Tarry, the gears are case hardened, about .060-.070" deep, the outer casing is probably around 58-60 on the rockwell C scale. Darned hard, once you get thru that it is just tough material, kind of like machining 4140. I suspect that it is sae 8620 which is what most modern gears are made from and induction heat treated. The insert in the picture is just a generic that was worn down. I think it is a Kennametal K68 general purpose (C3) TCN insert. You can also use K313 inserts (C3-C4) in its place. The main reason I use these is because I have 2 small fly cutters and several lathe tools that use the same insert. I have been finding these on Ebay and local flea markets. They are generally cheap compared to most others. There was no real reason for the 7* other than they were available easily and I have use for them in multiple tools. The 11* is little more fragile on the edge of tough material but does leave a better finish if the material is not to tough or hard. Sometimes its a crap shoot and you need a little finesse to get the job done. I have them in both .016" radius and 1/32" radius tip. I also grind a chip breaker on them with my diamond wheel as needed and hone them with a diamond or ruby lap. The one pictured is a 322 series insert. 3/8" inscribed, 1/8" thick and 1/32" radius. I do run these a little faster when boring to help with chip breakage, I do not generally use lube with carbide, I do use water soluble sometimes if the part is getting to hot. In the real world you would rather the chip be blue, that means its carrying the heat away from the part, and not keeping it all in the part your working on.