Drilling is a process of cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multipoint. The bit is pressed against the work-piece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the work-piece. In these machines used for drilling various metals are called as drilling machines. These drilling machines are of different shapes different sizes related to their work.
Drilling machine may affect the mechanical properties of the work-piece by creating low stresses around the holes opening and a very thin layer of highly stressed and disturbed material on the newly formed surface. This causes the work-piece to become more affected corrosion and crack propagation at the stressed surface. A finish operation may be done to avoid these detrimental conditions.
For fluted drill bits, any chips are removed via the flutes. Chips may form long spirals like of steel wood, or it depends on material, and process parameters. The type of chips formed can be an indicator of the work of machinery. If, these small flakes are of long chips it indicates the work of poor machinery.
Cutting fluid is commonly used to cool the drill bit, increase tool life, increase speeds and feeds, increase the surface finish, and aid in ejecting chips. Application of theses fluids is almost done by flooding the work-piece with the coolant, lubricant or by applying a spray mist. Deciding which drilling machine to use is important to consider the task at hand and evaluate which drill would best accomplish the task. There are different types of drills according to their style that each serves for different purpose. The subland drill is capable of drilling more than one diameter. The spade drill is used to drill larger hole sizes. The index able drill is useful in managing chips.
Spot drilling is used where a hole that will act as a guide for drilling the final hole. The hole is only drilled part way into the work-piece because it is only used to guide the beginning of the next drilling process.
Center drilling is used as the purpose of center is to drill a hole that will act as a center of rotation for possible following operations. Center drilling is typically performed using a drill with a special shape, known as a center drill.
Deep hole drilling is explained as a depth of hole deeper ten times than of diameter of hole. This type of deeper hole requires some special equipment to maintain the straightness and tolerances. Mostly deep hole drilling is done by generally achievable with few tooling methods, usually gun drilling or BTA drilling.