Very disappointed with this end mill. I was engraving on a flat sheet of 6061 aluminum and it broke after about 7 minutes of starting work. I didn't think I was going very fast, the spindle was running at 10,000 rpm, 14 ipm feed and 0.002 documents. For some reason it just came out. I used lube and air to get the tiny shavings off, but it still broke.