Asbestos friction material is usually made by high pressure moulding of a mixture of asbestos fibres, plastics etc.; it can also be made by compressing layers of woven or plaited asbestos which have been impregnated with plastics, pitch or rubber. It may be reinforced with brass, zinc or lead wire, or may sometimes be made up from metal wire or cotton yarn covered with asbestos. Owing to its high friction coefficient and its resistance to heat and wear, this material is used for lining brake shoes, clutch discs, etc., for vehicles of all kinds, cranes, dredgers or other machinery. The heading includes similar friction materials with a basis of other mineral materials (e.g., graphite, siliceous fossil earths) or of cellulose fibre.
According to the particular use for which it is intended, friction material of this heading may be in the form of sheets, rolls, strips, segments, discs, rings, washers, pads or cut to any other shape. The friction material may also be assembled by sewing, may be drilled or otherwise worked. The heading excludes :(a) Friction materials not containing mineral materials or cellulose fibre (e.g., those of cork); these are generally classified according to the constituent material. (b) Mounted brake linings (including friction material fixed to a metal plate provided with circular cavities, perforated tongues or similar fittings, for disc brakes); these are classified as parts of the machines or vehicles for which they are designed (e.g., heading 87.08).
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