I was thinking about something and could not figure it out....you know how if we spin a rod bearing they machine the journal down and then put in undersize bearings. what happens if we spin the center bearing and the thrust bearing gets damaged. do they machine that area down too? so like they machine the sides and then journal of the crank? and then put an undersize thrust bearing in? I was just wondering?
thanks
james

The thrust bearing is there to control thrust forces - the side-to-side movement of the crank.

Thrust bearings don't "spin" in the sense that rod bearings do, AFAIK, nor do mains, simply because the forces they resist are spread out across the length of the crank. They hold the crank in place - the rod bearings take most of the load abuse, which is why they tend to fail when underlubricated. You'll almost never hear of a main bearing failure - they are rare.

If a thrust bearing does fail, however, i assume they do machine down that journal, as well as the thrust surfaces...

If anyone knows better, feel free to correct me.