There are many reports on fundamental experiment of "Nylon-Steel" abrasion. But these are a little used for actual gear. This report discusses a nylon gear meshing with a hobbed steel gear and a ground steel gear. The load test of nylon cylinder was performed using a steel cylinder which has a different surface finishing. The abrasion, the allowable limit load, the surface temperature, the modes of breakage of nylon cylinder owing to a difference of a surface finishing of steel cylinder were investigated and useful data for design of nylon gear were collected.