On Friday, January 30, 2015 at 1:43:01 PM UTC-8, Leon wrote:
On 1/29/2015 5:05 PM, whit3rd wrote:
On Wednesday, January 28, 2015 at 7:16:37 AM UTC-8, dadiOH wrote:
"DerbyDad03" wrote in message



I took the shot from
above to show the shoulders left by the wobble dado.

In another reply, you said you were going to reduce the width of the dado.
Good idea. If you had it set to way beyond the 1/4" you need, reducing it
to a hair over 1/4" will markedly reduce the curve.

This may be misguided; wobble-dado blades are sharpened at the factory in
a manner that will be a bad match for either extreme (wide or narrow)
of the width setting. There IS likely a setting at which the wobble-blade cuts
a flat bottom.

For my (Sears Craftsman 720.3261) blade, the instruction sheet indicates
that width is 3/4" (0.750 inches).


Regardless of how a wobble blade is sharpened at the factory or where
ever, if it wobbles/cuts wider than the width of the teeth on the blade,
it will not produce a flat bottom.

Not true. The sharpening of a wobble blade is NOT RIGHT ANGLE at
all the tooth faces. That analysis holds only for straight-blade sharpened
blades used with wobble washers, not for wobble-dado assemblies.
Standard blades are sharpened in the zero-wobble-angle state, of course.

The only setting that the wobble blade will create a flat bottom is when
it is adjusted to not wobble at all.

That depends on the manufacturer's wobble-setting when the blade was
put into the tooth-grinder. For my blade, flat cuts occur at 3/4".

Think of it this way: to cut a flat bottom dado with a 24T blade tilted at 10 degrees,
the leftmost edge has to be cut by tooth #1 whose crest is 80 degrees to the
left sawblade face, and 100 degrees to the right blade face. The rightmost
edge has to be cut by tooth #13 whose crest is 100 degrees from the left
face, 80 degrees to the right blade face. And the middle of the cut
is made by tooth #6 which is 90/90 degrees, regular square-cut, but
at a slightly smaller distance from the axis of the blade rotation.
Dado blade teeth for wobble-dado assemblies are sharpened exactly
as required to make a flat-bottom cut, but ONLY AT ONE SETTING.