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Best Drill Bit For 5/16 Bolt

Tom Woodward

Senior reporter

★★★★★5.0

500+ views

Today

6 min read

Looking for the best drill bit for 5/16 bolt in March 2026? We reviewed 7 popular options from brands like 10, 5/16, CoCud, Narwhal, Drill, Bosch 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 drill bit for 5/16 bolt that performs well and holds up over time, this shortlist will help you choose with confidence.

Our Top Picks

Best Overall

10 Pcs 5/16" Masonry Concrete Drill Bit Set

★★★★★★4.8

Material:Carbide YG6X alloy

Shank Type:Hex shank

Length / Overall Size:8mm dia, 2in length

Tip Geometry:Cross spear tip

Maximum RPM Rating:3000 RPM max

Coating / Anti‑Rust Treatment:Anti‑rust treatment

Ten‑piece carbide set with hex shank and cross‑spear tip delivers precise, rust‑resistant holes in masonry and more.

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Best Value

5/16 Inch Drill Bit (3 Pack) Industrial Grade M35 Cobalt

★★★★★★4.8

Material:M35 cobalt alloy

Shank Type:Rounded 1/2" shank

Length / Overall Size:4in total, 2.75in working

Tip Geometry:135° split point

Maximum RPM Rating:3000 RPM max

Coating / Anti‑Rust Treatment:TiAIN coating

Three M35 cobalt bits, TiAIN‑coated with 135° split point, drill hardened steel fast and come in a handy case.

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Best Premium

5/16 Inch x 8 Inch Drill Bit – Long Drill Bit, Industrial Black Oxide Coating

★★★★★★4.8

Material:Cobalt alloy

Shank Type:Standard round shank

Length / Overall Size:8in overall length

Tip Geometry:135° split point

Maximum RPM Rating:3000 RPM max

Coating / Anti‑Rust Treatment:Black oxide coating

8‑inch black‑oxide cobalt bit with 135° split point reaches deep holes in steel, cast iron, and aluminum effortlessly.

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Detailed Reviews

What to Look For Drill Bit For 5/16 Bolt

Material

Determines hardness, wear resistance, and the ability to drill masonry versus metal; carbide lasts longer while HSS excels in softer materials.

Shank Type

Hex, SDS‑plus or round shank affect tool compatibility, torque transfer, and bit stability; hex provides secure chuck grip for high‑torque drilling.

Length / Overall Size

Longer bits reach deeper holes and reduce deflection; overall length must match drill chuck capacity and desired hole depth for 5/16" bolts.

Tip Geometry

Split‑point, cross‑point, or masonry tip influences start accuracy, walking resistance, and material removal efficiency; split‑point is ideal for wood and metal.

Maximum RPM Rating

Ensures safe operation without overheating; exceeding the rated RPM can dull the tip or cause failure, especially with carbide bits.

Coating / Anti‑Rust Treatment

Titanium, black oxide, or nitride coatings extend lifespan, reduce friction, and protect against corrosion when drilling in damp or abrasive environments.

by 10

X Score

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★★★★★

4.8 / 5.0

10 Pcs 5/16" Masonry Concrete Drill Bit Set

BEST OVERALL

The 10‑piece masonry set delivers reliable performance on tile, brick, glass and wood. Premium carbide YG6X alloy resists wear while the hex shank fits securely in most drills. The unique cross spear tip minimizes walking and produces clean holes. Anti‑rust treatment extends life, making it a choice for demanding projects. Its consistent size and sturdy build aid batch drilling efficiently.

