Best Drill Bits for Hardened Steel Reviews

What makes the best and top rated drill bits for hardened steel? If you have ever attempted drilling through hardened steel, or metal, then you know just how tough that can be.

Using an ordinary drill bit designed for normal metal materials will not work, and in fact will ruin that bit for other uses.

The perfect drill for taking on hardened steel is a “Cobalt HSS” drill bit which has been specifically designed for this purpose.

Understanding Hardened Steel

I always find that when I understand how something is made, that it is easier to understand how you can work with it. This includes how to drill it.

Hardened steel will take an ordinary steel that is high in carbon content and put it through the processes of quenching and then tempering.

To harden steel extremely high temperatures are used, and that type of steel must have a lot of carbon in it to begin with.

All hardened steels go through a four step process which I will not bore you with here. It is important to note that the carbon steel is heated to high temperatures which hardens the steel.

It is then dipped into cold water, pretty much in the way you would see a blacksmith working, but that makes it brittle.

The tempering process then reduces how brittle the steel becomes and the net result is you are left with a pretty tough steel product.

I have included a video below on how to check if the steel you are going to be drilling is actually made from hardened steel.

Video On How To Check If Steel Is Hardened or Not

Uses of Hardened Steel

Hardened steel is used for objects that are subject to high levels of force or abuse such as cranes, car parts, trucks, hand tools, guns, and knives to name but a few. Compared to ordinary steel, hardened steel is much more durable, more resistant to wear and tear and perfect material for all types of heavy duty applications.

Top 6 Drill Bits For Hardened Steel

So at least we now know what we are trying to drill through. If you have never done this before, then you are in for a pretty tough piece of drilling. Attempting to do this with any of the standard drill bits that you get will be impossible.

If you try to use any of those, then not only will you be wasting your time, but the hardened steel will ruin those bits for use on other types of softer metals.

You need a drill bit that has been designed to cut its way through the hardened steel and a cobalt drill is the correct type. I have listed below the best cobalt drill bits available on the market today. Just before you have a look at them I think it is important to understand how HSS drill bits are actually graded.

Cobalt Drill Bits

There are basically 5 different levels of HSS drill bits

  • T1
  • M2
  • M7
  • M35 – 5% cobalt
  • M42 – 8% cobalt

So for drilling through hardened steel you would want bits with an M42 rating

No 1 Rated Drill Bits for Hardened Steel – DEWALT DW1361 Titanium Pilot Point Drill Bit Set for Steel

The logic is that to drill through any material the drill bit that you are using has to be made of a material that is harder, than the material you are trying to drill through.

In addition to this, very high temperatures will be created when you perform any kind of drilling task. With the Dewalt DW1361 set, you get 21 high quality drills, at a very affordable price.


This set includes sizes from 1/16-inch to 1/2-inch and they come in a tough plastic case, which will help keep them safely stored. Just remember these need to be used in a Jacob’s style chuck.

They have a titanium pilot point which ensures a much longer life for each of your bits. As you can these are very highly rated and one of the best sets on the market right now, in my opinion.

No 2 Rated Drill Bits for Hardened Steel – Neiko Super-Hard 13 Pcs Cobalt Drill Bit Set for Steel

My second choice are considerably cheaper and yet these will also handle hardened steel. You get 13 drill bits here instead of the 18 in the Bosch set above. These also come in a nice looking metal box.

In my opinion these are not the same high quality as the Bosch ones above and I think that is reflected in the price. At the end of the day these are under $10 and will get the job done for you.


They are in my opinion though only suited for that. So if you are someone who will be using drill bits a lot, better to spend the extra money and get a really good set.

I have simply included these because of the price but they contain very low amounts of cobalt so will not last that long. They are ideal for a small job or infrequent use. Buyers give these a 78% satisfaction rating, and given the price that rating is fair.

No 3 Rated Drill Bits for Hardened Steel – Irwin Industrial Tools 63221 Cobalt Metal Index Drill Bit Set, 21-Piece for Hardened Steel

If you can afford these cobalt drills then these will last you for a very long time. These are very high quality and will last a long time. Buying cheap drill bits is never a good idea in my honest opinion.

I have done that in the past and the reality is that after a few uses you may as well throw them away as they become blunt and useless for drilling.


I think you are better with one good set that you can reply on to get the job done. The problem is of course you will have to pay to get that type of quality. Buyers rate this Irwin set with an overall 86% buyer satisfaction rating.

I guess therefore it depends on how much use they are going to get and how much you really need or depend on them.

This set gives you 21 high quality cobalt bits and are M42 rated with a 5% cobalt content.

No 4 Rated Drill Bits for Hardened Steel – Irwin Industrial Tools 316015 Cobalt Drill Bit Set

At number 4 on my list is this set from the higher end Irwin brand. This is a 15 piece set which is popular with many online buyers. Overall those same buyers have given this set of drills an online buyer satisfaction rating of 86%.


Most buyers say that these do a very good job and are made to last. The majority of buyers used these for drilling out broken off bolts. Quite a number of other buyers said they used these on manifolds for removing old exhaust systems.

Most buyers said they did a good job at that, though a small number of people said that these were poor quality, and would not drill out the really hard bolts, that has been rusted in place.

At a price point of around $30-40 for the set we think these are good value for money. We wouldn’t want to pay much more for them though.

No 5 Rated Drill Bits for Hardened Steel – Migiwata Metric M35 Cobalt Steel

Now we had not heard of this brand, but we did come across these when we were doing our investigative research for this article. One thing is clear and that these are a great price, and these are typically used for getting through stainless steel and also through cast iron.

We also think these work well for all types of hardened steel. There are around 100 online buyer reviews that we could find on the various online stores. Overall buyers rate these very highly with a 96% rating.


Now we also understand that is an unusually high rating and that may change as the number of buyers increase. That said we will of course keep a close watch on these and amend this review if anything changes. This is a good looking set though of 13 drill bits ranging in size from 1.5 mm to 6.5 mm.

These are self centering bits which ensure that there is no walking or wandering when drilling. The good news with a set of drill bits like this is that they can get through the harder metals, but are also suitable for normal metal drilling.

No 6 Rated Drill Bits for Hardened Steel – Drill America DWD29J-CO-PC Qualtech 29 Piece Cobalt Steel Drill Bit Set

Online buyers rated these overall at 86% buyer satisfaction levels, and although an expensive option, that does not seem to have put off those happy buyers. They are from the Drill America brand but just be aware that these are like many brand also made in China.


This is also a big set of cobalt drills with 29 pieces in total and they come in a circular carrying case. They have a 135 degree cutting angle and have been finished with a tough gold oxide coating. These bits range in size from 1/16″ to 1/2″ and are HSS drills.

That concludes our reviews, on what we believe to be the best drill bits for hardened steel. You can of course just buy a single drill bit on its own as long as you know the exact size. Drill bit sets though are always better value for money.

Hopefully you found my reviews on the best drill bits for hardened steel helpful and informative.

Enda McLarnon
 

Enda McLarnon is now retired and is now enjoying writing about his love of power tools. All types of these tools are now available and they make working on projects and DIY jobs around the home a great deal of fun