Reply by Dave

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Posted on An alternative to Saw Stop?

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154 posts in 3160 days

#1 posted 01-23-2013 06:02 PM

I love this thread! There are some creative folks here on Lumberjocks. In the interest of keeping everyone’s creative juices flowing, here’s my two cents. To keep fingers intact we need to stop the blade, keep it away from the fingers, or both. Stopping the blade takes the same amount of energy no matter how you do it. The sawstop uses up the energy by deforming its brake and retracting the blade, destroying it in the process.

One way to make stopping the blade take less energy is to disconnect the arbor from the motor (magnetic clutch, for example, like tedstor mentioned). Motors have a LOT of inertia and something called “back EMF” too that makes them want to keep turning. Disconnecting it means a brake takes a LOT less energy to stop the blade and creates a lot less heat.

I also like the idea of mounting something to the arbor for the brake to hit besides the blade itself like ripthorn suggested. If the brake released into, say, an arbor-mounted gear (or something similar but more substantial that would absorb the impact without breaking) it would stop the spinning blade AND retract it into the table. With the right design you might even be able to reset everything without replacing any parts (or destroying the blade).

Both ideas above could be combined with a drum or disc brake that helps slow down the blade, but you might not need it.

By the way, if we don’t destroy any parts the cost of a “false alarm” goes way down so a proximity sensor starts to look like a great idea. Creating a “safe zone” around the blade to trigger its retraction isn’t a big deal if all you need to do is reset a few things and get back to work. It also means you don’t have to stop the blade as fast.

By the way, a REALLY crazy idea would be to design a “smart blade” that turns its teeth around or retracts them when it senses flesh. That way you could use it on any saw. Just imagine how expensive it’d be to get THAT resharpened, LOL.

Anyway, I’m hoping to keep my fingers away from sharp fast-spinning objects regardless of what they’re connected to. You guys have put out some really creative ideas and I’m looking forward to seeing where this thread goes. If anybody pitches the ideas to Powermatic can you negotiate a good deal for all of us on their new saws?

-- "I'm not afraid of heights. I'm afraid of widths." - Steven Wright

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