Drilling a 7/8-inch hole through hardened steel or stainless steel without a pilot hole is one of the toughest tasks you can ask from a twist bit—walking, overheating, and dulling are the usual outcomes with cheap steel. The difference between a frustrating morning and a clean hole in minutes comes down to material grade, tip geometry, and shank design. Reaching that 7/8-inch diameter demands a bit that stays sharp under heat and resists the lateral forces that make smaller bits wander.
I’m Min — the co-founder and writer behind Gadgets Feed. I’ve spent countless hours analyzing M2 versus cobalt steel formulations, comparing 118-degree vs. 135-degree split point geometries, and evaluating real-world customer drilling reports across stainless steel, hardened steel, cast iron, and concrete to build this guide on the best options available.
After cross-referencing technical specs, material composition data, and verified user testing across dozens of drilling scenarios, I’ve narrowed the field to seven standout options that define the 7/8 drill bit market for different applications and budgets.
How To Choose The Best 7/8 Drill Bit
Selecting a 7/8-inch bit requires matching the material you are drilling to the bit’s steel grade and tip design. The three biggest factors are material composition, point angle, and shank configuration. Ignoring any one can turn a simple drilling job into a broken bit and a scrap workpiece.
Material Grade: M2 HSS vs. M35 Cobalt vs. Carbide
M2 high-speed steel contains 50% more tungsten and 150% more molybdenum than standard HSS, allowing it to withstand higher drilling temperatures without softening. M35 cobalt steel adds 5% cobalt to the mix, further improving red hardness for drilling stainless steel and hardened steel at higher feed rates. For masonry, carbide-tipped bits use sintered tungsten carbide inserts brazed to a steel body, designed to crush rather than cut through concrete and brick. Your choice hinges on whether you drill mostly mild steel, stainless, or concrete.
Point Geometry: 118°, 135°, or Split Point
A 118-degree point is the general-purpose standard for wood and soft metals, but it tends to walk on hard surfaces. The 135-degree split point is the superior choice for 7/8-inch drilling because the self-centering web reduces thrust by up to 40% and prevents the bit from skating across hardened steel or stainless. Even better, a true split point grinds a secondary cutting edge at the chisel that eliminates the need for a pilot hole in most metals.
Shank Type and Drill Chuck Compatibility
Full-size 7/8-inch bits often have a 1/2-inch shank (Silver and Deming style) to fit standard drill chucks, while the cutting body remains 7/8 inch. Reduced shank bits allow you to drill large holes without a drill press that accepts a 1/2-inch chuck. Step bits with 1/4-inch hex shanks are designed for impact drivers and quick changes. For rotary hammers, SDS-Plus shanks lock into the chuck with no chuck key required. Choosing the wrong shank type means the bit physically cannot mount in your tool.
Quick Comparison
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| Model | Category | Best For | Key Spec | Amazon |
|---|---|---|---|---|
| Jerax Tools M2 Step Bit | Step Bit | Multi-size holes in metal | 12 sizes up to 7/8″, M2 HSS, Nitride coating | Amazon |
| Narwhal M35 Cobalt Twist Bit | Twist Bit | Hardened steel and stainless steel | 5% Cobalt M35, 135° split point | Amazon |
| Milwaukee Step Drill Bit | Step Bit | Heavy-duty job site use | Cobalt steel, 3/16″–7/8″ step range | Amazon |
| Drill America Reduced Shank KFD3F | Twist Bit | Iron and steel family drilling | M1 HSS, 135° split point, 3-flat shank | Amazon |
| MAXTOOL HSS M2 S&D Bit | Twist Bit | Deep drilling in thick metal | M2 HSS, black oxide, 6″ OAL, reduced shank | Amazon |
| DKIBBITH SDS-Plus Masonry Bit 2-Pack | Masonry Bit | Concrete, brick, and stone | Carbide tip, SDS Plus shank, 12″ length | Amazon |
| Jerax Quick Change Hex Step Bit | Step Bit | Impact driver quick changes | M2 HSS, 1/4″ hex shank, 12 step sizes | Amazon |
In‑Depth Reviews
1. Narwhal 7/8 Inch Cobalt Drill Bit M35
The Narwhal 7/8-inch M35 cobalt bit uses 5% cobalt content in its steel matrix, delivering the red hardness needed to maintain cutting edge integrity when drilling stainless steel and hardened steel at higher RPMs. The fully ground 135-degree split point self-centers aggressively, so you can start the hole without a center punch on most metals.
Users report drilling 70 to 80 holes through thin stainless sheet before the first bit shows measurable wear, and the uncoated finish allows repeated sharpening without losing the geometry that coatings obscure. The 3-inch flute length and 6-inch overall length provide enough reach for through-holes in 3/8-inch plate while remaining short enough for tight drill press setups.
The included plastic storage case protects the cutting edge when not in use, though the round shank requires a drill chuck that can accept a 7/8-inch body—the bit does not have a reduced shank. This is the best choice for anyone who primarily drills hard metals and wants a bit that holds its edge through heavy use.
Why it’s great
- M35 cobalt formulation handles stainless and hardened steel with minimal heat softening
- 135-degree split point eliminates walking without a pilot hole in most materials
- Verified to exceed 80 holes in thin stainless before resharpening needed
Good to know
- Full 7/8-inch shank may not fit some handheld drill chucks—check your chuck capacity
- Uncoated finish requires proper lubrication for best performance in deep holes
2. Jerax Tools M2 Step Drill Bit 3/16″–7/8″
The Jerax step bit uses M2 high-speed steel with a nitride surface hardening treatment that raises surface hardness while maintaining a tough core, making it far more durable than typical cheap step bits. Each step from 3/16-inch up to 7/8-inch is CNC-ground and polished with size markings deep enough to read during drilling, so you don’t have to stop and measure halfway through a cut.
Real-world testing shows this bit cutting cleanly through 12-gauge stainless steel up to 2.7mm thick without requiring a pilot hole, thanks to the 118-degree tip geometry that initiates the cut on the smallest step. The double-fluted design evacuates chips effectively in aluminum, copper, and mild steel, reducing the risk of binding in deeper holes.
The protective case keeps all 12 steps organized, and the cost per step is lower than buying individual twist bits for each size. This is the ideal choice for electricians, fabricators, and DIYers who need a range of hole sizes in a single tool and don’t want to switch bits every time they encounter a different diameter.
Why it’s great
- 12 marked step sizes from 3/16″ to 7/8″ eliminate multiple bit changes
- Nitride-treated M2 HSS outperforms generic HSS on stainless and aluminum
- Polished steps let you read the size during drilling without stopping
Good to know
- Not intended for hardened steel or thick plate—step bits are limited to about 2.7mm thickness in stainless
- 118-degree point can walk on curved surfaces without a pilot dent
3. Milwaukee Electric Tool Step Drill Bit 3/16″–7/8″
Milwaukee’s step bit uses cobalt steel construction with a black oxide finish, giving it higher heat tolerance than M2 HSS bits when cutting through thicker gauges of mild steel and stainless. The all-metal ratcheting keyless chuck provides greater bit retention than plastic collets used on cheaper step bits, meaning the bit stays locked during aggressive drilling without slipping in the chuck.
Users report cutting through AC unit side panels and 3/8-inch thick steel plate without dulling the cutting edge, with multiple testers noting the bit still appeared sharp after several uses on steel. The soft grip handle on the included screwdriver body offers increased gripping surface for manual operation, though the bit itself is designed for power tool use.
The step range spanning from 3/16-inch to 7/8-inch covers the most common electrical and HVAC hole sizes, and the cobalt formulation resists the heat buildup that causes HSS bits to soften when drilling stainless. This is the best choice for tradespeople who need a durable step bit that can survive daily abuse on job sites.
Why it’s great
- Cobalt steel resists heat softening better than M2 HSS on thick steel
- Metal ratcheting chuck provides superior bit retention under heavy load
- Users report cutting through 3/8-inch steel without edge degradation
Good to know
- Premium price may not be justified for occasional home use on soft materials
- Slightly heavier than standard step bits due to metal chuck construction
4. Drill America 7/8″ Reduced Shank HSS Bit KFD3F
The Drill America KFD3F uses M1 high-speed steel and a 135-degree split point tip designed for iron and steel family materials, with the split point geometry significantly reducing thrust compared to conventional 118-degree points. The 3-flat 1/2-inch reduced shank creates three contact points in the chuck jaws, providing an extra secure hold that prevents the bit from slipping when drilling into tough metals.
This bit has a 6-inch overall length with a 3-inch flute length, giving enough clearance for drilling through thick stock while keeping the reduced shank compatible with standard 1/2-inch chucks. Users report it drills cleanly through aluminum and PVC with no chatter, and the black and gold finish provides some corrosion resistance for storage in workshop environments.
The plastic tube case is simple but effective for storage, and the contractor-grade build quality makes this a reliable choice for fabricators and machine shops that need a 7/8-inch bit that won’t break the budget. This is the top option for anyone who needs a reduced shank design for large-hole drilling in a standard drill press.
Why it’s great
- 3-flat reduced shank prevents chuck slippage better than round shank bits
- 135-degree split point self-centers on iron and steel without walking
- M1 HSS offers solid durability at a contractor-friendly price
Good to know
- M1 HSS is a step below M2 in heat resistance—not ideal for sustained stainless drilling
- Flute length of 3 inches limits reach through very thick material
5. MAXTOOL 7/8″ Silver and Deming HSS M2 Bit
The MAXTOOL S&D bit is made from M2 high-speed steel with a black oxide finish that reduces friction, resists corrosion, and helps retain lubricant during deep drilling operations. The 118-degree chisel point is precision ground for quick penetration and an accurate start, while the milled flute design ensures efficient chip evacuation through the full 6-inch overall length.
