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96-0041 Rev U
July 2010
Bull End Mill
A bull end mill is the same as a regular end mill except that there
is a radius on the corner where the side meets the bottom. This radius can be
up to ½ of the tool’s diameter.
Ball End Mill
A ball end mill is a bull end mill where the corner radius is exactly
½ the tool’s diameter. This gives the tool a spherical shape at the end. It can be
used to cut with the side of the tool like an end mill.
Work Holding
Work holding is one of the most important elements of setting up any machine
tool. Work holding is the method of clamping the work piece to the machine.
The work piece must always be held securely before any cutting can take
place. Three basic types of work holding are used in milling operations. They
are: a mill vise, clamps, and a chuck. The type used is dependant upon how
large the cutting pressure on the workpiece is going to be. The maximum
holding pressure of a manual clamp is determined by the strength of the
operator. Large work holding forces require a pneumatic or hydraulic fixture.
Fixtures should be kept close to the center of the table in order to maintain a
rigid setup. If placed at the ends of the table, harmonic vibrations could occur.
Before placing any type of work holding on your machine table, great care must
be taken to be sure that the table is clean and free of chips and other debris.
The work holding equipment also must be clean, free of debris, and have
no burrs or dings that may cause instability or damage the table. If you plan
to leave your work holding on the table for any length of time, a light coat of
rust-preventative oil will help keep your table and work holding free of rust and
corrosion.
The most common method of holding a work piece for machining is a mill vise.
The vise is attached to the mill table using tee nuts and bolts. The tee nuts
slide into the tee slots in the mill table and the bolts clamp the vise in position.
Two bolts on either side of the vise hold it in place. For precision work, the
vise must be set so that the clamping surfaces are parallel to the X or Y-axis of
machine travel. This is done using an indicator.
To indicate a vise parallel to a machine axis, you will need an indicator and a
magnetic base to hold it. Place the magnetic base anywhere on the bottom
of the Z-axis head or the spindle housing. Jog the machine axis to bring the
indicator tip to the clamping surface you want to indicate. Set the tip of the
indicator so it begins to register on the indicator dial. Use the jog handle to
move the axis you want the clamping surface to be parallel to and determine
which direction the vise needs to be moved to become parallel. If the right side
of the vise needs to be moved toward the back of the machine, tighten the bolt
on the left side of the vise to be snug and leave the bolt on the right side of the
vise loose. With a dead-blow Mallet, tap the vise until the clamping surface is
parallel with the machine axis. Check the result by jogging the axis back and
fourth. You may need to do this several times. When the vise is parallel, tighten
all the bolts and check the set-up again. Adjust if necessary.
