I have posted some information about my experiences with dados and trim saw blades about 2 weeks ago, but there is some additional information in the detail below.

From my experience in magazine reviews and in newsgroups it appears there is a need to provide information to woodworkers as to the purpose for each of the saw blade and dado designs in the marketplace.  I think I am learning, but it is not without a large amount of effort.   Does anyone know of a book or other information about the details of saw and dado blade design?  Follow me in the somewhat long-winded explanation below:

I bought a couple of Freud dados and a trim saw blade. 

Dados

I bought a Freud SD208 and an SD308 dado.  The SD208 is touted as the dado for woodworkers in the magazines.   I found that the SD308 was the best for my purposes (no blowout in crosscut of solid woods.).  The concept of what a negative hook and positive hook tooth does does not seem to be well known.  You can find info on the SD208 and the SD508 and now there has been a lot of interest generated in the SD608 (all negative hook blades).  The SD308 is called the “safety dado”.  What the heck does that title do for me?  I think the real message should be that it does a great job in solid wood with little chip-out for a reasonable price…oh, yes it also has an anti-kickback design (to me not the number one specification). 

 Since I am an engineer and a user of the product as well, I think that there is a disconnect between the engineering and the marketing people and between the marketing people and the end user.  I’ll bet if I asked the engineer why the anti-kickback feature is in the SD308 and not the SD208, he would answer:  “Because it would be very hard to feed wood into the SD208 fast enough to get kickback, where it is so easy to feed wood into the SD308 that you could create a kickback condition very easily.”  I purchased the SD308 dado from the recommendations of a Freud technical representative.  I used this to put grooves in the sides of a set of drawers about 3/4 inch wide by 1/4 inch deep.  Let me tell you.  Using this dado over the SD208 dado was safer, faster and less nerve wracking than using the SD208.  The reason it was safer was not the anti-kickback feature.  It was because it was easier to feed and I could do the dado in one pass where it took about 3 passes to do it with the SD208.  I realize that the easier feed pressure could necessitate the anti-kickback design, but why feature the part that keeps one from going too fast and deep in a dado.  Does Ferrari brag about the seat belts in their cars as the FIRST feature?  The seat belts and air bags are used if the driver pushes the car’s main feature too far.  The message to the end user should be that the SD308 is a Ferrari and needs seat belts.  …Quite a different message than the Ferrari has seat belts and, by the way, goes fast.

Trim saw blades

In researching blades for the Dewalt trim saw, I was completely confused.  The Woodcraft Supply and local wood machine suppliers do not really know the difference in blades that are available for this saw and the literature I have seen is not clear.  Freud says that their TK004 is the BEST for plywood.   I wonder if there are other people out there that would love to know that.  I don’t know where I can find that blade in the local area (Ann Arbor, MI).  Electric Tool and Supply on State Street was the only place locally that I know that had the TK003.  

In the full-line Freud catalog, the 5 3/8 trim saw blades are described.  Although the specifications are shown in detail, there is no performance distinction between the TK003 and TK004.  Is that really true?  I believe that if I were very concerned about plywood, I would want the TK004 (which no one sells locally and I would have to buy on the Internet).  I bought the TK003, but I think I would gladly pay the difference in price (about $18 for TK003 vs. $24 for the TK004) for (what I perceive would be) the difference in performance in plywood.