How many teeth in a dado set is too many teeth?

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Forum topic by Dan Corbin posted 09-23-2013 01:41 PM 6640 views 0 times favorited 19 replies Add to Favorites Watch
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Dan Corbin

57 posts in 2190 days

09-23-2013 01:41 PM

Topic tags/keywords: tablesaw blade question dado

Let me shed some history on the subject at hand:

Sometime last year, I bought a CMT Dado Blade set at my local box store on clearance for a pretty good price. But using it, I had a ton of tear out on both plywood and solid lumber, and the bottoms of the dados were anything but flat. Plus, it wouldn’t make the 3-1/4”-deep lap joints that I wanted it to make (an 8” blade in my 10” Ridgid tablesaw wouldn’t raise tall enough). Frustrated, I sold the set on Ebay for not much.

Now, I’m looking to get a new dado set. I have since abandoned my irrational “need” for 3-1/4”-deep lap joints from a dado blade set, so I’m good with the 8” diameter. But I am looking to avoid all of the tear out and uneven bottoms. I believe the tear out to be from the lack of teeth—the CMT only has 12 teeth on the blades and 2 on the chippers. I’ve found a DeWalt 24-tooth Dado Blade set for what I think is a good price—the blades have 24 teeth and the chippers have 4, which exactly twice the number of teeth that my previous set had!

But then I stumbled across this 42-tooth set made by Oshlun on Amazon that is very highly rated. But with 42 teeth on the blades and 6 teeth on the chippers, have I crossed into the realm of ridiculous? Are the extra teeth really going to benefit me? Can my 1.5HP Ridgid TS3650 Tablesaw going to be able to move all those teeth through the material? I am just fine inching my way through dado cuts (or doing incremental depths)....

Your advise is greatly appreciated! Thanks!

-- ~ Dan, North Carolina,

19 replies so far

View CharlieM1958's profile


16275 posts in 4246 days

#1 posted 09-23-2013 01:54 PM

All I can tell you is this: I have the same saw as you, and I have the 6” 30-tooth Oshlun dado set (I would guess that 30 teeth on a 6” blade is going to be similar in spacing to 42 teeth on an 8” blade). This thing makes beautiful, flat-bottomed, tear-out-free dados in any material I’ve tried it on so far.

-- Charlie M. "Woodworking - patience = firewood"

View bigblockyeti's profile


5140 posts in 1749 days

#2 posted 09-23-2013 01:59 PM

I’ve gotten by just fine with 2 teeth on the chippers and 12 on the side cutters. The key is a good quality set, sharp teeth and very tight tolerances between the bore of the blades and saw spindle. All other things equal, more teeth will allow for a faster feed rate while producing the same finish as a set with fewer teeth. This of course will require more power and will likely not be worth it if your not in need of the faster feed rate. It will also ad inertia to the set which will take more power to get going, but more easily plow through a dense area, like a knot with less bogging. If I were in the market for a new set right now, I would trust the reviews offered by others who have worked with what I’m considering.

View waho6o9's profile


8209 posts in 2605 days

#3 posted 09-23-2013 02:12 PM

“But using it, I had a ton of tear out on both plywood and solid lumber, and the bottoms of the dados were anything but flat.”

That’s strange behavior. Usually a ton of tear out means the blades needs sharpening.
On to better blades Dan, good luck on your decisions.

View PurpLev's profile


8536 posts in 3677 days

#4 posted 09-23-2013 02:25 PM

I wouldn’t worry about how many teeth are in the set – just whether it gets the job done or not. look at the whole package – if the dado set cuts good, the number of teeth as irrelevant (for comparing between sets).

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View jmartel's profile


7959 posts in 2178 days

#5 posted 09-23-2013 02:34 PM

One thing you could have done with the CMT set was to take a very low cut pass at first, maybe 1/32” or 1/16” into the wood, and then raise it up to full height after that.

I have 2 sets of the CMT dado stack as I got mine for $12 each.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View ajosephg's profile


1880 posts in 3589 days

#6 posted 09-23-2013 02:46 PM

Zero clearance saw insert will also minimize tear out.

-- Joe

View HorizontalMike's profile


7758 posts in 2942 days

#7 posted 09-23-2013 03:40 PM

I used to think that I would be required to acquire/buy a Dado Blade Set. I no longer feel that way. Don’t get me wrong, I still make and use dados in my projects. I just use alternative methods of cutting my dados.

If I only need a few, shorter, dados then I will use my table saw sled with my 1/8in FK rip blade and set my T-Threaded stops to the size of dado I need. My sled gives me the ZCI and the rip blade gives me the flat bottom cut.

