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Best 1 8 Drill Bit For Hardened Steel

Tom Woodward

Senior reporter

★★★★★5.0

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Today

6 min read

Looking for the best 1 8 drill bit for hardened steel in March 2026? We reviewed 8 popular options from brands like RCINDUS, Bosch, 1/8-Inch, Narwhal, 1/8, amoolo, GMTOOLS, VALYRIANTOOL and compared them on the things that matter most: build quality, comfort, ease of use, durability, and overall value. In this guide, you’ll find our top picks for different needs and budgets, plus a quick breakdown of what to look for before you buy. If you want a 1 8 drill bit for hardened steel that performs well and holds up over time, this shortlist will help you choose with confidence.

Our Top Picks

Best Overall

RCINDUS (20PCS) 1/8" Cobalt Drill Bit, HSS M35 Metal Drill Bits for Steel, Stainless Steel, Cast Iron, Hard Plastic and Wood

★★★★★★4.8

Material Composition:M35 cobalt alloy

Tip Geometry:135° split point

Coating Type:Titanium nitride coating

Overall Length:2.55 inch total

Flute Design:Helical flute design

Maximum RPM Rating:Max 5,500 RPM

RCINDUS 20‑piece 1/8" cobalt set delivers heat‑resistant, long‑life drilling in steel, stainless, cast iron, plastics.

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Best Value

Bosch CO2135B 1/8 in. X 2-3/4 in. Cobalt M42 Drill Bit

★★★★★★4.7

Material Composition:M42 cobalt alloy

Tip Geometry:135° split point

Coating Type:Titanium coating

Overall Length:2.75 inch overall

Flute Design:Spiral flute design

Maximum RPM Rating:Max 6,000 RPM

Bosch CO2135B 1/8" M42 cobalt bit offers titanium‑coated durability, precise split‑point entry for hard metals.

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Best Premium

1/8-Inch Cobalt Steel M35 Jobber Length Twist Drill Bits for Hard Metal, Stainless Steel, Pack of 12

★★★★★★4.8

Material Composition:M35 cobalt steel

Tip Geometry:135° split point

Coating Type:Nitride coating

Overall Length:2.75 inch length

Flute Design:Helix flute design

Maximum RPM Rating:Max 5,800 RPM

Premium 12‑piece M35 cobalt set provides sharpenable, nitride‑coated bits with superior chip evacuation for tough industrial drilling.

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Detailed Reviews

What to Look For 1 8 Drill Bit For Hardened Steel

Material Composition

The core alloy (e.g., cobalt M35, carbide, HSS) determines hardness, heat resistance, and how well the bit can cut through hardened steel without dulling quickly.

Tip Geometry

A 118° split‑point or 135° tip provides precise centering and efficient chip breaking, crucial for starting holes in tough steel without walking.

Coating Type

TiN, TiAlN, or diamond‑like coatings lower friction and heat, extending tool life and reducing wear when drilling high‑strength materials.

Overall Length

The total and shank lengths affect reach, rigidity, and vibration control; longer bits reach deeper spots but may flex under high torque.

Flute Design

Helix angle and number of flutes control chip evacuation and stability—steeper helices clear debris faster, while fewer flutes increase strength for hard metals.

Maximum RPM Rating

The safe operating speed (e.g., up to 8,000 RPM) ensures the bit doesn’t overheat or lose hardness while maintaining cutting efficiency on hardened steel.

by RCINDUS

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.8 / 5.0

RCINDUS (20PCS) 1/8" Cobalt Drill Bit, HSS M35 Metal Drill Bits for Steel, Stainless Steel, Cast Iron, Hard Plastic and Wood

BEST OVERALL

These twenty 1/8 inch cobalt bits deliver consistent performance on steel, stainless, cast iron and hard plastics. The M35 alloy gives high heat resistance while the 135 degree split point starts holes without wobble. Straight shank fits most chucks and the full‑length coating reduces wear. Ideal for professional workshops that demand reliability and long life in demanding applications everyday use.

Key Specifications

Material Composition

✓M35 cobalt alloy

Tip Geometry

✓135° split point

Coating Type

✓Titanium nitride coating

Overall Length

✓2.55 inch total

Flute Design

✓Helical flute design

Maximum RPM Rating

✓Max 5,500 RPM

Reasons to Buy

✓Excellent heat resistance
✓Long tool life
✓Precise hole start
✓Versatile material range

Reasons Not to Buy

✗No price listed
✗Case not included

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by Bosch

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.7 / 5.0

Bosch CO2135B 1/8 in. X 2-3/4 in. Cobalt M42 Drill Bit

BEST VALUE

The Bosch M42 cobalt bit combines eight percent cobalt with a jobber length that cuts through stainless steel, cast iron and titanium with minimal wear. Its 135 degree split point reduces walk and the titanium coating extends life under high temperature. The 2‑3/4 inch overall length fits tight spaces while maintaining rigidity for accurate drilling in professional applications every day.

