A screwdriver is a mechanical handheld tool that can be manual or powered. It can be used for screwing and unscrewing screws. A simple screwdriver is made up of a handle and a shaft that ends in a tip. The user can put the tip of the screwdriver into the screw head before turning the handle to screw or unscrew. These tools find application in woodwork, metalwork and electrical work and almost any household work. There are different types of screwdrivers to fit every screw. A screwdriver can be broadly classified by its tip which can fit into any driving surfaces like slots, grooves, recesses, etc. It can also be classified as – manual, electric or pneumatic.
Different Types of Screwdrivers
A. Classification based on operating mode
- Power screwdriver
- Manual screwdriver
- Pneumatic screwdriver
1. Power screwdriver
This operates on electricity or air motors to rotate the bits and is the most heavy-duty of screwdrivers. This one is the most versatile and with this type the job gets done much faster and with ease. This type of screwdriver has torque which is much stronger compared to an ordinary battery operated screwdriver. These generally come with bits which can be easily changed. For example cordless screwdriver.
2. Manual screwdriver
Unlike a battery or electricity operated screwdriver, it is a handheld manual tool. These types of screwdrivers have a thick handle with a cylindrical steel shank that ends at the working tip of the screwdriver. In some cases, the bit is interchangeable to match a number of screw head patterns. For example flat/slotted, Phillips screwdrivers, etc.
3. Pneumatic screwdriver
These types of screwdrivers are powered by compressed air. These are generally used on an assembly line. It allows the user to place many screws without causing any hand fatigue. Examples of these types of screwdrivers are flat-head, Phillips and Torx head versions. A pneumatic screwdriver can be configured to a preset torque setting to prevent stripping of screw heads due to over-tightening.
B. Classification based on drive types
- Slotted drives
- Cruciform drives
- Square drives
- Internal hex drives
(i) Slotted drives
1. Slot screw drive
These have a single horizontal indentation or a slot in the fastener head which is driven by a common blade.
2. Coin-slot drive
They have a curved bottom at the recess, allowing them to be driven with a suitable coin as they can be used even if the user does not have a suitable screwdriver.
3. Cross or double-slot screw drive
It has two slots that are perpendicular to each other, in the fastener head. Its advantage is that if one slot is deformed in service, the second slot can still be used and the tool cannot slip out.
(ii) Cruciform drives
1. Phillips screw drive
This has an angled tip which means that one can fit a screwdriver deeper into the screw head without any risk of the blade sliding out sideways. These drivers are deliberately designed to cam out or slip out of the head when a certain torque above a threshold limit is exceeded. Because of its features, it is used in almost every field.
2. Pozidriv screw drive
It is basically an improved version of the Phillips screw drive. Pozidriv screwdrivers are often referred using the letters “PZ” followed by a size code of 0, 1, 2, 3, 4 or 5. PZ1 can be used on screw diameters from 2-3mm, PZ2 from 3.5-5mm and PZ3 from 5.5mm to 8mm. These screws have radial indentations or tick marks which are set at 45° from the main cross recess at the head of the screw. This makes them visually distinct from Phillips screws.
3. JIS B 1012
These types of screw drives are commonly found in Japanese made equipment. It is an improved version of the Phillips screw but with narrower and more vertical slots. In this type the bottom of the recess is flat and the point of the driver is blunt. JIS heads can be identified by a single dot or an “X” at one side of the cross slot.
(iii) Square drives
1. Robertson screw drive
These are also known as a square or Scrulox screw drive. It has a square-shaped socket in the screw head with a square protrusion on the tool. Both the tool and the socket possess a slight taper. This taper provides two advantages. It makes inserting the tool easier, and secondly, it tends to help keep the screw on the tooltip intact without the need of holding it. These are self-centring which reduces cam-out.
2. Multiple square drives
a. LOX recess
It has four overlapping square recesses and 12 contact points. It is designed to increase torque and decrease wear and cam-out.
b. Double square
It has two squares that are superimposed at 45° rotation which forms an 8-pointed star.
c. Triple square
These are also known as XZN. It has 12 equally spaced protrusions with each having a 90° internal angle. The design has overlapping three equal squares to form a pattern with 12 right-angled protrusions or a 12-pointed star.
(iv) Internal hex drives
1. Hex socket screw drive
It has become increasingly popular and resembles a small, six-sided metal shank that is bent into an L-shape. They are usually with packaged furniture at no extra cost. These are also called Allen wrench, hex key, hexagon, security hex version, etc. These are commonly used in bike maintenance and furniture companies.
2. Double hex
These screw drives have a socket that is shaped as two coaxial offset hex recesses which can be driven with standard hex key tools. The shape is similar to triple square and spline screw drives.
Other types of drive heads can be pentalobular sockets, hexalobular sockets and combination drives. Combination drives have heads that are designed to accommodate more than one kind of driver.
