Bolted Connections

High Strength friction grip bolts

• Friction grip bolts are made from high-strength steel so that they can be tightened to give a high shank tension .
• The shear in the connected plates are transmitted by friction & not by bolt shear as in black bolts .
• These bolts are used where strong joints are required mainly in the joints of rigid frames .
• Care must be taken to ensure the bolts are tightened up to the required tension , otherwise slip will occur at service loads & the joint will act as an ordinary bolted joint .
• The bolts must be used with hardened steel washers to prevent damage to the connected parts .

Ordinary Black Bolts

• Ordinary black bolts comes with a black hexagonal head with nut & washer . It is the most commonly used steel fastener .
• Black bolts comes in 2 strength grades :
• Grade 4.6 - Mild steel ( Yield stress = 235N/mm2)
• Grade 8.8 - High - strength steel ( Yield stress = 627 N/mm2)
• Main diameter used are 16 , 20 , 24 , 30 , 32 mm .