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

[Dave Rotigel]

Hi Jim,
         Yes, the 1/2 X 12 was a "standard" size until sometime early in 
the last century. (Can anyone help me here as to when 1/2 X 13 became the 
"standard" size?) I've run into it (ie 1/2 X 12) on some old iron 
applications. They tell me that Glenn Karch sometimes still uses  1/2 X 12 
set screws, but with a 1/2 X 13 tapped hole. I can not verify this, 
however, since I've only heard it from one person!
         Dave

At 06:01 PM 3/12/2006, you wrote:
>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.
>
>
>_______________________________________________
>SEL mailing list
>SEL at lists.stationary-engine.com
>http://www.stationary-engine.com/mailman/listinfo/sel