The screw Angle of twist drill mainly affects the size of cutting edge Angle, edge edge strength and chip removal performance, which is usually 25 32 Spiral grooves can be processed by milling, grinding, hot rolling or hot extrusion, and the front end of the drill bit forms a cutting part after grinding. The cutting Angle of the standard twist drill is 118, the bevel Angle of the cross edge is 4060, and the back Angle is 8 20. Due to structural reasons, the rake Angle is large at the outer edge and gradually decreases to the middle, and the transverse edge is negative rake Angle (up to about -55), which acts as extrusion when drilling. we are a professional manufacturer of power tool accessories, we are specilized in various cutting tools and tool set, drill bits, hole saw, cutting discs, etc. Our Twsit drill bits are exported to many countries all over the world. We produce HSS twsit drill bits for metal working, carbon steel drill bits for wood working, and also masonary drill bits for concrete works. We provide OEM if you have large quantity, custom the twist drill bits as customers' request. We can produce various sets include different size in metric and inch. and hope we can start our cooperation in the future.