Best Drill Bits for Hardened Steel: Expert Shopping Guide

Tackling tough metals like hardened steel demands more than ordinary tools—choosing the right drill bit is crucial for clean, precise results and tool longevity. This essential shopping guide spotlights the best drill bits designed to cut through hardened steel, helping DIY enthusiasts and professionals alike make informed decisions and achieve flawless finishes on every project. Let’s find the perfect bit for your needs!

Comparison Table: Types of Drill Bits for Hardened Steel

Drill Bit Type	Material/Coating	Typical Application	Durability	Heat Resistance	Cost
High-Speed Steel (HSS)	HSS, sometimes Black Oxide	Basic steel, softer metals	Moderate	Moderate	Low
Cobalt (M35, M42)	Steel with 5–8% Cobalt	Hardened steel, stainless	High	High	Medium
Carbide	Solid Carbide/Carbide Tipped	Extreme hardness steel, rebar	Very High	Very High	High
Titanium Coated	HSS + Titanium Nitride	Soft metals, occasional hard steel	Moderate	Moderate/Good	Medium
Black Oxide Coated	HSS + Black Oxide	General use, mild steel	Moderate	Good	Low
Step Drill Bits	Cobalt/Titanium	Multiple hole sizes, sheet metal	High	High	Medium
Stubby/Cut Down Bits	Cobalt HSS/Carbide	Tight spaces, narrow clearance	High	High	Medium

Everyday Usage of Drill Bits for Hardened Steel

Drill bits for hardened steel aren’t just for the factory floor—they’re vital for both professionals and DIYers tackling tough metal. Everyday uses include:

Modifying automotive parts, brackets, or axles
Installing fasteners or hardware on steel beams or doors
Repairing or customizing tools and machines
Drilling holes in durable equipment (anchors, heavy-duty shelves, safes)
Construction projects involving steel frames, rebar, or industrial fittings

Because hardened steel is designed to resist abrasion and deformation, only specialty drill bits—often cobalt or carbide—can cut into it cleanly and efficiently.

Benefits of Using the Right Drill Bits for Hardened Steel

When you choose the right bit for hardened steel, you unlock several important benefits:

Increased Drilling Efficiency: The correct bit powers through metal faster, saving effort and time.
Cleaner, More Accurate Holes: Precision tip designs (like split points) start exactly where you want, reducing “bit wandering” and jagged holes.
Longer Tool Life: Premium bits made from cobalt alloy or carbide maintain their edge for much longer, reducing replacements and downtime.
Improved Safety: Bits made for hard steel are less likely to snap or shatter, reducing risks.
Cost-Effectiveness: Though specialist bits cost more up front, their durability ensures lasting value, especially for frequent use.

How to Choose the Best Drill Bits for Hardened Steel

Selecting the right bit is key to success. Consider these factors:

1. Drill Bit Material

Cobalt (M35, M42): Contains 5–8% cobalt, offering high hardness and excellent heat resistance. Go for M42 for the toughest jobs. Best for most hardened steel.
Carbide: Hardest option, ideal for extreme applications (rebar, tool steel), but can be brittle and requires careful handling.
High-Speed Steel (HSS): Fine for mild steel, not suitable for actual hardened steel.
Coating: Titanium nitride or black oxide add heat resistance, but coating wears off over time. Cobalt and carbide’s properties are intrinsic.

2. Tip Design

Split Point (135°): Reduces walking/stretching, starts accurately, needs no pilot hole.
Bullet/Parabolic Point: Good chip removal, reduces heat.
Standard Point (118° or less): Not recommended for hardened steel—tends to drift.

3. Size and Length

Stubby/Short bits: Offer less flex and greater control, good for hand drills or tight spaces.
Long bits: Necessary for thick materials, but prone to bending—use with a drill press for accuracy.

4. Shank Type

Three-Flat Shank: Resists slipping in the chuck.
Hex Shank: Quick-change compatibility (impact drivers).
Round Shank: Common, but may slip in high-torque applications.

