What Are HSS Drill Bits (And What Are They Used For)?
Mar 27, 2023
Choosing the right drill bit for the job is incredibly important. Working with the wrong bit can damage the material you’re drilling, damage the drill, break the bit, or result in imprecise or poor quality workmanship.
The two main factors to consider when selecting a drill bit are the material you are drilling into, and the size or diameter of hole that you need to make. A good rule of thumb is to select a drill bit with a hardness rating slightly higher than the material you plan to drill. When it comes to size, find one that matches the desired depth and diameter of your required hole. It’s best to use metric measurements as they are more precise and reliable. You should also look at the bit’s shape and flute design. Some shapes can easily remove chips while others may not be suitable for certain materials. Taking all these factors into account will ensure you choose the right drill bit for any job.
One of the most common types of bit is the HSS (high-speed steel) drill bit. HSS drill bits are made from carbon steel with the addition of other elements like tungsten, molybdenum, vanadium, and chromium steel.
Heat resistant and highly durable, they are specially designed for drilling metals including hardened steel, iron and soft metals like brass, copper, and aluminium alloy. They can also be used for drilling plastics. However, HSS drill bits are not recommended for wood or masonry drilling.
Let’s find out a little more about HSS drill bits, what they are, how to maintain them, and whether they are right for you.
What is High Speed Steel?
High speed steel is a specialised form of tool steel with a high carbon content, designed, developed and patented by Massachusetts-based American engineer Frederick Winslow Taylor in 1901.
To make high speed steel, the base element, typically an iron-carbon alloy, is mixed with additional elements in a furnace. These elements include tungsten, chromium, molybdenum and cobalt which are added in varying quantities to develop different types of alloys. During the production process the elements are melted together then cooled quickly; this process helps ensure all the components remain in solution thus providing better overall properties than forging or casting methods alone.
When it comes to drill bits, the finest bits are fully ground, which means they have been ground from a single piece of raw material and are very precise and strong.
HSS drill bits offer exceptional strength and durability even at high drilling speeds. They retain their hardness even when heated up to many hundreds of degrees, making them an ideal choice for tools used in high-temperature cutting environments such as metalworking, machining, and drilling. High-speed steel is also sometimes called “power tool steel” because its increased hardness gives it added strength and durability which allow it to handle harsh mechanical processes.
Some HSS drill bits will be treated with an anodised coating, such as black oxide or titanium nitride, to help prevent corrosion and reduce friction.
HSS bits are suitable for use with both hand-operated tools and power-driven drills. With a sharper point than standard drill bits, they can easily navigate through creative curves and hard plastics. The spiral flutes of an HSS bit also help to quickly move the chips away from the cut area, leading to a more efficient performance. This feature makes these drill bits ideal for many industrial applications that require precise drilling in small, confined spaces.
Different Types of HSS Drill Bits
HSS drill bits are classified as Group M steels, with ratings ranging from M1 to M10. The M grouping is based on the composition of the metal and will determine the hardness of the bit. In general, the higher the higher the M rating, the harder the drill bit.
For example, M1 HSS bits are softer compared to other HSS bits, but are also more resistant to shock as they flex more.
M7 HSS drill bits have a higher carbon and molybdenum content than lower graded bits and are often used for drilling work in heavy construction jobs.
M35 and M42 HSS drill bits have 5% and 8% added cobalt, respectively. These are considered specialty drill bits. The added cobalt enhances the heat resistance capacity and durability of the bits. Primarily used for drilling stainless steel, these bits work best when used at slow working speeds with a lubricant as the addition of cobalt can make the bits more brittle. They can, however, be sharpened relatively easily and will maintain a cutting edge and won’t dull easily.
Tips for Maintaining HSS Drill Bits
Excessive heat is the number one enemy of the drill bit. While HSS drill bits are designed to withstand greater heat than many other drill bits, excessive heat will still damage even the best bits over time.
There are a number of things you can do to minimise heat and extend the working life of your HSS drill bits. These include:
- Reducing drill speed: Higher speeds will generate greater heat
- Using a lubricant: Lubricants help to reduce friction, thereby reducing the heat generated while drilling
- Using coated drill bits: Titanium Nitride (TiN) coatings can increase wear resistance and lubricity, allowing for faster drill speeds without damaging the bit
- Reduce pressure: Allow the bit to do the cutting and avoid unnecessary pressure when drilling
To protect your tools and ensure the best outcome for your project, it’s worth doing a little research to ensure that you are using the right drill bit for the job.