LATHE-Head stock and Lathe Bed

Head stock and lathe bed

. function of the headstock

. differentiate between cone pully headstock and all geared headstock

Function

Provide a means to assemble the work holding devices. Transmit the drive from the main motor to the work.

Accommodate shafts, gears and levers for a wide range of varyingwork speeds.

Ensure arrangement for lubricating the gears, shafts and bearings.

Types of headstocks

All geared headstock

Cone pulley drive headstock

All geared headstock

It is box section casting having a removable top cover. It has internal webs for stiffening, and to take shaft bearing. It has an input shaft which is connected by means of V belts to the main moto, and it runs at a constant speed. It is equipped with clutches and a brake.

There may be two or more intermediate shafts on which sliding gears are mounted. The main spindle is the last driven shaft in the headstock assembly. The nose of the spindle is outside the headstock casting, and is designed to accommodate the work holding devices.

The levers operating the forks for the sliding gears are situated outside in front of the headstock casting.

In the all-geared headstock, lubricating oil is filled for splash lubrication the internal gears. A sight glass with an oil level mark is provided to see the oil level.

Cone pulley headstock

It has a stepped cone pulley mounted on the main spindle, and it is free to revolve. It is connected by means of a flat belt to a similar cone pulley, with steps arranged in the reverse order. This cone pulley gets the drive from the main motor.

The spindle is mounted on the bearing on the headstock casting and has a gear wheel called 'bull gear' keyed to it. A pinion is coupled to the cone pulley.

The back gear unit has a shaft which carries a gear and pinion. The number of teeth of the gear and pinion on the back gear shaft corresponds to the number of teeth on the bull gear and pinion on the cone pulley. The axis of the back gear is parallel to the axis of the main spindle. The back gear  is engaged or disengaged with the cone pulley system by means of a lever. The back gear unit is engaged for reducing the spindle speeds.

A three stepped cone pulley headstock provides 3 direct ranges of speeds through a belt connection. With the back gear in engagement, 3 further ranges of reduced speeds can be obtained

Advantage

Can take up heavy load.

Less noise during work.

Easy to maintain.

Disadvantage

The number of spindle speeds is limited to the number of steps in the cone pulley.

It takes time to change the spindle speeds.

LATHE BED

Functions of lathe bed

The fountions of lathe bed are:

-to locate the fixed units in accurate relationship to each other

-to provide slide ways upon which the operating units can be moved

Constructional features lathe bed

The lathe bed generally consists of  a single casting. In larger machines, the bed may be in two more sections accurately assembled together. Web bracings are  employed to increase the rigidity. For absorbing shock and vibration, the beds are made heavy.

A combained swarf  and coolant tray is provided on lathes. This may be an integral part will the lathe bed.

The bed is generally carried by cast iron or wielded sheet metal legs of box section. This provides the necessary working height for the lathe. Very often the elctrical swith gear unit and the coolant pump assembly are housed in the box section of the legs at the headstock end.

Bed-ways

The bed ways or slideways assist in accurate location and sliding of the accessories /parts mounted on this. The bed ways are of three types.

Flat bes ways

V bed ways

Combination bed

Normally the bed ways stop at a distance away from the headstock with a gap at this point. This enables to mount larger diameter of the work.

Some lathes have a detachable section of the bed, which can be fitted when desired, to enable the saddle to operate close to the headstock.

The bed-ways are highly finished by grinding. Some lathes have their bed-ways hand scraped. Some have their bed-ways hardened and ground. The wear resisting qualities of bearing surfaces are improved be employing chilled iron casting.

The beds are mostly made up  of closely ground, grey cast iron.