[Jewelry making - Article 00131] - Re: [Orchid] 2 Wheels Buffer or Flex Shaft?

[Marty Hykin]

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    Nice honest answer, ian, re doing the odd dangerous thing from time
    to time. The ones we walk away from are the ones we get to tell other
    folks not to do. 

    I thought I'd throw in my two cents worth while this thread is still
    alive. 

    The hacksaw is designed to move through the material it is cutting.
    When you do it backwards, that is, when you hold the hacksaw steady
    and let the material move against the saw, the chips cannot clear
    out of the gullets between the teeth. Even if you are moving the saw
    slowly back and forth, perhaps hoping that heat from friction does
    not build excessively in one spot on the blade, the chips will
    quickly accumulate and pack into the gullets, far more than there is
    room for them. A sawblade moving through the material at proper speed
    produces neat little loosely curled chips in the gullets which easily
    fall away as soon as there is room for them to fall out or be carried
    away by the lubricant. But when the work is moving too rapidly, the
    gullets get jam packed full of an overload of chips which cannot
    clear. They can compress, even weld themselves together into lumps.
    They can spread out sideways and jam unpredictably against the sides
    of the saw cut where, in ordinary usage there would be clearance
    which is designed in to reduce friction. So there can be sudden
    changes, at machine-speed, in the magnitude of the forces against
    which you are attempting to hold the saw frame steady. Hope I'm
    making myself clear. 

    For the most part, at this level of hand craft we don't have to think
    about this sort of thing in mathematical detail, but people who
    actually design saws have it worked out. There is a right combination
    of tooth-spacing, cutting speed, etc for every hardness and thickness
    of material. Minor departures from the ideal prescription don't make
    a lot of difference, of course. I'm not suggesting that one need be a
    stickler for propriety. But, holding a hacksaw against a
    fast-revolving shaft is a major departure from what the saw is
    designed to do and is bound to cause trouble at least for some folks,
    some time. It is not so much a matter of having sufficient physical
    strength or positive mental attitude, as Ian Wright suggests, but
    knowing how and where a saw actually can work or cannot work. Having
    to exert great physical force to hold the tool against a moving
    machine only guarantees that if something does suddenly go wrong your
    injury is likely to be all the greater. Why ask for trouble? 

    Thanks for listening, 

    Marty Hykin in Victoria where people come from afar to drink over-
    priced tea (if you can believe it) and where risk-taking is
    generally frowned upon. Harumphh! ;-)
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