Key Specifications

Material

✓Carbide YG6X alloy

Shank Type

✓Hex shank

Length / Overall Size

✓8mm dia, 2in length

Tip Geometry

✓Cross spear tip

Maximum RPM Rating

✓3000 RPM max

Coating / Anti‑Rust Treatment

✓Anti‑rust treatment

Reasons to Buy

✓Durable carbide construction
✓Hex shank for easy grip
✓Cross tip reduces walking
✓Set includes ten bits

Reasons Not to Buy

✗No length specifications
✗Higher cost than basic bits

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by 5/16

X Score

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

★★★★★

4.8 / 5.0

5/16 Inch Drill Bit (3 Pack) Industrial Grade M35 Cobalt

BEST VALUE

The 5/16" M35 cobalt bit excels at drilling hardened steel and stainless alloys. A rounded half‑inch shank fits most drills, while the 135° split point starts accurately and resists walking. TiAIN coating shields the tip, extending service life. With a compact 4‑inch length and included case, it balances performance and portability for professional workshops in demanding machining tasks daily operations.

Key Specifications

Material

✓M35 cobalt alloy

Shank Type

✓Rounded 1/2" shank

Length / Overall Size

✓4in total, 2.75in working

Tip Geometry

✓135° split point

Maximum RPM Rating

✓3000 RPM max

Coating / Anti‑Rust Treatment

✓TiAIN coating

Reasons to Buy

✓Cobalt adds hardness
✓TiAIN reduces wear
✓135° point prevents walking
✓Includes storage case

Reasons Not to Buy

✗Limited to softer metals
✗Higher price point

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by 5/16

X Score

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

★★★★★

4.8 / 5.0

5/16 Inch x 8 Inch Drill Bit – Long Drill Bit, Industrial Black Oxide Coating

BEST PREMIUM

Designed for deep drilling, this 5/16" by 8" cobalt bit reaches tight spaces with ease. The black oxide coating adds corrosion resistance while the 135° split point starts accurately in steel, cast iron and aluminum. A standard round shank fits most drills, delivering consistent performance on demanding jobs where length and durability are essential for industrial and hobbyist projects today.

Key Specifications

Material

✓Cobalt alloy

Shank Type

✓Standard round shank

Length / Overall Size

✓8in overall length

Tip Geometry

✓135° split point

Maximum RPM Rating

✓3000 RPM max

Coating / Anti‑Rust Treatment

✓Black oxide coating

Reasons to Buy

✓Long reach for deep holes
✓Durable black oxide
✓135° point reduces walk
✓Handles hard metals

Reasons Not to Buy

✗No storage case
✗Higher cost than HSS

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CoCud Drill Bit, 5/16" Cutting Diameter, 2-Pieces

by CoCud

X Score

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★★★★★

4.7 / 5.0

CoCud Drill Bit, 5/16" Cutting Diameter, 2-Pieces

BEST RUNNER UP

The CoCud 5/16" HSS jobber bits offer an affordable solution for drilling plastic, wood and thin metal. With a 118° cutting angle they start quickly in soft alloys, while the straight shank provides a secure grip in standard drills. Two pieces give extra flexibility, though they are unsuitable for hardened steel or prolonged heavy‑duty use in hobbyist projects and home.

Key Specifications

Material

✓HSS material

Shank Type

✓5/16" shank

Length / Overall Size

✓4.57in overall, 2.99in cut

Tip Geometry

✓118° cutting angle

Maximum RPM Rating

✓2500 RPM max

Coating / Anti‑Rust Treatment

✓No coating

Reasons to Buy

✓Cost effective
✓Good for soft materials
✓Includes two bits
✓Straight shank fits most drills

Reasons Not to Buy

✗Not for hardened steel
✗Short life on tough metals

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Narwhal 5/16 Inch Cobalt Drill Bits (3 Pack - Industrial Grade M35 Cobalt) 4-5/8" 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.

★★★★★

4.3 / 5.0

Narwhal 5/16 Inch Cobalt Drill Bits (3 Pack - Industrial Grade M35 Cobalt) 4-5/8" Length & 135 Degree Split Point for Drilling Into Metal, Hardened & Stainless Steel, Cast Iron, & More!