One user reported drilling three holes through 0.3-inch hardened 4140 steel at 470 RPM using a pilot hole and cutting fluid, noting that the bit performed flawlessly with no chipping and only oxide removal as visible wear. Another user used this bit to enlarge the ID of two 3.5-inch thick-walled steel tubes from 0.625 inches to 0.672 inches for 3/4-10 tapping, demonstrating the bit’s ability to handle deep, interrupted cuts in tough material.
The 1/2-inch reduced shank allows the 7/8-inch cutting body to fit standard drill chucks, and the bit comes in a protective coded cardboard or plastic box for easy identification. This is the best choice for deep drilling applications where a longer flute length is necessary to reach through thick workpieces.
Why it’s great
- M2 HSS with black oxide handles hardened 4140 steel without chipping
- 6-inch OAL provides reach for drilling through thick bar stock and tubing
- Reduced 1/2-inch shank fits standard drill chucks for large-bit use
Good to know
- 118-degree point requires a pilot hole for accurate starting on hardened steel
- Black oxide may wear off after heavy use, though the M2 steel remains effective
6. DKIBBITH SDS-Plus Masonry Drill Bit 2-Pack 7/8″ x 12″
The DKIBBITH SDS-Plus masonry bits feature a carbide tip brazed to a hardened steel body with a 2-flute design optimized for fast dust expulsion in concrete, brick, and stone. The 12-inch length provides the reach needed for deep anchor holes through foundation walls or block, and the carbide tip delivers accurate positioning on smooth concrete without skipping.
Users comparing these to premium brands like Bosch and DeWalt report that one DKIBBITH bit has outlasted multiple bits from bigger names, with over 20 holes drilled in concrete before showing signs of dulling. The SDS-Plus shank is compatible with all major rotary hammer brands including Bosch, DeWalt, Hilti, Makita, and Milwaukee, making this a universal replacement for any 7/8-inch SDS job.
The 2-pack value means you have a backup ready when the first bit eventually wears down, which is common when drilling into reinforced concrete or hard aggregate. This is the only real option on this list if you are drilling into concrete, brick, or stone rather than metal.
Why it’s great
- Carbide tip handles reinforced concrete and hard aggregate without premature wear
- 2-pack provides a spare bit at a lower effective cost per bit than single premium bits
- 12-inch length reaches deep anchor holes through thick masonry
Good to know
- Not suitable for metal, wood, or plastic—carbide tips can shatter on non-masonry materials
- Requires a rotary hammer with SDS-Plus chuck; standard drills cannot mount these bits
7. Jerax Quick Change Hex Shank Step Bit 3/16″–7/8″
The Jerax Quick Change step bit uses the same M2 HSS and nitride hardening treatment as the brand’s standard step bit, but with a 1/4-inch hex shank that locks directly into impact drivers and quick-change chucks. This design allows you to switch between drill bits and driver bits without touching the chuck, saving time on jobs that involve both drilling and fastening.
Users have drilled eight holes through high-strength steel with six of those at the full 7/8-inch step, reporting that the bit remained sharp even after the last hole. Another user drilled through 3mm stainless steel cleanly and effortlessly for ten holes without measurable dulling, highlighting the M2 material’s ability to handle hard materials even with the hex shank design.
The 12 marked step sizes are identical to the standard step bit, and the polished size highlights are visible during drilling. The hex shank does limit maximum torque transfer compared to a round shank in a drill chuck, but for most sheet metal and thin plate applications, the difference is negligible. This is the best choice for anyone who uses an impact driver as their primary drilling tool.
Why it’s great
- 1/4-inch hex shank allows instant bit changes in impact drivers and quick-change chucks
- M2 HSS with nitride treatment drills through 3mm stainless steel repeatedly without dulling
- 12 step sizes eliminate the need for multiple twist bits in common hole diameters
Good to know
- Hex shank may slip in standard three-jaw drill chucks designed for round shanks
- Impact driver hammer action can accelerate wear on step bits compared to drill press use
FAQ
Can a 7/8 inch drill bit fit in a standard 1/2 inch drill chuck?
What RPM should I use for a 7/8 inch HSS twist bit in steel?
Do I need a pilot hole for a 7/8 inch drill bit in metal?
Final Thoughts: The Verdict
For most users, the 7/8 drill bit winner is the Narwhal M35 Cobalt Twist Bit because its 5% cobalt content and 135-degree split point deliver exceptional durability in hardened and stainless steel without walking. If you need multiple hole sizes in a single tool, grab the Jerax Tools M2 Step Bit. And for drilling into concrete and brick, nothing beats the DKIBBITH SDS-Plus Masonry 2-Pack.