I am planning on making a arbor as follows. First swap to a four jaw chuck and then center drill both end of a piece of one inch round stock about a foot long. Then chuck up a piece of round stock about three inches in dia anb about four inches long. Drill and bore a hole to fit the one inch round stock and also cut a 60 degree taper on the outside so the small end of the taper is a bit urnder 2 inches . And repeat for another matching piece.. And make two retaining rings about !.5 inches in diameter and with a one inch hole with at least one set screw.

The reason for doing this is to bore a fairly well centered hole on some cast gears. After boring the hole in the gear so it is a machined surface instead of a cast surface, mount it on the arbor and rotate it to see how will centered the hole is. Bore it out some more trying to get the hole centered and mount on the arbor and repeat until the hole is pretty close to being centered. The gears are pretty nicely cast, but do have surface fluctuations so it is hard to figure out where to measure from. The gears are bevel gears which does not make it easier. Put a 1/2 inch diameter rod between two teeth and it tended to wobble.

Anyway while thinking about this, I remembered some arbors I had seen with a more gentle taper , but made with slots in the tapers so that one taper could go in the slots of the other taper and one would have a large range of adjustment. Tried searching on MSC and Ebay , but can not think of a good search term. Does anyone know what this type of arbor is called?

And it anyone has a better idea of how to bore out a cast iron bevel gear so the hole is well centered, please comment on that too. The gear will be turning at maybe 100 rpm so perfect is not needed, but it would be nice to have the run out to be less than a 1/16th of an inch.

Dan