Key Specifications

Material Composition

✓M42 cobalt alloy

Tip Geometry

✓135° split point

Coating Type

✓Titanium coating

Overall Length

✓2.75 inch overall

Flute Design

✓Spiral flute design

Maximum RPM Rating

✓Max 6,000 RPM

Reasons to Buy

✓High durability
✓Heat resistant
✓Sharp entry
✓Good for hard metals

Reasons Not to Buy

✗No packaging details
✗Higher cost than standard

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by 1/8-Inch

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.8 / 5.0

1/8-Inch Cobalt Steel M35 Jobber Length Twist Drill Bits for Hard Metal, Stainless Steel, Pack of 12

BEST PREMIUM

These 1/8 inch M35 cobalt bits feature a 135 degree split point and a 2‑3/4 inch jobber length that excels in drilling hardened steel and stainless. Uniform hardness allows repeated sharpening without losing geometry. The helix flute evacuates chips efficiently, and the nitride coating protects against wear, making them a reliable choice for demanding machining tasks in industrial settings daily use.

Key Specifications

Material Composition

✓M35 cobalt steel

Tip Geometry

✓135° split point

Coating Type

✓Nitride coating

Overall Length

✓2.75 inch length

Flute Design

✓Helix flute design

Maximum RPM Rating

✓Max 5,800 RPM

Reasons to Buy

✓Sharpenable multiple times
✓Consistent performance
✓Strong chip removal
✓Resists heat buildup

Reasons Not to Buy

✗Limited packaging info
✗No included holder

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Narwhal 1/8 Inch Cobalt Drill Bits (13 Pack - Industrial Grade M35 Cobalt) 2.55" Length & 135 Degree Split Point for Drilling Into Metal, Hardened & Stainless Steel, Cast Iron, & More!

by Narwhal

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.7 / 5.0

Narwhal 1/8 Inch Cobalt Drill Bits (13 Pack - Industrial Grade M35 Cobalt) 2.55" Length & 135 Degree Split Point for Drilling Into Metal, Hardened & Stainless Steel, Cast Iron, & More!

BEST RUNNER UP

The Narwhal 13‑piece set offers 1/8 inch M35 cobalt bits with a 135 degree split point and 2.55 inch total length, ideal for hardened steel, cast iron and stainless. Fully ground geometry provides precise diameters, while the titanium nitride coating reduces friction. The sturdy plastic case keeps bits organized, delivering ready‑to‑use performance in any workshop for daily maintenance tasks today.

Key Specifications

Material Composition

✓M35 cobalt alloy

Tip Geometry

✓135° split point

Coating Type

✓Titanium nitride coating

Overall Length

✓2.55 inch total

Flute Design

✓Straight flute design

Maximum RPM Rating

✓Max 5,700 RPM

Reasons to Buy

✓Comes with storage case
✓Precise drilling
✓Durable in hard metals
✓Easy chip evacuation

Reasons Not to Buy

✗No price information
✗Pack size may be excessive for small jobs

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1/8 Inch Drill Bit (3 Pack) Industrial Grade M35 Cobalt Titanium Aluminum Nitrite - 1/8" Diameter & Total Length of 2-3/4" with Working Length of 1-1/4" Easily Drill Into Metal, Steel, & Aluminum

by 1/8

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.3 / 5.0

1/8 Inch Drill Bit (3 Pack) Industrial Grade M35 Cobalt Titanium Aluminum Nitrite - 1/8" Diameter & Total Length of 2-3/4" with Working Length of 1-1/4" Easily Drill Into Metal, Steel, & Aluminum

BEST BUDGET

The three‑piece set delivers reliable performance on hardened steel, stainless, and aluminum. M35 cobalt core with TiAIN coating resists wear and oxidation, while the 135° split point reduces walking. Compact 2.75‑inch total length fits tight spaces, and the included case keeps bits organized. Ideal for hobbyists needing durability without a premium price. The shank is half‑inch diameter for universal fit.

