Stupid Turner Tricks -- Stopping the lathe with your hand

Discussion in 'Woodturning Health & Safety' started by Bill Boehme, May 7, 2013.

  1. Bill Weaver

    Bill Weaver

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    Okay
    So we don't stop a spinning piece on a rotating machine, I get that. Question what is a fellow supposed to do when hand sanding a turning bowl inside with his hand.:eek:
    Do we go buy a tool that does that for us? Do we wear a glove and take a chance there will be no catch.
    I think we can all say we have hand sanded a turning while spinning.:)
    Odie you welcome to chime in here with one of your gadgets.
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    First, of all, you need to know whether it is safe to hand sand with the lathe running. Here are some guidelines:

    • If you are unsure then that is a good reason to at least learn more before proceeding.
    • If you would have to stick your hand in a hole then don't do it. One very real danger is the sandpaper/screen grabbing and winding your hand up before you can react. Only a fool thinks that his reaction time is sufficient to avoid such a catastrophe. DAMHIKT
    • If there are imperfections such as gaps, holes, bark inclusions or other irregularities, they pose as much if not more danger than the previous situation.
    • Don't hand sand a natural edge piece on the lathe. Besides rounding over the crisp edges, you are likely to have an encounter of the type that I described in the opening post of this thread.
    • Hand sand with light pressure and the direction of sanding trailing away from you and allow the paper to slip out of your grip if the force is too great. Never sand so that your fingers are being pushed towards you.
    • Avoid working with your fingers at the center where there can be a sudden reversal of forces.
    • Don't do anything that I would not do as well as a few things that I have done. :D In other words, have your "DON'T DO THIS" alarm system activated. If it is out of order then don't do any hand sanding with the lathe running.
    I do the great majority of my sanding with the piece OFF the lathe and using my Armstrong® sander in combination with elbow grease. I have a large collection of power and inertia sanders that I rarely use.

    There is no acceptable reason for wearing a glove while sanding. If you think that it is to protect your hand then you ought not be doing whatever it is that you feel the need for a glove while sanding. Some folks wear a glove while turning to protect themselves from hot shavings and pieces of bark. There is however a huge difference -- they are not sticking their hands someplace where they should not be. A glove will not save you from winding up your hand and probably will increase the risk of that sort of thing.

    My suggestion is to get a stack of sandpaper and a comfortable chair on your back porch and spend some time getting a superior sanded surface. The side benefit will be an incentive to get a better surface with your turning tools.

    ps -- I do have and use the Velcro® and leather Sanding Glove® from Bruce Hover. Please note that it is not meant to be used with the lathe running.
     
    Last edited: May 18, 2013
  3. Mark Mandell

    Mark Mandell

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    Sanding & Gloves

    Since it's been raised . . .

    If you are using a glove while sanding a rotating form (inside, outside, whatever) it's a primary indication that your sanding technique is in need of work. If the paper is getting warm to the point that you want a glove to hold it, you are using far too much pressure and defeating the idea. That much heat starts melting/fusing the resins in the wood which in turn clog your paper and defeats your effort. Lighten up and allow the abrasive to do its job. Not cutting well/fast enough? Move to a courser grit.

    You'll save a whole bunch of time and abrasives as your paper will cut better and last much longer.
     
  4. MichaelMouse

    MichaelMouse

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    Best answer, don't sand by hand. Go power and rotary. Think about it. When you rotate the piece to sand by hand, you're making scratches in the same direction as any tool marks. They will be there forever - or at least it will seem like it. What you really want to do is sand across them so they can be reduced quickly to a smooth surface. So stop the piece and sand along the grain, or put the mechanical fingers in there instead. Sanding along the grain by hand is the way you'll want to finish, anyway. That way the scratches can't be distinguished from the grain of the wood.

    http://s35.photobucket.com/user/GoodOnesGone/media/150Sand-1.mp4.html
    My method. Supporting the sanding mandrel on the tool rest as if it were any of the other cutting tools you just used will even allow you to sand irregular edge pieces under power without roundover.
     
  5. Betty Scarpino

    Betty Scarpino

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    I hand sand all the time because many of my bowls are small and have intricate details or shapes that don't lend themselves to power sanders. For larger bowls or platters with simple curves, power sanding is the way to go.

    I would add to Bill's list as a major priority: decrease the speed of your lathe when hand sanding. Slower speeds are safer and hand-sanding with abrasive works better. The smaller the grit, the lower the speed. Also, if the bowl is even slightly warped, and you are hand sanding, you can avoid "hydroplaning" (just hitting the high spots) if the speed is slow.


