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Why does SawStop use Brake?

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Forum topic by patcollins posted 04-01-2011 02:31 AM 1588 views 1 time favorited 11 replies Add to Favorites Watch
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patcollins

1004 posts in 1609 days


04-01-2011 02:31 AM

I’ve been wondering why a SawStop needs the brake. I would think it sufficient that pull the blade down and cut power, after the blade is below the table I don’t really see the benefit of the brake. Just curious what everyone thought


11 replies so far

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patcollins

1004 posts in 1609 days


#1 posted 04-01-2011 02:51 AM

I see that, I was mistaken in thinking the blade gets sucked into the brake. Probably easier to have it do this than design a high speed system that would suck the blade down quick enough to avoid a major cut.

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PurpLev

8476 posts in 2392 days


#2 posted 04-01-2011 02:54 AM

the blade dropping below the table is actually the after effect of the brake stopping the blade – it’s very clever design, all the rotational energy from the blade that gets stopped is then harnessed to draw the blade downwards, but what creates that energy transfer is the brake kicking in.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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patron

13156 posts in 2085 days


#3 posted 04-01-2011 03:02 AM

imagine the blade and trunnion and motor
coming lose from the speed of the explosion to lower the blade
and all that still running amok under the saw
maybe even out the side

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

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tedth66

458 posts in 1933 days


#4 posted 04-01-2011 03:07 AM

The brake slams into the blade and stops the blade within 5ms and then it pulls the blade down below the table. Without this brake action there’s no way that a blade spinning at 4000rpm can be stopped and only deliver a small nick to the finger or hotdog.

I haven’t tested this on my Sawstop and I don’t plan to anytime soon. :)

-- Ted

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nailbanger2

968 posts in 1887 days


#5 posted 04-01-2011 03:11 AM

Hopefully, this is the future! No damage, dust collection, able to retrofit to different saws!

http://www.youtube.com/watch?v=7ltFuEKCnM4

-- Wish I were Norm's Nephew

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patcollins

1004 posts in 1609 days


#6 posted 04-01-2011 04:33 AM

I ws thinking more along the lines of the brake causing a carbide tip to break off and hitting someone in the eye.

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Bovine

114 posts in 2072 days


#7 posted 04-01-2011 04:50 AM

Pat, that can’t happen as the brake is on the under-side of the blade. If a piece would actually break off, it would happen under the table. Once the brake hits the blade, it only rotates maybe 1/4 inch.

Besides, smacking that block of aluminum into the blade stops it from spinning much faster than it would take to drop it the distance under the table. I have always wondered why they chose to do that rather than to just stop the arbor from spinning (via teeth or some other mechanism) which would not destroy the blade and likely not have a removable brake.

-- Kansas City, KS "Nothing is as permanent as a temporary solution"

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dusty2

319 posts in 2173 days


#8 posted 04-01-2011 02:02 PM

Check out the Whirlwind. Here is where it is at!

-- Making Sawdust Safely

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tedth66

458 posts in 1933 days


#9 posted 04-01-2011 02:30 PM

How about a Whirlwind on a SawStop so when you need to remove the bladeguard (Whirlwind) to make a specific cut you’ll still have a backup safety solution (SawStop brake). There are many times when I need to remove the much slimmer SawStop blade guard to make a certain cut.

-- Ted

View agallant's profile

agallant

436 posts in 1630 days


#10 posted 04-01-2011 03:50 PM

I don’t thin the break is a very big deal. If you are tripping it all of the time than perhaps you should investigate other hobbies. I have not touched a moving tablesaw blade in over three years so if I tripped the sawstop today I could live with buying a new break and blade.

View JJohnston's profile

JJohnston

1593 posts in 2035 days


#11 posted 04-01-2011 05:35 PM

Bovine, the reason stopping the arbor wouldn’t work is that the blade would continue spinning, since it has its own angular momentum, and isn’t solidly attached to the arbor – only friction keeps it from spinning on the arbor under normal circumstances. Not only would it keep spinning, but it spins in the direction that would loosen the arbor nut. It might not cause the nut to come completely off, but it would almost immediately lose the friction between the nut/washer and arbor flange that might have helped it slow down sooner.

Another reason they chose to apply the brake action at the teeth is that they can produce the maximum torque that way. The torque is a function of the force applied and the distance from the center of the arbor. The tips of the teeth are the farthest thing from the center of rotation, about 5 times farther than the surface of the arbor shaft. To get the same amount of torque (and therefore stop the blade in the same amount of time), you would have to apply 5 times the force on the arbor that you would at the teeth. You could always build a 10” or bigger disc brake onto the arbor, but you’d have to make room for it (and you’d be adding mass, which makes it harder to stop), and the caliper, plus that wouldn’t solve the issue of the blade continuing to spin.

-- "Sometimes even now, when I'm feeling lonely and beat, I drift back in time, and I find my feet...Down on Main Street." - Bob Seger

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