Dado blades

[Mzdadoc]

Before you cringe yes I searched and read up as much as I can but........

Things I didn't see covered were 6" or 8" blades which and why? Also I would prefer blades that create a flat bottom but don't see which ones do that.

Lastly what's the difference between the Forrests Dado King's?

[knotscott]

The Infinity Dadonator is the best set I’ve used to date….very precise, very clean cutting. The Delta/DeWalt 7670 dado set can be one of the better values on the market right now if you can find it less than $120. It’s cleaner cutting than most of the sub-$100 sets, and gives a taste of the higher end sets for close to half the cost….great carrying case and shim stock too. CMT, Amana, Forrest, Freud, Irwin Marples, Ridge Carbide, Systimatic, and Tenryu are a few others I’d at least consider. Sale prices on Oshlun/Avenger sets can be attractive, but regular pricing doesn’t give them much advantage over other sets.  

 

8” sets have greater depth capacity and tend to have some performance advantage if all else is equal due to the increased cutting speed, but 6” will work well too, and are generally easier for the saw to spin.  They can be cheaper, but not always.  It’s hard to find a decent dado set for < $70. I’d avoid the Mibro, Skil, Vermont America, the Avanti set at HD, Oldham, most current Craftsman models, and HF sets.

 

All of the stacked dado sets I know of use beveled teeth on the outside cutters to help minimize tearout (Freud, Forrest, Infinity, Ridge Carbide, Systimatic, Oshlun, CMT, Amana, etc). In order to be of any benefit, the beveled teeth must protrude slightly above the flat teeth of the inside chippers....the same reason that most crosscut blades have top beveled teeth. 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 teeth in between the beveled teeth to minimize the depth of the bat ears, but they’re still there to some degree.  Box cutter sets don’t use beveled teeth, but are intended to cut mainly with the grain, and aren't as versatile as a stacked dado set....cuts across the grain will tend to exhibit more tearout.  The other option for truly flat bottom dados is from a router bit, but there are other drawbacks to that method as well… there’s never a free lunch!

 

This graphic from “Woodhelp” illustrates the “bat ears” effect and the cause:

 

[Mzdadoc]

What's the difference between the two Forrest dado sets?

[Mick S]

From looking at their website, it looks like the only difference in the sets are diameter, bore and an F model with pinholes for Felder saws.  They do have two sets for making only 3/16 and 1/4 widths.