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What wrench fits a 3/4" bolt?

Across-flats wrench/socket size by head type - a flange bolt often uses a smaller wrench than a standard hex bolt of the same diameter, so always check the head type.

Nominal diameter 0.75"
Standard hex 1-1/8"
Hex flange not commonly available in this head type
≈ 30 mm (M20)

Reference values only - always verify against the actual part before machining, tapping or tightening anything.