I've got no problem running a tap at 50 SPM. Assuming that the tap is a de cent brand and the steel not overly hard. I've run 1/4" 20 tap at 100 RPM.The taps last quite a long time; never had breakage at those speeds. I c an understand running the taps faster when high production is going on. Bu t be prepared for breakage. I hate running taps fast. Digging out a broke n tap is something I don't like to do. Some people say that you should run taps fast, and let the tap itself pull itself in(whatever that means). I disagree. Except as noted in a high production environment.