On 1/19/2017 6:46 PM, whit3rd wrote:
On Thursday, January 19, 2017 at 8:40:21 AM UTC-8, Leon wrote:
On 1/19/2017 4:44 AM, whit3rd wrote:

[about wobble-blade dados]
Actually the sides of the dado are square to the surface of the material
but the bottom is rounded so it is not square to the sides of the dado.

That's half-true; a wobble dado blade is sharpened for ONE width to
get a flat-bottomed cut, and narrower cuts have a ridge down the
kerf center, while wider have dished bottoms.

I'll bite, what is that one width?

For a Craftsman 720.3261, 720.3262, or 720.3263, aka "93261" the instruction sheet
indicates flat bottom for 3/4" width in the as-delivered condition.
Presumably, if you send a wobble set to a sharpening service, you can specify
a flat cut at any width you choose.

I don't recall the model, LOL but mine was a Craftsman that I bought in
1979. It had a very noticeable cupped bottom that got worse the wider
the cut.



The 'W' shape kerf indicated for narrower cuts than 3/4" is fairly easy to rework with
a sharp chisel, of course.