Classification of Lathe Machine Chucks

 Chucks

 A chuck is one of the most important device for holding
and rotating a workpiece in a
lathe.
 Workpieces of short
length and large diameter or irregular shape which cannot be conveniently mounted
between centers are held quickly
and rigidly in a chuck. 
A chuck is attached
to the lathe spindle by means of bolts with back plate screwed to the spindle nose.

 The different
types of chucks are:


   Four jaw independent chuck, Three jaw universal chuck,  
 Combination  chuck, Magnetic chuck,  Collet Chuck,  Air or hydraulic operated, Drill chuck     
   



1.  Four jaw independent chuck

  Four jaw
independent chuck has four jaws which may
be made to slide within
the slots provided in the body of chuck for gripping
different size of the workpiece.
 Each jaw may be moved independently by rotating the screw. Each jaw made of tough steel
has three inner and one outer gripping
surface. Outer gripping surface
is used for holding large
size workpiece by reversing of the jaw.
 This chuck
is particularly used in setting
up of heavy and irregular shaped workpiece.
The diameter of the body specifies the size of the chuck.


1 – Concentric circle, 2 – Chuck body, 3 – Jaw screw, 4 – jaw, 5 – Gripping surface,  6– Recess for back plate
1 Concentric circle,
2 Chuck body, 3 Jaw
screw, 4 jaw, 5 Gripping
surface,
6– Recess for back plate






Four Jaw Independent Chuck
Four Jaw Independent Chuck





2. Universal or self-centering chuck

  In three
jaw universal chuck
all the jaws may be made to slide simultaneously by an equal amount
within the slots provide on body.
  By rotating
any one of them pinion
which meshes with teeth cut on underside
of the scroll disk.
When the disc
is rotate by any one of pinions,
all the jaws
move backward or forward
by equal amount.
 The
chuck is suitable for holding round, hexagonal and any other similar shaped
workpieces and the job is centered automatically.
 It has less gripping
capacity as only
three jaws are
used and centering accuracy is soon lost due to wear.



1 –Bevel pinion, 2 – Scroll disk, 3 – Bevel teeth on scroll disc, 4 – Chuck body, 5 – Jaw
1 –Bevel pinion,
2 Scroll disk, 3 Bevel
teeth on scroll
disc, 4 Chuck body,
5 Jaw 






B. Universal or self-centering chuck
 Universal or
self-centering chuck





3.   Combination chuck

  As the name implies
a combination chuck may be used both as a self-centering and independent chuck to take advantages of both the types. 
The jaws
may be operated individually by separate screws
or simultaneously by scroll
disc.
 The
screws mounted on frame have teeth cut on its underside which meshes with
scroll and all the jaws move radially.



  

1 – Chuck body, 2 – Frame, 3 – Screw, 4 – Jaw, 5 - Scroll
1 Chuck
body, 2 Frame, 3 Screw,
4 Jaw, 5 Scroll 



Combination chuck

Combination chuck



     4.  
Magnetic chuck

 The chuck
is used for holding a very thin
workpiece made of magnetic material which cannot be held in an ordinary chuck. 
It is also used where any distortion of the workpiece
due to high pressure of jaws is undesirable.
 The holding
power is developed by magnetic flux
radiating either from
electromagnets or from the permanent magnets
within the chuck.
 In the ON position the flux passes
through the workpiece and grips it.
In OFF position “keepers” short
circuit the path of flux and cannot pass through
the workpiece.


1 – Workpiece, 2 – Nonmagnetic material, 3 – Keepers, 4 –Face plate, 5 - Magnet
1 Workpiece, 2 Nonmagnetic material, 3 Keepers, 4 –Face plate,
5 Magnet 

D. Magnetic chuck
Magnetic Chuck


5 .  Collet chuck


  Collet chucks are used
for holding bar stock in production work where quick
setting and accurate
centering is needed.
 The chuck is attached
to the spindle by a nut consists
of thin cylindrical bushing
known as “collet”.
 The inside
bore of collet
may be cylindrical, hexagonal, square etc. depending on the shape of the workpiece.
 The outside
surface of collet
which is tapered
fir in taper hole on the body of chuck.
 Different sizes of
collets are used for holding different size of bar stock.



1 – Bearing, 2 – Spindle, 3 – Nut, 4 – Key, 5 – Chuck, 6 – Collet
1 Bearing, 2 Spindle, 3 Nut,
4 Key, 5 Chuck, 6 Collet 


Collet Chucks
Collet Chucks





6.   Air or hydraulic operated
chuck

  This type of chuck
is used in mass production work for its fast and effective gripping capacity.
 In mechanism, a hydraulic cylinder
is mounted at the back end of headstock spindle and rotates with it. The movement
of piston is transmitted to the jaws by a connecting rod and links
and the jaws grip the workpiece
securely.



1 – Cylinder, 2 – Air Passage, 3 – Headstock spindle, 4 – Piston, 5 – Valves, 6 – Piston rod, 7 – Link, 8 – Jaw, 9 – Guide, 10 – sliding unit
1 Cylinder, 2 Air Passage, 3 Headstock spindle, 4 Piston, 5 Valves,
6 Piston rod, 7 Link, 8 Jaw, 9 Guide, 10 sliding
unit


Air or hydraulic operated chuck

Air or hydraulic operated chuck




7.  Drill chuck

 Drill
chuck is sometimes used in a lathe for holding straight shank drill, reamer and
tap for drilling, reaming and tapping operation.

The chuck
may be held either in headstock or tailstock spindle.
It has self-centering jaws which may be operated
by a rotating key.


Drill chuck
Drill chuck


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