Release time：2020-01-16 18:44 Browse：
Custom extra-long screws sometimes require turning (machining) instead of cold heading or other plastic forming processes due to the following technical reasons:
High-hardness materials (e.g., alloy steels, stainless steels) are difficult to cold-form without cracking.
Heat-treated materials (hardness > HRC 35) can only be shaped via machining.
Special alloys (titanium, nickel-based) exhibit significant work-hardening tendencies.
Tight diameter tolerances (e.g., ±0.02mm for precision instruments).
Non-standard threads (e.g., trapezoidal, multi-start threads).
Complex head features (e.g., internal hex sockets, custom grooves).
L/D > 8: Cold heading risks bending deformation.
Slender shanks (e.g., Φ3 × 200mm) require turning + straightening.
Micro screws (< M2): Difficult to form via cold heading.
Ultra-smooth surfaces (Ra < 0.8μm).
Avoid work-hardened layers that affect coating adhesion.
Special surface treatments (e.g., mirror polishing).
Low-volume production (< 1,000 pcs): High tooling costs for cold heading.
Prototyping & testing phases.
Complex geometries (e.g., stepped shafts) are easier to machine in one operation.
Aero-engine bolts (turning + thread grinding for high-temp alloys).
Medical bone screws (Swiss-type lathe machining).
Non-magnetic screws for semiconductor equipment (turning avoids work hardening).
Modern CNC turning centers enable combined turning & milling, allowing threads, grooves, and other features to be completed in a single setup—often more efficient than cold heading + secondary machining. For ultra-long screws (L/D > 15), a hybrid approach (turning + thread rolling) is typically used.
