Wes wrote:

Ignoramus17758 wrote:

In steel, however, this little 1/8" endmill works for a while, then
breaks after 1/2 hour.

Why not use carbide? If you push it too hard it will break quickly. If HSS is breaking
after 30 minutes on a cnc, I suspect you got the life time out of it.

Look at his cut parameters, as Dan noted, his chip load is 0.000125 per
tooth. His feed is too low and the end mill is rubbing and dulling.