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screw driver

Screw driver is a fastening tool. It consist of following parts:
1. Handle
2. shaft
3. tip
Classification according to tips
A) Slotted type


B) Cross/ Double Slot/ Cruciform type
Different types of Cruciform type screwdrivers are:

1. phillips
This type of head prevents from over tightening. This is done by allowing cam out.


  
2. frearson
Reed and Prince designed this kind of head. This gives high torque and does not cam out.



3. French recess
This has a protrusion.

4. JIS
Japanese origin head which is similar to fearson but has a bigger size.

5. Mortorq
This is light weight and high stress head which are generally more used in aero field.


6. Pozidriv
This is known as improved version of Philips. This decreases likelyhood of cam out thus providing more torque than Philips. It consist of a tick at 45  degrees.



7. Supadriv
This kind of head allows short offset between screw and screw driver. Resulting in increased efficiency and less cam out.



9. Robertson (square)Scrulox
This is easy to be used with one hand. It is self centering and less cam out. This helps in speeding up the production process.


10. Double square
This is a combination of 2 robertson square at an angle of 45 degrees. It forms a 8 point star. This results in a screw driver with more number of engaged angles.

11. Triple square
Superimposing 3 robertson square to form a 12 point star . The squares are at 30 degrees. the engagement angles are increased.

12. Hex square (Allen wrench)
Consist of 6 touch angles.



13. Double hex
This is a combination of 2 hex gives more torque.

14. Hexabular socket (torx) star drive torx plus
The main advantage of such bits are the extension of bit life.




C) conbination drive
1. Philips and square head Quardrex/ Pozisquadrex

2. Philips and slotted head


D) External types
E) Clutch typed

Type A
Bow tie


Type G
butterfly

F) Tamper Proof Screw driver heads
1. Slotted
One way screw(one way clutch)
Prevents from Vandals.

2. Spanner drilled

3. Spanner slotted


Phenomenon:
Cam out: this is the process by which the screw driver head slips out of the screw head when the torque exceeds certain limit. Repeated cam out can cause head damage so it should be prevented.


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