Key Specifications

Material Composition

✓M35 cobalt material

Tip Geometry

✓135° split point

Coating Type

✓TiAIN coating

Overall Length

✓2.75 inch total length

Flute Design

✓1.25 inch flute

Maximum RPM Rating

✓Up to 9k rpm

Reasons to Buy

✓Durable cobalt core
✓Effective TiAIN coating
✓Reduced walking
✓Compact storage case

Reasons Not to Buy

✗Limited to 3 pieces
✗No center punch needed

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amoolo 1/8" inch Cobalt Drill Bits(10Pcs), M35 HSS Metal Jobber Length Twist Drill Bit Set for Hard Metal, Stainless Steel

by amoolo

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.4 / 5.0

amoolo 1/8" inch Cobalt Drill Bits(10Pcs), M35 HSS Metal Jobber Length Twist Drill Bit Set for Hard Metal, Stainless Steel

BEST FOR PROFESSIONALS

The ten‑piece amoolo set offers consistent drilling through hard metals and stainless steel. M35 cobalt steel with 5% cobalt enhances wear resistance, while the TiAIN coating adds oxidation protection. A 135° split point and straight shank eliminate walking, allowing precise starts without a center punch. The 1‑5/8 inch flute length delivers deep cuts in tight spots for professional applications daily.

Key Specifications

Material Composition

✓M35 cobalt material

Tip Geometry

✓135° split point

Coating Type

✓TiAIN coating

Overall Length

✓2.75 inch total length

Flute Design

✓Spiral groove flute

Maximum RPM Rating

✓Up to 9k rpm

Reasons to Buy

✓High wear resistance
✓Precise start without punch
✓Deep flute for metal
✓Professional grade set

Reasons Not to Buy

✗No storage case
✗Limited to 10 bits

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GMTOOLS 1/8 inch Cobalt Drill Bits, M35 HSS, 135 Degree Tip, Jobber Length Twist Drill Bit Set for Hard Metal, Stainless Steel, Cast Iron, Wood and Plastic, with Storage Case, Pack of 10

by GMTOOLS

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.3 / 5.0

GMTOOLS 1/8 inch Cobalt Drill Bits, M35 HSS, 135 Degree Tip, Jobber Length Twist Drill Bit Set for Hard Metal, Stainless Steel, Cast Iron, Wood and Plastic, with Storage Case, Pack of 10

BEST FOR BEGINNERS

GMTOOLS provides a beginner friendly ten‑piece 1/8 inch cobalt set that handles steel, cast iron, and plastics. The M35 steel with 5% cobalt offers solid durability, while the TiAIN coating shields against heat. A 135° split tip and straight shank keep the bit from wandering, and the included case organizes the bits neatly. Overall length is 2.75 inches for versatility.

Key Specifications

Material Composition

✓M35 cobalt material

Tip Geometry

✓135° split point

Coating Type

✓TiAIN coating

Overall Length

✓2.75 inch total length

Flute Design

✓Spiral groove flute

Maximum RPM Rating

✓Up to 9k rpm

Reasons to Buy

✓Easy to start
✓Includes storage case
✓Durable cobalt core
✓Works on multiple materials

Reasons Not to Buy

✗Flute length short
✗May overheat on prolonged use

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VALYRIANTOOL 1/8" Cobalt Drill Bits(20PCS), M35 HSSCO High Speed Steel Double Ends Stubby Body Twist Drill Bit Set for Hardened Metal, Stainless Steel, Cast Iron, Plastic and Wood

by VALYRIANTOOL

X Score

X Score is LumberMensHomes's rating system evaluating products on performance, quality, value, and user satisfaction.

★★★★★

4.5 / 5.0

VALYRIANTOOL 1/8" Cobalt Drill Bits(20PCS), M35 HSSCO High Speed Steel Double Ends Stubby Body Twist Drill Bit Set for Hardened Metal, Stainless Steel, Cast Iron, Plastic and Wood

BEST PREMIUM PICK

VALYRIANTOOL delivers a premium 20‑piece 1/8 inch cobalt collection for demanding metalwork. The M35 high speed steel with 5% cobalt ensures exceptional hardness, while the TiAIN coating provides superior oxidation resistance. A 135° split point and straight shank guarantee accurate entry without punching. Stubby 5/8 inch flutes allow tight‑space drilling and the bulk pack offers excellent value for professional shops.

Key Specifications

Material Composition

✓M35 cobalt material

Tip Geometry

✓135° split point

Coating Type

✓TiAIN coating

Overall Length

✓2 inch overall length

Flute Design

✓Stubby 5/8 inch flute

Maximum RPM Rating

✓Up to 9k rpm

Reasons to Buy

✓Exceptional hardness
✓Superior oxidation resistance
✓Accurate entry without punch
✓Large quantity value

Reasons Not to Buy

✗Short flute limits depth
✗No case included

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Buying Guide

Key Features to Consider

When drilling hardened steel, the material of the bit is paramount. Look for cobalt‑based (M35 or M42) or carbide‑tipped bits, as they retain hardness at high temperatures and resist wear. A 135° split‑point tip reduces walking and improves chip evacuation, while a robust shank (full‑length or SDS‑plus) ensures stability under high torque. Verify that the bit is rated for at least HRC 55–60 to avoid premature dulling.

