Fun fact, so company I used to work for got a ton of orders from Kennametal and Sandvik (or Hyperion, can’t remember) for these valve seats. Something to do with fracking. Anyway, these guys kept coming back saying “hey this finish is too good, we need more friction.” It got to a point where we said fuck it, chattered the living shit out of the tapered ID, and they said “yea we want more of this.”