Walter Harley wrote:
I see these things called "roughing mills" that look sort of like a tap. I
assume they're end mills that are optimized for removing a lot of material
fast, rather than getting a good finish. Am I right? And if so, what are
the particulars - like, how much of a cut can they take, and how long before
they get dull? How much better are they than a regular end mill?

The thing that prompts the question is that I have some 5"x5"x3/4" steel
(10L12, I think) blocks that I want to take a 4"x4" notch out of the middle
of, to make a "C" shape. I was going to use a bandsaw, but I don't have
access to it any longer; all I have is a small mill/drill and a (manual)
hacksaw. I could chain-drill and use the hacksaw, and then finish with a
mill; but I was wondering how else the problem might be approached, and got
to thinking about what it would take to just take it all out with a mill.

Thanks!


Walter
The rougher endmills work very well, the serrations on the teeth cut
the chips up into small bits instead of the long sharp shards that will
stick in your fingers. :-) And because of the interuped cut I find they
don't chatter as much when taking a full width cut. A good quality
rougher will last longer than a compareable regular endmill but is a
little more difficult to sharpen, as you hace to grind the flute and not
the circumfrance of the tool. It can be ground on a standard tool and
cutter grinder but I have only done them on CNC T&C grinders myself.
As for price a rougher will be about 40% more than a comparable
regular endmill (as per KBC pricing on Niagara cutters) You will also
want to get them in the TiN or TiCN coating, it only adds a couple of
dollars and should double the life of the cutter in most materials.