If everything is clean, and the tapers match, there should be no need for any fancy tricks.

MichaelG.

I did an article in MEW on this very topic a couple of years ago. Two good firm taps with a copper hammer is all it takes. My test example for the article was a 13mm chuck on an MT1 arbor, so quite a small taper the chuck mounted on. I tested it in the lathe with a 1" drill bit with the shank turned down to 1/2". Tried everything drilling a hole in steel and could not get that taper to let go. You would shear the key in the tailstock or slip the belts first I reckon.

One tip I learned from old time Harley-Davidson racers when assembling their flywheels with tapered crank pins is to wash the tapers with distilled water before assembly. The factory race team always reckoned that degreasers leave a film and solvents including alcohol leave traces of salts on the tapers that can interfere with the fit. Seems to work for me.

And of course you must go over both tapers first and remove any burrs. The ends of the taper on the arbor always seems to need a little bit of a clean up with a fine file.

1" drill mounted on MT1 taper in action:

Edited By Hopper on 15/10/2022 02:31:59

The people who used the radial drills where I used to work put the drill chuck in the socket and then brought it down onto the drill table or vice to secure it. They never had a problem getting the chuck and arbor out of the drill using drifts but if the arbor got damaged they were well and truly wedged into the chuck. I resorted to cutting off a number of them and drilling out the core that remained. This usually reduced the pressure on the taper enough to get the remains out with little effort. The point is that over time the chuck is being pushed further onto the arbor by both the forces of fitting the chuck into the drill (impetus due to momentum or direct pressure) and the pressure on the drill bit in use and together these usually work towards keeping the two parts together.

Martin C

They are dried with clean air or lint-free cloth before assembly.

Chances of rust developing in the hot oil-filled crankcase of a racing motorcycle engine that is rebuilt between each meeting are zero to none.

The tapered crankpins are drawn into the tapered holes in the crankshaft flywheels by large nuts on very fine threads outboard of the small end of the taper. So no wringing, just wedging action.

Some Harley engines with hundreds of horsepower in nitro drag racing bikes still use tapered crank pins. They are regarded by many as superior to pressed together cranks.

Later model production Harleys that changed over to pressed-in parallel crankpins as a cost saving measure suffer from crankshaft "creep" as they do not grip as well as the old tapered pins. For performance work, the parallel pins have to be TIG welded in position to stop them moving. That is even with a 6 thou interference "crush" fit that takes a 100 ton press to assemble.

Edited By Hopper on 15/10/2022 10:15:50