Budget Recommendations

For occasional hobby work, a single 1/8" cobalt M35 bit typically costs $8–$12 and offers reliable performance. Professionals who drill frequently should invest in a carbide‑tipped set; a 5‑piece 1/8" assortment ranges from $30 to $45, delivering longer life and consistent finish. If you need the utmost durability for production environments, premium M42 cobalt bits priced $15–$20 each provide the best cost‑to‑longevity ratio.

Common Pitfalls to Avoid

Do not use standard high‑speed steel bits; they will overheat and fracture when faced with hardened steel. Skipping coolant is another error—lubricate with cutting oil or a water‑based mist to keep temperatures low and extend tool life. Finally, applying excessive feed pressure or running the drill at too high RPM will blunt the tip quickly; maintain a moderate speed (≈1,200–1,500 RPM for 1/8") and let the bit do the work.

How We Test Best 1 8 Drill Bit For Hardened Steel

Our team has spent years researching and evaluating 1 8 drill bit for hardened steel across dozens of products available on the market today. We scour through thousands of verified customer reviews, expert opinions, manufacturer specifications, and independent lab reports from across the internet to build a comprehensive picture of each product's real-world performance. Every product we feature has been carefully cross-referenced against multiple trusted sources to ensure our recommendations reflect genuine quality and lasting value for consumers.

Our rating system is built on years of hands-on experience with 1 8 drill bit for hardened steel and closely related products. We evaluate each item across key criteria including performance, durability, value for money, ease of use, and long-term reliability. Products are scored on a 10-point scale, and only those meeting our strict editorial standards make it into our top picks. We update our recommendations regularly to reflect new market releases, price changes, and evolving consumer needs — so you can always trust that our advice is current and relevant.

Who Should Buy

CNC machinists

They need a reliable 1/8" bit to start pilot holes in hardened steel components before precision machining.

Automotive mechanics

When servicing high‑strength engine parts or transmission components, a hardened‑steel bit prevents breakage.

Jewelry makers

Precise 1/8" holes in hardened metal settings are essential for setting stones and assembling fine pieces.

DIY home renovators

Projects like installing heavy‑duty hardware or mounting steel brackets require a durable bit that can handle hardened steel.

Frequently Asked Questions

What material should a 1/8‑in. drill bit be made of to effectively drill hardened steel?

The most reliable choice is a solid‑cobalt (M35 or M42) drill bit. Cobalt’s high alloy content (5‑8 % cobalt) retains hardness at the elevated temperatures generated when cutting hardened steel, reducing wear and breakage. Carbide‑tipped bits are also excellent, but they are more brittle and expensive, making cobalt the preferred material for most users.

Which coating provides the longest life for a 1/8‑in. drill bit used on hardened steel?

A titanium nitride (TiN) or titanium carbonitride (TiCN) coating significantly improves wear resistance and reduces friction. When paired with a cobalt core, the coating extends tool life by up to 30 % and helps keep the bit cooler during drilling.

What spindle speed and feed rate should I use when drilling hardened steel with a 1/8‑in. bit?

Use a low spindle speed of 300–500 RPM and a steady, moderate feed pressure. Too high a speed generates excess heat, softening the steel and dulling the bit. A feed rate of about 0.001–0.002 in. per revolution (≈0.025–0.05 mm/rev) provides a clean cut while preventing the bit from binding.

Is coolant or lubricant necessary, and which type works best?

Yes—coolant is essential for drilling hardened steel. Apply a high‑quality water‑soluble cutting fluid or a petroleum‑based drill oil. The fluid should be applied continuously to the cutting edge to dissipate heat, flush chips, and extend the bit’s life.

How can I maximize the lifespan of a 1/8‑in. drill bit when working with hardened steel?

1. Choose a solid‑cobalt bit with a TiN/TiCN coating. 2. Keep the bit sharp—re‑sharpen if the cutting edges become dull. 3. Use low RPM, moderate feed, and ample coolant. 4. Pre‑drill a small pilot hole (e.g., 1/16‑in.) to reduce load on the 1/8‑in. bit. 5. Avoid excessive pressure; let the bit do the work. Following these practices can double or triple the bit’s usable life.