Construction of Lathe: Bed, Tailstock, Carriage, Saddle, Cross slide, Compound slide


Construction of Lathe: Bed, Tailstock, Carriage, Saddle, Cross slide, Compound slide
Construction of Lathe

Following are the principal
parts of center
lathe:

1.       Bed                          4.  Carriage

2.       Headstock                5.  Feed mechanism

3.       Tailstock                  6.  Screw cutting mechanism

           
The Bed

·       
The lathe bed forms the base of the
machine. The headstock and the tailstock
are mounted on lathe bed and the carriage
rests over the lathe bed.

·       
For accurate machining work, must satisfy
the following conditions:

Ø It
should be sufficiently rigid to prevent deflection under tremendous cutting
pressure transmitted through
the tool-post and carriage to the lathe bed.

Ø It must be massive
with sufficient depth
and width to absorb
vibration.

Ø It
must resist the twisting stress set up due to the resultant of two forces- the
downward cutting force on the tool and the force tending to move the tool away
from the workpiece in a horizontal direction.

Ø The bed
should be seasoned naturally to avoid
distortion or warp
that may develop when it is cooled after the bed
is cast.

·       
On the top of the bed there are two sets of slides
or guideways.

                   A.    
Outer
guideways

                   B.    
Inner
guideways

·       
Outer
guideways provide bearing
and sliding surfaces
for the carriage, and the Inner guideways for the tailstock.



1
– Inverted – V bedways, 2 – Flat bedways, 3 – Rack, 4 – Box section,

 5 – flat bedways for saddle


                                                            1  Diagonal rib, 2  Bedways

                                           


·   
The headstock is permanently mounted
on the inner ways at the left side of the lathe
bed. It provides the rotating
of workpiece at multiple speeds.

·   
The headstock spindle
is shown in Fig is made of carbon
or nickel chrome
steel. This is usually
of a large diameter to avoid bending
and it should
be perfectly aligned for accurate machining.

·   
The
long bar or work holding
devices to pass
through, the headstock spindle is made hollow.

·   
There
are common two types of spindle noses:
Threaded nose which carries
the chuck, driving plate and face plate, and Flanged nose which
enable them to be directly attached. The lathe
most commonly used has a threaded spindle
nose.

Tailstock

Tailstock
Tailstock

·   
The tailstock is located on the inner ways
at right hand end of the bed.

·   
Main uses of tailstock:

A.     It
supports the other end of workpiece when it is being machined between two
centers.

B.    
It holds a tool for performing operations like drilling,
reaming, tapping etc.

·    The tailstock
may be adjusted as length of workpiece
is different or vary by clamping
of bolts.

·    Upper casting
of body can be moved away from the operator
by means of offseting
the tailstock for taper turning.

·    The
body is bored to act as the barrel which carries tailstock spindle which can be
moves in and out of barrel by means of handwheel.

·   
The front of the spindle
has taper hole into which
dead center or tools are mounted.

·    Other features
of tailstock are graduated spindles
and micrometer dials
on handwheel for accurate
length setting.

     Carriage

·    The carriage
of lathe has several parts that to support, move and control
the cutting tool.

·   
It consists of the following parts:

A.       Saddle                    D.  Tool post

B.       Cross slide               E.  Apron

C.      Compound slide

A.    
Saddle

·   
The
saddle is an H shaped casting
that fits over
the bed and slides along
the ways.

·   
It carries the cross
slide and tool post. Some attachments are generally provided
for locking the saddle
to prevent any movement when surfacing operations are carried out.

B.     
Cross slide

·       
Cross
slide is a casting and
attached to the saddle and carries tool
post and compound slide.

·       
Cross
slide is attached to the saddle
at right angles
to the center axis of the lathe.

·       
When
taper turning attachment is used, the binder screw
is opened to disconnect the cross slide from the cross feed screw.

·       
Micrometer dials may be fitted on cross slide so that a known
amount of feed can be applied.

C.     
Compound slide

·   
The
compound rest or compound slide
is mounted on the top
of cross slide
and has a circular base in degrees.

It is used for obtaining angular
cuts and short tapers.

·   
By loosening of two set screws, rest may be swiveled to any angle within circle.

·   
There
is no power feed to the compound
rest and it is hand operated.

·    The compound
slide handle is also equipped with micrometer dial
to determining the depth of cut.




                      

     1 Tool
post screw, 2 Tool
post, 3 Rocker, 4 Tool,
5 Concave ring, 6 Compound
rest swivel base, 7 Cross
feed screw, 8 Binder
screw, 9 Cross slide,
10 Cross slide nut, 11 Saddle, 12 Pinion
on Cross feed
screw for automatic
feed, 13 Cross slide
hand wheel, 14
Compound slide hand
wheel, 15 Compoundslide feed
screw, 16 Compound rest,
17 – Compound slide nut.

A.     Tool post

·       
This
is located on the top of compound
rest to hold the tool
and able to be adjusted to a convenient working position.

·       
The type and mounting of tool post depends on the class
of work for which it is to be
used.

·       
Following are the common
types of tool post:

1.        
Single
screw tool post         3.    Open side tool
post

2.        
Four bolt tool post             4.    Four way tool post

1.    Single
screw tool post

·       
This
tool post consists
of a round bar with slotted hole in the center for fixing the tool
by means of set screw.

·       
The height can be adjusted
by tightening of rocker and clamping it in bye set screw.

·       
The
tool post is not rigid
enough for heavy
work as only
one clamping screw
is used to clamp
the tool. The tool post can be swiveled about the vertical
axis.

   



                   

where:


             1 – Toolpost screw, 2 – Toolpost body, 3 – Tool,
 4 – Convex rocker,
 5 – Concave ring  Single screw tool post

Tool Post
Tool Post

                                                                       

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