Special Screwdrivers and their Uses - ITI Online Note

 Standard and Special Screwdrivers and their Uses 

1- Screwdrivers are used to tighten or loosen screws which are fixed in the machine element . 

Classification of Screwdrivers 

1- Standard type Screwdrivers with tips to suit recessed head screw slots . 

2- Special type Screwdrivers with tips to suit recessed head screws . 

Features of standard screwdrivers 

1- Screwdrivers must have : 

i- Tips to turn screws with slotted heads.

ii- Handles of metals , wood or molded insulating material , shaped to give a good grip for turning .

Parts of screwdrivers

iii- Blades of hardened and tempered carbon steel or alloy steel . 

iv- Round or square blade with length ranging from 40 mm to more than 350 mm. 

v- Flared tips which vary in length and thickness with the length of the blade . 

Standard Screwdrivers 

1- Standard screwdrivers are classified as 

i - Heavy duty screwdrivers . 

ii- Light duty screwdrivers .

iii- Stumpy screwdrivers . 

Heavy duty screwdrivers

1- This screwdriver has a square blade for applying extra twisting force with the end of the spanner . 

2- Heavy duty screwdrivers of London pattern have a flat blade and are mostly used by carpenters . 

Heavy duty screwdrivers

Light duty screwdrivers

1- This screwdriver has a round blade with parallel tips . 

2- This screwdriver is used by electricians.

3- The blades are sheathed in insulation to avoid short - circuiting live parts . 

Light duty screwdrivers

Stumpy screwdrivers 

1- These are small sturdy screwdrivers . 

2- They are used when other types of screwdrivers cannot be used due to the space limitations.

Stumpy screwdrivers

Offset Screw Driver

1- Offset screwdrivers are used on screws which cannot be reached from above . 

2- They are made with short blades and with the tips at right angle . 

3- Greater turning force can be applied on screws by these screwdrivers because of their leverage . 

Offset Screw Driver

Ratchet Screwdrivers 

1- These screwdrivers are made with a three - position ratchet control for screwing unscrewing of a screw and also providing a neutral position.

2- They are used for turning screws in confined spaces . 

3- They can be operated without changing the hand grip . 

4- They are used for slackening or tightening with a medium force .

Ratchet Screwdrivers

Phillips ( cross - recess ) screwdrivers 

1- Phillips screwdrivers have cruciform or cross - shaped tips that are unlikely to slip from the cruciform slots in Phillips recessed head screws .

Phillips ( cross - recess ) screwdrivers

2- The end of the four flats is tapered to an angle of 53°

3- The extreme end is ground to 110° . 

4- Four different sizes to cover the full range of screws are available . 

5- These are specified by point sizes 1 , 2 , 3 & 4 which correspond to the size of the Phillips screw heads.


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