different dumb drill press question


Inspired by the recent dumb DP question, here's mine:
Is it safe to put the belt at different heights on the pulley cones? It works with a semi-rigid bicycle chain, after all. I wouldn't want to mismatch by more than one pulley, because the belt is relatively short. One could get finer control of the drill speed that way.
Just curious.
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Consider that a bicycle chain has an idler to take up the slack. The belt on different pulleys that are no coplanar would wear out very quickly if you were able to figure out a way to take out the slack.
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On my cheap Chinese DP, the motor swings on a hinge. Slacken to switch pulleys, tighten back to run. The edges of the belt would certainly wear as they rubbed the edges of the pulleys instead of riding the vees.
Photos I've seen in catalogs show that better DPs have three pulley cones instead of two. I dimly recall that arrangement in high school woodshop class. If very precise speed settings matter for some application, the nature of which I am totally ignorant, the wider variety of speeds offered by triple stacks would be useful. Perhaps in a one-off situation, one could finesse a two-stack DP into providing an intermediate speed close to some desired speed. I dunno.
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On Tue, 20 Jun 2006 18:41:49 GMT, Australopithecus scobis

In a home shop especially for woodworking the exact speed doesn't matter. Usually you have a maximum speed, not a minimum so you leave the drill press set at a slow speed most of the time. The limitation usually encountered is that the drill press does not have a slow enough speed, say for a circle cutter, which you aren't going to get any slower without modification.
-Leuf
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On Tue, 20 Jun 2006 16:01:35 GMT, Australopithecus scobis
No. If the belt isn't flat in the groove (i.e. the pulleys are also aligned correctly) then you lose an awful lot of friction and you're likely to have the belt start slipping.
If you must insist on doing this, then use a link belt, not a solid belt.
Why do you need ultra-fine drill speed control anyway?
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I don't need it. I'm just naturally curious. "Bang the rocks together, guys."
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Australopithecus scobis wrote:

If you need that kind of control you might want to look into variable pitch sheaves. Go to www.grainger.com and search on "variable speed pulley".
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As others have asked - "Why?" As for the bicycle chain analogy, not many cyclists spin their cranks at 1700+ rpm. And cyclists prefer to keep their chains relatively straight, avoiding the gear combinations with the most severe angles.
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Not good for the belt, of course, and there's always the possibility that a belt could be thrown, though I have seen some misaligned belt drive pulleys run for quite a while without trouble. I don't think it would work too well on the typical drill press setup, though; how would you tension the belt?
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Larry Wasserman Baltimore, Maryland
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