milling.
ADJUSTING THE LOCATION OF THE WORK PIECE TO THE CUTTER
A surface of the work piece should be located by adjustment so that it just contacts the milling cutter
when the latter is rotating. I use a thin piece of paper, of a known thickness. It is held on the work piece
surface, while the work piece is carefully moved toward the rotating cutter. Once this contact is made,
the work piece is moved accurately a desired distance from this reference to remove the desired depth
of material. An edge finder can be used to locate the surface with better accuracy.
The depth of material removed can be held to within 0.001 inch. Tolerance of from 0.002 to 0.005 inch
is more practicable for milling. To align a machined surface of a work piece, vise, or milling fixture with
the movement of the table, saddle, or knee, a dial indicator is attached to the spindle or arbor. This test
indicator is positioned to contact the machined surface.
The table, saddle, or knee then is moved, and slight changes of the machined surface location are
made, usually with light hammer blows. This is done until the reading of the test indicator either does not
change or remains within the desired tolerance.
The principle function of attachments is to increase the variety of work that can be accomplished on
milling machines. These attachments position and hold the work piece to the table. Two other important
milling-machine attachments are the rotary table and the dividing head. These will be discussed in
following paragraphs.
ANGLE PLATE
If your milling machine head does not rotate, the adjustable angle plate can be used. It is bolted to the
table of the milling machine, and any angle can be set on it. A vise can then be bolted to it to hold small
work.
ROTARY TABLE
A rotary table is mounted on the table of a milling machine as an auxiliary table to superimpose a rotary
motion upon the other movements for the work piece. This rotary movement may be used for feeding or
for adjustment in locating a cut. This rotary movement is about a vertical axis, and since the rotary table
is mounted on the regular milling machine table.
A worm gear directly fastened to the rotary-table vertical shaft is rotated by a worm on a horizontal shaft.
The horizontal worm shaft may be turned by hand. If power is used, suitable shafting may bring the
power, when desired, from the milling machine feed-power mechanism.
The work piece may be accurately rotated by turning the worm shaft by hand with the aid of a
micrometer dial, or an index plate.