Here are some more pics.
Notice how the short tube seats in the counter bore
just short of the steel liner.
You can use a high quality 1.5 inch hole cutter
instead of this shell mill to rough it out before
final boring.
--  Paul Lamar ...No rotor no motor.

This part has people scared but there is nothing to it.  It has been
awhile but I think I drilled a 1.25 i.d. pilot hole and then opened
up with a boring head.
.  It does not take long.  One practice hole and you will have
confidence to do the real thing.     Jerry

Here is an interesting thread that Cary Beasley found where the builder
shows using  a hole saw to make the final hole.
http://www.rx7club.com/showthread.php?t=144200&page=1&pp=15

Even if you plan to finish with boring tool, the hole saw would be
cheaper than a big end mill and safer than a fly-cutter to make the
rough cut.  You will need a high quality bi-metallic (such as Dewalt)
hole saw.  Drill the pilot hole as a separate operation.  Replace the
pilot drill in the hole saw arbor with a solid rod to guide the hole saw.

It occurs to me that if you mount the hole saw in the mill and gently
dress the tooth set on the outer edge with a die grinder, that it would
make a hole with a surface finish very nearly as good as the boring
tool.  The tube could then be turned to fit to the hole.   One benefit
of doing it this way is that you could set it up for the cut with a much
less rigid angle plate.

Aubrey



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