TS kickback question

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Was watching a prerecorded episode of Woodsmith tonight. The man was cutting deep 3/4" wide dados using a sled and the rip fence at the same time (the blade was 6" from the fence), in 3 passes.
Is kickback not a problem here because the height of the blade is less than the height of the wood, or is this a safety issue?
Thanks, Bill
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On 12/14/11 11:30 PM, Bill wrote:

1. There will be no cut-off piece to bind between the blade and fence. 2. The piece is being held (presumable) against the sled fence.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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-MIKE- wrote:

I see. As long as you hold it snug (or use a clamp), it should be okay.
I guess if the end of the work binds against the fence, one better duck! :)
Thank you!
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On 12/15/2011 1:25 AM, Bill wrote:

The other point is that since there's no cut through there's no possibility of the kerf closing behind the blade.
--
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dpb wrote:

dpb, I didn't think of that. Good point. Thank you! -Bill
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On 12/15/11 1:25 AM, Bill wrote:

No, snug really has nothing to do with it, although snug is always a good idea. What makes kickback a virtual impossibility in the case is that there is no lose piece on the rip-fence side of the blade. Also, as another pointed out, there is no chance of binding on the forward side of the blade.
I was pointing out, in reference to using a sled, that since there is a fence on the sled to keep the "cut-off" side from backing away from the blade, there is no chance of it twisting between the blade and rip-fence which is a main cause of kickback.
In the case of cutting a dado on a table saw without a sled, it would be perfectly safe to do so with a miter gauge (with or without an extended miter fence). Again, there will be no cutoff piece to bind between the blase and rip-fence.
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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No lose piece? Where's Larry.
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wrote:

Hold one. Got the elevation, setting his azimuth...
OK, FIRE FOR EFFECT!
-- Silence is more musical than any song. -- Christina Rossetti
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On 12/15/2011 3:07 PM, -MIKE- wrote:

Be careful with the suggestion that this is safe. Every thing has to be done correctly to prevent kick back.
If you pull the sled and work back through the blade and you let the work move at all a kick back is going to happen unless you continue to hold the work piece firmly in place. Kick back does not require a loose piece between the blade and fence, it merely requires for the blade to catch the wood and throw it back.
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Two schools of thought here. One is that if you aren't cutting through the wood, you won't get kickback because the wood won't close in behind the blade. Which is true.
But you still have a possible source of kickback, which is that if your work somehow gets hung up against the fence, it can twist againt the blade and you can still get kickback. Not as likely, but still can happen. I wouldn't do the sled + fence move because there are other ways to get the job done.
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1" offset block does wonders to ease your mind with cuts like this.
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Father Haskell wrote:

Yep, there it is (IMHO), the evasive "best idea"!
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"Bill" wrote:

What episode #?
Lew
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Lew Hodgett wrote:

Lew,
Woodsmith: "Through Mortise & Tenon Projects" (2011) That's what I get from my DVR, I don't know the episode #.
Bill
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Bill wrote:

If anyone else has seen the episode, maybe we can offer opinions on the strategy used of making a mortise by cutting a dado into the edge of each of two pieces of wood and then glueing these edges together. Maybe one can argue that the glue is stronger than the wood, but my intuition tells me that one is inviting the glue joint to fail.
Bill
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<snip>

Cutting dado's increases the mating surface areas.
--
Jack Novak
Buffalo, NY - USA
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Nova wrote:

That's a good point I had certainly not considered.
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On Fri, Nova wrote:

More than mortise surface area? _Cute_ trick, mon.
-- Silence is more musical than any song. -- Christina Rossetti
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Not arguing, but also not sure how that relates to the question asked.
If I understand Bill correctly, the technique he described entails cutting 2 dados and then 'butt joining' the pieces together to form a mortise.
That does indeed seem to introduce an extra point of failure.
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On 12/18/2011 8:25 AM, DerbyDad03 wrote:

The problem is that Bill is ambiguous in his _terminology_ when asking the question, therefore no answer will be correct until that is determined.
When gluing wood you are basically dealing with faces, edges and end grain ... the correct answer would depend entirely upon which he was talking about.
--
www.eWoodShop.com
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