GatesFacts Technical Information Library
The curvilinear or rounded tooth profile, Fig 1b, was developed in the early 1970s. Called high torque drive (HTD), these synchronous belts have teeth that are fully rounded, deeper, and more closely spaced than trapezoidal timing belts. HTD belt pitches range from 3 to 20 mm. Many of these belt pitches are available with double sided teeth.