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Broach:
Broach: A metalworking tool with a series of chisel points
mounted on one piece of steel.
Broach: A sudden instability in the heading of a sailboat
when sailing downwind.
Broach: Submarines operating submerged are said to have
broached the surface when a portion of the ship (such as the
sail, bow, or screw) other than a mast or antenna comes out
of the water. This is similar in intent, if not in 3-D
direction, to the use of broach to describe instability in
heading of a sailing ship.
BROACH warhead
Brooch (or broach): Decorative item designed to be attached
to garments.
Bharuch (also known as Broach): A district in south Gujarat
state in India.
A push style 5/16" keyway broach A broach is a
series of progressively taller chisel points mounted on a
single piece of steel, typically used to enlarge a circular
hole into a larger noncircular shape such as a square or
other desired shape.
Another typical use of a broach is to cut splines or a
square keyway (see image) on objects such as gears,
driveshafts, pulleys etc. The amount of material removed by
each broach tooth (or chisel) varies with the material being
cut. A broach tooth designed to cut steel might remove only
0.05 mm (0.0025 inch), while a broach tooth designed to cut
brass might remove as much as 0.10 mm (0.004 inch). The
succession of teeth (chisels) removes the total amount of
material required. A broach may also be designed to be
pushed or pulled through an existing hole; broaching
machines are therefore designed accordingly.
Wobble Broach
A somewhat different design of tool that can achieve the
irregular hole shape of a broach is called a wobble broach.
This type of tool is often used on rotating machines such as
lathes.
The tool has a contour similar to the desired final shape
but the leading edge of the tool is wider than the body. The
tool is free to rotate but the axis of rotation is inclined
slightly to the axis of rotation of the work. A typical
value for this misalignment is 1 degree. As the work
rotates, the broach is pressed against it and rotates
synchronously with it. However, since the axis of rotation
is different, the leading (cutting) edge of the broach
"wobbles" with respect to the work.
If the tool is inclined at an angle of 1 degree to the work,
the sides of the tool must have a 1 degree or greater draft.
Ideally the tool advances at the same rate that it cuts. So
a 1/2" diameter tool should advance at 0.009" per
revolution. 1/2*sin(1). If it advances any faster than that
then the tool becomes choked, if it advances any more slowly
then you get an interrupted or zig-zag cut. Since all work
material is elastic, you would actually cut a little less
than the ideal rate just to release the load on the
non-cutting edge of the tool.
There is some spiraling of the tool as it cuts, so the
bottom of the hole may be rotated with respect to the top of
the hole. Spiraling may be undesirable because it binds the
body of the tool and prevents it from wobbling freely. One
solution to this is to reverse the rotation in mid cut
causing the tool to spiral in the opposite direction. If
reversing the machine is not practical, then interrupting
the cut is another possible solution.
In general, a wobble broach will not cut as accurately as a
push or pull broach. However, the ability to use a wobble
broach on high production machinery such as a screw machine
makes this a desirable manufacturing method.
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