Safety Article in AW

Discussion in 'Woodturning Health & Safety' started by Andy Chen, Dec 16, 2012.

  1. MichaelMouse

    MichaelMouse

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    You certainly can improve your guess. If you're doing a "pull cut" while turning outside a bowl, even though you may only have your knuckles inside the throw zone, you are exerting force toward yourself with the movement of the tool and the shape of the object. If you pull a loose piece, it has a vector toward you. It is not a free release object that tries to go in a straight line out from the arc, but to nit-pick Bill a bit, is affected as well by the tug of gravity to fall in a ballistic curve.

    If, on the other hand, you are pushing away, any piece you knock loose will have a vector away from you. That's a good thing. You get the benefit of a clean face, too, because what you're releasing as shavings are directed out and away.

    I think this is where people get into trouble. They have a blank with a rough surface which might be hiding any number of faults, and they read somewhere that they should turn the rpm of their electronic marvel up until it shudders before backing off a few turns. Then they try that pull cut they saw on the DVD. Excess energy and the wrong presentation.

    Inside, the biggest danger is the "catch", which is really a push up and perhaps some out. Once again, the piece will try to move opposite the applied force. Break a tenon and things can happen. I like to improve my chances by holding the entire piece between centers. I also prefer to cut at low rpm, so there is barely enough energy to release the shaving, not enough to throw the piece.
     
  2. AlanZ

    AlanZ

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    "You certainly can improve your guess."

    Absolutely...but it's still just a guess.

    A few years back I watched as a club member mounted an 8" chunk wood between centers to rough it to round. The wood still had its bark on.

    Fortunately, he did bring up the tailstock for additional support.
    Unfortunately, the member did not check the speed before turning on the lathe.

    The lathe (which during a previous pen turning demo) was set to 3,000 rpm.

    Two things occurred to me:

    1) how quickly the auto debarking feature worked (all of the bark flew off of the wood in a matter of a few seconds)

    2) the scatter pattern of the bark was very very wide... it was all over the place (not in some neat pile or strip on the floor)


    So, I agree that keeping tailstock support as long as possible and keeping the speed down are very fine things.

    I also agree that when things are going well, you can often predict and direct the output of a cut.

    All I'm trying to point out is that things don't always go well. Unanticipated catches, wood stress points, nails, voids, and the general "having a bad day" can make things go very wrong very quickly.

    Some people who just advocate the "stay out of the line of fire" approach, to my mind, are just kidding themselves because they are guessing about the trajectory of the wood, the light bulbs in the ceiling, and all the other things in the shop that are out to get them.

    Personal protective gear can greatly help mitigate the damage done, whether in an instant (perhaps a chip flying into one's eye), or over years (like dust entering the lungs).

    Combining safer turning practices with personal protection more often than not gives us cool stories to tell when things go wrong, instead of having to send flowers to the family.
     
  3. robo hippy

    robo hippy

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    Debarking Feature.... Oh, that is a good one.

    As far as push/pull cuts forcing pieces towards you or away from you, I would think that rotational forces would trump push/pull any time. Push/pull is a pretty minimal force, even when I am really hogging things out.

    robo hippy
     
  4. Ian Robertson

    Ian Robertson

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  5. MichaelMouse

    MichaelMouse

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    Well, it is rocket science, but perhaps if you re-read the law, you'll understand. It says that force applied to any object is met by a force equal in magnitude but opposite in direction.

    Thus, the tool hits back at the rotating piece with precisely the same force as the rotating piece hits it.

    Not to complicate unnecessarily, it is an inelastic collision as some of the kinetic energy is used up removing and propelling some mass, but it can move a chunk with pretty good force nonetheless.
     

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