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On Thu, 1/10/19, Jody <jp4lsu@...> wrote:

Subject: Re: [atlas-craftsman IO] Internal Threading - Compound Setup
To: [email protected]
Date: Thursday, January 10, 2019, 8:24 PM

You're
absolutely correct Jim.A fastener in tension will
obviously fail at the minor diam or thread root and at the
nut.?
Being an airframe stress analyst and also working
in the fatigue and damage tolerance analysis field for
airframe stress concentrations or risers are a big concern
in the life of parts.
Stress concentrations occur and fastener holes,
fillets, cutouts in skin, radius', etc.The
higher the stress? concentration, the shorter the
life.-Jody






-------- Original message --------
From: Jim Irwin <jimirwin@...>
Date: 1/10/19 1:19 PM (GMT-06:00)
To: [email protected]
Subject: Re: [atlas-craftsman IO] Internal Threading -
Compound Setup

For those who care about tensile strength of screws, the
root of screw threads very significant affects screw tensile
strength!
A sharp bottom V is a stress concentrator/riser, and defines
the minor diameter of the screw. Rounded is better, as is
maximizing the effective diameter of the screw.

Conversely, the top of the thread has esentially nothing at
all to do with tensile strength.

And we are talking about SAE (60 deg) and British (55
deg(?)) V type threads here.

Buttress threads are pretty cool, but who knows about
these?

Jim I


On Jan 10, 2019, at 1:05 PM, Charles
<xlch58@...> wrote:

A full profile insert makes the entire thread, flank, root
and crest. Because the root and crest width varies by
pitch, they are only good for a limited number of threads.
A partial profile essentially only cuts the flank and root,
but you have to finish the crest. A pass with a file will
do it generally, depending on how picky the thread is. A
tool with an 8-48 tpi range is not going to have the proper
root width across that whole range, it is only going to be
right for the top end of that range (48). From watching
youtube, only a limited number of the "machinists"
there bother with root or crest shape, using a sharp v tool
for everything. Whitworth and some other threads have a
radius at root and crest.