Data Sheet

-28-
Securing the Workpiece
The rst problem encountered will be holding the work
and aligning it to the machine. It is important for reasons of
safety and accuracy that the workpiece be solidly secured.
This may be the most dicult task, since once the work is
clamped in position, the method of doing the entire job has
been established. Usually, a rectangular block can be easily
held in a mill vise. Note that round stock may also be held
in a “V” shaped vise slot. Mill vises are specially designed
to pull the movable jaw downward as they tighten on it. (See
Mill Vise P/N 3551 shown on page 34 and in the Sherline
Tools and Accessories Catalog.)
Certain objects can be secured with a 4-jaw lathe chuck, which
is, in turn, clamped to the machine. Some irregular shapes
such as castings may present greater diculties. Often they
may be clamped directly to the table. Very small or irregular
shapes can be secured by epoxying them to a second, more
easily held piece of material. They are broken loose after
machining. A mill tooling plate (P/N 3560) is a very useful
xture for holding parts. It has a number of holes pre-drilled
for holding clamps, and additional holes can be drilled and
tapped as needed. It also provides additional stiness and
protection for your mill table.
Locking the Axes
To keep the table from moving in a particular direction during
an operation, there is a lock available on each axis. To lock
the X-axis table from moving side-to-side there is a barrel
lock on the front of the saddle. (See Figure 55.) The Saddle is
locked by means of a thumbscrew on the left side that presses
a nylon plug against the gib to pull the saddle tight against the
dovetail. The Z-axis can be locked during milling operations
by means of a brass lever that tightens against the saddle nut
on the back of the column. (See Figure 66, page 33.)
Things to Consider Before You Start Cutting
The following steps should be considered before commencing
any part:
• Is the material about to be machined best suited for the
job, and is it machinable with available cutting tools and
equipment? Work with aluminum, brass, plastic or cast iron
whenever possible. Too often a hobbyist will pick up the
rst correctly-sized piece of material he nds at his local
salvage dealer thinking that, if it is rusty, it’s steel, and that
all steels are pretty much the same. Not so! Anyone who
has ever tried to machine an old automobile axle can attest
to this. If the part must be steel, grade 12L14, commonly
called “lead-loy,” is about the best material for machining.
It was developed for screw-machine use and is available in
round stock only. However, it works so well that many times
it may be advisable to machine rectangular parts from it. It
can also be case hardened. Your local screw-machine shop
will usually have scrap pieces available and may be a good
source for obtaining it.
• Avoid exotic materials, such as stainless steel, unless
absolutely necessary because of machining diculty and
poor milling cutter life. (If each new mechanical engineer
were given a block of stainless steel to mill, drill and tap
upon his graduation, stainless steel sales would probably
drop considerably!)
• Before beginning, carefully study the part to be machined.
Select the best surface from which to work (usually the
attest).
• Decide if work should be “rough cut” to size. Some materials
will warp while being machined. Close tolerance parts can
be ruined by attempting heavy machining at the end of the
job rather than at the beginning.
• The method of holding the work is also determined by the
type of machining to be performed. For instance, work that
involves only small drilling jobs does not have to be held
as securely as work to be milled.
• Lay the job out so that it can be machined with the minimum
number of setups.
• Be sure to have all needed cutting tools available before
beginning a job.
• Do not start o with a job so complex that the odds of success
are limited. Making complex machined parts requires a great
deal of intelligence, planning and skill. Skill is acquired only
through experience.
In summary, you should be aware of the fact that milling
is difficult, but not impossible. There are many more
considerations than just moving the handwheels, and you
should not start your rst step until your last step has been
determined.
Purchasing Materials in Small Quantities
Commercial metal suppliers are not set up to serve the
home shop machinist. They usually have large minimum
order quantities and high “cutting charge” fees that make it
impractical to purchase small amounts from them. However,
there are now a number of suppliers that cater to the hobby
market. They have complete catalogs of the materials most
commonly used by hobbyists, and you can order as much or as
FIGURE 55—Large or odd shaped parts are usually clamped
to the mill table as shown here. Smaller parts can be held in a
milling vise. Here a center drill is used to accurately locate the
holes to be drilled in a clamped part.
P/N 3012 HOLD-DOWN
SET SHOWN. A NEWER
P/N 3013 STEP BLOCK
HOLD-DOWN SET IS NOW
ALSO AVAILABLE
TABLE LOCK
SADDLE LOCK
(NOW A THUMBSCREW)
CAUTION! Because the tool spins on a mill, hot chips can be
thrown much farther than when using a lathe. Safety glasses
and proper clothing are a must for all milling operations.