Tc 9-524 fundamentals of machine tools

8-27

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TC 9-524
Milling Keyslot for Square-End Machine Key
The workpiece should be properly mounted, the cutter
centrally located, and the workpiece raised until the milling
cutter teeth come in contact with the workpiece. At this point,
the graduated dial on the vertical feed is locked and the
workpiece moved longitudinally to allow the cutter to clear
the workpiece. The vertical hand feed screw is then used to
raise the workpiece until the cutter obtains the total depth of
cut. After this adjustment. the vertical adjustment control
should be locked and the cut made by feeding the table
longitudinally.
Milling Keyway for Round-End Machine Key
Rounded keyways are milled with an end milling cutter Of
the proper diameter. As in the case of square-ends machine
key keyways, the workpiece should be properly mounted and
the cutter centrally located with respect to the shaft. The shaft
or cutter is then positioned to permit the end of the cutter to
tear a piece of thin paper held between the cutter and the
workpiece. At this point the graduated feed dial should be
locked and used as a guide for setting the cutter depth. The
ends of the keyway should be well marked and the workpiece
moved back and forth making several passes to eliminate
error due to spring of the cutter.
T-SLOT MILLING
Cutting T-slots in a workpiece holding device is a typical
milling operation. The size of the T-slots depends upon the
size of the T-slot bolts which will be used. Dimensions of T-
slots and T-slot bolts are standardized for specific bolt
diameters. The dimensions for bolt diameters commonly used
are given in Table 8-6 (Appendix A).
Selection of Milling Cutters
Two milling cutters are required for milling T-slots, a T-
slot milling cutter and either a side milling cutter or an end
milling cutter. The side milling cutter (preferably of the stag-
gered tooth type) or the end milling cutter is used to cut a slot
in the workpiece equal in width to the throat width of the T-
slot and equal in depth to slightly less than the head space
depth plus the throat depth). The T-slot milling cutter is then
used to cut the head space to the prescribed dimensions.