form - G-ra
- four-jawed chuck
- four-link mechanism
- four-pallet machine
- four-part alloy
- four-pass broaching
- four-pin driven nut
- four-point press
- four-point suspension press
- four-port
- four-port control valve
- four-port valve
- four-post toolholder
- four-roll
- four-roll bending machine
- four-roll forming machine
- four-roll sheet bending machine
- four-sheaved block
- four-sided
- four-sided bore
- four-sided pallet
- four-sided tombstone
- four-sided tombstone fixture
- four-sided trunnion fixture
- four-square scraper
- four-square torque loop
- four-stage compressor
- four-start worm
- four-station pallet system
- four-strand continuous casting machine
- four-stroke cycle
- four-stroke engine
- four-support
- four-support cross-bar
- four-tier
- four-tier quality system
- four-way
- four-way control valve
- four-way piece
- four-way tool block
- four-way tool post
