05-30-2012, 01:16 AM
One approach I have used with good success is, lacking a proper reamer, use a standard sized single bearing ball. They are hardened, and smooth. If you drill a little undersized, the finish will allow the ball to burnish the hole to a precise size when pressed through. Then the mating part (shaft in this case) can me made to have the appropriate interference fit. Finish is very important, because in the case of an interference fit, assuming the shaft is solid and the hole is in a massive piece, there is no where for the displaced material to go, except for into the microvoids left in the surface finish. The ball method leaves a very smooth hole, and if the mating part is also turned or polished smooth, the amount of interference should be minimal.
Also to be considered is length of engagement. Naturally, the longer the engagement, the more pressure it takes to assemble, and you must consider the compressive strength of the shaft when calculating the fit. Some people actually use a little taper to make the fit a bit tighter at the makeup point, thus reducing the stress on the pressed part.
I believe that Machinery's Handbook has a bit of data on this subject as well.
Also to be considered is length of engagement. Naturally, the longer the engagement, the more pressure it takes to assemble, and you must consider the compressive strength of the shaft when calculating the fit. Some people actually use a little taper to make the fit a bit tighter at the makeup point, thus reducing the stress on the pressed part.
I believe that Machinery's Handbook has a bit of data on this subject as well.