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Line shaft speed

M

Megar arc 5040dd

Super User
I am finally after years getting the the end of restoring my big old lathe from the late 1800's but I have run into a choice that I am not sure what to do. This lathe used to be run off of a line shaft and then someone made a very crude electric motor conversion. I redid the motor mound and am finishing up the new and now straight counter shaft but I am not sure what speed it should run at. For context this is a flat belt about 2 inches wide, the lathe is 16 inch swing with plain bearings that off the top of my head I would say are about 3 inches wide. The plain bearings are in absolutely beautiful shape and are made out of brass or possibly bronze but they look like brass to me. So my question is how fast should I spin the counter shaft? I don't know how fast a line shaft used to spin and really have know way of knowing if there was a speed reduction or increase from the line shaft the the original counter shaft. I want to be able to spin the lathe fast enough to be usable but not so fast that i risk damaging the headstock plain bearings. I am open to all suggestions.
 
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The back gear shaft is removed right now while I am working on the counter shaft to give me a little more room to work.

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Sadly the 12 inch 4 jaw chuck is really bell mouthed so if any one has some good ideas to fix that or knows where I can get a good one for cheap please let me know.

There are still a few things I want to do to this machine but they can wait until after it is up and going. I did make some chips with it last year but there was a ton of chatter and that was when I realized the counter shaft had some wobble to it. Right now it has a 5hp motor that is 3400 rpm. Way faster than I would like but its what I have so I added a jack shaft in between the motor and the counter shaft to reduce the speed. I know that the shafts are to close together for the V belt to get an ideal bite on the pulleys but the little bit of testing I did with it seemed to work just fine. After all this is for hobby use I don't need to be able to take a .250" depth of cut or anything crazy.
 
The 4J looks like a “Union” chuck. The jaws probably are not very hard, you could simply machine them. The trick will be to make up a loading ring for the jaws (couple options there).
 
Megar arc 5040dd said:
So my question is how fast should I spin the counter shaft? I don't know how fast a line shaft used to spin and really have know way of knowing if there was a speed reduction or increase from the line shaft the the original counter shaft. I want to be able to spin the lathe fast enough to be usable but not so fast that i risk damaging the headstock plain bearings. I am open to all suggestions.
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Your lathe looks quite similar to my old FE Reed 1880s lathe. I don't know what speed the input runs at. But I can probably measure it for you. It is driven by a small 120V motor. It's been running like that for at least 40 years and probably 40 years before that. So whatever it is, I can at least say that it works.

Also, I was once told that 540 rpm was the standard belt drive speed back in the day and that is why most PTOs run at 540 rpm today. I have nothing to back that up with other than it makes some sense given that early tractors actually had a side drive to turn the main belt in a machine shed. That's how the machine shed on the farm where I was born was driven. Not many folks are still alive to remember those days.
 
Susquatch said:
That's how the machine shed on the farm where I was born was driven. Not many folks are still alive to remember those days.
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Well I don't remember them running the machine shed but that makes sense. I thought they were just used to run a threshing machine. I'm only old enough to remember running the old tractors with the drive pulley, not actually using the drive pulley. I think the Johnny popper tractors that I used to run with the separate start up engine are still sitting in the neighbors yard. I wouldn't be surprised if it didn't take much to get them going again.
 
Megar arc 5040dd said:
So my question is how fast should I spin the counter shaft? I don't know how fast a line shaft used to spin and really have know way of knowing if there was a speed reduction or increase from the line shaft the the original counter shaft.
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I had a chance to measure my input shaft speed. It is 320 rpm +/- about 7 rpm. It bounces around a fair bit due to the flat belt joint and the flimsy motor mounts.

In so doing, I noticed that my pulley steps are not uniform. The input (drive) pulleys are slightly bigger than the outputs (driven) on the lathe. This implies a speed increase vs standard same-size pullies. There are 3 steps. From fastest to slowest, the diameters are drive:driven 7.5:2.75, 6:4.25 & 4.5:5.75 (all in inches of diameter). Mine more or less lived on the fastest speed for the time I owned it. I didn't do much large diameter work until I got the new gear head lathe.

I would again emphasize that this is what I measured them to be as it sits now. However, it may or may not be the original speeds. It is highly unlikely that it had an electric motor when it was built in the 1880s. But it has worked that way for me for 40 years, prolly worked like that for the guy before me for 40 years, and who knows how many before that for other even older machinists. The lathe is around 140 years old. It has probably worked at the speeds I measured for 80 years or more. And it did some pretty darn good work for me during the 40 years that I used it.
 
