In the first stage reducer, why don't the driving shaft and the gear connect with the key?
In order to reduce the structure size, speed reducer drive shaft gear to reduce weight, make the smallest, which is the number of teeth at least (minimal number of teeth without undercutting). Therefore, the driving shaft generally adopts the gear shaft structure (gear and shaft as a whole). If you use the key connection, will inevitably increase the driving shaft gear size, tooth number, reducer size, weight will increase accordingly. Therefore, the structure of the gear shaft is adopted, and the structure without the key connection is adopted.
You can use the key to connect the way to draw the first try, you will find either the strength and stiffness of the shaft is not enough, or the safety factor of the gear will be very high, the center will be very large distance
In one case, when the torque is not great, the winning gear is used to reduce the cost of the milling key, and the other is to use the gear shaft in order to be more robust and reliable.
