Pulley alignment on a DIY lathe stand

[Doug Hobkirk]

The drive belt must reach from the left-most pulley to the right-most pulley, vice-versa, and all the positions in between. There are 4 pulleys on each shaft. I now understand that a "hollow tuber" lathe may not work well, but I've got it and I want to experiment. I would like to take advantage of your experience:



The belt that came with the lathe is short - I think I would need to make the motor mounting so it can slide right-left as well as closer-farther. If I use a long V-belt, the alignment won't probably be an issue?
If I mount the motor on a pivoting horizontal platform, will the weight of the motor probably be sufficient to provide tension? The motor is 1/2 HP.


Thanks.

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FYI - Yesterday I posted questions about an old lathe I bought at a garage sale - in the "General Woodworking and Power Tools" forum. My mistake - force of habit. Below is a copy of the gist of that post. I asked some questions about mounting plates where I incorrectly recalled that the bosses were not threaded. And I learned that hollow tube lathes can be troublesome. I learn. Eventually!
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I picked up a 1060's Craftsman 12" lathe at a garage sale, 54" wide, a set of little used gouges (?), a 1725 RPM 1/2 HP motor, a wide tool rest, and some miscellany. In that last category are two drive centers (one a spike, one a cup), two different sized mounting plates (?), one new buffing pad, a plate for sanding, and a package of sandpaper for it. The lathe is not mounted on a board. The motor is not mounted and makes some minor noise after 60 seconds - possibly I need to heed the plaque that says "Oil Every 10 Years." Or it needs brushes, or it's bad, or whatever. Everything, with the possible exception of the motor, seems to be unused or in good condition. Plus the manual, printed in 1964. $40. Looks like:
http://www.sawmillcreek.org/attachment.php?attachmentid=288355&d=1398803090&thumb=1 (http://www.sawmillcreek.org/attachment.php?attachmentid=288355&d=1398803090)

So I figured out what pulley grooves (4 on both the motor and the lathe) will produce what speed - 825 - 4100 RPM using a 1725 RPM motor. I worked out a design that will allow me to adjust belt tension by adjusting the motor mount (pivot or sliding, yet to be determined), which I plan to do below the lathe pulleys. Workshop space is limited and this seems like it will take less space. I doubt I will use it much, so I imagine 1/2 HP is adequate.

[Dennis Ford]

Using the motor weight is a common method of providing belt tension and will work for most 1/2 hp motors (especially the older heavy ones). 1/2 hp is about right for that machine. Use a flexible belt to reduce vibration (the link belts are good because they don't take a "set" between uses). I doubt that you will need the highest speed but you should make it fairly easy to change speeds between the 1st three.

[Harry Robinette]

If you have 2 4 step pulleys the belt will be the same. Small motor pulley to large lathe pulley will equal the same as large motor pulley to small lathe pulley, the main change is just the speed. You well need motor up and down adjustment for belt tension,easy way( bend a piece of all thread L shaped connect small leg to the bench under the motor plate,the long leg will connect to the motor plate with nuts on both sides of plate.Turn the nuts will raise and lower the motor plate). Cheap easy way to adjust the belt tension.
Hope this helps

[Dave Cullen]

I have a 1/2 hp motor on a hinged plate driving my DIY bench grinder and it works fine. The load on a lathe is a bit different though, and a 'catch' could cause the motor to jump.

A 4-step pulley on both shafts should match up groove to groove if they're the same design, you don't need adjustment in that axis. As already mentioned, the belt length required will be the same for each position, assuming the pulley diameters are the same but reversed on the shafts. If they're different, you will need the range of adjustment to cover for that.

[bernard feinerman]

I have a Craftsman monotube lathe and probably had it since it was sold. I also have a Sears Jackshaft mounted between the lathe motor and the lathe. The advantage of the jackshaft is that you can change the motor pulley and the driving pulley on the jackshaft so as to get additional speed ranges. With the right pulleys I have operated my lathe at speeds as low as 200 rpm which makes it possible to turn an unbalanced bowl to get it balanced so that you raise the speed up.

You can make your own jackshaft or look for the old Sears version. There are a few other changes that can make the lathe better but they may be more trouble than its worth. The lathe is handy for turning canes.

Bernie
288612288611

[Doug Hobkirk]

I have a Craftsman monotube lathe and probably had it since it was sold. I also have a Sears Jackshaft mounted between the lathe motor and the lathe. The advantage of the jackshaft is that you can change the motor pulley and the driving pulley on the jackshaft so as to get additional speed ranges. With the right pulleys I have operated my lathe at speeds as low as 200 rpm which makes it possible to turn an unbalanced bowl to get it balanced so that you raise the speed up.

