What are hand scrapers

A hand scraper is a single-edged tool used to scrapeon the work piece will be colored by the dye on the
metal from a surface. This may be required where astandard. These high spots are scraped off and the
surface needs to be trued, corrected for fit to aprocess repeated until there is an even spread of high
mating part, needs to retain oil (usually on a freshlyspots which total about 60% or more of the surface
ground surface), or even to give a decorative finish.area. If desired the surface can then be
Surface plates were traditionally made by scraping.“Frosted”. A surface prepared in
Three raw cast surface plates, a flat scraper (asthis way is superior to any machining or grinding
pictured at the top of the image) and a quantity ofoperation, although lapping can equal it. Grinding and
bearing blue were all that was required in the way ofmachining stresses the metal thermally and
tools. Methodology, skill, patience and tenacity was tomechanically, scraping and lapping do not.
be supplied by the tradesman.Although well done scraping provides an extra
The scraper in the center of the image is a threemeasure of accuracy, for most applications it does not
corner scraper and is typically used to deburr holes ormatter. A ground lathe bed or milling machine ways
the internal surface of bush type bearings. Bushes areare perfectly adequate for almost all types of work.
typically made from bronze or a white metal.With precision ground surfaces, any oil film applied to
The scaper pictured at the bottom is a curvedthe surface will lack the means to adhere to the
scraper. It has a slight curve in its profile and is alsosurface, especially between two mating parts of
suitable for bush bearings, typically the longer ones.exceptional finish. The oil film will be swept away
The task of scraping has been the bane of mostleaving nothing but bare metal and the risk of seizure.
engineering apprentices, however its versatility andCarefully scraping the surface will leave the original
appropriateness far outweighs the hard work ithigh quality surface intact, but provide many shallow
requires, or is perceived to require. Its effective usedepressions where the oil film can maintain its depth
requires skill and concentration. An often overlookedand surface tension. When a scraping is used for this
advantage of scraping is the ability to take the tool topurpose it is more accurately called "Frosting",
the workpiece. When the workpiece weighs several"Spotting" or "Flaking" as opposed to actually fully
tons and towers head and shoulders over the worker,scraping an accurate surface. Typically a scraped
the apprentice's solution of chucking it on the mill issurface is scraped to highly accurate flatness and then
impractical, if not outright impossible. A skilled craftsman"frosting" is applied over it for oil retention. The
can wield a scraper and turn out work that is the envyadvantage of this oil retention "frosting" is debatable.
of his peers; it just takes more time than the usualScraping can leave an attractive pattern on the
methods.surface and was in fact, the physical evidence of a
The man who scrapes is called a "hand". It is done bycraftsmen built machine. It is therefore still treated as
using a precision surface such as a surface plate or aevidence of craftsmanship by the astute buyer, or the
straight edge as a standard (a straight edge in thismore market savvy machine builders. Even machines
context is not a ruler it is a miniature surface plate ofthat have been ground and not scraped often have
extreme accuracy). A professional scraping tool will befrosting applied. Presumably this is at least partly to fool
a special made tool, not an old file. The standard isthe unsavvy buyer into thinking the machine was truly
coated with a very thin coating of some material suchhand scraped. That this frosting is applied not only to
as Prussian blue. The work piece and standard areway surfaces but also to table tops and other non
touched together by gravity alone and the high spotsbearing areas shows that it is ornamental.