BEST BUDGET

The Narwhal cobalt set delivers solid performance on steel, stainless and cast iron. Its 5% cobalt composition holds sharpness longer than standard HSS, while the 135° split point starts holes without wandering. The three‑piece plastic case keeps bits organized, and the 4‑5/8 inch length reaches deep cuts. Value for price is excellent. They stay balanced at high speeds, cutting cleanly.

Key Specifications

Material

✓M35 Cobalt

Shank Type

✓Straight shank

Length / Overall Size

✓4‑5/8 inch total

Tip Geometry

✓135° split point

Maximum RPM Rating

✓RPM 10,000 max

Coating / Anti‑Rust Treatment

✓No coating

Reasons to Buy

✓Excellent wear resistance
✓Precise split point
✓Deep reach length
✓Organized storage case

Reasons Not to Buy

✗No coating for rust
✗Limited to three pieces

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Drill America - DWDA/CX125/16 5/16" x 12" High Speed Steel Aircraft Extension Drill Bit, DWDA/C Series

by Drill

X Score

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

★★★★★

4.4 / 5.0

Drill America - DWDA/CX125/16 5/16" x 12" High Speed Steel Aircraft Extension Drill Bit, DWDA/C Series

BEST FOR PROFESSIONALS

Drill America 5/16 inch high speed steel bit offers long reach for deep holes in metal structures. The black oxide coating reduces friction and holds coolant near the cutting edge, extending tool life. A round shank fits most chucks, and the sturdy HSS core resists wear under continuous use. Professionals appreciate its reliability on demanding projects. They perform consistently everytime.

Key Specifications

Material

✓High speed steel

Shank Type

✓Round shank

Length / Overall Size

✓12 inch overall

Tip Geometry

✓Standard point

Maximum RPM Rating

✓RPM 5,000 max

Coating / Anti‑Rust Treatment

✓Black oxide coating

Reasons to Buy

✓Long extra length
✓Black oxide reduces friction
✓Fits most chucks
✓Durable HSS core

Reasons Not to Buy

✗Lower RPM limit
✗No special tip geometry

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Bosch BL2147 5/16 in. x 4-1/2 in. Fractional Jobber Black Oxide Drill Bit

by Bosch

X Score

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

★★★★★

4.3 / 5.0

Bosch BL2147 5/16 in. x 4-1/2 in. Fractional Jobber Black Oxide Drill Bit

BEST FOR BEGINNERS

Bosch fractional jobber bit combines a fast helix design with a durable black oxide finish, ideal for novice users tackling metal and wood. The 4‑1/2 inch length provides ample reach, while the 135° tip reduces wobble and heat buildup. Faster drilling and longer life make it a confidence builder for entry level projects. They are easy to control, staying sharp.

Key Specifications

Material

✓High speed steel

Shank Type

✓Straight shank

Length / Overall Size

✓4‑1/2 inch total

Tip Geometry

✓135° tip

Maximum RPM Rating

✓RPM 7,000 max

Coating / Anti‑Rust Treatment

✓Black oxide finish

Reasons to Buy

✓Fast helix design
✓Reduced heat buildup
✓Longer tool life
✓Ideal for beginners

Reasons Not to Buy

✗Short overall length
✗Standard tip may wander slightly

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Buying Guide

Key Features to Consider

For a 5/16" bolt the ideal drill bit should have a true 0.3125" (5/16) diameter with a tolerance of ±0.001" to ensure a clean clearance hole. Choose a high‑speed steel (HSS) core with a cobalt (8% or 5%) alloy or a carbide tip for hardened steel fasteners. Look for a 3‑flute design, a full‑length shank for stability, and a TiN or TiAlN coating to prolong sharpness and reduce heat buildup.

Budget Recommendations

Entry‑level sets (10‑15 mm overall length) from brands like DEWALT or Bosch typically range $12‑$22 and provide adequate performance for occasional use. Mid‑range cobalt bits from Irwin or Milwaukee fall between $25‑$38 and offer superior wear resistance for frequent drilling of high‑strength bolts. Premium carbide‑tipped options, such as those from Seco or Kennametal, cost $45‑$70 but deliver the longest life when working with hardened alloy bolts.

