Just found out the standard tolerance for a Class 2 fit on a 1-inch shaft is +0.0007/-0.0000 inches. Found it buried in an old ASME B4.1 PDF from 2009.

Was cleaning up some old reference files on my hard drive and stumbled across it. I'd been using a rule of thumb from a senior guy for years that was way looser. Makes me wonder what other specs I've been approximating that are actually written down somewhere. Anyone else have a 'well, actually' moment with a standard they thought they knew?

3 comments

3 Comments

parkerbrown4d ago

Hold on, sometimes that old guy rule of thumb came from real world build problems the print didn't catch. Maybe his loose fit kept things from binding after thermal expansion or saved a production line from a jam. The book gives you a perfect world number, but the shop floor gives you the number that actually works.

dakota4154d ago

Classic. The old guy rule of thumb is always off by a factor of two. Been burned by that before.

murray.jana4d ago

My buddy followed the spec exactly on a gear housing and the whole thing seized up after a week. The old timer in the shop just laughed and said to double the clearance. Worked fine after that.