I have been looking for possible line shaft speeds, nothing so far. As Susquatch said, most tractors have a 540 PTO/ drive pulley on them, so this maybe a good starting point. Another point he made was that his old lathe is running at 320 rpm,and has been for a great number of years, most likely also has plain bearings like yours. The larger the shaft in those plain bearings the slower it should turn, surface speeds, and lubeing by gravity oiling, being big factors. And something we don't think about/realize was that high carbon steel was in wide use as cutting tools into the 1940s and later some places. This meant lower speeds by at least 1/3 compared to high speed steel cutting speeds, possibly even slower, almost like comparing carbide to high speed steel.
140mower also stated he is running a line shaft speed of 240 rpm, starting to seem like a good ball park speed. 240-320 rpm, can always go faster if the bearings seem to be holding up O.K. That would be my main concern, plus lubeing the thrust part of the bearing under high speed/heavier cuts.
Anyway, my 5 cents worth as we don't have pennies any more. LOL.
 
Have found one mention of line shaft speed in a South Bend note, powering line shaft with a 2hp motor at1750 rpm, turning line shaft at 250 rpm, turning counter shaft at 255 rpm for a 9in lathe, 13in at 250 rpm, 15in at 225 rpm, 18in at 167 rpm. Note again these speeds are at counter shaft, speeds of lathe were varied from pulleys on lathe head stock to counter shaft pulleys.
I think these are all plain bearings here, line shaft, counter shaft, and lathe. Maybe even hard wood blocks on line shaft bearings. Yes, life was simpler. Just different ways to get hurt.
 
Ok so I have some updates both on what I have found out and what I have done. I started looking in some of my books and in Lathe Design Construction and Operation, With Practical Examples of the Lathe Work (1919) there is a page where the author mentions what he believes the SFM should be at the max of the lathe swing when in the slowest back gear. From that I kind of work backwards with trial and error. For a 16 inch lathe the book says the SFM of a 16 inch face plate should be 90 SFM. The author mentions these speeds are for high speed steel tools. I am not sure if it is ok to post a picture of the page of the book it is a reprint that they scanned the original pages and printed them. The only copyright I see is the original one of in the scans.

This is what I have. The counter shaft is currently at about 300 - 340 ish RPM (was hard to get an exact reading). My slowest speed in Back gear is 19 RPM giving me 79 SFM so a bit slower than the book says. My fastest speed is 685 RPM. The SFM of the spindle in the brass bearings is 305 SFM at the outside bearing (the left side) and 358 SFM at the chuck side bearing (right side). The left side of the spindle has a shaft diameter of 1.7" and the right side (chuck side) has a diameter of 2". Both bearing are about 3 inches long the left side is a tad shorter. All that being said I don't know if that is to fast for those bearings or if I could still go faster. 19 rpm is really slow and I can't imagine ever needing it to be that slow.

The bearing aren't as quite as good as I thought they were but it has been at least a year since I looked at them last. But they are still pretty good given that this lathe is between 100 and 140 years old.

My other question is how much end play should there be in the spindle when set correctly? the nob on the end of the spindle has a threaded piece in it that pushes on a thrust washer against the end of the spindle. The thrust washer as a notch in the outside that fits over a key so it cant spin.

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Megar arc 5040dd said:
I'm not yet sure how I am going to fix those. That gear is part of the cone pulleys and I don't yet know how to cut gear teeth to a shoulder. It seems to run ok in back gear without those teeth.
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Mine lost a few teeth in a fight with a previous owner before I got it and it works ok too.
 
It's alive :D. Made my first test cuts and so far it works great. With one exception the slowest feed on the power feed is .005" per revolution. That's almost twice the feed I have my atlas set at. With the feed engaged i got an absolutely horrendous finish. It looks like a beaver tried to chew it to size. I was using a very sharp to with almost no radius on it. would a large nose radius on the tool help with faster feed? How did they use a lathe 100 years ago with this fast of a feed? I can't imagine people hand cranked it for anything that wasn't a roughing cut. Especially on something longer than a couple inches? I am going to have to solve this problem or I will never be able to move out of my atlas lathe into a big boy lathe. I'm sure I am the problem so any advice would be nice.
 
Megar arc 5040dd said:
It's alive :D. Made my first test cuts and so far it works great. With one exception the slowest feed on the power feed is .005" per revolution. That's almost twice the feed I have my atlas set at. With the feed engaged i got an absolutely horrendous finish. It looks like a beaver tried to chew it to size. I was using a very sharp to with almost no radius on it. would a large nose radius on the tool help with faster feed? How did they use a lathe 100 years ago with this fast of a feed? I can't imagine people hand cranked it for anything that wasn't a roughing cut. Especially on something longer than a couple inches? I am going to have to solve this problem or I will never be able to move out of my atlas lathe into a big boy lathe. I'm sure I am the problem so any advice would be nice.
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Larger radius would help but that also carries the price of more tool pressure. May not be an issue for the machine.
 
Megar arc 5040dd said:
With the feed engaged i got an absolutely horrendous finish. It looks like a beaver tried to chew it to size. I was using a very sharp to with almost no radius on it. would a large nose radius on the tool help with faster feed?
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Ya, the lathe can handle a bigger radius on the tool tip just fine.

Don't know what you are cutting, but keep in mind that exotic metals were not as common back then.

The feed rate is keyed to the spindle so the only way to reduce it is with your change gears. Do you have a full set?
 
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