All the tools you need in the house explained


What are hand scrapers

A hand scraper is a single-edged tool used totogether by gravity alone and the high spots
scrape metal from a surface. This may beon the work piece will be colored by the dye
required where a surface needs to be trued,on the standard. These high spots are scraped
corrected for fit to a mating part, needs tooff and the process repeated until there is
retain oil (usually on a freshly groundan even spread of high spots which total
surface), or even to give a decorativeabout 60% or more of the surface area. If
finish.desired the surface can then be
“Frosted”. A surface prepared in
Surface plates were traditionally made bythis way is superior to any machining or
scraping. Three raw cast surface plates, agrinding operation, although lapping can
flat scraper (as pictured at the top of theequal it. Grinding and machining stresses the
image) and a quantity of bearing blue weremetal thermally and mechanically, scraping
all that was required in the way of tools.and  lapping  do  not.
Methodology, skill, patience and tenacity was
to  be  supplied  by  the  tradesman.Although well done scraping provides an extra
measure of accuracy, for most applications it
The scraper in the center of the image is adoes not matter. A ground lathe bed or
three corner scraper and is typically used tomilling machine ways are perfectly adequate
deburr holes or the internal surface of bushfor  almost  all  types  of  work.
type bearings. Bushes are typically made from
bronze  or  a  white  metal.With precision ground surfaces, any oil film
applied to the surface will lack the means to
The scaper pictured at the bottom is a curvedadhere to the surface, especially between two
scraper. It has a slight curve in its profilemating parts of exceptional finish. The oil
and is also suitable for bush bearings,film will be swept away leaving nothing but
typically  the  longer  ones.bare metal and the risk of seizure. Carefully
scraping the surface will leave the original
The task of scraping has been the bane ofhigh quality surface intact, but provide many
most engineering apprentices, however itsshallow depressions where the oil film can
versatility and appropriateness far outweighsmaintain its depth and surface tension. When
the hard work it requires, or is perceived toa scraping is used for this purpose it is
require. Its effective use requires skill andmore accurately called "Frosting", "Spotting"
concentration. An often overlooked advantageor "Flaking" as opposed to actually fully
of scraping is the ability to take the toolscraping an accurate surface. Typically a
to the workpiece. When the workpiece weighsscraped surface is scraped to highly accurate
several tons and towers head and shouldersflatness and then "frosting" is applied over
over the worker, the apprentice's solution ofit for oil retention. The advantage of this
chucking it on the mill is impractical, ifoil  retention  "frosting"  is  debatable.
not outright impossible. A skilled craftsman
can wield a scraper and turn out work that isScraping can leave an attractive pattern on
the envy of his peers; it just takes morethe surface and was in fact, the physical
time  than  the  usual  methods.evidence of a craftsmen built machine. It is
therefore still treated as evidence of
The man who scrapes is called a "hand". It iscraftsmanship by the astute buyer, or the
done by using a precision surface such as amore market savvy machine builders. Even
surface plate or a straight edge as amachines that have been ground and not
standard (a straight edge in this context isscraped often have frosting applied.
not a ruler it is a miniature surface platePresumably this is at least partly to fool
of extreme accuracy). A professional scrapingthe unsavvy buyer into thinking the machine
tool will be a special made tool, not an oldwas truly hand scraped. That this frosting is
file. The standard is coated with a very thinapplied not only to way surfaces but also to
coating of some material such as Prussiantable tops and other non bearing areas shows
blue. The work piece and standard are touchedthat it is ornamental.



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