On Sunday, July 29, 2012 8:53:54 AM UTC-7, Tim Wescott wrote:
On Sun, 29 Jul 2012 05:00:32 -0700, phaedrus wrote:

I've seen pictures of threaded tapers being machined on lathes and was

wondering what the hell use they are?

No one's mentioned wood screws yet, which are tapered along their length,

or sheet metal screws, which are tapered at the nose.

Aren't taps tapered?

Modern taps aren't really tapered, the threads are just on a tapered shaft
(the top of the crest is ground off of the leading teeth, so cutting is
progressive and not done all with the first tooth). But, old-timey taps
WERE tapered, so you could get any tightness of nut you wanted.

This was important when bolts were made with threading-plate type
dies (with poor diameter control) on forged rods (again, with poor
diameter control).

Another tapered-screw application is seen on the pilot of auger-type
wood boring bits. Yet another, is sometimes seen on citrus juicers.