And a nice one it is. But it's not representative of all flails. My Ford 917H for example, is as I described. That is, the multiple rows of staggered knives are staggered respective to each other. It leaves no "serrations". That said, I use yet a different type knife, something of a cross between your 920 and 946 knives. So in retrospect, I guess mine may more appropriately be described as a "T" rather than a "Y". Three rows of 11 uni-directional double edged knives, each 2.6" wide overall, with right and left cutting edges. There are 66 edges that cut a 74" swath. But if you consider that 33 x 2.6" = 85.8", you can see that works out to quite an effective overlap.
I have seen the "T" knives and yes, I can see where they would make a smooth cut. Thanks for the compliment on my flail. It's a beast and it's the lightest version that Rear's made at the time I bought it. I'm excited to get my grass knives. As good a job as it does, serrations and all, with the "Y" blades, I know it's going to do an outstanding job on my lawn. I just wish I had some sort of catcher. Actually, I won't do the lawn much with it, the tractor is too heavy but I have very nicely groomed ditches around my place. That's where I will primarily use the flail. And when I need to go back to brush cutting, it only takes a few moments without tools to change back to the "Y"'s.
I highly recommend them, and I'm reasonably confident they're hardened as well. I put on a new set in 2009, and put sharpening on my list of things to do this spring. But when I took off the deflector to start the job, I saw nothing but clean edges. 3 cutting seasons, and no sharpening needed (yet).
