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Thread: Wood Turning RPM Question

  1. #1

    Wood Turning RPM Question

    What speeds do you normally turn hardwood? I might have to turn some wood here in the near future (cocobola) and this is what I have for choices. I normally run at 360 rpm with a .0019 chip per revolution with stainless steel, but I can take as much as a .0049 chip at any speed on either the carriage feed or cross feed.

    At the same time, what should I use for cutting inserts, carbide or high speed steel? And should that insert be lined up with the centerline of the stock, or should it be higher or lower for wood? And if so, by how much?

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    Last edited by Travis Johnson; 03-13-2008 at 09:46 AM.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  2. #2
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    There are several schools of though on lathe speed, but the recommended RPM varies, depending on the diameter of the turned piece. The real issue is surface speed. Here's one guy's recommended speeds:

    http://www.draigsffau.org/Interests/...theSpeeds.html

    And here's another write-up by Dale Nish. This set of guidelines is probably the most common one I've seen recommended:

    http://www.ssusers.org/files/JOB-AID...atheSpeeds.pdf

    If the speeds you were listing are your lathe speed, then chances are you're looking at either 760 or 980 RPM, unless you're spinning something pretty big.

    Given a choice of cutters, I'd take the carbide. I have a few carbide lathe tools, and they're the bomb. Oh, and the cutter should be at or near the centerline. I find that I adjust up and down a bit, depending on the tool I'm using, and the type of cut I'm doing. If you're doing it with a carriage, shoot for the centerline to start. As far as the depth of cut, that will really depend on the wood. I'd suggest just monkeying around with it until you get a cut you're happy with. Too deep, and you'll start getting tearout. Too shallow, and you'll be there all night.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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  3. #3
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    Thanks for the question Travis. And thanks for the links Vaughn.
    I was wondering about that my self.

  4. #4
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    "What speeds do you normally turn hardwood?"

    600 RPM. Can't go any slower with me lathe!

    "I normally run at 360 rpm with a .0019 chip per revolution with stainless steel,"

    I normally just kind of lean into it, and hope...

    "At the same time, what should I use for cutting inserts, carbide or high speed steel?"

    I say, go with the carbide. I use HSS, and you'll want better results than I get! Trust me on that one...

    Kidding aside, If you're turning spindles, you want to be over 1000, for sure...

    Thanks,

    Bill

  5. #5
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    Travis, your desire for precision is understandable, you being a machinist and all, but wood turning is a whole different animal, forget your very precise measurements and such, they don't count here

    Now if you have a lathe that is not variable speed, then you are locked into certain spindle speed, but if you do have a variable speed lathe, you just adjust it up and down until it is spinning as fast as it can be with out excessive vibration. I used to look at the RPM display all the time on my lathe, but now, I basically run it up until things start to vibrate, then back it off until the smooth out. While working one something like a hollow form, or a winged bowl, it is entirely possible that the balance of the piece will require a speed adjustment up or down as you turn it, as wood is removed from one spot, the balance changes. Turning wood is more of a "seat of the pants" kind of thing than turning steel etc.

    Hope this helps!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  6. #6
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    I'm not sure if carbide will work that well. As you know, most carbide tooling has an edge radius because it's quite brittle. I don't know how well it will hold up if you sharpen it too a razor edge. Many of the wood lathe tools are made from HSS. so i'm sure they would work. Scrapers do their cutting with the burr left when you grind them on a pedestal grinder. It willl be rather slow going on a metal working lathe useing the the feed mechanisms. You could probably take a heavy cut. You might pick up a wood turning video to get a general idea of how the different tools are used.

  7. #7
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    Paul, carbide works well cut like a scraper. It seems to have a finer burr, but it holds up well. Then there's the Hunter tool...I don't know how I'd describe the shape of the cutter, but it's more of a knife edge.

    You raise a valid point, though. The typical carbide cutters used on a metal lathe might not cut wood well at all.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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  8. #8
    Wow, 1000 rpm, now this is spinning. I once chucked up a long piece of 3/4 inch stainless solid round into the lathe and cranked it up to 700 rpm to get a super smooth finish. Anyway I was just starting to get the lathe wound up when the solid round whipped around so much that I thought the thing was going to hand grenade on me. Now I am much more timid on speeds over 360 rpm. (Of course for long pieces I could always go get the hydraulic steady rest, but that is crazy talk right there)

    As for the high speed steel, or carbide inserts, I am not sure which one would work better. Cocobola is pretty hard wood so I assumed carbide would work better. We have had good luck with Veletine solid Carbide Inserts with a radius for cutting stainless steel, a metal that tears more then shears. I have used it on plastic (delrin) and it does work, but a bear to get a nice finish on. How well it works on wood is yet to be determined.

    The approach angle will be 95 if I use carbide, but only 90 if I use a a high speed steel blank. I suppose I could grind my own cutting edges to a different angle if the approach angle would make a huge difference, or adjust the tool holder in relation to the centerline of the spindle? The problem with that is, you would have to offset the tail stock off of centerline to cut a straight cut along the axis of the spindle. Not a big deal, but it would involve a bunch of guess work.

    Maybe by the time I am all done, I would just be better off chucking this wood up into my Craftsman lathe, as crappy as it is, and making my spindles on that? The problem with that lathe is, it does not have a four jaw chuck, nor does it allow stock to put pushed through the headstock, which together kind of limits what I can do on it. Oh that and it only has three speeds. It doesn't have a carriage either which means I would actually have to do something while the machine spins. I guess I got used to making set-ups, then pulling the carriage feed quill and watching the machine do all the work for the next twenty minutes.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  9. #9
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    Travis, I regularally turn bowls at around 1500 rpm, 1000 rpm is not that fast when doing things like finishing cuts, when the bowl is nicely balanced.

    On spindle turning, I turn at 1500 to 2000 rpm all the time
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  10. #10
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    Quote Originally Posted by Stuart Ablett View Post
    Travis, I regularally turn bowls at around 1500 rpm, 1000 rpm is not that fast when doing things like finishing cuts, when the bowl is nicely balanced.

    On spindle turning, I turn at 1500 to 2000 rpm all the time
    Just for contrast, I seldom turn bowls faster than about 800 rpm. I finish turned a 17" to 18" natural edge bowl tonight and I don't think I exceeded 500 rpm. (Like you, I don't watch the numbers on the control panel, I just set it for what feels comfortable...usually a fair amount below the vibration stage.) Granted, you've watched and learned from some top-notch turners in person, and I'd guess they turn faster than I tend to also. I suspect as my experience increases so will the speed, but I'll always have my brother-in-law's voice in the back of my head, telling me about the time he took a bad hit in the head from a piece that came off a lathe in high school shop class. He was in the hospital for three days as the result of the concussion.

    On the few pens I've done so far on the PM, I've been in the 1000 to 1200 rpm range. I could have gone higher, but I was too lazy to move the belt on the PM. (It takes all of about 5 seconds.) On the Craftsman, I used to run it pretty much full out on pens and bottle stoppers...about 2000 rpm. I've got to do some more pens tomorrow night, so I'll probably try the PM in the high range for the first time.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
    When the weird get going, they start their own forum. - Vaughn McMillan

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