<VV> Re: valve seat set screw retention/tap sizes

[N. Joseph Potts]

Folks, we're mixing up screw numbers (5, 8), with numerators (the upper
number in a fraction) and thread pitches (32, 40, 44) with denominators (the
lower number in a fraction). I feel self-conscious even discussing this
foolishness on a list containing members who live in countries that use the
metric system, which dispenses with all this nonsense by using decimals
(e.g., 4.32).
     Ignore SCREW NUMBER 5 (the one followed by a DASH and then either a 40
or a 44). Its diameter is LESS than 1/8 inch (er,  0.125 inch - you can use
decimals with inches, too, but . . .). By the time you use that 9/64
(0.1406) bit, you're ALREADY over that diameter (compare the decimal
renditions). The screw DIAMETER is 5/32 (0.156) inch. This is the diameter
of screw SIZE 8. The common Size 8 thread has a pitch of 32 per inch,
leading to the designation 8-32.
     The tip-off is in the punctuation. 5/32 is a fraction (note diagonal
between the numbers). 8-32 is a thread designation for something nominally
5/32 (0.156) inch in diameter with 32 threads per inch of the length of the
fastener. Note dash between numbers.
     AND, there are 5,280 feet in a mile. This stuff goes on forever. Give
me a meter anytime.

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C

-----Original Message-----
From: virtualvairs-admin@corvair.org
[mailto:virtualvairs-admin@corvair.org]On Behalf Of John
Sent: Monday, April 19, 2004 10:26 PM
To: virtualvairs@corvair.org; bakwudz@rcn.com
Subject: <VV> Re: valve seat set screw retention/tap sizes


5-32 is not a standard tap size, 5-40 or 5-44 is standard.  You can
order them from a industrial supply house, for example MSC Industrial
Supply Co.

<http://www.mscdirect.com/>

When ordering ask for a catalog.  You will get a 4 inch thick, hard
bound, fine print, 20 pound monster over 5000 pages!  Great for
flattening out creased gaskets.

John

> From: "Tom Willcox" <bakwudz@rcn.com>
> To: <virtualvairs@corvair.org>
> Date: Mon, 19 Apr 2004 19:32:58 -0400
> Subject: <VV> valve seat set screw retention/tap sizes
>
> I have a question regarding the "cromwell method" of valve seat retention:
> according to two different sources, I am supposed to finish drilling 1/4
> inch deep with a 9/64 drill, then tap with a 5/32 bottom tap, then insert
a
> 5/32 set screw.  After searching for hours, my question: is there such a
> thing as a 5/32 tap OR fastener?  The only things I have found smaller
than
> 1/4-20 are 8-32, 10-32, 4-40, etc.  Am I missing something obvious, or is
> this information incorrect?  Where can I find this stuff?  This is driving
> me nuts!  (short drive, btw)
>
> Thanks,
>
> Tom Willcox
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