a method of making tooth belts by formation thereof about the outer peripheral surface of a building drum having a generally cylindrical configuration and a surface defining a series of parallel , tooth - shaped grooves . the belts are formed by wrapping a fabric circumferentially around the building drum and winding a cord of tensile material helically about the fabric . a layer of thermoplastic material is formed about the cord of tensile material , and a cord of shrink material is wrapped helically about the layer of thermoplastic material . the shrink material has a higher softening temperature than the thermoplastic material and will shrink at a temperature below its softening temperature . pressurized steam is applied to the shrink material at a temperature below its softening temperature and between the softening temperature and the melting temperature of the thermoplastic material . this shrinks the shrink material and extrudes a thermoplastic material through the tensile material , against the fabric and into the tooth - shaped groves of the building cylinder .