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Optimum machining conditions were determined for various materials,
steels, cast irons, brasseses, bronzes and an aluminium alloy. Surface
finish readings were taken with the Sigmatex and the Surtronic and values
of 10 micro-in and below were obtained at 0.001 ipr feed both under dry
and wet conditions. The tests were extended to higher feeds, the
maximum being 0.004 ipr; at this feed, the surface finish fell, in most
cases, below 20 micro-in.
it was found necessary to use high cutting speeds of the order of
800 to 1000 fpm in most cases. The most efficient tool used was a
Titanium Carbide which successfully machined the whole range of test
materials.
The factors which were found to discourage the production of a good
surface finish, given the right feed and speed, were scratching of the
chip on the finished surface, bad blending of the nose radius with the
two cutting edges, wrong order of grinding the flank clearance faces and
the top rake face. The factors which encouraged a good surface finish
were the choice of the right tool material, a suitable facet or chip
deflector. |
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