The second and third blades have the little nub behind each tooth, that’s supposed to be a safety thing, reduces the amount of material it can take or something like that. When i bought my Frued stack dado about 25 yrs ago, i think thst was one of the advertised features.
I believe that little nub is required by European safety regulations, at least for industrial use.
As fat as the general question goes, Bosch owns Diablo and Freud, and seems to be one of the world’s largest producers of certain types of blades, such as jigsaw blades, to the point that most power tool manufacturers sell Swiss made blades under their own brands, that were made by Bosch.
Back in the 1980s and 1990s, Bosch sold router bits and other tooling under the Bosch brand, and in certain markets and categories still does, but the router bits were not considered “the best” and came out poorly in some testing, so presumably Bosch decided to purchase Freud Group, since Freud was considered a fairly decent blade and bit manufacturer.
I don’t know who came up with the technology, but I presume Freud may have developed automated technology to make small carbide toothed blades, which has led to carbide toothed oscillating blades, with fairly tiny teeth, and carbide toothed reciprocating saw blades, and carbide toothed jigsaw blades, etc.
From what I recall, these only entered the marketplace around the time Bosch bought Freud Group in 2009, give or take, when previously, “carbide” blades where usually either larger carbide teeth on circular saw blades, or carbide grit used grit abrasive cutting on Other types of blades.
“Bimetal” blades where a thing, but that is a different technique involving welding or fusing a strip of harder more durable steel on the edge of a more flexible alloy, before using an automated system to grind the blade teeth on, similar to the way normal bandsaw and hacksaw blades are made.
Stellite toothed blades were also a thing, but mire of a niche thing, which I presume uses an automated system to weld a glob of stellite onto the teeth of blades such as bandsaw blades, before using an automated grinding system.
With the individual carbide teeth, the individual teeth need to be placed, and brazed onto the blade, before final grinding.
Bosch, or Freud, the owner/s of the Diablo brand, likely developed a highly efficient automated system To place and braze and grind the teeth, making production costs incredibly low.