You can make your own jackshaft or look for the old Sears version. There are a few other changes that can make the lathe better but they may be more trouble than its worth. The lathe is handy for turning canes.

Bernie
288612288611

Learning, learning...



A "jackshaft" is a shaft with more pulleys that is between the motor and the lathe - right?
And those pulleys must offer about a 4:1 relative size to each other if you can get your lathe turning at 200 RPM - right? (That seems like that would be a good option to have.)


FWIW, as I said earlier, I am a complete novice and I just had my first visit to the Turners' World.


When I asked about pulley alignment, I had expected that each motor pulley should be able to hook up with any of the different sized pulleys on the headstock. I now understand that belting each pulley to the one pulley it lines up with is sufficient.

In my case, that yields approximately 825 + 1200 + 2500 + 4,000 RPM (I did not measure the pulleys precisely and I've rounded the results).


It seems like almost all you guys are either into bowls or pens and stoppers. My interest (I think) is going to be spindles, tool handles, etc.

Which means I want SPEED! Dividing 6000-9000) by 2" diameter = 3,000-4500 RPM.



Babble, babble. At any rate, thanks for your help teaching me.

[Bill Boehme]

The speed that you calculated for turning spindles would be the absolute maximum safe speed, but not the best speed. The formula really is meant for face grain turning and approximating the maximum safe speed of larger diameter turnings. For your spindle turning, a top speed of 1500 RPM is sufficient for anything other than pens and thin finials. I would be more concerned about getting the lowest speed down to something reasonable --825 RPM is much too fast.

BTW, never, ever cross the drive belt out of the plane of the pulleys. You need to use a straightedge to make sure that each sheave lines up perfectly on each shaft. Otherwise, the belt will wear out quickly and might also wear out the pulley. It also reduces power transfer efficiency and invites slippage.

[Duane Meadows]

It seems like almost all you guys are either into bowls or pens and stoppers. My interest (I think) is going to be spindles, tool handles, etc.


Which means I want SPEED! Dividing 6000-9000) by 2" diameter = 3,000-4500 RPM.

[/LIST]

Babble, babble. At any rate, thanks for your help teaching me.

Hmm. 9000 - 6000 = 3000. 3000 divided by 2 = 1500, No?

4500 is MUCH faster than I'd want to turn anything wooden... even pens!

Oh I think I see where you getting that.. Seems something not quit right with that formula.

Wow! I see that is published several places. Still don't think it is good advice especially for spindles... if that were true, means I could turn slim line pens at what 22.5k? Yikes:confused:

[Doug Hobkirk]

The speed that you calculated for turning spindles would be the absolute maximum safe speed, but not the best speed. The formula really is meant for face grain turning and approximating the maximum safe speed of larger diameter turnings. For your spindle turning, a top speed of 1500 RPM is sufficient for anything other than pens and thin finials. I would be more concerned about getting the lowest speed down to something reasonable --825 RPM is much too fast.

BTW, never, ever cross the drive belt out of the plane of the pulleys. You need to use a straightedge to make sure that each sheave lines up perfectly on each shaft. Otherwise, the belt will wear out quickly and might also wear out the pulley. It also reduces power transfer efficiency and invites slippage.



So the "standard formula" I quoted is for maximum speed. Logical.
825 RPM is too high for a lathe's slowest speed. I had expected it would be slower - I've watched Norm Abrahms and a few others and the lathe often seems to be going quite slowly, like knocking the corners off square stock. I was surprised the pulleys didn't have a larger range of diameter.
Align the pulleys precisely. Good

[Doug Hobkirk]

Hmm. 9000 - 6000 = 3000. 3000 divided by 2 = 1500, No?

4500 is MUCH faster than I'd want to turn anything wooden... even pens!

Oh I think I see where you getting that.. Seems something not quit right with that formula.

Wow! I see that is published several places. Still don't think it is good advice especially for spindles... if that were true, means I could turn slim line pens at what 22.5k? Yikes:confused:

My very limited research found several sites that recommended a formula for a maximum lathe speed of 6000 (or 9000 - both were usually mentioned) should be divided by the number of inches of diameter of the workpiece. My example used 2x2 stock.

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NOTE: I am asking questions BEFORE I setup and start experimenting with the new lathe. I am quite sure the general recommendation of just about everyone who posted is "go slow!" When I actually start turning for the first time, I am very sure 825 RPM is going to seem very, very fast. I have grinders that turn at 3500 and 1750 RPM, and I would not want to be diving into something spinning that fast.

I will keep my eyes peeled for a way to install a jack-shaft - an intermediate shaft that would allow me to alter the effective ratios.