    Betty Scarpino, Editor, American Woodturner
     
  6. john lucas

    john lucas

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    Learn to cut cleaner. That promotes hand sanding. When I do it correctly (and I sure don't all the time which is why I still have my power sanding discs) I can start sanding with 220. Since sanding at this level takes so little time I usually hit it quickly with the lathe on and then stop the lathe and hand sand to get the scratches to follow the grain.
    I find that quite often when hand sanding under power that there will be an area that just doesn't want to sand out. So in the old days I would go to a course grit and sand like crazy. Now I find that I can quite often just shut the lathe off, hand sand that one area with the grit I'm using, and then go back and turn the lathe on and hit it lightly and it will be fine to move on up in the grits without having to use that courser paper.
    When I was at Arrowmont a few weeks ago I decided that I wasn't in a hurry to finish anything so I concentrated on my cutting techniques and didn't have to go below 220 for any of the pieces.
    The advantages of cutting cleanly pay off in that you aren't using the course paper and forcing it into the wood. You use finer paper with less pressure and less speed because it doesn't take as much effort. You need to use slower speeds on the finer papers simply because they heat up faster and slower speeds mean less danger and less heating of the paper for cleaner cutting.
     
  7. Bill Weaver

    Bill Weaver

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    I just want to thank all of you for your comments. I picked up on some things I could improve upon. Note like slower speed for finer grit......ah that's why paper was getting hot and also I think i was creating some surface scratches by my sanding methods.
    I watched the video on power sanding very enlighting, I'm assuming that it was an air powered die grinder with mandrel and i do like the use of tool rest. Thanks MM
    My last turnings are by far smoother surface. I changed some tooling and method.
    So again Many Thanks to All:D
     
    Last edited: May 19, 2013
  8. MichaelMouse

    MichaelMouse

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    No, Bill it's a flex shaft turning at 1725. The noise of a pneumatic grinder does not appeal in a small basement shop where even the compressor can get no farther than 20 feet away. http://i35.photobucket.com/albums/d160/GoodOnesGone/P3140057.jpg Far right, fitted with a 3" soft back.

    Slower rotation on the piece is ALWAYS safer. But friction, the cause of heat, is independent of velocity, so do what's comfortable. You are already sanding at a much higher velocity than most of us with the pneumatics, I would imagine. Don't press. Friction is the product of the coefficient of friction and ("normal") contact force. You press you increase the second, and if you trap dust under the paper, you also increase the first. That's how you'd get that shiny burnished/case-hardened surface with the ugly background scratches that people who hand sand and complain about heat get for their efforts. With your handpiece supported on the tool rest you can easily maintain just enough pressure to keep the sawdust flowing into your collector. After a bit of experimentation, you'll develop a pattern and placement that directs the dust right where you want it to go, rather than scattering. If you have to rely on your own arm rather than the rest, you have a tendency to press and support the disk on the work. When the work rotates faster, it has more energy for you, rather than the rest, to fight. Natural tendency is to press harder, thus the warning to go slow.

    One thing not terribly obvious in the sanding video is the disk is not contacting on the rim area, but favoring center on the convex surface. Since you can't avoid use of the edge inside, even the wear on your paper by using the inside on convex areas.
     
  9. hockenbery

    hockenbery AAW Advisor Staff Member

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    My philosophy exactly!
     
  10. robo hippy

    robo hippy

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    Since I am not doing production work any more, I am spending more time cleaning up my cuts. Some thing I have observed over the years, is that I can turn dry wood cleaner than wet wood that I turn to final thickness and let warp before sanding and finishing. Maybe the warping magnifies the minor cutting flaws that wouldn't matter with dry wood. If you try to sand warped bowls by hand, or even under power, you need rpm in the range of 20 or so. Any more than that, and you skip over the low spots, and believe me, I have tried. With the warped bowls, I generally start with 100 or 120. With dry wood, more like 180 or 220. I try to avoid 80 grit because some times the 80 grit scratches are harder to get out than tool marks.

    robo hippy
     
  11. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Everybody who likes to sand, raise your hand

    A die grinder is good for power carving and they are cheap, but I do not like the noise. Like MM, I would not choose one for general purpose sanding.

    I'll admit that I have cheated and used the infamous "80-grit gouge" more than once to "fix" an interior curve. However, the thing about sanding is that it is far less satisfying than using a gouge or other turning tool.
     
  12. Mark Mandell

    Mark Mandell

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    Necessity's A Mutha

    With the onset of a condition known as Macular Pucker it's become much more difficult to read a long fair curve such as make up the external shapes of my jars (hollowforms).

    I have to use a light at low angle to sight along the axis to see minor valleys and bellies in the surface revealed by variations in the light's reflections. I've then had to resort to an abrasive fix. I mark the valleys with a pencil. I then use a 3x6 block of wood to which heavy weight 120 is glued. With the piece spinning at about 400 rpm, this "tool" allows me to remove the slight variations in the curve quite nicely. When the pencil marks are gone, the entire surface will have a uniform scratch pattern. Final sanding then goes quite easily because my paper is not skipping over scratches in the "low" area(s).
     
    Last edited: May 19, 2013
  13. john lucas

    john lucas

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    My friend Joe Looper taught me to close my eyes and run my hands over the form. Particularly from lip to foot. It's amazing how easy it is to feel imperfections. It' also amazing how hard it is to get it right in the first place :) Don't know if any of you ever met Joe. He had built a lathe out of a gigantic metal lathe. It had a swing of 54" and had a 5hp DC motor. This was back about 1990. He had tools that were 8 feet long.
     

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