What Are Cobalt Drill Bits and How to Use Them
Learn what cobalt drill bits are, how they differ from standard HSS bits, how to choose, use, and care for them when drilling hard metals, with expert tips from Drill Bits Pro.
Cobalt drill bits are a type of high speed steel drill bits that contain cobalt to improve heat resistance and durability, especially for drilling hard metals.
What cobalt drill bits are and why they matter
What are cobalt drill bits? They are a type of high speed steel drill bits that incorporate cobalt alloy to improve heat resistance and durability. The cobalt makes the cutting edges harder and more resistant to the high temperatures generated when drilling hard metals. This means you can push your drill a bit harder before the bit loses its edge. According to Drill Bits Pro, understanding the basic composition helps DIYers and professionals choose the right tool for metalworking projects. A cobalt drill bit is typically used for drilling through stainless steel, tool steel, cast iron, and other hard materials where standard high speed steel or titanium bits may quickly dull. While they cost more than basic bits, their longevity in demanding metals can yield savings over time. The bite is still dependent on the right speed, lubrication, and feed rate, which Drills Bits Pro emphasizes for consistent results.
- When to reach for cobalt: hard metals that gouge ordinary bits, high heat during cutting, and situations demanding repeated accuracy.
- What to expect: less heat buildup, slower wear, and the need for careful technique to avoid work hardening or edge chipping.
In practice, cobalt bits are not a universal cure-all. They shine in metalworking scenarios where heat and abrasion would degrade standard bits. For softer metals or delicate work, standard HSS bits may suffice and can be more economical. Drill Bits Pro recommends matching the bit to the material and process rather than blindly choosing the most expensive option. For many DIY projects, a single cobalt bit set can cover stainless, aluminum, and mild steel with strong results, provided you use appropriate settings and lubrication.
Got Questions?
What materials are cobalt drill bits best suited for?
Cobalt drill bits excel on hard metals such as stainless steel, tool steel, and cast iron, where standard HSS bits wear quickly. They also perform well on hard alloys, offering better heat resistance and longer cutting life when used with proper speed and lubrication.
Cobalt bits work best on hard metals like stainless steel and tool steel, giving you longer life and less dulling compared to regular bits when you drill at the right speed with lubrication.
Are cobalt drill bits harder than standard HSS bits?
Yes, cobalt bits are generally harder and more heat resistant than standard HSS bits because of the cobalt alloy. However, performance also depends on drill speed, feed rate, and coolant usage.
They are harder and resist wear better, but technique and cooling matter for the best results.
Can cobalt drill bits be sharpened?
Yes, cobalt bits can be sharpened, but it requires proper grinding with a suitable wheel and careful heat management to prevent tempering. Avoid overheating during grinding to maintain hardness.
You can sharpen them with a bench grinder, but watch for heat and use a slow, controlled pass.
What is the difference between five percent cobalt and eight percent cobalt bits?
Five percent cobalt (often labeled M35) and eight percent cobalt (M42) denote different cobalt content. Higher cobalt generally means better wear resistance and heat tolerance but higher cost and potentially more brittleness if not used correctly.
Bits with more cobalt last longer under heat but can be pricier and require careful handling.
Should I use slow or fast speeds with cobalt bits?
Drilling hard metals with cobalt bits benefits from lower speeds and appropriate lubrication to reduce heat buildup. Too high speeds can prematurely dull or chip edges, especially in thick sections.
Go slower than you would with softer metals, and lubricate to keep the cut cool.
Is cobalt drilling safe for stainless steel and other hard metals?
Yes, with proper technique, lubrication, and the right speed. Using a pilot hole and secure workholding helps prevent wandering and maintains edge integrity.
Cobalt bits are safe for tough metals when you control speed, use coolant, and hold the work steady.
Top Takeaways
- • Cobalt bits are a hardened alloyed version of high speed steel designed for hard metals.
- • They handle heat better, reducing edge dulling on tough materials.
- • Use slower speeds and proper lubrication to maximize life.
- • They are more expensive but offer longer life in hard metals.
- • Always start with a pilot hole for accurate drilling on hard steels.