Thanks for all the quick replies. I went to the hardware store and
bought the next drill size up, 17/64". The website mentioned below as
well as an earlier website I checked had formulas indicating a drill
size of .257" which is just slightly larger than 17/64". I also bought
another 5/16-18 tap, made in the USA. It cost about half of what I paid
for the 40 piece Harbor Freight tap and die kit I was using. The new tap
I bought suggested the "F" drill bit and naturally there were no drill
bits sold that referenced letters.
Anyway, with the slightly larger bore and the more robust tap (the
square tip on the end was even larger), the hole is now tapped, going
quite smooth as expected. I am not a professional mechanic by any means
but I am experienced enough to know when things are right and when they
are not. The previous tap was not going well and I did not want to force
it, thereby really making problems worse.
David Councill
67 BGT
72 B
________________________________
From: Richard Ewald [mailto:richard.ewald@gmail.com]
Sent: Sunday, August 19, 2007 10:47 AM
To: Councill, David
Cc: mgs@autox.team.net
Subject: Re: [Mgs] exhaust system flange
Personally I would buy a top quality tap. if you bust the tap off in
the manifold the cost of extraction will far exceed the cost of a
quality tap. Also according to this page
http://www.fairburyfastener.com/tap_drill_decimal_inch.htm the correct
tap drill for a 5/16-24 is an I which is .272" in diameter. somewhat
bigger than a 1/4" drill.
Have you considered converting to bolts instead of studs? I find them a
lot easier to work with. YMMV of course.
Good luck,
Rick
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