M35 and M42 Cobalt Drill Bits – Do You Need Both?

Cobalt drill bits are widely used in both woodworking and metalworking. Due to the hardness of cobalt, it can be used to drill metal, hardwood, and many more hard and tough materials. Cobalt drill bits are two types according to the cobalt percentage. The higher percentage is 8%, and it is named M42, and the lower percentage is M35 which includes 5% of cobalt. Due to these different percentages, both have different physical properties, which help to drill hard material in high RPM and longer service life.

What Is M 35 Drill Bit?

As mentioned earlier, M35 is a type of Cobalt drill bit. It contains 5% Cobalt in addition to steel. This Cobalt drill bit is highly resistant to high heat. According to that, the melting point of M35 is 2723 oF.

This type of drill bit can use to drill a hole into any metal. As for the performance of the M35, we can surely say that the M35 drill bits are the best in the market. Specifically, it is designed to deal with heavy-duty drilling in tough materials like iron.  

What Is M 42 Drill Bit?

M42 is a type of Cobalt drill bit. It contains 8% Cobalt in addition to steel. This Cobalt drill bit is also highly resistant to high heat. According to that, the melting point of M42 is 2853 oF.

As for the performance of the M42, we can surely say that the M42 drill bits are also the best in the market. Specifically, it is designed to deal with heavy-duty drilling in tough materials like iron.  Mainly, the M42 will work a fantastic job of drilling a hole in the heaviest surface than the M35 drill bits. Both M35 and M42 cobalt drill bits are good for metal drilling.

Cobalt Drill Bit Set
Cobalt Drill Bit Set

Differences Between M35 Vs. M42 Drill Bits

M35 vs. M42 cobalt drill bits are different in their base material. M35 has 5% cobalt, and M42 has 8% cobalt. Hence the physical characteristics also vary, and it affects the drill bit performance. Due to the high percentage of cobalt, M42 is harder than M35. Below is the comparison table for both M35 and M42.

CharacteristicsM35 Drill BitM42 Drill Bit
Percentage of Cobalt5%8%
Melting Point (oF)27232853
Resistant to heatResistant to heat but less than M42 drill bits.Higher resistance to heat
Status of sharpeningEnough sharp to drill a hole in any metal.Sharper than M35 drill bits.
DurabilitySharp Enough to drill a hole in any metal.Less than M35 drill bits because of consisting of more percentage of Cobalt.
CostLittle cheaper than the M42Expensive
M35 vs M42 Cobalt Drill Bits Comparison Table

How to Identify Cobalt M35 or M42 Drill bits

The color of the new Cobalt drill bits is dull gold. There is no painting or plating involved; the color develops as a result of the drill bits being baked during manufacture. You can identify the cobalt drill bit by following this guide.

Because of this, they can be reasonably quickly sharpened using cutting fluid and still be strong and durable. Although during the sharpening, the gold color can fade. The tip angle is 135o.

What Is Better, M35 or M42 Drill Bit?

Cobalt drill bit designed for hard tasks. Therefore, when concerned about the hardness of those two types of drill bits, the M42 drill bit is better than the M35 drill bit. The hardness of the M42 is 68-70 HRC (Rockwell Hardness Scale) but the M35 drill bit takes the hardness in 65-67 HRC.

The added M35 Cobalt drill bits have the extra benefit of being utilized in a handheld drill without much concern for breakage. The higher the percentage of Cobalt in Cobalt drill bits, the more likely they are to break. Therefore, the durability of the M35 drill bit is higher than the durability of the M42 drill bit. Therefore, M42 Cobalt drill bits are better suited for use in a foot drill where the drilling direction is controlled better than in a hand drill.

In Conclusion

M35 and M42 are both cobalt drill bits. M35 includes 5% cobalt and M42 includes 8% cobalt. Due to the different cobalt mixing, both have different physical characteristics. Overall, M42 is stronger and has more thermal resistance than M35. Hence M42 is good for harder metals. Obviously, M42 is a bit expensive than M35.


Tom Mackency

Tom Mackency

Hi, I am Tom Mackency. It has been 10 years that I have been working as a professional woodworker since 2013. I am really enjoying my carrier by creating many kinds of projects in my workshop. But mostly I like for home improvement projects. Home improvement and DIY projects are the most interesting things for me. More than that, the coolest things are power tools. Those are very precious and efficient than a decade ago. So I try to introduce so many things about power tools, woodworking, DIY projects, home improvement and many more interesting topics here.