5. Coating

Titanium Nitride (TiN): Increases life and reduces friction for moderate hard steel.
Black Oxide: Basic, helps with corrosion and chip flow.
Carbide-Tipped: Only tip is carbide, rest is steel for balance of toughness and cost.

6. Brand & Quality

Reputable manufacturers are more likely to provide uniform, sharp, and durable bits. Look for Bosch, Drill America, Milwaukee, Irwin, DeWalt, and others known for quality.

7. Value

If you regularly drill hardened steel, invest in a quality set. If it’s a rare job, there are still value options that offer adequate performance.

User Tips & Best Practices for Drilling Hardened Steel

Follow these steps to get the best results and extend bit life:

Go slow and steady: Use lower drill speeds. High speed generates excessive heat, dulling bits more rapidly.
Apply consistent pressure: Don’t force the bit, let its cutting edge do the work.
Use cutting oil or lubricant: This keeps the bit cooler and reduces wear. Reapply as needed.
Mark your hole: Use a center punch to create an indentation—this helps the bit grip and start without wandering, even if using a split point.
Keep bits sharp: Dull bits cause heat and can damage both the tool and material. Sharpen or replace as needed.
Clear chips often: Periodically lift the bit to remove metal chips, which build up heat and jam the bit.
Secure your workpiece: Clamp or vise your steel to prevent movement; uncontrolled motion leads to accidents or poor results.
Use a drill press if possible: This ensures precise, perpendicular holes and maintains steady pressure.
Take breaks: For large holes or dense material, let the bit cool down to prevent loss of hardness.
Wear safety gear: Always use goggles and gloves—shards of steel and broken bits can cause injury.

Drill Bit Models Technical Comparison Table

Model Name / Brand	Material / Type	Tip Design	Size Range	Shank	Ideal Use Case	Pros	Cons
Bosch CO14B 14-Pc Set	Cobalt M42	Split Point (135°)	1/16–1/2 in	3-Flat/Round	General/Automotive	High durability, anti-slip shank, case	Higher cost, set weight
Drill America M42 (DWD29J-CO-PC)	Cobalt M42	Split Point (135°)	1/16–1/2 in (29x)	Round	Industrial, pro use	Top cutting speed, aerospace certified	Brittle, price
Milwaukee Red Helix M35	Cobalt M35	Quad Edge (135°)	1/16–1/2 in	3-Flat	General, cordless use	Fast start, variable helix, affordable	Needs more sharpening
Toolant Pro Cobalt, TiAlN coated	Cobalt + TiAlN	Bullet Point	1/16–1/2 in	Round	Pro/DIY, longevity	Premium coating, extended bit life	Expensive, specialist
NordWolf M35 Stubby Set	Cobalt M35	Split Point	3/32–5/16 in	1/4″ Hex	Tight spaces, impact	Fits impact drivers, control, case	Limited sizes, heavier
DEWALT Titanium Nitride (DW1361)	HSS + TiN	Pilot Point (135°)	1/16–1/2 in (21x)	3-Flat	General, soft metals	Long-lasting, precise, good price	Not best for very hard steel
Irwin M35/42 Cobalt Sets	Cobalt M35/42	Split Point	1/16–1/2 in	Round/Reduced	Versatile, value	Variety, reliable, cost effective	Case/carry issues
Carbide Tipped Rebar Demons (Diablo)	Carbide Tipped	4-Cutter	9–26 in	SDS-Plus/Max	Concrete w/ steel	Super hard, dust collection	Price, heavy tools needed

Practical Guide: Choosing and Using Drill Bits for Hardened Steel

Step 1: Assess Your Project & Tools

Identify the type of steel (mild, tool, spring, etc.) and thickness.
Assess if you have access to a drill press or will use a handheld drill.
Note if you require a special shank (e.g., hex for impact drivers).

Step 2: Select Appropriate Bit Material and Design

For general hardened steel, choose a cobalt M35/M42 or carbide bit.
For deep holes and frequent drilling, invest in top-end (e.g., M42 or carbide).
For confined or awkward angles, stubby or hex-shank bits are ideal.

