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About the bolt clearance holes
ISO 273 close, normal and loose clearance hole sizes for metric bolts, and whether plasma can cut each hole cleanly in your plate.
How it works
Pick the bolt size and plate thickness; the table gives the three ISO 273 classes and marks holes smaller than the plate thickness for drilling.
Questions
What clearance hole is used for an M20 bolt?
ISO 273 gives 21 mm close, 22 mm normal and 24 mm loose; structural steelwork commonly uses 22 mm.