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Thread: spiral tool marks

  1. #1
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    spiral tool marks

    Working on a handle for my Thompson bowl gouge. I rough turned the handle, drilled the hole and put the cone center in the tailstock. The other end of the handle is chucked on a tenon.

    First, I saw a little smoke while boring the hole. Is this problematic or is a little smoke acceptable?

    Second, with both skew and gouge I am getting spiral toolmarks (see picture).

    Click image for larger version. 

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    I tried sharpening my skew but still had the marks. Are these marks a turning technique issue, a tool sharpening issue or just something to be sanded away?

    When I sharpened the skew, I freehanded it on the side of my half-speed 8" grinder. I had a heck of a time getting it burr-free. Might just be time to get my butt moving and put together a leather stropping pad for honing the skew. I'm open to suggestions for skew sharpening though.

    Thanks!

  2. #2
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    Slow you speed down on the drilling, I'd suggest no faster than 300 rpm, and back the bit out after about an inch, to clear the shavings.

    The spiral cutting is just you being too aggressive, you have to work at taking a fine finishing cut.

    It will happen, you just need the practice.

    I seldom sharpen my skew on the grinder, maybe once a year, I mostly do it on a diamond hone, but a good sharpening stone works just fine, at least a 600 grit for that final honing. A leather strop certainly speeds things up.

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

  3. #3
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    Mark,
    Don't take this as gospel, but I'm thinking you may be moving your tool too quickly along the handle... that's what it looks like to me... try moving your skew slower along the line of your cut and see if you don't get a smoother cut.

    I get those grooves from my bowl gouge if I get the angle wrong and go along my cut too quickly, so might be part of the problem.

    Stu beat me to the post... but he's in the middle to tomorrow already.
    Last edited by Chuck Ellis; 04-01-2009 at 01:03 AM.
    Chuck
    Tellico Plains, TN
    https://www.etsy.com/shop/TellicoTurnings
    My parents taught me to respect my elders, but it's getting harder and harder to find any.
    If you go looking for trouble, it will usually find you.

  4. #4
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    I did my boring at 500 rpm, the slowest speed that my lathe goes to. I was getting the toolmarks at 1800 rpm - should I also increase my speed now?

    I'll practice slower tool movement next time I get out to the shop. Took some drowsy medicine a little while ago, so it won't be tonight. I was taking nice light passes that were doing a good job at cleaning up tearout - that felt nice to see at least.

    Learned something else tonight - just because I now have a 9" tool rest doesn't mean I have to take 8" passes of the tool if my body only wants to move 6" before changing the angle of the tool. Also, I still need to pay attention to the ends of the tool rest - a 9" rest doesn't magically keep you from working right off the edge, it just doesn't happen as often as with the 6" rest.

    For whatever it is worth, I turn spindles left-handed (with my right hand on tool, left hand holding the handle tight against the old "turning muscle"). If I ever get to bowls and hollow forms I guess I'll need to switch hands.

  5. #5
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    How sharp is your smoking drill bit? That might be part of the cause.

    On the right hand vs. left hand stuff, I find I sometimes need to switch between the two, depending on where and what I'm trying to cut. I'm probably more ambidextrous with turning tools than anything else I do. When you start turning bowls and such, you'll likely find yourself switching back and forth some, too.
    When the going gets weird, the weird turn pro. - Hunter S. Thompson
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  6. #6
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    As said above, pull drill out often and push in only a little at a time. When using a drill by hand you are aware of how hard you are pushing it into the wood, with a lathe you perhaps don't realise the pressure you are putting on it.

    Spiral marks ar often accompanied by chatter. Practice taking very thin cuts. Don't be fooled into thinking you can jusat get ridd of them when you get them roughing out as they can be a righ pig to remove as I'm sure you have found out.

    Pete

  7. #7
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    End grain drillining/boring presents a different set of circumstances for your bit than cross grain, especially when going deep. As others have said, back out often to clear chips and allow cooling. I get smoke, or moisture vapors, almost everytime I end grain drill on the lathe. Your 500 rpm should be OK. Jest take yer time.
    As others have pointed out, the spiral thing is tekneek. One day the spirals will go away and you won't even know why.

  8. #8
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    Those spiral marks are from moving the tool too fast along the tool rest. Your tool has traveled the spacing between each cove for each revolution the spindle rotated. Tuck the tool to the side of your body and move your body as a whole. When each spiral are closer together to a point that you can't feel the valley of each spiral, you will feel it is smooth. Speeding up the lathe to your comfort level would help.

    The spirals from chattering look different. They don't stay even, usually they magnify in intensity.
    Gordon

  9. #9
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    Let's look at this from another angle. The spirial tool marks allow for a better grip on the handle. Think of them as a feature.



  10. #10
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    Quote Originally Posted by Frank Fusco View Post
    End grain drillining/boring presents a different set of circumstances for your bit than cross grain, especially when going deep. As others have said, back out often to clear chips and allow cooling. I get smoke, or moisture vapors, almost everytime I end grain drill on the lathe. Your 500 rpm should be OK. Jest take yer time.
    As others have pointed out, the spiral thing is tekneek. One day the spirals will go away and you won't even know why.
    My "quill travel" is only an inch and I think I'm feeding slow. Only so fast you can crank the wheel even if you wanted to feed the bit fast. I think eventually I should drop an air line near the lathe and blow out the hole periodically while boring.

    I hope I don't not know why if the spirals stop - with my luck I'll not remember how to not make spirals!

    Quote Originally Posted by Gordon Seto View Post
    Those spiral marks are from moving the tool too fast along the tool rest. Your tool has traveled the spacing between each cove for each revolution the spindle rotated. Tuck the tool to the side of your body and move your body as a whole. When each spiral are closer together to a point that you can't feel the valley of each spiral, you will feel it is smooth. Speeding up the lathe to your comfort level would help.

    The spirals from chattering look different. They don't stay even, usually they magnify in intensity.
    I was practicing moving my whole body with the tool. I'm making this handle with the Harbor Freight HSS set mostly, and am finding that those handles are just barely long enough for me to use properly set against my "turning muscle". I'm starting with 27" - 30" stock to get at least 24" handles for my Thompson gouges. Also, I'm hoping to get into the bigger handle "contest" at Five Barns sometime soon. Everyone knows what they say about turners that use big handles.

    Quote Originally Posted by Frank Townend View Post
    Let's look at this from another angle. The spirial tool marks allow for a better grip on the handle. Think of them as a feature.
    Right - and then, if I use the gouge as a self-centering drill for mini hollow forms like Molly Winton does, I can just use a loose grip on the spirals and the tool will self feed right into the blank - great idea Frank!

    In all seriousness, I'm using these handles not so much simply as constructing a utility device (where, really, these small marks will have no impact on usage) but more as an exercise of learning and training good technique at the beginning of my turning experience.

    Thanks for the advice so far!

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