304 stainless, the edge was gone in one pass

Customer showed up with 304 and a sketch on a napkin. HSS that cuts 12L14 all week was rounded off in one pass. I know stainless work-hardens. I still did the polite depth and the polite speed and it laughed. What are you actually running.

Slower than you think, and a cut deep enough that you are under the skin you just hardened. Rubbing 304 is how you make a file. Sharp HSS or a grade meant for stainless, not the insert you use on mild. Coolant if you have it. If you don't, don't linger.

I cut 304 with the same CCMT I use for everything and it was fine. Maybe your tool was already dull.

Ken, it wasn't. I watched the edge go. Your 'fine' is a different bar or a different memory. I went slower, deeper, and it cut. The napkin sketch is now a part. I'm billing him for the insert he didn't think he needed.

304 punishes a timid cut. You already found that. Don't sand the work-hardened skin and try again with the same tool. You'll just polish the lesson.