RPM's

[Jerry Marcantel]

Hi folks, I'm building a stand for a Boice Crane lathe I recently aquired. The stand will be made from my old lumber racks that I had made using 1/4" x 3" x 4" rectangular steel when I was self employed. Instead of rusting in my yard, I've decided to turn them into something of importance.
I'm using a variable speed 2hp treadmill motor that runs from 0- 3210 RPM if both the motor and headstock pulleys are the same size. I'm not sure, but I think thats too high, so if I get a 3" pulley for the headstock, that would decrease my maximum RPM's down to 2140 rpm..... Does that sound more like the maximum speed that I should run at, or should I use the same size pulleys?
I want to turn mostly local mesquite from all around Tucson... It's all old stuff, drier and harder than some of the woods I hear you guys talking about, so starting at 0 rpm and creeping up til I can balance the wood sounds better than throwing a switch and reaching 4-500 rpm instantly... can someone please help with the rpm question.Thanks in advance..... Jerry (in Tucson)

[bob svoboda]

My first lathe would only slow to about 500 RPM. A large out of round blank would make it dance across the floor-way too fast!. About the only time I exceed 2000 RPM is when I do small spindle work-pens, goblet stems and the like. Hope this helps.

[Wally Dickerman]

Hi Jerry...With a 2 hp motor you have plenty of power, so either top speed should work. You'll be turning at whatever speed is comfortable for you. If you think that you may get into pen turning or other small turnings, then the higher speed would be more suitable. I turn pens and finials at around 3000 rpm.

I'm curious about your old lathe. What is the capacity?

You indicate that you live in or around Tucson. I live in Green Valley, south of Tucson.

Wally

[Frank Van Atta]

I turn a lot of Mesquite. Small to medium pieces at 1500, larger pieces and those with a lot of "air" (winged bowls and the like) I creep up to the highest possible "stable" speed, usually starting around 200 and increasing as the piece gets smaller and more balanced.

[Bernie Weishapl]

If you can go to zero I sure wouldn't worry about the high end. Don't worry about another pulley. My top end on one lathe is 3250 and around 4000 on the other. I turn a lot of pens and spindles at 3000 to 4000 rpm. Also I make it a note when I quit for the night to turn my pot down to zero rpm so the next time I start if I forget it will be ok.

[Edward Bartimmo]

Jerry,

The size of the pieces of wood and its shape are the major issues for how slow you should turn, both for starting to rough turn and finished turning. A small piece that is out of round (unbalanced) will have less centripital force (make the lathe dance) then a larger piece. Your ability to pre-cut / shape the wood using a bandsaw or chainsaw in advance of mounting the wood to the lathe will reduce the inbalance allowing you to start at higher RPM's.

With larger pieces you really aren't going to be above 1000 rpms during turning...sanding still won't jump that much higher. All of the following discussion is caviated on your comfort level, which is based on you skill, equipment, and wood to be turned. Depending upon how out of round (unbalanced) the piece is you will most likely start somewhere in the 100 - 500 range to rough turn the piece. Once you have balanced the piece (rough turned it circular) you will most likely be turning somewhere in the 600 - 800 rpm range. The higher RPM's become less of an issue when turning small pieces and spindle work.

In addition to the size of the piece and ability to balance it, the type of wood (wood density and internal grain characteristics) will also play a big part in RPM. I have turned some very hard mesquite that threw sparks as I turned it .... I turned at lower RPM's to rduce the chatter. Also, if you are going to turn any wood that has inclusions (gaps, holes, cracks, etc) or irregular grain (aka mesquite root ball or burl) then you will also turn at lower RPM's to reduce impact of a catch until it is rounded.

These characteristics combine to form what I call the "Pucker" factor. How fast is ultimately determined by how safe you feel that the wood will stay on the lathe, your tools will stay in your hand, and you won't need to visit the hospital. If you feel the need to ask someone to periodically come in an check on you then you should either turn really slowly or simply pass on the piece and use it to cook a nice steak.

Hope this helps

[Jerry Marcantel]

So Wally, you have that Green Valley grin yet??....hehehehe I live off Valencia and Mark Road, about 6 miles west of I-19....The lathe has a 16" swing, and 56" between centers. It didn't have a faceplate nor centers, but it has a MT #2, and I can use the centers from my other lathe, which is a piece of junk. Had it since '82, and have only done a few things with it. I have a friend that has a mill and lathe in his welding shop, so I'll make my own faceplate, and those carbide tipped tools. Email me at gmwoodworking78@msn.com.