TS Cutting not quite flat bottoms

Folks,
I'm cutting a double tenon on the TS, with about 0.17 between tenons. Using a shop-made tenon jig to cut the space between the tenons I wind up with an inverted V shape on the bottom, sticking up maybe 0.010" (that's a guestimate).
Tried two blades: a Freud 80 toother, and a Freud 50 tooth combination blade.
Any ideas why this wouldn't be flat? The 80 tooth blade is only a year old and hasn't seen too much wood.
Thanks, Jack
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snipped-for-privacy@ganssle.com wrote: | Folks, | | I'm cutting a double tenon on the TS, with about 0.17 between | tenons. Using a shop-made tenon jig to cut the space between the | tenons I wind up with an inverted V shape on the bottom, sticking | up maybe 0.010" (that's a guestimate). | | Tried two blades: a Freud 80 toother, and a Freud 50 tooth | combination blade. | | Any ideas why this wouldn't be flat? The 80 tooth blade is only a | year old and hasn't seen too much wood.
I'm not familiar with those two blades; but most are ATB (alternate tooth bevel). Take a really close look at the blades and you'll see that the teeth aren't flat on top.
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto
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snipped-for-privacy@ganssle.com wrote:

blades. To get a flat bottom you will need a blade with a flaat topl tooth grind.
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On Mon, 15 Jan 2007 14:52:59 -0800, snipped-for-privacy@ganssle.com wrote:

Examine the blade closely and you should find that there are no flat teeth, they are set to either the left or to the right--this is called an "Alternate Top Bevel" grind and it is the most commonly encountered.
Not a function of the age or sharpness of the blade, but of the design.
If you need a flat bottom you need a special grind on the blade. Forrest has custom grinds on the Woodworker II blade for various purposes--<http://www.forrestblades.com/woodworker_2.htm . TheWW10401125 is probably what you need but you may want to call them and explain what you are trying to do and ask for a recommendation.
--
--John
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snipped-for-privacy@ganssle.com wrote: <snip>
> Tried two blades: a Freud 80 toother, and a Freud 50 tooth combination > blade. > > Any ideas why this wouldn't be flat? The 80 tooth blade is only a year > old and hasn't seen too much wood.
You can't get there from here with either of those blades (I have both of them), time to add the Freud dado set to your arsenal if you want a flat bottom.
Lew
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Others have identified the cause of your problem and a couple have provided some not so inexpensive solutions. If it were me I'd just use a file on edge to scrape the ridge from between the tenons, or use a chisel to lower the bridge between the mortises till it clears the tenon ridge.
Art

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What about using a rip blade? Don't those have flat teeth?
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MB wrote:

And there are ATBR blades out there (ATBRaker).
--
It's turtles, all the way down

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