We devised a Mason-type machine, a kind of Couette-type viscometer, and studied the buckling of fibers in the shearing field, a matter related to fiber entanglement problems, such as hooks, nep formation and pilling. We concluded that bent fibers increased in number with an increase in the viscosity of liquid.We studied what bearing the roughness degree of the cylinder surface had on fiber entanglement. With the cylinders finished at degree W, slivers disordered and buckled fibers increased in number.We were able to see the process of slivers buckling and forming fiber assemblies when emery paper was stuck on the cylinder surface. We found that two fiber balls in a row merged easily into a larger ball.We attached ordinary cloth wires or metallic wires to the cylinders and thought of it as a service carding machine because of its dynamic similarity. We observed nep formation by varying the sliver density and the number of cylinder revolutions. More neps formed with an increase in the sliver density. The larger the number of cylinder revolutions, the smaller the rate of nep formation per revolution.The mechanism of nep formation, in our opinion, consists of the buckling of slivers and the tightening of buckled slivers. The larger the number of fibers sinking among wires, the larger the number of neps forming. We were able to explain nep formation and disappearance by the rate process theory.