Step 3: Prepare Your Work & Mark the Starting Point

Clearly mark the spot to be drilled.
Use a center punch to create a small dent for easy, accurate drilling.

Step 4: Lubricate

Apply cutting fluid or light machine oil to the mark.
Lubricate both before and during drilling as friction/heat increases.

Step 5: Drill Slowly and Safely

Set your drill to the lowest speed (around 400–600 RPM for 1/4″ bits).
Begin drilling at a perpendicular angle until the hole is established.
Apply steady, moderate pressure—don’t force the bit.

Step 6: Clear Chips & Reapply Oil

Every 10–15 seconds, back the bit out slightly to clear metal chips.
Add a drop of oil as needed.

Step 7: Cool Down and Finish

Upon completion, wipe the bit and workpiece.
Inspect the hole and bit. If you notice dullness, consider sharpening or swapping out for a fresh bit.

Maintenance and Longevity Tips

Store bits clean and dry, ideally in a case.
Sharpen split point or standard bits regularly for best performance.
Replace worn-out bits—a dull bit generates excess heat, risking your project and drill.
Avoid using impact drivers for delicate or narrow bits unless rated.

Conclusion

Drilling into hardened steel is a demanding but manageable task when you have the right drill bits and know how to use them effectively. Whether you’re a DIYer modifying a tool, a mechanic working on automotive repairs, or a professional fabricator, choosing the correct bit material (cobalt or carbide for most jobs), design (split point or bullet for accuracy), and using proper technique will dramatically increase your efficiency, safety, and satisfaction.

Invest in reputable brands and understand your project’s specific needs in terms of size, shank, and bit length. Maintain your bits well by keeping them sharp, lubricated, and stored correctly. With good preparation and attention to technique, even the toughest steel becomes a job you can tackle with confidence.

FAQ

What kind of drill bit do I need for hardened steel?
For most hardened steel, choose a cobalt (M35 or M42) drill bit or a solid carbide bit for extremely hard applications. Avoid regular HSS for anything except mild steel.
Can I use titanium-coated bits for drilling hardened steel?
Titanium-coated bits are better than plain HSS and work for soft or slightly hardened metals, but for high-carbon or fully hardened steel, cobalt or carbide bits are much more effective.
Do I need to use cutting oil when drilling steel?
Yes, applying cutting oil or lubricant is highly recommended to keep the bit cool, extend its life, and produce a cleaner hole.
What tip angle works best for hardened steel?
A 135-degree split point is ideal for hardened steel as it penetrates efficiently and reduces walking.
How do I avoid breaking drill bits when drilling hard steel?
Use a slow speed, apply moderate pressure, keep the bit cooled and lubricated, and do not force the bit. Let the tool do the work.
What’s the difference between M35 and M42 cobalt drill bits?
M42 contains a higher percentage of cobalt (typically 8%), making it even harder and better suited for the toughest jobs. M35 (5% cobalt) is suitable for most hard steel applications.
Can I drill hardened steel with a cordless drill?
You can, but for larger holes or thicker material, a drill press is preferable for accuracy and control. If using a cordless drill, select short or stubby bits for stability, and drill at low speed.
How do I know when to sharpen or replace a drill bit?
If you experience increased resistance, heat, or burnishing rather than cutting, or if holes become jagged, inspect the bit for dullness and sharpen (if possible) or replace.
What is a stubby drill bit, and when should I use it?
Stubby bits are shorter than standard bits, offering better control, less flex, and easier use in tight spaces—perfect for hand drills or portable work.
Is it safe to drill hardened steel at an angle?
It’s best to start perpendicularly for accuracy and to avoid breaking the bit. Non-perpendicular drilling is difficult and should be avoided unless absolutely necessary and with specialized equipment.

Use this guide as your roadmap to choosing and using the best drill bits for hardened steel—empowering your next project to be precise, efficient, and frustration-free!

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