Common Driver Types

It is important to use the correct size driver bit within each style of recess to help prevent stripping or what is commonly known as cam-out.

Cam-out is where the driver strips or smooths the shaped recess in the screw head, making future use difficult. Cam-out is caused when excessive torque (power) is applied which is more likey to happen when a power tool is used to drive the fastener.

SLOTTED                                                             

Dating back to the 1500s this is the oldest type of drive. It's still a common design but it's now used in less applications where a power tool will be used to drive the fastener due to their tendancy to cam-out. 

PHILLIPS

Also known as turnscrews, they have a cross slotted design which is less likely to cam-out than the standard slotted type. Named after Henry F. Phillips the owner of the company which purchased the design from John P. Thompson, who invented it in 1932.

POZI

Similar to Phillips with a self-centering design and modified shape for improved engagement between bit and fastener which increases torque. They have extra parallel flutings which provide greater resistance to cam-out and help prevent the ejection force during tightening or loosening. Also known as Pozidriv which is an acronym of 'positive drive'.

ALLEN or INTERNAL HEXAGON

Also known as Hex drive, these are a compact fitting driver with six contact surfaces between fastener and driver. However they are prone to cam-out when used with power tools.

SQUARE

Also known as a Robertson drive after their invention by P. L. Robertson in 1908. Their square head provides greater contact between the bit and fastener, making them markedly more resistant to cam-out.

TORX

Developed in 1967 by Camcar Textron, this trademarked type of screw drive is characterized by a 6-point star shaped pattern. Hence they are also known as star drive or 6-lobe bits. The use of Torx screws is becomming increasingly popular in construction industries as they are more resistant to cam-out and excellent for when a fastener needs to be tightened to high level of torque.

PIN TORX

Similar to Torx these drives are used with tamper proof security screws. Often referred to as 6-Lobe Pin drives as the Torx screws have a central pin inside their 6-lobe recess preventing removal with standard Torx tools.

EXTERNAL HEXAGON

For use with hex head fasteners with no recess in their head. External hexagon drivers fit directly over the hex head of fasteners providing greater surface contact and making cam-out less likely.