Features DEEP PROCESSING: CNC milling cutter holder with straight extension handle is suitable for deep processing, bringing great convenience. R8 THREAD: This R40 tool holder is used for R8 collet, with a maximum speed of 8000RPM per minute, the drawbar end is 7/16 20. HIGH HARDNESS: The milling shank holder is made of 40CR material, repeatedly tempered and forged, has a very high hardness and stable structure. IMPROVE EFFICIENCY: The collet chuck holder uses fewer extension tools, thereby reducing costs and improving efficiency. HIGH PRECISE: The milling cutter holder is made by fine workmanship with high precise, ensuring the lathe work more accurate and reliable. Specification: Item Type: Milling Tool Holder Material: 40Cr Model: R8 ER40 (7/16 20) Shaft: R8 Thread Shaft Drawbar: 7/16 Application: R8 Special Machine, R40 Tool Handle Total Tightening Accuracy: ≤0.005 Roundoff: <0.8u Body Accuracy: 0.001 Carburization Depth: >0.8mm Surface Roughness: >0.8mm Runout Tolerance: 0.0004in Standard Speed: 8000RPM Per Minute Package List: 1 x Milling Tool Holder 1 x Storage Box Package List 1 x Milling Tool Holder 1 x Storage Box