Aluminum is a soft metal hence metalworking is easy and precise. When you need to drill aluminium, it is easy, and you can use a metal bit. But some aluminium metals are mixed with other metals, and hardness and softness have increased. When you drill aluminium, you can use many drill bits, but for the high speed and efficiency cobalt drill bit is the best solution.
Cobalt drill bits are highly recommended for aluminium drilling tasks because of the hardness, toughness, and higher melting point it can use to drill the aluminium efficiently.
In 1809 British chemist Sir Humphry Davy prepared (1809) an iron aluminium alloy by electrolyzing fused alumina. Currently, there are many types of aluminium, such as 6061, 1100, and many more are used in different industries. Due to its lightweight softness and lower density, it can cut, drill, and weld easily. Obviously, it is a silver colour, white metal, and an excellent electric conductor.
Why is Cobalt Drill Bit Good for Aluminium?
When you need to drill aluminium, you can use many drill bits because it is a soft metal and many metal drill bits can be used to drill. But why should you use a cobalt drill bit for the aluminium mostly? It is due to the below factors.
Cobalt Drill Bits Have Higher Hardness Than Aluminium
The hardness of the cobalt drill bit normally is 66HRC (Hardness Rockwell Scale). Aluminium is a soft metal with lower HRC value.
Pure aluminium lacks strength and is relatively brittle. Because of their greater strength and hardness, various aluminium alloys are used in the majority of applications. Therefore, the normal cobalt drill bit is enough for the drilling of aluminium. There is no need to use harder cobalt drill bits types such as M35 or M42.
Aluminium has Higher Heat Dissipation than Cobalt
A soft metal, aluminium, has a low melting point of 660oC(Celsius). For comparison, the melting point of stainless steel is 1510oC.
It is crucial to limit heat buildup as much as possible when drilling because of its low melting point. Otherwise, the drill bit will become stuck with melted metal.
As aluminium is known as a soft metal above, it is appropriate to use a basic drill bit like HSS for it. Still, attention should be paid to reducing the heat generated during drilling and the damage. The cobalt drill bit will help reduce heat buildup by quickly dissipating heat.
Aluminum has a Lower Melting Point and Density Than Cobalt
An aluminium can float on water. The density of aluminium is less than that of water.
The melting point of pure aluminium is 660oC. The density is 2.70 g/cm3. Almost all drill bits used for drilling aluminium have a higher melting point than soft aluminium.
Can Cobalt Drill Bits Use for Aluminium?
Normally, cobalt drill bits can be used to drill aluminium using the below RPM and surface cutting speed (SFM)
| Material | SFM | Assumed SFM | 1/8″ | 1/4″ | 5/16″ | 3/8″ | 7/16″ | 1/2″ |
| Aluminum | 200-300 | 250 | 7639 | 3820 | 3056 | 2546 | 2183 | 1910 |
- RPMs = (3.82 x SFM) / Diameter.
As pure aluminium is soft, aluminium alloy is produced according to the requirements. An alloy in which aluminium predominates is referred to as an aluminium alloy. Copper, magnesium, manganese, silicon, nickel, zinc and tin are common alloying elements.
It is the distance a place on a spinning component moves in a straight line in one minute. SFM is most frequently used to measure the surface speed of cutting tools during machining. It is a measurement of velocity that expresses the speed of the cutting tool’s cutting edge.
Surface footage of 500–1000 SFM is advised for cast aluminium alloys (such as 308, 356, and 380), with RPMs varied depending on cutter diameter.
Surface footage of 800-1500 SFM is advised for wrought aluminium alloys (such as 2024, 6061, and 7075), and the same calculation is used to determine a starting point for RPMs.
Due to the higher hardness, cobalt drill bits can be used on many metals such as both soft and hard metals efficiently.
Can You Use Titanium Drill Bits On Aluminium?
As mentioned, whether the titanium drill bit can dissipate the heat generated during aluminium drilling should be investigated. Titanium drill bits are the same as cobalt drill bits. The titanium coat on its surface prevents unnecessary temperature rise.
Another method to enhance heat build-up is to apply excessive pressure. Therefore, when drilling with a titanium drill bit, do not exert more force. Drilling a soft metal like aluminium doesn’t take long. Therefore, even a titanium drill bit can be used for this.
Can You Use HSS Drill Bits On Aluminium?
Generally, HSS drill bits cannot be used to drill hard metals. But since aluminium is a soft metal, there is almost no problem in drilling. The hardness of the drill bit alone does not affect the drilling of soft metals such as aluminium. The drill bit tip required for this is a drill bit with a sharp point. The 118-degree angle drill bit is ideal.
A good drilling lubricant will reduce friction between the HSS drill bit and the aluminium and this will minimize heat buildup.
