Compressor Refurbishment – Part 4

Mounting the crankshaft on my little lathe turned out to be pretty straight forward: using my Noga indicator holder again, this time with the cheap Fowler indicator from my last post followed by a 0.0005″ B&S indicator, I got the rear main journal bearing  centered in the chuck. I then followed the same procedure to get the front main journal bearing centered in the steady rest.

The plastic sheeting is to keep the carbon in the cast iron from getting on the ways. In retrospect I should have use something hard, at least between the chuck and the follow rest, to make cleanup a bit easier. Still, no harm no foul.


I’ve done long work a few times on this lathe (primarily drilling out aluminum paintball barrels for sizing inserts), and knew I’d need to add a modification to turn cast iron (because of the force involved). The original steady rest jaws are bronze with no rolling components. I added some small bearings with simple shoulder bolts into the jaws. Not my favorite solution, but very easy. I think it’s likely I’ll go back and make a set of jaws that supports the bearings on both side in the future.

The original shaft was 01.375″, I took it down to 1.290″.


You can kinda see this in the above photo, but this makes it very obvious that the old center (which I used to mount the gear puller when I removed the pulley) is no longer centered on the new shaft. This should not be a problem.


Similarly, the keyway is no longer parallel to the shaft. This could be recut on the mill, leaving a little unused slot on each end, but I decided to accept a shorter key in this case.


I forgot to take pictures while making the spacer (made from 1.185″ ID, 1.375″ OD 4130 tube) and test fitting everything, so we’ll skip to putting the bearings on. I initially tried to hand fit them by putting them in the oven, but I guess the clearance wasn’t quite enough at 250°F, so I pushed them the rest of the way on. They slide around two tons of applied force.


To be followed by some cleanup on the rest of the unit, then reassembly!