I recently found myself doing an output shaft replacement to a gear case that had been subjected to violent happenings and had a crack welded up. Removing the bearing carrier proved nearly impossible, and it had to be driven out with wedges and a sledge hammer with the case gently warmed to 60 degrees C with a heat gun. Uh-Oh.
On re-installing the outer conical roller bearing, the case bound up. Uh-Oh indeed. This spurred suspicions that welding heat and / or prior violence had rendered the bore out-of-round, but I had no inside micrometer on hand to confirm this, and this went down deep in the boonies where tools and equipment was a long way away. What do?
1: Obtain a screw slightly longer than the bore to be measured.
2: Take the head off the screw with a hack saw.
3: Install a cap nut on the screw along with a lock nut.
4: File down the cut end of the screw until it comfortably fits in the bore to be measured.
5: Round off the cut with a file, finish with 600 grit sand paper and a battery drill.
6: Use improvised tool in the same manner as a traditional I.D. micrometer.
Using this method I was able to ascertain that the bore was 0.15mm out of round at the outer end, warping to 0.25mm in the other direction at the inner end. Scrap gear case confirmed.
I’ve never heard of this method before, it just sort of came to me while pulling my hair out, so figured I’d share.