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I hit a brad with a SawStop and ...

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Forum topic by clin posted 06-01-2016 10:54 PM 584 views 0 times favorited 5 replies Add to Favorites Watch
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clin

510 posts in 457 days


06-01-2016 10:54 PM

... nothing happened.

I was cutting through something I made with several layers of plywood glued together. When gluing it, I put a brad in at either end just to hold the pieces in place while clamping. Because of multiple layers some brads were buried. I made a point to put the brads where they wouldn’t interfere.

I decided to make the piece 1/4” longer, which is why the brad was now in the cut line. I thought it might be and even thought to disable the brake on the SawStop. But when I lined up the cut, I thought it would be well clear, so I didn’t bother disabling the brake.

Well I clearly did hit the brad. I saw some sparks, but the SawStop didn’t trigger the brake. This was also a cut that was in line with the brad not across it. Which meant, the odds of hitting it were low, but it also meant the entire brad was cut away.

Anyway, just thought I’d I’d throw out a data point on a SawStop hitting a brad. It’s of course no guarantee that it can’t trip the brake. I assume if a chunk of the brad got carried around to the underside of the saw blade it could connect the blade to the brake and cause it to trigger.

-- Clin


5 replies so far

View Mark Shymanski's profile

Mark Shymanski

5314 posts in 3173 days


#1 posted 06-01-2016 11:14 PM

The brad was possibly too short to connect a circuit, so while it may have been in the wood it was not also touching the frame of the Sawstop so no circuit was closed triggering the brake.

-- "Checking for square? What madness is this! The cabinet is square because I will it to be so!" Jeremy Greiner LJ Topic#20953 2011 Feb 2

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JeffP

573 posts in 852 days


#2 posted 06-01-2016 11:15 PM

Time to break out the hot dogs and give it a real test!

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.

View clin's profile

clin

510 posts in 457 days


#3 posted 06-01-2016 11:25 PM



Time to break out the hot dogs and give it a real test!

- JeffP

Send my about $150 for a new brake and blade and I’ll get right on that.

-- Clin

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JeffP

573 posts in 852 days


#4 posted 06-01-2016 11:32 PM



The brad was possibly too short to connect a circuit, so while it may have been in the wood it was not also touching the frame of the Sawstop so no circuit was closed triggering the brake.

- Mark Shymanski

Just a point of clarity here…sawstop does NOT operate on any “close a circuit” basis.

The finely tuned circuitry detects changes in the magnitude of a “broadcasted” signal as it is modified by the specific characteristics of everything in contact with the blade. It can tell the difference between how a (relatively dry) board changes the signal, and how some “meat” changes the signal.

It cannot, however, tell the difference between having “meat” directly connected to the blade vs. having the same meat indirectly connected to the blade via some metal. It also cannot tell the difference between meat and a large hunk of metal (like an aluminum fence), or a soggy board (like a piece of PT lumber you just pulled out of the ground).

A tiny piece of metal (like the OP’s brad nail) is not perceptibly different from the saw blade itself, which has considerably more mass and size than the brad nail).

For the curious owners of a SawStop, I highly recommend turning the saw to it’s “on” state, but with the blade not running, and doing some experimentation. In this “on but not running” state, the lights on the control box are active, and will show you when it thinks you are feeding it some “meat”.

With the saw in that state, just push various things up against the saw blade and watch the lights.
1) dry board, no red light
2) moderately wet board, no red light
3) soggy PT board that’s been laying on the ground – Danger Will Robinson
4) finger – red light
5) screw driver held by plastic handle – no red light
6) screw driver with finger touching the metal – red light
7) hot dog – red light
8) zzzzziiiiiiippppp, plop…. red lights a flashing!!!!

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.

View clin's profile

clin

510 posts in 457 days


#5 posted 06-01-2016 11:50 PM



Just a point of clarity here…sawstop does NOT operate on any “close a circuit” basis.

- JeffP

It’s probably using capacitance, but I have no doubt that if a piece of metal, like a brad or part of one, created an electrical path from the blade to a metallic portion of the saw, perhaps the brake itself, the brake would trigger.

Just hitting small bit of metal, no. I agree with the idea that any small bit of metal you hit would effectively behave like it was part of the saw blade. And therefore as long as this metal didn’t contact anything else, like your finger OR a conductive portion of the table saw, nothing should happen.

But there is always the chance that something like a brad could touch the blade and something else at the same time, and cause the brake to trigger.

-- Clin

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