Oh Crap


Chet
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I was cutting some angled tenons using my tenoning jig on the table saw.  I have cut a bunch of tenons before using the same jig but this was the first time with an angle so I was checking my measurements, checking my layout, checking my layout lines and then checking it all again a couple of more times. and finally went to make the cut... Turns out the one thing I for got to check was if any part of the jig itself would hit the blade with the blade at an angle.  

 

 

IMG_0506.thumb.JPG.9a8960e7521fbd0462470

 My table saw is a SawStop and it did.  Blade is actually okay, just needs to be sharpened, the brake not so much.  This happens so quick that there isn't even a mark on the jig where the blade hit.

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I don't have a sawstop, but I do dry runs of every pass and keep the tools to adjust my fences and such from miter gauge jigs nearby so the blade doesn't hit them. I'd be weary of using that blade even after sharpening, unless they are brazing on new carbide where it smashed, and rebalancing the blade. Flying carbide is a legit reason to not use it.

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Or better yet, hang that sucker on the wall with the brake still attached as a reminder to triple check blade path :)

(I have a sawstop and I'm just waiting for the day when I forget to adjust my miter gauge and cost myself a WW2).

Awesome idea!  Along with the receipt for the replacement parts!

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How does this happen? I keep seeing reasons not to buy a Sawstop. 

The SawStop works by running a low voltage current through the blade, so if the blade touches your finger and the current finds another path, the SS detects the differential and fires the brake.  Unfortunately, if your miter gauge/tenon jig is conductive and the blade comes in contact with it while your hand is also in contact, it will fire the brake.  Just means you have to be extra careful when using metallic fixtures on the TS.  Not too big a deal.

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Good point guys about the blade... It won't get used again.  

Llama touching the blade with anything that will complete an electrical circuit will fire the brake.  They don't even recommend cutting pressure treated lumber on it because of the moisture in it.  I would never cut something like that on my saw anyway.  They do have a lock out system that you can turn on with a key so you can cut things like that or even metal with a proper blade.

Janello, it was a metal part.

Edited by Chet K.
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Yep, it's a decent blade but it's not worth risking a chunk of carbide lodged in your forehead.  Just because it doesn't look damaged doesn't mean it isn't.  That blade goes in the garbage.

Absolutely. Unless you have an xray machine somewhere in your shop to examine it - toss it.

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Fair points about the metal. I didn't realize it was hitting a metal part when I first read through this. The other one is old, but I've seen other recent ones floating around the interwebs. It's hard to know how many of those were people not taking the correct precaution.  

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i'd guess 98-99.5% user error.   

I respect this saw and its spinning blade just as I would any other table saw and yea, mine was definitely a user error.  But I did read a review of a guy going through 4 brake cartridges because he kept hitting the blade with his miter gage and he claimed that the manual didn't mention this,  I guess he missed the part about coming in contact with metal.

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Bummer about the false positive.  I'm sure Sawstop has figured out an NPV  of annuity payments for every sawstop sold for replacement brakes.  That said I am really thinking hard about getting one, pay for a little peace of mind.  While I have respect for all my power tools, the stress level is a tad higher than others when I flip the TB power switch to "on".  

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For me this is just another reason to get a Sawstop. I know it's unrelated but I had a bad experience with my router table. My Incra Positioner was not properly attached to the router table and as a consequence of this, my fence made contact with the router bit while I was feeding a narrow piece of wood. All I can tell is that that terrible noise made me jump and loose control of my hands for a fraction of a second. Nothing happened, but it scared the heck out of me.

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I'm curious,  if you hit a brad nail that your saw would normally laugh at,  would it fire the cartridge? 

Not unless your finger is touching the brad nail.  I have done this before when making a crosscut sled.

(Or if your finger is touching something else conductive which is also touching the brad nail).

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I don't think resistance is involved, only inductance. A human body part will induce a currency, also a spark from cutting metal.

That doesn't seem likely, I would expect resistance or maybe capacitance.  Inductance would seem harder.

 

This seems to say it is capacitance not inductance.

http://machinedesign.com/guest-commentary/capacitance-system-stops-table-saws-amputating-fingers

So a small brad nail would likely not have the capacitance necessary though enough metal certainly would.

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I would not call it a false positive.  The machine worked as intended.  I don't want to seem pedantic, but there is this sentiment out there that the things misfire.  Really they don't.    

I respectfully edit my post:  Replace "bummer about the false positive" with "Glad to hear your jig is ok." ?

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