Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. There are also certain specialized drill
Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. There are also certain specialized drill bits that drill bit geometry pdf create holes with a non-circular cross-section. Harder materials require a larger point angle, and softer materials require a sharper angle. The correct point angle for the hardness of the material influences wandering, chatter, hole shape, and wear rate.
A greater lip angle will cause the bit to cut more aggressively under the same amount of point pressure as a bit with a smaller lip angle. Both conditions can cause binding, wear, and eventual catastrophic failure of the tool. The proper amount of lip clearance is determined by the point angle. A very acute point angle has more web surface area presented to the work at any one time, requiring an aggressive lip angle, where a flat bit is extremely sensitive to small changes in lip angle due to the small surface area supporting the cutting edges. While longer bits can drill deeper holes, they are more flexible meaning that the holes they drill may have an inaccurate location or wander from the intended axis. Most drill bits for consumer use have straight shanks.
Other types of shank used include hex-shaped, and various proprietary quick release systems. The diameter-to-length ratio of the drill bit is usually between 1:1 and 1:10. The best geometry to use depends upon the properties of the material being drilled. The following table lists geometries recommended for some commonly drilled materials. Many different materials are used for or on drill bits, depending on the required application. These bits can be used on wood or metal.
HSS bits are hard and much more resistant to heat than high-carbon steel. They can be used to drill metal, hardwood, and most other materials at greater cutting speeds than carbon-steel bits, and have largely replaced carbon steels. The main disadvantage of cobalt steels is that they are more brittle than standard HSS. However, it is becoming common in job shops to use solid carbide bits. 1 mm, solid carbide bits are used. It consists of a layer of diamond particles, typically about 0. PCD into a vein in the tungsten-carbide “nib”.