and 2.5"].
Once refurbed I took slightly more exact measurements, of what I hope is the "effective" diameter of the initial train pulleys, those are 2.75" and 9.75" [the 10" original is still in use but more accurate measurement gets to 9.75"]
This means speeds become 924 rpm, 486 rpm, 255 rpm.

I can't give exact speeds in back gear now...that's part of the plan towards completion for tomorrow :rolleyes: