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Speed?

skipd1

Cast Iron
Joined
Jan 6, 2010
Location
Bismarck, ND
I didn't really phrase my last thread as a question and I would like to know what the speed or RPM should be for the countershaft driving a 9" lathe??

Skip
 
The old 9 jr used a 255 rpm countershaft, later 9 inch workshop was a little faster, something like 290, IIRC. Some models had a two step countershaft pulley. I don't know what those speeds were.

allan
 
Aha! I was struggling to see what you were asking earlier!

Standard countershaft speed is 300RPM, but I have been struggling to decide how you work out the drive ratio for a V-flat drive (motor and pulley are not original). V drive is fine (based on diameter at the tension fibres), flat is fine (surface diameter) but the V-flat has me slightly confused.
Someone told me that it is the same as a V drive, which makes sense, since it depends on how far the belt moves at a given reference point - even though it grips in a different place on the flat. It is driven by the V so moves on by the circumference at the V-belt fibres each revolution (because thats where the V pulley grips the V belt) so the fraction of revolutions of the flat pulley is based on the diameter to the V belt fibres.

I think.

Only way to be sure is to use a tacho.

For the 12 speed versions with double pulleys on motor and countershaft, I don't know the answer but it should be easy enough to work out the factor between the 2 drives from the published speeds.
 
lathe speed

Thanks guys for the response. As I have the drive setup now with the 3 step countershaft running about 350rpm. I will use that for a start and use a tach on the lathe once its up and running. Got the drive almost fabbed out and when its running I'll have some pictures.

Skip
 
Skip,

I looked it up.

SB 1930 catalog Bltn # 9

counter shaft speed 300 rpm

spindle speeds 40, 75, 128, 246, 410, 700

Any faster on those plain bearings and you risk warm journals and premature bearing wear. You can go slower but not faster.

Ed S
 
If you run your wide bed 9 or early 11 inch SB faster than factory recommended speeds you run into vibration problems. I have seen several old SB lathes setup to double the spindle speed but unfortunately they wanted to run out of the shop. My friends 11 inch at 1000 rpm shook like crazy. I tried to run a early 0 series 9 Jr. at 1000 and it did not like it. Just something to keep in mind when you want to try and speed one of these old girls up.

With the very late 30's S and T series lathes you can get away with a higher spindle speed for several reasons. One they have a hardened and ground spindle and with the S series its a side oilier capillary oil feed system like the later workshop lathes. The T series also has a harder spindle than earlier models though its still a top oilier. Both of these series of lathes have a much better balanced rotating spindle assembly.

Turk
 
Thanks Dennis-
I certainly don't want to overclock this old girl, especially as the spindle bearings have a little grooving in them now(see my pictures). My countershaft with a 3-step pully is running now at 360RPM. I'll stay with that for a start and if its too fast I will put a larger pully on the countershaft and slow it down. I need a leather belt now. Do you have an recommended sources?

Skip
 
Counter shaft speeds vs. lathe speeds

I measured my 3-step cone pully and my 3-step pully on the counter shaft and as I now have it set up with the drive motor the lathe speeds work out at; 804,471,276 & 402,235,138

Do you think I should slow these down a little or are these okay??

Skip
 








 
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