Attachments are available to increase the capabilities of
milling machines, particularly for toolroom applications
where only a few parts are made or for limited production
where the expense of a special machine would not be warranted.
A vertical milling attachment is used on horizontal
milling machines to make possible both vertical and angular
Devices for toolholding, such as arbors and adapters
for horizontal milling, will be studied in this section. Tablemounted
attachments such as rotary tables,indexing/dividing heads, and work-holding devices such as clamps and vises will also be studied.
Milling machines can be equipped with accessory measuring
equipment, digital readouts (DROs), to reduce the
chance of operator error when machining expensive complex
parts (Figure K-3). These measuring systems can be switched
to present information in either inch or metric dimensions,
which is a great time-saver and eliminates the possibility of
making errors in converting between the two systems.
It is important for you to learn to use vertical and horizontal
milling machines competently, because the cutting and
locating principles apply to the most complex numerically
controlled machine tool. Few companies are willing to risk
damage to an expensive and complex numerically controlled
machine by an operator without a background in conventional
An operator must be able to determine
readily when something is going wrong with the cutting operation
and make appropriate corrections by replacing tools or manually overriding
the machine control.
horizontal machining centers (Figure K-4) are high-performance machines.
As many as 120 preset tools are stored in tool-changing magazines, ready to be automatically inserted into the machine spindle. Many of these machines are equipped with multiple machine tables, so that one can be
loaded while machining takes place on the second one.
In this section you will observe specific safety precautions
that relate to horizontal milling,identify components
and functions of horizontal mills, and perform routine
maintenance. Various mounting systems used to drive
milling cutters will be covered, and you will be able to match
cutters to their respective applications. You will calculate
rpm and feed rates for milling cutters and set the values into
the machine controls. You will learn about a variety of workholding
methods and alignment
In addition, you will use side milling
cutters in various combinations and you will use face milling
cutters to machine flat surfaces. Horizontal and vertical
milling machines are as basic as the lathe, particularly where
one-of-a-kind or small quantities of workpieces are
involved. Both of these machine types will be in use for a
long time to come. It is important for you to learn to set up
and use these machines quickly, accurately, and safely.
Horizontal Milling Machine Safety
Before operating the rapid traverse control on a milling
machine, loosen the locking devices on the machine axis to
be moved. Check that the handwheels or hand cranks are disengaged,
or they will spin and injure anyone near them when
the rapid traverse is engaged. The rapid traverse control will
move any machine axis that has its feed lever engaged singularly
Do not try to position a workpiece
too close to the cutter with this control, but approach the
final 2 in. by using the handwheels or hand cranks.
Individuals concentrating on a machining operation
should not be approached quietly from behind, because it may
annoy and alarm them, and they may ruin a workpiece or
injure themselves. Do not lean on a running machine; moving
parts can hurt you. Signs posted on a machine indicating a
dangerous condition or a repair in progress should be removed
only by the person making the repair or by a supervisor.
Measurements should be taken on a milling machine
only after the cutter has stopped rotating and after the chips
have been cleared away.
Many milling machine attachments and workpieces are
heavy; use a hoist to lift them on or off the table. Do not walk
under a hoisted load. The hoist may release and drop the
load on you. If a hoist is not available, ask for assistance.
Injuries can be caused by improper setups or the use of
wrong tools. Use the correct-size wrench when loosening or
tightening nuts or bolts, preferably a box wrench or a socket
wrench. An oversized wrench will round off the corners on
bolts and nuts and prevent sufficient tightening or loosening;
a slipping wrench can cause smashed fingers or other
injuries to the hands or arms.
Milling machine cutters have sharp cutting edges.
Handling cutters carefully and with a cloth will prevent cuts
on the hands. Check all machine guards to see that they are
in good condition and in place. Center workpieces in a vise
with only enough extending out to permit machining. Clean
the working area after a job is completed. A clean machine is
safer than one buried under chips.