Drill bit materials are very important in metalworking. Because we should always use harder material than the workpiece. Material hardness is measured by the HRC (Rockwell hardness values). Higher HRC values are easy to use on most metals. The most used drill bit materials are HSS, cobalt, and titanium. More than that, Tungston, Aluminum are also used with mixing other metals. As well as some coats are also applied on the drill bits in order to improve the hardness, durability, and thermal resistance. Black oxide, TiN, TiCN, and TiAlN are the most used coating on metal drill bits.
1. High Carbon Steel Drill Bits
When drill bit material mix with a higher percentage of carbon, these drill bits can be produced. Those are used to drill mild steel which is mixed with a lower percentage of carbon. We can see higher carbon steel and low carbon steel drill bits here that is according to the carbon percentage.
A lower carbon percentage can’t be used for drilling steel. It will tamper due to heat. But higher carbon steel can be used to drill steel without any problem. These bits are extremely good for the woods. These are really cheap, but I highly recommend you move one of the below drill bits if you need a durable drill bit.
2. HSS Drill Bits
Suitable For
HSS drill bits can be used to drill iron, steel, and other metals such as brass, copper, and aluminum alloy can be drilled by using HSS drill bits because it has a 63-65 HRC value.
A drill bit has two cutting surfaces on either side of the center axis and is cut at an angle of approximately 60 degrees. This cutting angle is selected according to the nature of the material required to drill.
Cutting Angle
There are various cutting angles. 118 degrees is the most common cutting angle for the HSS drill bit. Other than that 120, 130, 135, and 140 degrees of drill bits are also available.
HSS is an abbreviation of High-Speed Steel. This drill bit is made from a combination of carbon steel and other elements. Vanadium and chrome to form an alloy can be used as other elements. Under that, most HSS drill bits consist with,
- 18% of tungsten,
- 4% of chromium,
- 1% of vanadium,
- only 0.5–0.8% of carbon.
- Can withstand high temperatures produced during metal drilling
- A more robust drill bit type
- Higher heat resistance – These drill bits can be used even at temperatures below 600oC
- Repeatability and high shelf life are special features of HSS drill bits.
3. Black Oxide Drill Bits
Suitable For
HSS drill bits are suitable for drilling metals also. Black oxide drill bits can be used to drill wood, plastic, as well as metals and alloys including steel, copper, and aluminum
This is also a type of HSS drill bit that is coated with iron oxide. According to that, the HSS drill bit must have to heat at 950 degrees of Fahrenheit to make a black oxide drill bit.
- Can withstand high temperatures produced during metal drilling
- A more robust drill bit type
- Higher heat resistance – These drill bits can be used even at temperatures below 600oC
- Re-sharpen ability and high shelf life than HSS drill bits
Such a coating offers great lubricity to ensure minimum heat accumulation, thereby enhancing the longevity of these bits considerably. Black oxide drill bits are made by subjecting high-speed steel (HSS) drill bits to a temperature of around 950 Fahrenheit.
4. Cobalt Drill Bits
Suitable For
Cobalt drill bits can be used t drill harder metal such as bronze, cast iron, stainless steel, titanium, etc. It can drill harder metals due to its higher HRC value of 68 – 70 HRC.
- HSS is a stronger drill bit type than drill bits because it has high-speed steel and 5% to 8% cobalt element.
- 5% cobalt mixture is named M35 and 8% cobalt mixture is named as M42
- They are highly resistant to heat.
- Very hard and abrasive.
- The cobalt drill bit is a strong drill bit used to drill hard materials. So the cutting angle here is mostly 135 degrees.
- Compared to the HSS drill bit, the cobalt drill bit can be used faster and longer without cooling. Therefore, the durability of these is high.
This Cobalt drill bit guide will solve all your problems.
5. Titanium Nitride Drill Bit (TiN)
Titanium nitride is a coating that is coated on the HSS drill bits in order to increase the abrasion resistance, reduce the friction and increase thermal condensation. This will increase the durability of the drill bit.
Suitable For
Titanium nitride drill bits can use for drilling on several types of metals, such as mild steel, iron, copper, magnesium, wood, and plastic. (Not recommended for aluminum)
And also, titanium nitride has been named trinite, azanylidynei titanium, and nitrido titanium.
- When it comes to physical properties, titanium nitride has a high hardness level (HV 2400-2800) and a high melting point (2950°C).
- Because of its high thermal resistance, it can be used to make devices that use in high temperatures. Further,r it does not react with acids and base.
- Because of a hard ceramic material, titanium nitride can be used in making drill bits.
- Usually, titanium nitride drill bits make from steel and apply titanium nitride coating. A titanium nitride drill bits can be sharpened but with sharpening, the coating will remove from the cutting edges.
- 135 Degrees can be identified as the suitable cutting angle for titanium nitride drill bits
- The titanium drill bit has six times more durability than steel.
7. Titanium-Carbonitride Drill Bits (TiCN)
Suitable For
Aluminum, Brass, Bronze, Fiberglass, Hardened Steel, Iron, Nickel, Plastic, Stainless Steel, Steel, Titanium, Tool Steel
Titanium-carbonitride (TiCN) drill bits are superior to the TiN drill bits. These drill bits have a hard, smooth finish that resists chipping and wear. It can prevent material accumulation at the edge. Hence these are very good for aluminum drilling.
6. Aluminium Titanium Nitride Drill Bits (TiAlN)
Suitable For
Brass, Bronze, Fiberglass, Hardened Steel, Iron, Nickel, Plastic, Stainless Steel and Steel can be drilled using aluminum titanium nitride drill bits.
Aluminium Titanium Nitride drill bits are the same as AlTiN coated on the HSS drill bits. A thin Al203 film will be formed on the drill bit surface. This will increase the hardness, durability, and thermal resistance and reduce the friction of the drill bit.
- Further, according to the content, aluminum has high content (50%).
- Aluminum titanium nitride has a higher hardness level (2600 to 3300 HV) and a high melting point (2,947 °C).
- The physical vapor deposition method is usually used industrially to make aluminum titanium nitride drill bits
- Brass, Bronze, Fiberglass, Hardened Steel, Iron, Nickel, Plastic, Stainless Steel, and Steel can be drilled using aluminum titanium nitride drill bits.
- Further, 118.0 degrees is the suitable cutting angle for this drill bit
Aluminum titanium nitride drill bits can be sharpened. But with the sharpening, the coating will remove from the cutting edges.
Titanium Vs Cobalt Drill Bits
Among the drill bit types, titanium and cobalt drill bits can be used successfully for metal drilling. The titanium drill bit is a type of high-speed steel (HSS) bit with a titanium oxide coat. Therefore, these drill bits are the strongest and most corrosion-resistant type of drill bit.
| Characteristics | Titanium Drill Bits | Cobalt Drill Bits |
| Hardness | Harder than cobalt drill bits | Less than titanium drill bits |
| Re-sharpenable | Cannot | Can |
| Made from | High-speed steel with titanium nitride coating. | Cobalt steel |
Bits that can drill metals are usually identified in black, among other drill bits. Another feature is that the tip of the drill bits has a wide angle at the tip.
Identify Your Metal Piece Before Drilling It
It has been identified that the use of metal by man took place at the earliest level or from the beginning of human civilization. However, it was not until much later that man learned to make an alloy of iron called steel. The properties of these types of drill bits vary depending on the amount of alloy they contain. There are four such variables but there are many more subtypes as well. Those are,
- Carbon steel
- Stainless steel
- Alloy steel
- Tool steel
No matter what drill bit you use, using a lubricant will make the drill easier.
Suitable RPM for Steel Drilling For Drilling Metal
