(7) Feed Rod.

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clutch to prevent damage to the gears if excessive

strain is put on the feed mechanism. If clutches are

not provided, there is some form of safety device that

operates to disconnect the feed rod from its driving

mechanism.

(d) A selective feed lever or knob

provided

for

engaging

the

longitudinal feed or crossfeed as desired.

(e) Half-nuts are used to engage and disengage the lead screw when the

lathe is used to cut threads. They are opened or closed by a lever that is

located on the right side of the apron. The half-nuts fit the thread of the

lead screw which turns then like a bolt in a nut when they are clamped over

it. The carriage is then moved by the thread of the lead screw instead of

by the gears of the apron feed mechanisms. (The half-nuts are engaged only

when the lathe is used to cut threads, at which time the feed mechanism must

be disengaged. An interlocking device, that prevents the half-nuts and the

feed mechanism from engaging at the same time, is usually provided as a

safety feature.)

(f) The manufacturers of lathe aprons differ somewhat in their

construction and in the location of the controlling levers and knobs.

However, they are all designed to perform the same function. The principal

difference is in the gear trains for driving the automatic feeds.

For

example, in some aprons there are two separate gear trains with separate

operating levers for longitudinal feed and crossfeed. In others, both feeds

are driven from the same driving gear on the feed rod through a common

clutch; they have a selective lever for connecting the drive to either the

longitudinal feed or the crossfeed.

(7) Feed Rod.

(a) The feed rod transmits power to the apron to drive the longitudinal

feed and crossfeed mechanisms.

The feed rod is driven by the spindle

through a train of gears, and the ratio of its speed to that of the spindle

can be varied by