what is a twist drill bit?

The twist drill bit is a complex-shaped double-blade slotting tool. It has been more than a hundred years since its birth, and it is still the most widely used hole processing tool, especially in manufacturing industries such as automobiles and aerospace where hole processing plays an important role.

What types of twist drills can be included?

  1. Standard Twist Drill : The most common type of twist drill bit, typically made from high-speed steel (HSS) or carbide. Suitable for drilling holes in various materials.
  2. Straight Shank Twist Drill: Features a straight shank, suitable for smaller drill bit sizes. Commonly used in hand drills and light-duty drilling machines.
  3. Taper Shank Twist Drill: Has a tapered shank design, suitable for larger drill bit sizes. The tapered shank provides better grip and stability.
  4. Carbide Twist Drill: Made from carbide, suitable for drilling hard materials such as stainless steel and cast iron. Offers high hardness and wear resistance.
  5. Long Twist Drill: These drills have a longer length and are suitable for drilling deep holes.
  6. Stub Twist Drill: These drills have a shorter length and are suitable for drilling shallow holes or softer materials.
  7. High-Speed Steel Twist Drill: Made from high-speed steel, offering good wear resistance and toughness. Suitable for drilling a variety of materials.
  8. Super Hard Twist Drill: Made from super-hard materials such as cubic boron nitride (CBN) or polycrystalline diamond (PCD), suitable for drilling extremely hard materials.

How prevalent are twist drills in machining?

According to CIRP statistics, in the machining industry, drilling time accounts for approximately 22% of the total machining time, and drill bit production accounts for approximately 60% of all tool production. The world consumes hundreds of millions of drill bits every year.

What role does China play in twist drill bit production?

The high-speed steel used in China’s drill bit production accounts for more than 70% of the total high-speed steel used in tool production. The export value of straight-shank twist drills accounts for 69.1% of the total export value of all tools.

twist drill bit
twist drill bit

Why is twist drill bit design complex?

Twist drills may seem simple, but in fact, the structure of the drill tip is very complex. The rake surface is a spatial spiral surface, and the flank surface is usually a spatial curved surface; the two rake surfaces intersect with the two flank surfaces to form two main cutting edges respectively.

How do twist drill bit geometric parameters impact performance?

The two flank surfaces intersect to form the chisel edge: three cutting edges. The rake angle and relief angle of each point on the cutting edge are different, and their calculation and measurement are also very complicated.

By understanding the basic structure of twist drills, one can learn and master the characteristics of twist drills and their cutting processes.

What are the structural parameters of a twist drill bit?

twist drill bit
twist drill bit

What are the composition and structural terms of a twist drill bit?

Basic structure of twist drill

  • Drill Shank (Shank): This part connects the twist drill bit to the machine tool, ensuring clamping and positioning. It transmits power (axial force and torque) for drilling. Drill bits with diameters >13mm feature tapered shanks with a flat tongue (flat tail) at the end for torque transmission. Drill bits with diameters <13mm typically have straight shanks.
  • Drill Neck (Neck): This is the transition part between the drill body and the drill shank, providing space for the grinding wheel during sharpening. Straight shank drill bits often lack a drill neck.
  • Drill Body: The working part of the drill bit consists of the cutting part (drill tip) and the guide part.
taper shank drill bit
taper shank drill bit

What Is the Cutting Part of a drill bits?

The cutting portion of the drill refers to the area made up of the cutting edges formed by the front, rear, and secondary rear surfaces of the drill tip. This includes:

  • Front surface: The surface of the helical groove close to the main cutting edge, which allows the chips to flow out during drilling.
  • Rear surface: The surface opposite the cutting surface (hole bottom) and extending from the main cutting edge to the heel.
  • Clearance flank: Also known as the first rear surface, adjacent to the cutting edge.
  • Heel clearance flank: Also known as the second rear surface, extending from the clearance flank to the heel.
  • Major cutting edge: The intersection of the front and rear surfaces forms the main cutting edge.
  • Minor cutting edge: The intersection of the front surface and secondary rear surface (margin) forms the minor cutting edge.
  • Chisel edge: The edge formed by the intersection of the two rear surfaces.
  • Outer corner: The intersection point of the major and minor cutting edges.
  • Chisel edge corner: The intersection point of the chisel edge and the major cutting edge.
  • Point: The working part of the drill, comprising elements that generate chips, including the major and minor cutting edges, front, and rear surfaces.
parts of a drill bit
parts of a drill bit

What is the guiding portion of a drill bit?

The guiding portion consists of two helical flutes, which guide and discharge chips during drilling and provide room for regrinding after wear.

  • Flutes: Two helical grooves on the drill body that provide channels for chip discharge and cutting fluid flow.
  • Lands: The uncut helical portions of the drill body, including the body clearance and margin.
  • Body clearance: The surface lower than the margin on the lands, reducing the drill body’s outer diameter for radial clearance with the hole wall, thereby minimizing friction and improving drilling quality.
  • Margin: Also known as the guiding surface, the cylindrical or conical guiding surface of the drill, which is the secondary rear surface.
  • Rear margins: The edges formed by the intersection of the rear surface with the body clearance and the helical flutes.
  • Heel corner: The point of intersection of the heel, rear margin, and rear flute edge.
  • Web: The center part of the drill body connecting the two lands.

Based on the structural terms of twist drills, the cutting portion can be divided into one point (drill tip point) and three cutting edges (two major cutting edges and one chisel edge).

Welcome to follow us

We will attend the 2024 China International hardware Fair
March 20 to 22, 2024
Welcome to our Booth: H8-02

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *