[SEL] Tap & Die Set Help Needed--OT

[Jim and Diane]

Hi Dave,

I did quite a bit of poking around in the 15th edition of Machinery's 
Handbook and was not able to find any reference that would account for 
standard threads that are 1/32 oversize.  It wasn't a complete blank though 
as I found that 1/2-12 is still a standard size.  It is no longer part of 
the standard commonly used for ordinary American nuts and bolts which is the 
UNC or Unified National Coarse threads.  If you go way back, this series was 
known as USS or United States Standard threads.  You can still see this 
designation and it's companion, SAE in auto parts stores although neither 
standard has existed for well over 60 years.

!2 thread is a standard that was used, and maybe still is, for things like 
packing glands and valve seats which are threaded 12 threads per inch 
without regard to diameter. 1/2-12 would probably not be used for this kind 
of application but the standard exists, or did in 1957.

Jim

Jim and Diane Kirkes
Hemet, CA , U.S.A.
jd.kirkes at verizon.net
----- Original Message ----- 
From: "Dave Rotigel" <rotigel at alltel.net>
To: "The SEL email discussion list" <sel at lists.stationary-engine.com>
Sent: Sunday, March 12, 2006 1:41 PM
Subject: Re: [SEL] Tap & Die Set Help Needed--OT


Hi Arnie,
         I just looked at the taps carefully and all of them (except the
1/2" X 12--which is marked GTD and not Wiley & Russell) have 1/32 stamped
on them as well. I just measured the Wiley and Russell taps ( 3/4', 5/8",
and 7/16") and found them to be between .025" and .031' OVERSIZE. 1/32"
equates to .03125". That would seem to mean that the whole set (dies and
taps) are 1/32 oversize.
         The question would now seem to be "Why would anyone want a set
that is 1/32 oversize?"
                 Dave
PS, The 1/32 is NOT an owners mark nor does it indicate 1 out of 32. I'm
sure it indicates 1/32 oversize--the question is WHY?
PPS, "Fig 222" is stamped in black in on the front of the wooden box.