John wrote:
Ed Huntress wrote:
wrote in message
...
We have to replace a 6" diameter x 1.5" wide cast iron gear that has two
broken teeth. It's in the middle of a 4' long 1.25" dia. shaft. The
original gear was pinned to the shaft with a .5" taper pin through a
boss
on the gear, but the pin bore was drilled and reamed by hand at the
factory and it's not centered. A mechanic wants to try to hit the
tapered
hole in the shaft and I don't think that will ever work. If anything,
the
new pin should go 90 degrees from the original.

My idea is to turn down the boss from 2.75" to 2.25" and saw-cut across
the boss in two places (+) and clamp the gear on the shaft with a split
collar on the bisected boss. I think it'll hold almost as good as the
pin.

It may hold, but you're taking a chance putting a highly-loaded chunk of
cast iron under stress while it's simultaneously under another load --
the
shear load that will appear between the inner diameter of the gear and
the
split collar.

The tapered pin was there for a reason.

Why not get a steel gear to replace it? That would solve your problem;
the
clamp should work fine.



A good right winger could weld it and then say a prayer that it will
hold for ten years.

And a left winger could pass a stimulus bill to pay
disadvantaged people to turn the shaft by hand...