Hardened steel is often used in industrial settings or for products designed for strength and durability and made to last. Because hardened steel is specifically made to resist damage and breakage, drilling a hole into it can be difficult.
While cutting into hardened steel can be challenging, it isn’t impossible, and with the right drill bit set, you can do it with great precision and a smooth, clean finish.
Before you begin working on your next hardened steel project, quickly examine the specs ideal for the perfect drill bit.
What Is Hardened Steel?
Before discussing the types of drill bits best used to puncture holes in hardened steel, let's quickly discuss what hardened steel is to understand better why certain bits are necessary.
Hardened steel is typically medium to high-carbon steel that goes through a hardening process. To strengthen the metal, it is exposed to extremely high temperatures, then tempered (cooled down quickly) and heated again, creating a chemical reaction that hardens the outer layers of the material and forms a durable core.
This rigid material is often used to create industrial equipment, including but not limited to:
- Boat anchors
- Heavy-duty tools
- Surgical equipment
- Crushers
- Rock processing plates
- Axles
- Driving pinons
- Mechanical engineering industry
- Automotive industry
Because hardened steel is made to be durable, long-lasting, and wear-resistant, drilling into it isn’t an easy task that you can accomplish with any drill bit. You need one that is just as strong as the material itself.
The Best Drill Bits for Hardened Steel
Like stainless steel, hardened steel needs a strong and durable bit to get smooth precision when drilling into it. However, stainless steel doesn’t have as high a carbon content as hardened steel, making it a little easier to work with.
Hardened steel is specifically designed to hold up against the most rugged conditions and jobs, so choosing the right size, material, coating, length, number of flutes, and angles will help ensure the hole is precisely how you want it.
Drill Bit Size for Cutting Hardened Steel
The drill bit size you use when cutting hardened steel should depend on the hole size you are looking to create. There are various options offered, including:
- 1/4 inches
- 5/16 inches
- 3/8 inches
- 25/64 inches
- 15/32 inches
- 1/2 inches
- 9/16 inches
- 5/8 inches
- 11/16 inches
- 3/4 inches
When it comes to the appropriate length, you need to get a bit long enough to make its way through the steel item with a clean cut.
Remember that extra long bits are great when drilling through thicker hard metal but are much easier to snap. If you must use a long drill bit, keep your drill as straight as possible.
Drill Bit Metal for Drilling Hardened Steel
High-speed steel is the most popular material to use for drilling hardened steel. This bit has the strength and ability to puncture hardened steel with a smooth, clean cut.
Because this steel material is so rigid, using a bit that can’t withstand high speed and intense heat can result in a burnt-out drill and a very messy cut.
Cobalt bits and carbide bits are other favorites in this space because they are heat-resistant and more durable than high-speed steel options.
Drill Bit Tip Styles for Drilling Hardened Steel
While browsing your local hardware store, you will come across an array of metal drill bit styles and shapes, each made for a specific type of cut. While you can use any drill bit you desire if it is rated for hardened steel, the best kind is a spiral or twist bit.
A spiral bit or twist drill bit is made up of flutes – twisted parts of metal with sharp edges on each side. The most common number of flutes for cutting hardened steel is 4.
A multi-diameter bit is another favorite used to drill multiple holes of different sizes without changing the bit.
Other tips to consider when drilling hardened steel include the following:
- Straight flute
- Parabolic spiral flute
- Split point
- Standard point
- Four faucet point
- Notched point
The tip of your bit will provide a unique cut and entrance point for the rest of the tool, so you must identify the type and size of hole you need to make and pick the bit designed for that job.
Drill Bit Coating for Drilling Hardened Steel
Having the proper coating on a drill bit can reduce the heat created when the high speed and pressure of the bit come into contact with the metal. Titanium nitride and black oxide are excellent coating options due to their ability to reduce friction, thus reducing heat.
Angle When Drilling Hardened Steel
The best way to drill through hardened steel is by applying ample pressure at a downward angle, avoiding tilting or turning. Even the slightest angle can cause an aggressive and uneven cut or even break the bit's tip.
If an angled hole is needed, it is best to reposition the metal material rather than drill at an angle.
Another angle to look for is the point angle of the drill bit. This feature also comes in various options, each ideal for a specific task.
- 79°
- 88°
- 90°
- 118°
- 120°
- 130°
- 135°
- 140°
- 145°
For hardened steel, aim for a wider angle for a more accurate and clean cut, preferably 130° or more.
Bit Shanks When Drilling Hardened Steel
The shank of the bit is just as important as the bit style. The type of shank on your bit will assist in getting the smooth cut you want for every scenario. The shanks can differ in length and shape.
Lengths of a bit shank range from 0.0135 inches to 1 ½ inches or 1mm to 15mm. The larger your shank, the longer the bit is overall.
The different types of shanks also vary significantly in shape or design, with options like:
- Round
- Reduced round
- Tapered
- Hexed
- Quick change hex
- Square
- Threaded hub
- Three-flat
The style of shank you need will depend on the drill you use and the attachments you have to ensure they fit correctly.
The Top Drill Bits for Drilling Hardened Steel
Where can you get the top drill bits for drilling hardened steel that meets the above criteria? Consider purchasing quality products from these top manufacturers in the industry:
- Cleveland Twist Drill
- Chicago-Latrobe
- Cle-Line
- Viking Drill & Tool
- Triumph Twist Drill
- Steelmax
When browsing these sites, remember to key in on the specific details, recommendations, and requirements for the project you are about to tackle.
Final Thoughts
Hardened steel is one of the most challenging metals to cut through when it comes to drilling. Please use the information and tips to choose the right drill bit the next time you work with this rugged and tough material.