Chose the cheap end mill over the coated one, 60 parts later I regret it
Had a job last Tuesday, stainless steel parts for a local shop in Phoenix. My usual coated end mill was out of stock at the supplier, so I grabbed the uncoated carbide since it was $18 less and I figured one batch wouldn't matter. By part 40 the finish looked rough, and by 60 I was getting chatter on the corners. Ended up swapping mid-run and redoing the last 15, which ate up the savings anyway. Should I just keep a spare of the good ones now, or does anyone run cheap tooling successfully on stainless and just change it more often?
That chatter on the corners is the real tell here, not the rough finish. Stainless work hardens the second your tool rubs instead of cuts, and a cheap uncoated mill dulls faster, which means more rubbing, which means the surface gets harder right where you're cutting. So it's a loop. The tool wears out, the part gets tougher, the next tool wears out even quicker. On stainless that loop bites you way harder than it would on aluminum or mild steel. You can run cheap tooling on stainless if you keep the feed up and never let the tool dwell, but the margin for error is tiny. Keeping a spare of the good ones is cheaper than redoing 15 parts.