So you are wondering what are the hardest drill bits?
If you just want to short and direct answer then that is an easy one.
The hardest material known to man on Earth is diamond, and there are drill bits made from diamonds.
The short answer is that the hardest drill bits made are the ones made from diamonds.
But just because diamond drill bits are the hardest does not best they are the best for all materials and drilling applications.
If you are interested in knowing more about other types of drill bits made from different materials then please read on, otherwise I guess you have the answer you were looking for.
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More About Drill Bit Hardness
When you are drilling a material the drill bit you are using must be harder than the material being drilled for the bit to cut through the material efficiently.
If the drill bit you are using is not hard enough for the material it will dull very quickly.
I learned this as a kid when trying to drill through hardened steel with a normal high speed steel drill bit.
The bit would cut a little and then become dull very quickly.
It also did not help that I had the drill RPM way too high for even a bit suitable for drilling hardened steel such as a cobalt drill bit.
Drill bits are made from various materials with different levels of hardness.
We will start with the softer drill bit materials and then work up to the harder ones.
Carbon Steel
Carbon steel is the softest drill bit material on our list.
There are two versions of these types of bits, low carbon steel and high carbon steel.
The main advantage of these types of drill bits are they are very inexpensive.
Low carbon drill bits are the softest of the two and are used for drilling things like soft woods and plastics.
The high carbon version is harder and suitable for drilling hardwoods and soft metals.
High Speed Steel Drill Bits
This is probably the most common drill bit you will see today when buying drill bits.
You will commonly see high speed steel abbreviated as HHS.
High speed steel has has a high alloy content, mostly in the form of tungsten or molybdenum as well as a high carbon content.
It is created using a multiple step heat treatment process that tempers the steel and changes the chemical structure of the steel.
High speed steel drill bits are good for most metal and wood drill purposes.
There are also some coatings that are commonly applied to high speed drill bits to make them even more durable.
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Titanium Coated Drill Bits
There are coatings that can be applied to high speed steel drill bits that make them even more durable.
One of the common coatings is titanium nitride (TiN).
This coating helps to reduce friction which helps reduce heat.
Friction and the heat are the enemies of any cutting or machining process.
Titanium coated drill bits are commonly used in things like mass production where many holes are drilled.
It allows drills to operate at a faster RPM and reduces the time needed between drilling cycles.
One disadvantage of titanium coated drill bits is that then cannot be sharpened when they become dull since the process of sharpening the bits will remove the TiN bit coating that gives these bits their extra durability.
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Cobalt Drill Bits
To make drill bits that are even harder and more heat resistant they can be made from cobalt steel.
As the name implies, cobalt steel is made by adding cobalt to steel.
When talking about cutting tools such as drill bits, you will most commonly find steel alloys with between 5% and 8% cobalt content.
Cobalt drill bits are usually a gold color which is due to the heat treating process used to make the bits.
During use the gold color may wear off, but that does not impact the performance of the bit.
Cobalt steel is very hard and is much more resistant to heat than the previous bit materials we have discussed.
This allows for even faster drilling RPM and feed speeds.
One disadvantage of cobalt steel is that it is more brittle than regular or coated high speed steel.
Carbide Tipped Drill Bits
The next step in drill bit hardness on our list is the carbide tipped drill bit.
Carbide tipped drill bits have tips made from tungsten carbide.
These drill bits can drill through hard and abrasive materials and are considered the best drill bit for ceramic tile.
Other materials carbide bits are good for are concrete and cast iron.
Since carbide is very hard it stays sharp longer even when drilling these types of abrasive materials.
They can also be sharpened until the carbide tip is gone, which is good since they are usually more expensive than the previous bits we discussed.
There are also drill bits made completely of carbide, not just the tips, but carbide is very hard and can be easy to break.
Because of that most bits you will likely come across will be carbide tipped.
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Diamond Drill Bits
The last and hardest type of drill bit on our list are diamond tipped drill bits.
Diamond is the hardest material known, so diamond tipped drill bits are king when it comes to hardness.
These are used on the toughest materials such as rock, gemstones, ceramic, porcelain, glass, and other diamonds.
Diamond tipped drill bits are considered the best drill bits for porcelain tile.
You should not use diamond tipped drill bits on materials like metal, wood, or plastic.
When drilling softer materials the bits of material removed will clog up the bit’s diamond tip and prevent it from cutting.
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Final Thoughts
One thing to keep in mind about drill bit hardness is that a harder material does not mean the bit is more durable.
Although harder materials have some nice advantages there are some downsides as well.
Materials such as cobalt and carbide are hard, but they are also brittle.
Brittle materials can break due to things like vibration during the drilling process.
You should always use the best suited drill bit for whatever material you are drilling.
Each type of drill bit is suited and designed with certain materials and applications in mind.
There is no one best drill bit for all drilling scenarios.
Just picking the hardest drill bit available will not necessarily be the best choice for your project.
We recommend you take the time to research the best drill bit for your particular situation.
One of the most important parts of any drilling project is selecting the best RPM for drilling.
