Bolts in various dimensions & head-shapes are available. Bolts, preferably used in through holes with the help of an appropriate nut, are generally with of square/hexagonal heads. Bolts can be supplied unfinished, semi-finished & fully finished conditions. Automotive bolts have hexagonal head. These bolts have greater head depth than regular bolts but have less width across flats. Limits of tolerances are well defined by international standards for over all dimensions. Top of the head is flat and chamfered at an angle 30Âº while the bearing surface is washer-faced. Either coarse or fine threads of class- 2A are used. Leaf springs are used in automobile vehicles as suspension members. There are two basic types of leaf springs: Multi leaf spring, and Single leaf spring. The multi leaf spring is made up of a series of flat steel plates of graduated length placed one above the other. These plates or leaves are held together at the centre by a centre bolt which passes through concentric holes made in all the leaves. The longest or `master leaf is rolled at both ends to form spring eyes through which bolts are placed to attach the spring ends. U-bolts are used at appropriate distances on the length of leaf springs to hold all the individual leaves intact at their places. This means that with each leaf spring, one centre bolt and more than one U-bolt are used in any leaf spring design. U-bolts and centre leaves are also used on loco suspension leaf springs like auto leaf springs by cold forging of special alloy steels which is the proper technique to make such high tensile bolts. Header, pointer, trimmer and mechanical/hydraulic thread rolling operations are successively undertaken on selected alloy steel wire/rod coil to manufacture bolts. Thereafter, these are drum washed, degreased and dried prior to heat treatment. Also phosphating and zinc plating can be done on these bolts to protect surface from erosion/corrosion. Technical know-how for these bolts is indigenously available. U-bolts are made by press bending straight bolts threaded at both ends. 10 mm to 25 mm steel rods are used as the starting raw material for making these bolts, depending on size of the leaf spring. Fasteners mainly cover nuts, bolts, screws, studs and rivets and are segmented between MS (mild steel) and HT (high tensile) fasteners. These fasteners are used in engineering systems. All types of fasteners, except high tensile and special type fasteners, are reserved for the SSI sector. The overall fasteners market is estimated at about Rs 28 bn. While the organized sector (HT fasteners) has a share of 65%, the balance of 35% is shared by unorganized sector and imports. The imports in 2006-07 were Rs 8 bn, leaving Rs 2 bn or 7% as the market for the unorganized sector in value terms. The market is heavily dependent on imports which have been growing at close to 28.5% in recent period. The boom has been due mainly to the upswing witnessed by the automobile sector, the main end-user industry, accounting for almost half of the demand for fasteners. There is a very good scope in this sector and new entrepreneurs should venture into this field. Few Indian Major Players are as under: Agarwal Bolts Ltd. Brihan Maharashtra Steel Inds. Ltd. Caparo Engineering India Pvt. Ltd. Coventry Spring & Engg. Co. Ltd. Dev Fasteners Ltd. G K W Ltd. G S Auto International Ltd. Gripwell Industries Ltd. Hindusthan Engineering & Inds. Ltd. Holtzman Systems Ltd. I S P L Industries Ltd. Indian Fasteners Ltd. Indian Steel & Wire Products Ltd. Jaico Steel Fasteners Ltd. M C S Fasteners (India) Ltd. Mangal Steel Enterprises Ltd. Map Auto Ltd. Mohindra Fasteners Ltd. Needle Industries (India) Pvt. Ltd. Patheja Forgings & Auto-Parts Mfrs. Ltd. Pooja Forge Ltd. Rambal Properties Pvt. Ltd. Ramesh Auto Inds. Ltd. Rockfort Fasteners Ltd. Simmonds Marshall Ltd. Sky Industries Ltd. Steelite Engineering Ltd. Sundram Fasteners Ltd. T A L Precision Parts Ltd. Technocraft Industries (India) Ltd. Viraj Profiles Ltd.