S-SP deep hole with spiral screw specially designed for tapping the wire length of large diameter 2 times or 2 times above the barrier screw thread tapping hole. The length of the S-SP tooth is shorter than the general spiral filament, but the spiral angle is larger than the common screw. Acidification is applied to the surface to reduce the friction resistance produced by the cutting and increase the tapping life of the silk.

·Screwdriver precision grade：YAMAWA P level
·Screwdriver material：HSS-E
·Tooth number of cutting edge：S-SP 2.5 tooth

·Surface treatment: acidification treatment
·Suitable for cutting materials: carbon steel, alloy steel, cast iron, Quenched and tempered steel and so on, which are less than 750N/mm2 of tensile strength...