Sherline 5000 Mill Assembly Instructions

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reasonable angle to the indicated part or surface. When
the part is properly aligned, there will not be any deflection
on the indicator. If you wish to locate the spindle over an
existing hole, place the indicator in the spindle and read the
inside surface. Move the X- and Y-axes until there is no
deflection when the spindle is rotated. At this point, the
spindle is in perfect alignment with the hole’s center.
When aligning the spindle to used bearing holes, remember
that the hole may be worn out-of-round, and it may be
impossible to attain zero indicator deflection reading.
Boring out a worn bearing hole to a larger diameter and
sleeving it with a simple bushing made on a lathe is a fairly
common machining operation. With the new bushing
pressed in, the bearing will be like new.
The squareness of your machine may also be checked with
an indicator. For instance, alignment of the head can be
checked by offsetting the indicator in the spindle so the tip
will move on about a 5-inch diameter circle. The amount of
reading relative to the table is the amount of error. Don’t
be discouraged to find a few thousandths of an inch error
in your machine. This machine has been designed to have
the most accuracy commensurate with reasonable cost. In
machine tool manufacturing, accuracy and cost run hand-
in-hand. To increase accuracy only a few percentage points
could double the selling price, because entirely different
manufacturing processes would be required. However, you
can personally improve the accuracy of your machine with
a few shims, if needed, by employing your dial indicator.
The column bed is aligned with the column block at the
factory. If you remove it, it will have to be realigned by
mounting a known “square” on the mill table and adjusting
FIGURE 56—Indicating in a head tilt using a mill vise
and draftsman’s triangle
placement of the bed by running an indicator on the square
as the headstock is raised and lowered. (See Figure 21,
page 16.) The same method can be used to check alignment
of the column bed to ensure it is square with the Y-axis. To
correct any error (which should be small), place a shim
between the column block and the mill base.
LOCATING THE EDGE OF A PART
IN RELATION TO THE SPINDLE
There are two quick methods of “picking up an edge” of a
part on a mill. The first is to put a shaft of known diameter
in the spindle and see that it runs perfectly true. Using a
depth micrometer against the edge of the part, measure
the distance to the outside diameter of the shaft. To that
dimension add half the known shaft diameter. You now
have the distance from the edge of the part to the centerline
of the spindle. Rotate the handwheel on the axis being set
exactly this distance and you will have the centerline of the
spindle lined up with the edge of the part from which you
measured.
The second method is much easier.
It involves the use of a clever tool
called an “edge finder.” These
devices have been around for
years and have two lapped
surfaces held together by a spring.
One surface is on the end of a shaft
that fits in a 3/8" end mill holder
and is held in the spindle. The other
is a .200" diameter shaft held to
the larger shaft with a spring so it
is free to slide around. With the
spindle running at approximately
2000 RPM, the shorter shaft will
be running way off center. As this
shaft is brought into contact with
the edge you are trying to locate in
relation to the spindle, the .200"
shaft will be tapped to the center
as the spindle rotates. This keeps making the .200" shaft
run continually truer. When the shaft runs perfectly true it
makes contact with the part 100% of the time. This creates
a drag on the surface of the shaft that will “kick” it off
center. (See Figure 57.) At this point you know the part is
exactly .100" (half the diameter) from the centerline of the
spindle. Advancing the handwheel on a Sherline mill two
revolutions (.050" per revolution) will bring the edge of the
part into alignment with the spindle.
It is important to use a high quality edge finder such as the
Starrett 827A shown in the drawing. It must have a 3/8"
shaft to fit the end mill holder on the Sherline mill. Metric
sized edge finders are also available which work in the
same manner.
For those who like to own the newest gadgets, electronic
edge finders are now available. Import models start at
around $100.00.
FIGURE 57—Using
an “edge finder” to
accurately locate
the edge of a part
3/8" SHAFT
SPINDLE
PART
.200" DIA. SHAFT