1. The weight tolerance between different choppers must be ± 6g, to keep the Stable Ratation. 2. How to keep good quality: 1) cut the raw material according to the pattern of steel, and the chopper length direction must be along the pattern such as below, or it will be easily brocken; 2) Heat treatment: Firstly, increase the hardness by integral quenching, then tempering to 25-30 HRC, finally add the cutting edge hardness to 50-55HRC by high-frequency quenching. We use salt bath quenching, by which the temperature is more homogeneous 3) Chambering in the hole or add a bushing in the hole. That's because the hold is tapered after the punching, it will abrade the hold the matched parts.