PA: Physician Assistant: PA: Public Address: PA: Pennsylvania (US postal abbreviation) PA: Purchasing Agent: PA: Port Angeles (Washington) PA: Public Affairs: PA: Para (Brazil) PA: ParÃ¡ (Brazilian state) PA: Public Address system: PA: Princess Anne (high school in Virginia Beach, Virginia) PA: Public Administration: PA: Port Authority (of NY and NJ) PA
Intro: When a Phillips Is Not a Phillips! Cross-head, Cross-Point, Cruciform, Square Drive Screws and Drivers These screw types have a + shaped recess on the head and are driven by a cross-head screwdriver, designed originally ... Step 1: Early Screws.
By design, Torx head screws resist cam-out better than Phillips head or slot head screws. Where Phillips heads were designed to cause the driver to cam out, to prevent overtightening, Torx heads were designed to prevent cam-out. The development of better torque-limiting automatic screwdrivers for use in factories allowed this change.