Sj-42型缩径机属于无切削加工设备，具有生产效率高、工艺简单、易于操作、节约原材料、质量稳定等优点。它是利用液压技术将圆钢、螺纹钢等须缩径部分送入专用磨具内经冷缩压成型，压缩部分钢材密度可大大提高，从而提高材料的抗拉强度。而塑性、冲击韧性不减，使丝扣部分和杆体部分强度一致，解决了因车床剥皮而减小抗拉力和冲击韧性的弊端。

SJ-42 type shrinkage machine belongs to the non-cutting processing equipment, with high production efficiency, simple process, easy to operate, save raw materials, quality stability and so on. It is the use of hydraulic technology will be round steel, threaded steel and other shrinkage parts into the special abrasive through the cold shrinkage pressure molding, compressed part of the steel density can be greatly improved, thus improving the tensile strength of the material. The plasticity and impact toughness are not reduced, which makes the wire buckle part and the strength of the rod part consistent, and solves the drawbacks of reducing the tensile force and impact toughness due to the peeling of the lathe.