The "pioneer" of the modern straight slot drill is the dierills, which are of a short size, good rigidity, strong tip, suitable for drilling hard steel at lower spindle speeds and smaller feed rates. Of high strength and high rigidity to enable it to process the straightness and roundness of the hole. Mold bit has been able to achieve good processing results, because the design of the drill when the processing material is usually produced short chip metal. Chip control is still a key issue in the machining applications of straight slot drills. (P / M), medium-high silicon content (6% or higher) of silicon-aluminum (P / M), medium-high silicon content (6% or higher) is only possible in the case of processing materials that do not produce long rolls of chips Alloy and so on.
However, with the machine tool technology, coolant transport technology and tool geometry design progress, straight groove drilling processing applications are constantly expanding. The traditional way of thinking that the spiral groove of the drill bit is essential for chip removal, straight groove drilling can only be used in aluminum and cast iron drilling hole depth of 2D ~ 3D (D for the aperture) of the shallow hole. But now the development of high-pressure cooling system and higher machine tool spindle speed, making the use of internal cooling straight groove drill chip and chip performance greatly improved.
In the case of suitable processing conditions, the straight bit drill can show far better than the spiral groove bit good processing performance. The advantage of the straight bit is to be able to process rounded and straightened holes with faster cutting speeds than standard cobalt or high speed steel drills. For example, with a diameter of 0.394 "(φ10mm) GuhringRT150GG straight groove instead of twist drill aluminum processing, twist drill cutting speed of 50sfm (15m / min), feed 0.005ipr (0.127mm / r); and straight Slot drilling speed of up to 800sfm (245m / min), feed up to 0.007ipr (0.178mm / r). Straight groove drilling time is only 10 times the twist drill.
Partial reasons for the significant improvement in machining efficiency by straight-groove drilling are based on the basic design of the drill bit, which provides a direct channel for the chip discharge orifice. However, since the cutting edge of the straight bit bit lacks a positive rake angle, its crumb and chip breaking capacity is poor, especially when machining ductile materials.
Cutting speed (especially high enough cutting speed) is another factor in the successful application of straight groove drilling. The faster the cutting speed, the smaller the chip is formed. Straight groove drilling is achieved by a faster spindle speed rather than a higher feed rate to achieve high productivity.
Many high-performance, high-drilled twist drills have a large chamfer on the cutting edge, which requires the drill to enter the work of the feed should be more than the cutting edge of the chamfer size, so that the cutting edge to the workpiece material Cut it and not just push it. For some processing applications and machined materials, the cutting edges of the twist drill are in good working condition, and these twist drills are usually drilled at a feed rate higher than the straight slot and a cutting speed below the straight slot The