SJ-50 Necking Machine

Unlike cutting or lathe-peeling methods that remove material and weaken the cross-section, the SJ-50 forces steel into a precision die under hydraulic pressure. This cold-forming process compresses the grain structure at the necked zone, increasing local density, tensile strength, and impact toughness — exactly the properties required for load-bearing mining anchor rods and structural anchor bolts.

The machine handles diameters from 16 mm to 50 mm and necking lengths from 10 mm to 400 mm, covering the most common anchor rod and bolt specifications in a single setup. A necking rate of ≤3 mm and post-necking extension of 10%–15% are tightly controlled by the hydraulic system and die geometry, ensuring each part meets dimensional and mechanical targets.

A 22 kW hydraulic motor delivers consistent forming force across the full diameter range, while a dedicated 0.09 kW cooling motor maintains stable hydraulic fluid temperature during extended shifts. The dual-actuator layout with hardened linear guides distributes load evenly, reducing wear on seals and cylinders.

At 2500 × 900 × 1600 mm, the SJ-50 fits into standard workshop bays and can be positioned inline with upstream straightening or downstream thread rolling equipment. The 3,000 kg steel frame absorbs forming vibration without requiring a special foundation, and the side-mounted electrical cabinet keeps wiring accessible for maintenance.

Cold hydraulic necking produces no chips or swarf, eliminating scrap disposal costs. Integrated cooling nozzles extend die service life, and the chipless process means no secondary deburring is needed — reducing both labor hours and total cost per finished part.