Shoddy Hardware (Was: Re: WW fixtures (was Re: "New" PDP-8))

From: Pete Turnbull <>
Date: Sat Apr 6 01:31:25 2002

On Apr 5, 19:54, Merle K. Peirce wrote:
> Peter, could you address how Acme threads fit into these schemes? I
> should expect that they are always relatively coarse.

In a sense, they don't. They're not normally used for fasteners, which is
what the others are for (arguably with the exception of BSP) :-)

Yes, they're usually fairly coarse, and used for things like leadscrews on
machine tools and vise jaws. For leadscrews, they're usually made to some
specific pitch that equates to some nice decimal number of turns per inch,
or millimetres per turn. They're also unusual in having large flats on
both the crests and troughs (most other threads are rounded on one or the
other); in fact they're almost square -- the thread depth is 0.5 x the
pitch, and the walls slope at only 14.5 degrees, so the included angle is
29 degree, much less than most threads which are typically either 55 or 60
degrees. And the clearance between screw and nut is very small, typically

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Sat Apr 06 2002 - 01:31:25 BST

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