flat surfaces from which one can transfer that accuracy through to other surfaces by means of grinding. Lapping and grinding do not achieve the long distance flatness scraping can, as they act on the entire surface rather than local high or low spots. With precision ground surfaces, any oil film applied to the surface will lack the means to adhere to the surface, especially between two mating parts of exceptional finish. The oil film will be swept away leaving nothing but bare metal and the risk of seizure. Carefully scraping the surface will leave the original high quality surface intact, but provide many shallow depressions where the oil film can maintain its depth and surface tension. When scraping is used for this purpose it is more accurately called "frosting", "spotting" or "flaking" as opposed to fully scraping an accurate surface. Typically a scraped surface is scraped to highly accurate flatness and then "frosting" is applied over it for oil retention. It is claimed to stop the so-called "stick-slip" phenomenon where a machine member might move in a jerky fashion rather than moving smoothly, allowing vibration and chatter. Such frosting will definitely increase oil retention but will also drastically reduce bearing area and capacity. There is no possibility of achieving hydrodynamic bearing performance on normal sliding machine ways. The velocity is far too low. Most of the time the ways will run under boundary lubrication conditions while at the highest speeds it might achieve mixed lubrication. This makes oil additives important in ways lubrication. However, this view is somewhat contradicted by the external link "Scraping methods". Hand scraping leaves a distinctive pattern on the surface that is scraped. This can be suggestive of a high level of precision in the ways, however, sometimes a surface can be marked to appear hand scraped, but it is really just a superficial surface treatment designed to give the impression of a scraped machine way. Hand scraping can also be done by a power tool that has a reciprocating blade and is usually adjustable for stroke length and number of strokes per minute. References Bibliography . Moore's monograph is a seminal classic of the principles of machine tool design and construction that yield the highest possible accuracy and precision in machine tools. The Moore firm epitomizes the art and science of the tool and die maker. External links Scraping methods. Hand Scraping Class. History of