3/8 x 16 tap hole size is 5/16 (.3125)
3/8 x 24 tap hole size is Q = .3320
You have .320 so a fine thread should work "fine":)
-----Original Message-----
From: O'Farrell, Fergus [mailto:Fergus.OFarrell@ngc.com]
Sent: Tuesday, December 28, 2004 8:15 AM
To: datsun-roadsters@autox.team.net
Subject: Tap my alternator bracket?
I am swapping out my alternator for a passenger side GM one wire, and have a
question for the veteran machinist crowd. The alt bracket (from an early
car) has .320 thru hole. The new alt and the steel triangle support on the
front cover have .390 thru holes. (clearance holes for 3/8" bolt) While I
know I can get a bushing to take up the large hole in the
alternator/support, I am still left with a really long, reallly thin thru
bolt. How about running a tap into the alt bracket and just bolting to it?
My Machinist manual is in a box, does anyone know the preliminary hole size
for for 3/8 Coarse or Fine threads? In other words do I have to pre-drill
to larger diameter or just tap out from the existing .320? If the fwd end
of the alt was unsupported I wouldn't consider it, but but I am already
having a time trying to find M8-1.25 x 100mm bolts for the triangular
bracket back onto the front cover (100mm due to add'l .800 spacers to line
up the
belts). Sorry, too many questions at once. Fergus O, roadster in
hibernation, HB, CA
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