Plastiage is what used to be known as taking leads. Off with the main top cap, ( or big end ) and lay lead wire across the journal complete width. These rolls were not unlike a roll of fuse wire, and were in different diameters. Box it up, torque it up and let it all go. Out with your micrometer ( still got mine from 1960 Brown and Sharpe 1-2 inch imperial,) no mm (Mickey Mouse ) then and Mike it up. You could do the same with a vernier. Clearances were specified by the engine manufacturer and shell bearings replaced/ crank grind carried out as necessary. Back in the old steam days when I started out in 1960 taking leads on a big old up and downers it was a long job with brass shims sometimes half an inch thick downwards fitted. Mains and big ends were flogged off, caps chain blocked off, several leads laid many times before getting to the final scrape in using engineers blue to perfect the job. Any blow holes exposed during scrape ins of the 2 inch plus thick whitemetal of the cap spelt trouble, unless they could be half round chiselled into a nearby oil-way the job was scrap. This would mean a complete strip down, back to workshops and into the plumbers shop, melt out all the bearing caps both top and bottom, black casting sand with a wooden centre mandrel made up and the whole lot recast. Up on a large faceplate on the lathe and bore it out to size. If the casting process was not stirred/ vibrated correctly and any further blow holes exposed back to square one. Often a long and tedious job. Don't forget all the shims had to be present when boring so as to facilitate future scraping etc. Hold your breath jobby alright here on the final cut or what . This was just one of the things you were taught back then along with lots of other work.Back to the ship, reassemble, flog it up, further leads taken, maybe thin shims taken out, engineers blue out and appliedand in with the turning gear, off with the caps and so on and so on. Long job indeed. Used to have to achieve so many high spots from the crank on the White metal surface, can't remember how many, apprentices would get fed up and falsify the blue markings but the charge hand would have to check it over before the final box up, he had seen it and done it all before and would not be fooled. So there it is, sorry for the long drawn out explanations but you have to say I did own up to " taking leads ) and not perhaps attempt to hive years off my age by saying The perhaps more modern " plastic approach " ?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.