MILLING MACHINE OPERATIONS - OD1644 - LESSON 1/TASK 1
(6)
Holding Workpieces in the Vise.
Three types of vises are
manufactured in various sizes for holding milling machine workpieces. These
vises have locating keys or tongues on the underside of their bases so they
may be located correctly in relation to the T-slots on the milling machine
table.
(a)
The plain vise, similar to the machine table vise, is used for
milling straight workpieces; it is bolted to the milling machine table at
right angles or parallel to the machine arbor.
(b)
The swivel vise (figure 7 on the following page) can be rotated and
contains a scale graduated in degrees at its base to facilitate milling
workpieces at any angle on a horizontal plane. This vise is fitted into a
graduated circular base fastened to the milling machine table and located by
means of keys placed in the T-slots. By loosening the bolts, which clamp
the vise to its graduated base, the vise may be moved to hold the workpiece
at any angle in a horizontal plane. To set a swivel vise accurately with
the machine spindle, a test indicator should be clamped to the machine arbor
and a check made to determine the setting by moving either the transverse or
the longitudinal feeds, depending upon the position of the vise jaws. Any
deviation as shown by the test indicator should be corrected by swiveling
the vise on its base.
(c)
The universal vise is constructed to allow it to be set at any
angle, either horizontally or vertically, to the axis of the milling machine
spindle. Due to the flexibility of this vise, it is not adaptable for heavy
milling.
(d)
When rough or unfinished workpieces are to be vise mounted, a piece
of protecting material should be placed between the vise jaws and the
workpiece to eliminate marring the jaws.
(e)
When it is necessary to position a workpiece above the vise jaws,
parallels of the same size and of the proper height should be used (figure 8
on page 21).
These parallels should only be high enough to allow the
required cut, as excessive raising reduces the holding ability of the jaws.
When holding a workpiece on parallels, a soft lead hammer should be used to
tap the top surface of the piece after the vise jaws have been tightened.
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