Hack sawing (Material Removing Method)
Hack sawing (old) (better)
In hack sawing, a straight,
relatively short, blade is tensioned in a bow, powered back and forth via an electric
motor and a system of gears, and fed through a stationary, clamped workpiece
either by gravity or with hydraulic assistance. The hacksaw therefore basically
emulates the manual saw ingaction. Cutting is generally done on the “push
stroke,” i.e., away from the pivot point of the bow. In more sophisticated
models, the bow is raised slightly (relieved) and speeded up on the return, or
noncutting, stroke, to enhance efficiency. By its very nature, however, hack
sawing is inherently inefficient since cutting is intermittent. Also,
mechanical restrictions make it impossible to run hacksaws at anything but
pedestrian speed. The advantages of hack sawing are: low machine cost; easy
setup and maintenance; very low running costs; high reliability and universal
application—a quality hydraulic hacksaw can cut virtually anything, albeit very
slowly. For this latter reason, in mainstream industrial applications hack
sawing has all but disappeared in favor of band sawing or circular sawing . (Geng
H., Manufacturing Engineering Handbook, p. 32.1)
Hack sawing (new)
Hacksawing is a process variant with a repeated, usually linear
cutting motion (fig.). according to DIN 8589-6, hacksawing, gangsawing, and
jigsawing are all hacksawing processes [DIN8589f]. From this definition, we can
already see that hacksawing is a process with a discontinuous cutting motion,
i.e. with machine hacksaws, material is removed only in the forward stroke. In the
return stroke, the saw blade is mechanically or hydraulically lifted. The result
is that the material removal rate is lower compared with bandsawing or circular
sawing. On the other hand, the cutting loss is relative small.
The saw baldes are made either of solid HSS or of HSS segments that
are riveted on a blade body. Blades made of tool steel are generally only used
for manual hacksaws.
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