I was hoping others have found a successful solution

for this fitting/hole.  It measures .670".
A 1/2-14 NPT pipe requires a
23/32 hole, which would open the hole to approximately 0.718.
I'm afraid that there would not be very much material left after
drilling this and attempting to tap it with the pipe tap.
I might be able to turn a sleeve on my lathe that would terminate
with a 3/8 female NPT, which I could tap into the hole.
Any other suggestions or remedies?  Thanks in advance for your
replies.   Paul Conner....engine turns over now....hook up
 radiator and oil cooler, and we'll see if she runs.

The hole size is almost perfect for a 11/16 24 straight thread.
A bolt will then seal the hole. If necessary you can then drill
and tap the bolt for 1/4 NPT.

Or... how about a steel plug high temp epoxied in with a small set
screw installed  from the front side to mechanically lock in the
plug/ 1/4 NPT adapter?

Paul Lamar

Hi, Paul....I did some more research regarding tap and drill sizes.  The
hole measures .670.  The charts show that the tap drill for a 3/4-12 thread
should be 43/64ths, which is .6719.   Looks almost like it is already
drilled for a 3/4-12 thread !  Sometimes we get lucky?    Paul Conner

That should work great. In the 3/4 bolt you should be able to drill & tap
for 1/2 NPT.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2003 All world wide rights reserved.