Abstract: A portable frictometer employing the principle of passing a standard yarn sample across a cylindrical surface under test at a fixed wrap angle and detecting the ratio of the yarn tensions at the output and input ends of the wrap. This ratio is related to the coefficient of friction of the surface under test. The apparatus includes a yarn guiding system of two guide pulleys at the extremities of two rigid arms so as to achieve a predetermined fixed yarn wrap on the cylindrical surface under test when the arms are placed to contact and straddle the surface and a tension ratio monitor consisting of a disc rotatably mounted about its center with two small concentric central yarn guide pulleys and two separated peripheral guide pulleys thereon.