MILLING MACHINE OPERATIONS - OD1644 - LESSON 1/TASK 1
b.
Collets and Spindles.
(1)
Description.
Milling cutters that contain their own straight or
tapered shanks are mounted to the milling machine spindle with collets or
spindle adapters which adapt the cutter shank to the spindle.
(2)
Collets. Collets for milling machines serve to step up or increase
the taper sizes so that small-shank tools can be fitted into large spindle
recesses. They are similar to drilling machine sockets and sleeves except
that their tapers are not alike. Spring collets are used to hold and drive
straight-shanked tools.
The spring collet chuck consists of a collet
adapter, spring collets, and a cup nut. Spring collets are similar to lathe
collets.
The cup forces the collet into the mating taper, causing the
collet to close on the straight shank of the tool. Collets are available in
several fractional sizes.
(3)
Spindle Adapters.
Spindle adapters are used to adapt arbors and
milling cutters to the standard tapers used for milling machine spindles.
With the proper spindle adapters, any tapered or straight shank cutter or
arbor can be fitted to any milling machine, if the sizes and tapers are
standard.
c.
Indexing Fixture (figure 6 on the following page).
(1)
The indexing fixture is an indispensable accessory for the milling
machine.
Basically, it is a device for mounting workpieces and rotating
them a specified amount around the workpiece's axis, as from one tooth space
to another on a gear or cutter.
(2)
The index fixture consists of an index head, also called a dividing
head, and a footstock, similar to the tailstock of a lathe. The index head
and the footstock are attached to the worktable of the milling machine by T-
slot bolts.
An index plate containing graduations is used to control the
rotation of the index head spindle. The plate is fixed to the index head,
and an index crank, connected to the index head spindle by a worm gear and
shaft, is moved about the index plate. Workpieces are held between centers
by the index head spindle and footstock. Workpieces may also be held in a
chuck mounted to the index head
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