分度圆直径：D=mz齿顶圆直径：D2=278全齿高：h=2.25m齿根高：h1=1.25m齿根圆直径：D1=D2-2h=D2-2×2.25m=D2-4.5m=278-4.5m=269上式化简：4.5m=278-D1=278-269=9即：m=9/4.5=2
