1236 Bolt data Hole sizes – for ordinary bolts and friction grip connections Nominal Clearance Oversize Short slotted Long slotted diameter hole hole holes a holes a (mm) diameter b diameter a (mm) (mm) (mm) (mm) Narrow Slot Narrow Maximum dimension dimension dimension dimension M12 a 14 17 14 18 14 30 M16 18 21 18 22 18 40 M20 22 25 22 26 22 50 M22 24 27 24 28 24 55 M24 26 30 26 32 26 60 M27 30 35 30 37 30 67 M30 33 38 33 40 33 75 a Hardened washers to be used b In cases where there are more than three plies in joint the holes in the inner plies should be one millimetre larger than those in the outer plies Bolt strengths Bolt grade Steel grade 4.6 8.8 S275 S355 S460 Shear strength, p s (N/mm 2 ) 160 375 Bearing strength, p bb (N/mm 2 ) 460 1000 a 460 550 670 Tension strength, p t (N/mm 2 ) 240 560 a The bearing value of the connected part is critical Bolt data