Z₂==z₁*i=23*4=92 d₁=m*z₁=3*23=69mm，  
d₂=m*z2=3*92=276mm d_a1=m*z₁=+2m=69+2*3=75，d_a2= m*z₂+2m=276+6=282
d_f1=m*z₁=-2.5m=69-2.5*3=61.5mm， 
d₁=m*z₂=-2.5m=276-2.5*3=268.5mm a=m*（z₁+z₂）/2=3*（23+92）/2=172.5mm）

特点：传动比大、动平稳、自锁性、传动效率低、造成本高
圆柱蜗杆传动、环面蜗杆传动和锥面蜗杆传动