What are drill bits and what are the common types of drill bits?

Drill bits are more common in our daily life, they are the cutting tools used by general drills or drilling and digging machines to cut out round holes. So do you know what are the types of drill bits? Let's learn about it together next.

[What is a drill bit

Drill is a rotating and the head end of the cutting ability of the tool, generally to carbon steel SK, or high-speed steel SKH2, SKH3 and other materials by milling or rolling and then quenched, tempered heat treatment and then ground, used for drilling of metal or other materials on the processing of holes, it is a very wide range of uses, can be used in drilling, lathes, milling machines, hand drills and other tools used on the machine.

Types of Drill Bits

1、Twist drill

Twist drill is the most widely used hole processing tools. Usually the diameter range of 0.25 ~ 80 mm. It is mainly composed of the working part and shank. The working part has two spiral grooves, shaped like a twist, hence the name.

In order to reduce the friction between the guiding part and the hole wall when drilling, the twist drill gradually reduces its diameter from the tip of the drill to the shank in the direction of an inverted cone. Twist drill spiral angle mainly affects the size of the cutting edge on the front angle, edge strength and chip removal performance, usually 25 ° ~ 32 °.

Spiral grooves can be processed by milling, grinding, hot rolling or hot extrusion, etc. The front end of the drill is sharpened to form the cutting part. The cutting part of a standard twist drill has a top angle of 118, a cross-blade bevel angle of 40° to 60°, and a back angle of 8° to 20°. Due to structural reasons, the front angle is large at the outer edge, gradually decreasing to the center, and the negative front angle at the transverse edge (up to -55° or so), which plays the role of extrusion when drilling.

In order to improve the cutting performance of the twist drill, according to the nature of the material to be processed will be cutting part of the grinding into a variety of shapes (such as group drill). Twist drill shank form has a straight shank and taper shank two kinds, when processing the former clamped in the drill chuck, the latter inserted in the machine tool spindle or tailstock taper hole. General twist drill made of high-speed steel. Welded carbide inserts or crown of the twist drill is suitable for processing cast iron, hardened steel and non-metallic materials, etc., the whole carbide twist drill for processing instrumentation parts and printed circuit boards, etc.

2、Flat drill

The cutting part of flat drill is spade-shaped, simple structure, low manufacturing cost, cutting fluid can be easily introduced into the hole, but the cutting and chip removal performance is poor. The structure of flat drill has two types: integral type and assembly type. Integral type is mainly used for drilling micro-holes with a diameter of 0.03 to 0.5 mm. The assembled flat drill has replaceable inserts and internal cooling, and is mainly used for drilling large holes with a diameter of 25 to 500 millimeters.

3、Deep hole drilling

Deep hole drilling usually refers to the processing of hole depth and hole diameter ratio greater than 6 hole tool. Commonly used gun drill, BTA deep hole drilling, jet drilling, DF deep hole drilling. Socket drill is also commonly used in deep hole processing.

4, reaming drill

Reaming drill has 3 to 4 teeth, its rigidity is better than the twist drill, used to expand the existing hole and improve the machining accuracy and finish.

5、Countersinking drill

Countersinking drills have more teeth, to form the hole end processing into the desired shape, used for processing a variety of countersunk head screw countersinking holes, or flatten the outer surface of the hole.

6、Center Drill

The center drill is used for drilling the center hole of shaft workpiece, which is essentially a twist drill and countersinking drill compounded by a small helix angle, so it is also known as composite center drill.

7、Hollow Drill

The center of the drill shaft is a hollow drill, mainly used for drilling and coring.