An instrument is described which allows variation of capstan contact angle with single cotton fibers. Fiber to metal and fiber to fiber frictional coefficients can be determined. Stainless steel and aluminum capstans are available. Speeds can be varied from .03 mm/min to 400 cm/min. Preliminary fiber to fiber coefficients of friction have been found to decrease with increased initial tension. The decrease appears to be exponential in nature and is probably due to crimp removal and untwisting of fiber as the tension is increased. The coefficient of friction gradually decreases to what appears to be a lower limit for a constant initial tension with continuous motion. This may be due to the redistribution and polishing of wax on the surface of the fiber.