APRON MECHANISM IN LATHE

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APRON MECHANISM IN LATHE


Apron Mechanism:
Apron is attached to the carriage and hangs over the front side of the lathe bed. It is useful in providing power and hand feed to both carriage and cross-slide. It is also used to provide power feed to the carriage during thread cutting through two half nuts. The construction of apron is shown in Fig.
Construction
Power is transmitted from the spindle to the lead screw and feed rod through the spindle gear and tumbler gear arrangement. A worm is mounted on the feed rod by a sliding key. The worm meshes with a worm gear on whose axis another gear G1 is attached. Gear G1 is attached to a small gear G2 by a bracket as shown in the diagram. Gear G4 is positioned to be in mesh with the rack gear always. Another gear G3 is mounted on the same axis of gear G4. The carriage hand wheel meant for longitudinal feed is attached to the gear G5 on the same axis. The gears G3 and G5 are always in mesh. The gear G6 is attached to the cross slide screw.

The feed selection lever can be kept in neutral, up and down positions to obtain the following movements.
1. Hand feed and power feed to the carriage
2. Hand feed and power feed to the cross slide

Hand feed to the carriage
Feed selection lever is kept in neutral position and the carriage hand wheel is rotated. The gear G4 attached to the rack gets rotation through the gears G5 and G3. The carriage moves longitudinally.

Power feed to the carriage
When feed selection lever is kept in up position (U), the gear G2 will mesh with gear G3. Gear G4 gets rotation through gear G3 and the carriage gets automatic (power) feed.

Hand feed to the cross slide
Feed selection lever is kept in neutral position. The cross slide will move on rotation of the cross slide hand wheel.

Power feed to the cross slide
When the feed selection lever is kept in down position (D), gear G2 will be in contact with gear G6. The rotation of G6 will make the cross slide screw also to rotate and the cross-slide moves automatically.

Power feed to the carriage for thread cutting
When the two half nuts in the apron are made as one unit, lead screw makes the carriage to move automatically and cut threads of required pitch value.

REFERRED BY :- ER. MANDEEP KANDHOL (A.P.), MECHANICAL ENGG. DEPTT., SGI

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