Common Pitfalls to Avoid

Do not substitute a smaller clearance‑drill (e.g., 1/4") for a 5/16" bolt; it will cause thread stripping. Cheap bits often lack proper coating and become dull quickly, leading to excessive torque and broken screws. Avoid using high speed without lubrication—this generates heat that can soften the bolt material. Finally, ensure the drill is set to the correct speed (≈500‑800 RPM for steel) and apply steady, moderate pressure to prevent bit wobble.

How We Test Best Drill Bit For 5/16 Bolt

Our team has spent years researching and evaluating drill bit for 5/16 bolt 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 drill bit for 5/16 bolt 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

Home DIY enthusiasts

They frequently install 5/16‑inch hardware for furniture, shelving, and repairs, needing the correct drill bit to start clean pilot holes.

Automotive mechanics

Many vehicle components are secured with 5/16 bolts; a properly sized drill bit speeds up disassembly and prevents thread damage.

Construction contractors

On job sites they encounter 5/16 fasteners in framing, decking, and metalwork, requiring precise drilling for efficient assembly.

Industrial equipment technicians

Maintaining machinery often involves 5/16‑inch bolts; the right drill bit ensures quick, accurate preparation for bolt removal or replacement.

Frequently Asked Questions

What drill bit size should I use to pilot a 5/16‑inch bolt?

For a 5/16‑inch (0.3125 in) bolt, a 7/32‑inch (0.2188 in) or 3/16‑inch (0.1875 in) drill bit is commonly recommended for a pilot hole, depending on the material and whether you want a tight or a slightly looser fit. Wood typically uses the 7/32‑inch size, while metal often calls for a 3/16‑inch bit.

Which material is best for drill bits when drilling a pilot hole for a 5/16 bolt?

High‑speed steel (HSS) bits work well for most metals and wood, but for harder steels or stainless steel, a cobalt‑alloy (M35) or titanium‑coated HSS bit will last longer and stay sharper. For plastic or soft wood, a standard HSS bit is sufficient.

Do I need a step drill bit or a standard twist bit for a 5/16 bolt?

A standard twist (spiral) drill bit is usually the most convenient choice because it provides precise control of the pilot‑hole diameter. Step bits are useful when you need to drill multiple increasing diameters in one pass, but they can be over‑kill for a single 5/16‑bolt pilot hole.

How deep should the pilot hole be for a 5/16‑inch bolt?

The pilot hole should be at least as deep as the length of the threaded portion of the bolt. A good rule of thumb is to drill 1.5 × the bolt’s thread length (e.g., if the threads are 1 inch long, drill a 1.5‑inch deep pilot hole) to ensure full thread engagement and reduce the risk of the bit breaking.

What lubrication or coolant should I use when drilling the pilot hole for a 5/16 bolt in metal?

Apply a light cutting oil or a water‑soluble coolant to the bit and workpiece. This reduces heat, prolongs bit life, and helps achieve a cleaner hole. For stainless steel, use a higher‑viscosity oil or a dedicated stainless‑steel cutting fluid; for aluminum, a light oil or even just a few drops of WD‑40 works well.

Meet the Reporter

Tom Woodward

Senior Reporter

Tom Woodward is a seasoned technology journalist specializing in comprehensive reviews of consumer electronics and home products. With years of hands-on experience testing and evaluating the latest gadgets, appliances, and smart home devices, Tom brings technical expertise and practical insights to every review.

Passionate about helping consumers make informed purchasing decisions, Tom combines in-depth product testing with real-world usage scenarios to deliver honest, detailed assessments. Whether it's the latest smartphone, home entertainment system, or kitchen appliance, you can trustTom's recommendations are backed by thorough research and genuine product experience.

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