Originally Posted by
Rambozo
Scraping is how you get the ways truly flat and perpendicular to the other axis. It also reduces friction as when scraping you shoot for a certain number of contact points per square inch. Even after precision grinding, hand scraping is what it takes to get things as near perfect as possible. Flaking is the decorative pattern that is put in after scraping. They also serve to hold the way oil. There are very few people that can do good scraping anymore. I missed out on my chance to learn form a real scraping hand, as he went and died before passing on that skill. I did get to see some of his work, and he did fix a lathe in our shop that had a twist in the bed. There are a couple of good books on the subject. They are back in print so not hard to find anymore, but not cheap.
Machine Tool Reconditioning by Edward F. Connelly 1955
Foundations of Mechanical Accuracy by Wayne R. Moore 1970 (One of the Moores from Moore tools)