Re: Adjustable Die For Crank Threads

[green-thumbs]

I hacksawed and split a nut (7/16"x 20) then used vice grips as above. Had to go up thread
a number of times to get a "start" for die. Yes it does wear out the nut thread….a throw away
tool that served its purpose. Keep correct size nuts on hand to protect end of crankshaft
and propshaft. Ounce of prevention is worth a pound of cure.
Louis

I used a nut on hand . High grade nuts are available but maybe more difficult to saw and
split.

Mercury Service Tool Catalog lists two taps

1) for early tanks 1 1/8" x 18 N.S. (National Standard)
2) for later tanks with the ‘hex" filter in tank 1 3/16" x 16 N.S. (National Standard)
National Standard can be looked up in Machinist’s Handbook for specific detail to
make a tap to repair the threads.

There is a commentary on change from N.S. to U.N. that sums up change as refinement
of minor nature that affects gauge standards but the threads of both fasteners and threads
are fully mechanically interchangeable. Manufacturing allowances are great enough to
absorb refinements in gages.
Making a tap to restore thread in aluminum would not require hardening. Just a matter of turning 16 or 18 threads per inch on proper size bar stock and then cutting relief(s) lengthwise using milling machine. Simple if you know how and have the machines and
the tooling. Because it isn’t all that simple it might take several attempts to make a
tap that works. A situation where 30 or 40 years in the trade make it seem simple
until you try it. My late father in law was a very good old school machinist.