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HSFG NUT

Diameter: High Strength Friction Grip Nut & Bolts

IS 4000 gives diameters of HSFG bolts as M16, M20, M24, M30 and M36. Other sizes given in IS 1367 include M18, M22 and M27 (Referred to as ‘non-preferred’ sizes also). … Maximum grip length of all plies, including packings and packing washers, shall not exceed 10 times the nominal diameter of the bolt.

HSFC nuts are durable from other nuts and can tolerate the extreme stress. Some types of nuts are; Nylon insert lock, jam, Hex, Heavy Hex, Nylon insert lock, jam, Nylon insert jam lock, wing, Tee, Cap, Acorn, Square, Flange, Prevailing torque lock, K lock or Kep, torque lock, Coupling, Slotted Castle. The dimension of the High strength friction grip nut or HSFG Nut is accurate, the finish of these nuts is flawless, and it has robust designs. For the advance industry, HSFG Nuts are in heavy demand.

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HSFG BOLT

Bolt Tightening Techniques

• When slip resistant connections are not required, high strength bolts are tightened to a ‘snug-tight’ using an ordinary spud wrench.

• When slip resistant connections are desired with HDFC bolts, three methods are used:
> Turn-of-the-nut tightening (part-turn method) -Cheap, more reliable, and common method.
> Direct tension indicator tightening,
> Calibrated wrench tightening (torque control method).

Advantages of Bolted connections

Bolted connections offer the following advantages over riveted or welded connections:
  • Use of unskilled labour and simple tools.
  • Noiseless and quick fabrication.
  • No special equipment/process needed for installation.
  • Fast progress of work. Accommodates minor .
  • discrepancies in dimensions.
  • The connection supports loads as soon as the bolts are tightened (in welds and rivets, cooling period is involved).

Main drawback of black bolt is the slip of the joint when subjected to loading

Advantages of HSFG Bolts

•HSFG bolts do not allow any slip between the elements connected, especially in close tolerance holes, Thus they provide rigid connections.
• Because of the clamping action, load is transmitted by friction only and the bolts are not subjected to shear and bearing.
• Due to the smaller number of bolts, the gusset plate sizes are reduced.
• Deformation is minimized.
• Holes larger than usual can be provided to ease erection and take care of lack-of-fit. However note that the type of hole will govern the strength of the connection.
• Noiseless fabrication, since the bolts are tightened with wrenches.
• The possibility of failure at the net section under the working loads is eliminated.

Since the loads causing fatigue will be within proof load, the nuts are prevented from loosening and the fatigue strength of the joint will be greater than in welded/connections.
• Since the load is transferred by friction, there is no stress concentration in the holes.
• Unlike riveted joints, few persons are required for making the connections.
• No heating is required and no danger of tossing of bolt. Thus safety of the workers is enhanced.
• Alterations, if any (e.g. replacement of defective bolt) is done easily than in welded connections.

HSFG bolts on Bridges