Do you get "perfectly flat" bottoms from your stacked dado set?

[scott spencer]

With several recent discussions on stacked dado sets, I frequently see comments about "perfectly flat" or "truly flat" bottoms in regards to the performance of various dado sets. In an effort to be accurate with the claims, I often challenge those claims because AFAIK the vast majority of high quality stacked dado sets like the Forrest Dado King, Infinity Dadonator, Freud, CMT, Amana, Oshlun, DeWalt/Delta, and Systimatic sets all use beveled teeth on the outside cutters to help minimize tearout. In order to be of any benefit, the beveled teeth must protrude slightly above the flat teeth of the inside chippers. The protruding beveled teeth leave tiny grooves at the outside of the cut…a trait often called “bat ears”. The better sets tend to stagger some flat top ground (FTG) teeth in between the beveled teeth to minimize the depth of the bat ears, but they’re still there. It’s minor enough that a lot of people may not even realize they're there, but it’s not realistic when manufacturers or owners claim that these sets leave "truly flat" bottoms, if indeed they don’t. It’s likely that there are sets available that don’t have any beveled teeth on the outside cutters and use all FTG teeth, which will leave a flat bottom, but those sets will also exhibit more tearout, especially across the grain that the better sets that use beveled teeth.

I'd like to hear from owners of stacked dado sets. Please check the teeth on your outside cutters. What set do you have, and does it use any beveled teeth on the outside cutters? Does anyone have a set that uses beveled teeth on the outside cutters that gives a truly flat bottom with no bat ears? Anyone have a set with all FTG teeth on the outside cutters?

Here’s a pic I copied from Forrest’s website that shows the correction orientation of the cutters…it also illustrates the bat ears left by the beveled teeth:

http://forrestblades.com/graphics/outblades.gif

[scott spencer]

Do you get "perfectly flat" bottoms from your stacked dado set?

I see them advertising products everyday on Tv claiming to give you that "perfect round" bottom. Never seen anyone seeking a "flat: one. LOL!!!! Sorry, I just read a topic on one of the other threads about how what we say can be taken differently than what we intended.......

Now you can go back to being serious....

I must be getting old....I definitely used to be more concerned with those perfect round bottoms than the perfectly flat ones! :eek::D

[Van Huskey]

Freud 508 currently and bat wings are present, I have never had a set that didn't at one level or another and I have never seen a quality set that had flat ground teeth. I had a frend years ago that used a stack of old non-carbide blades that left a flat bottom...but tore out like a murderer escaping from prison.

[Tom Veatch]

My answer to your question is, "No". I have two dado sets, Freud SD508 and SD608, and neither give a perfectly flat dado. Both show small "bat ears". The next question is "Do I lose any sleep over that?". The answer to that question is also an emphatic, "No".

I've yet to cut a dado in any project where the "bat ears" were apparent or visually distracting from the appearance of the finished article. In my opinion, the whole "bat ears" topic is a very large tempest in a very small teapot.

[Greg Dykes]

Do you get "perfectly flat" bottoms from your stacked dado set?

I see them advertising products everyday on Tv claiming to give you that "perfect round" bottom. Never seen anyone seeking a "flat: one. LOL!!!! Sorry, I just read a topic on one of the other threads about how what we say can be taken differently than what we intended.......

Now you can go back to being serious....

[bob hertle]

I have two dado sets both dating from the '80s. The Freud is an 8 inch, and leaves significant bat ears. The other is a Delta 6 inch set that came with my Unisaw as part of a promotion--mod 35-551-R. It leaves a perfectly flat bottom. The bevel angle of the outer blades is only about 22 degrees, where the one on the Freud is about 45 degrees. Surprisingly I've never had a problem with chipout with the Delta, where I have with the Freud--just the opposite of what I'd expect. The Delta is the "go-to" set, and I only use the Freud for rough work.

Bob

[scott spencer]

Bob - Since Freud tends to be one of the more progressive companies, it's likely that the newer sets are different.

[Zach England]

I seem to recall once seeing a router bit--like a wide and narrow flush-trim bit--designed to remove this. It seems like a superfluous step to me, but someone might find it useful.

[Wayne Jolly]

If you use something like this after your table saw dado set you will have a FLAT bottom dado.

http://www.toolstoday.com/p-5675-dado-clean-out-router-bits.aspx

I remember seeing some bits similar to this where the cutter was very shallow so the bearing would ride the existing dado even if it was as shallow as about 1/4" IIRC.

xeddog

[Ray Newman]

The old steel dado stacked cutters could be sharpened to give flat bottoms.

I have a 6" and 8" dia. sets, and when they require sharpening, the whole set goes out with instructions to sharpen all to the same dia. And they do cut a flat bottomed dado.

On a cross cut dado, I control tear with a subfence on the miter gauge. On some materials, I apply a strip of wide clear palstic type wrapping tape, or make score marks, etc.

I recently acquired a Forrest 8" Dado King, but have not tried it, so I can‘t speak to how flat the bottom is. As in the case with the steel dado sets, it maybe be a case of how a dado set is sharpened to eliminate or reduce the non flat dado bottom..

And as one poster mentioned if it that much of a concern, use a router , Or a router plane.

[Paul Ryan]

Scott,

I have the Ohslun set and have bragged about its quality compared to price many times. However it does suffer ever so slightly from the "bat wing" illness as well. I consider it flat bottoms compared to other sets I have used in the past.

[Leo Vogel]

For 1/4 and 3/8 inch, I use a Freud SBOX8 Box Joint Cutter Set. Cuts perfectly square and flat bottom dado.

PS: I still like round bottoms

[Glen Butler]

I used my freud sd508 today. There are small bat ears. But otherwise flat.