HOW TO CHOOSE THE RIGHT METAL DRILL BIT – PART 1

HOW CAN I IDENTIFY A METAL DRILL BIT?

1. Distinctive shape: A metal drill bit can be easily recognized by its tip and the shape of its flutes. Here's a description of its individual parts:
• Tip (Point): The point angle is typically 118°, 130°, or 135°. The tip has two main cutting edges (lips) that start at the centre of the drill bit and extend towards the outer edges. These two main cutting edges perform the actual drilling work by cutting away the material. The main cutting edges are connected by the chisel edge. The chisel edge is located at the centre of the drill point and has no cutting action. However, it is an essential part of the twist drill design because it connects the two main cutting edges.
• Spiral flute: It is used to collect and remove the chips produced during drilling. Along its entire length, the spiral flute is equipped with two guiding lands and a secondary cutting edge. The guiding lands further machine the sides of the drilled hole and help guide the drill bit accurately within the hole. The quality of these lands also affects the quality of the hole wall. The secondary cutting edge forms the transition between the guiding land and the flute. It loosens and cuts away chips that become trapped in the material.
• Drill body: The diameter of the drill body determines the size of the hole produced by the drill bit.
2. Colour: Metal drill bits are generally available in three basic colours: black, silver and golden brown. Simply put, the colour is the quickest way to identify the type of metal drill bit.
3. Packaging label: The packaging should clearly state that it is a drill bit for metal. Look for markings such as "HSS" or "HSS-Co".

HSS metal drill bit detail

WHAT DO THE ABBREVIATIONS HSS, HSS-R, HSS-G AND HSS-Co MEAN, AND HOW CAN THEY HELP YOU CHOOSE THE RIGHT DRILL BIT?

• HSS: High Speed Steel – the material from which metal drill bits are manufactured. If a drill bit is marked only as HSS without any additional designation, it can generally be assumed to be a roll-forged drill bit, i.e. the equivalent of HSS-R.
• HSS-R: Roll-forged drill bits.
• HSS-G: Ground drill bits.
• HSS-Co: Cobalt drill bits.

These abbreviations help you quickly identify the type of drill bit and choose the right one for your needs, whether you require flexibility, precision, or resistance to high temperatures and hard materials. You'll learn more about this in the following section.

WHAT ARE THE MAIN TYPES OF TWIST DRILL BITS FOR METAL, AND HOW DO THEY DIFFER?

There are three main types of twist drill bits for metal. Each type has its own specific characteristics, advantages and disadvantages, making it suitable for different applications.

HSS roll-forged drill bit

HSS Roll-Forged Drill Bits

• Typical appearance: Black colour, less precise flute geometry, drill point without a split point.
• Material: Standard HSS.
• Advantages: The most affordable type, more flexible and therefore, when used correctly, less prone to breaking than ground drill bits.
• Disadvantages: Lower accuracy and wear resistance compared to ground drill bits. This type is the most affected by price pressure. As a result, you can find not only high-quality products on the market but also drill bits made from inferior materials or manufactured using compromised production processes. You can learn more in the article
  WHAT TO WATCH OUT FOR – THE DIFFERENCE BETWEEN APPARENT AND TRUE DRILL BIT QUALITY.
• Applications: Ideal for DIY use and less demanding tasks such as drilling into softer metals and steels.

HSS-G ground drill bit

HSS-G Ground Drill Bits

• Typical appearance: Silver colour, precise sharp flutes. From a diameter of 3 mm, the drill point should feature a split point, which improves the drill bit's ability to start drilling accurately without the need for centre punching. Lower-cost ground drill bits may not have a split point. We therefore recommend checking this feature before purchasing.
• Material: High-quality HSS.
• Advantages: Greater accuracy, better wear resistance than roll-forged drill bits, and suitable for professional use.
• Disadvantages: More expensive than roll-forged drill bits.
• Applications: Suitable for precision drilling in steel, alloy steel and other harder materials. For professionals, this quality should be the standard. DIY users will benefit from higher performance and a longer service life compared to roll-forged drill bits, making even demanding projects possible.

HSS-Co cobalt drill bit

HSS-Co Cobalt Drill Bits

• Typical appearance: Most commonly golden brown in colour, highly precise flutes, drill point with a split point (from a diameter of 3 mm).
• Material: Premium-quality HSS with added cobalt.
• Advantages: The highest hardness and heat resistance. This makes it suitable for drilling very hard materials such as stainless steel. Ideal for the most demanding applications.
• Disadvantages: The most expensive type and, due to its cobalt content, also the most brittle. Incorrect use therefore increases the risk of breakage.
• Applications: Perfect for drilling very hard materials such as stainless steel and titanium.

The difference between a drill point with and without a split point is shown in the image below

Drill point with and without a split point

If you'd like to learn even more about metal drill bits, also read How do the manufacturing process and the material used affect drill bit quality? andWhat to watch out for – the difference between apparent and true drill bit quality.