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Tap Used to create screw threads inside of a drilled hole. NOTE: Care must be taken
when using a milling machine to perform a tapping operation. For example, the spindle
speed and feed must be synchronized.
End Mill Shaped similar to a drill, but with a fl at bottom (end). It is used primarily to cut
with the side of the tool, to contour the shape of a work piece.
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 fi xture.
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.
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96-0041 Rev T
January 2009
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