My second most used method is to use an adjustable router jig that lets me set the exact width of the desired dado within seconds. And all dados are the same size and all are at 90* to the piece being cut.

All said and done, I prefer the router jig for cutting dados the best. It is pretty much fool proof IMO.

-- HorizontalMike -- "Woodpeckers understand..."

View pwgphoto's profile


70 posts in 2244 days

#8 posted 09-23-2013 03:56 PM

I have the Delta 35-7670 8-Inch Stacked Dado Set and think it does a great job. It has 24 teeth on the blades and four on the chippers. With a zero clearance TS insert there is no chip out. The bottoms are flat. Only problem is it seems to be discontinued. I got mine new on ebay last year for around $80.

-- Paul, Brooklyn Park, MD.

View dschlic1's profile


433 posts in 1998 days

#9 posted 09-23-2013 05:59 PM

I have the Harbor Freight *” dado Item #44566. It has 42 teeth. I am very happy with the cuts it makes. No tearouts even without a ZCI. The first set I received did not cut a smooth bottom, so I exchanged it for another which cuts just fine. I have an older Craftsman TS with a 1.5 hp motor running on 120VAC. I do not have any power problems cutting dados even in red oak.

View pintodeluxe's profile


5706 posts in 2841 days

#10 posted 09-23-2013 06:47 PM

I use the Freud Diablo 8” dado set. The tooth geometry has angled teeth on the inner and outer blade. Set them so the angles face inward (in other words there is an inside blade, and an outside blade). If they are installed correctly they cut splinter-free dados in plywood and hardwood. The angled teeth are set slightly taller than the chippers, which scores the wood to prevent chipout. If you cut a 3/4” wide groove in one pass, it will be a perfectly flat bottom groove like the picture above. If you cut multiple passes, you will see little scoring lines. I think that type of blade is good because what I really want is a crisp shoulder on my tenon or dado.
My set has chippers with only two teeth, and it works great for fine furniture.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View teejk's profile


1215 posts in 2713 days

#11 posted 09-23-2013 07:31 PM

My old Delta 8” stack set uses the 2 tooth chippers. I never counted the teeth on the outside blades. It owes me nothing and if I could find another one I would buy it.

But you are carving 3 1/2” deep dadoes? Means you are dealing with 7” stock to do a half-lap? How do you support that on your cuts? Am I missing something here?

View knotscott's profile


8057 posts in 3404 days

#12 posted 09-23-2013 10:37 PM

Tooth count is only one factor in the overall performance. Precision manufacturing, hook angle, top grind, etc., all play a part. The DW/Delta 7670 set is similar to the design the Forrest set uses. The Oshlun is a copy of the Systimatic 42T/6T design. $113 shipped seems to be the going bargain rate for the 7670 these days. IME, it’d take top end set like the Freud 508/608, Infinity Dadonator, Forrest, or Ridge Carbide to eclipse the 7670 set. The Oshlun and the 7670 are both good value sets, but it appears to me that the 7670 has the upper hand. You decide:


Oshlsun 42T/6T:

FWIW, the 7670 also offers a great carrying case and very nice shim stock.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View ajosephg's profile


1880 posts in 3589 days

#13 posted 09-24-2013 02:22 AM

I agree with Horizontal Mike – especially with large boards.

-- Joe

View Dan Corbin's profile

Dan Corbin

57 posts in 2190 days

#14 posted 09-24-2013 09:31 AM

Thanks all for your advice and opinions! And extra thanks to those who included pictures. They say they can be worth a thousand words, but I don’t think I could use only a thousand words to describe a picture. ;)

Until knotscott posted, I was leaning so heavily towards the Oshlun 42T set that I already put it on order. I have been looking at the 7670 for quite a while – Grizzly had a sale on it until just a few days ago. I literally waited a few hours too long to order it. Since my order hasn’t shipped yet, I’m debating canceling and buying the DW7670.

In response to teejk, I was trying to make full lap joints using a piece of 1×8 lumber, so the dado was actually going to be 3 3/4” deep (the 3 1/4” in my original post was a typo), which my tablesaw can do, but only with a 10” blade. I was designing a shelf that used no fasteners and was strong enough to support a fair bit of weight. I might still make that design, but I will cut the dados with my regular saw blade.

-- ~ Dan, North Carolina,

View FaTToaD's profile


394 posts in 3169 days

#15 posted 09-24-2013 02:24 PM

Dan, I have the Oshlun 8” dado stack you mentioned and I’ve had great success with it in m Rigid 3650. The only time I had tear out was at the end of the cut and I belive that’s more my fault to due to the feed rate. They’re great blades!

-- David

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