... for manufacturing high strength, wear-resistance, high-duty, vibration proof and exchangeable bolted connections in metallic and non-metallic materials ... rusting, stucking, trip with perfect corrosion, high heat and abrasion resistant in many kinds environments, it also can ... type: 6H, 5H, 4H Advantage: 1. Enhancing the connected strength of internal thread. 2. Improving the working life. 3. Reducing ...