118 vs 135 Drill Bit | The Real Trade-Offs in Steel & Aluminum

Choosing between a 118-degree and a 135-degree drill bit comes down to three things: the material’s hardness, your machine’s rigidity, and whether you care more about the hole’s entry or its exit. The 118° bit is the generalist, sharper, better for wood and softer metals, and drills a cleaner through-hole. The 135° split-point bit is the specialist, flatter, built for harder steels, resists walking on curved surfaces, but can bell-mouth or burr the exit side in soft materials like aluminum.

That’s the textbook answer. The real one is messier. A 135° split point doesn’t magically prevent walking, and the “heavy-duty” label often means a thicker web that demands more thrust. Your drill press loves that rigidity; your cordless drill’s battery does not.

What follows is a breakdown of the geometry, the documented failure modes manufacturers don’t highlight, and the specific brands, like the NACHI 135° cobalt jobber or the Chicago-Latrobe 150ASP, that actually deliver on the promise for the jobs they’re built for.

Key Takeaways

• The 135-degree split point excels in hardened steels, stainless, and titanium because its flatter angle and split tip reduce walking and spread cutting pressure. It’s the default for portable drills on metal.
• The 118-degree point produces cleaner through-holes with less exit burr, especially in soft metals and wood. It’s the better all-purpose choice for mixed materials and drill-press work.
• Split point design is not a walking cure-all. Independent testing shows 135° bits can still wander and, in some cases, produce a bell-mouthed, oversized hole compared to a standard 118° bit.
• “Heavy-duty” often means a thicker web behind the point. This adds rigidity for hard materials but increases the thrust required, which can stall a handheld drill.
• For a home shop tackling varied projects, a quality HSS 118-degree set covers 80% of needs. Add a few specific 135-degree cobalt bits (like a 1/8″ and 1/4″) for bolts and stainless.

The Core Mechanical Difference: Point Angle & Web Thickness

Look at the business end of two bits. A 118-degree bit comes to a sharper, more needle-like point. A 135-degree bit looks flatter, blunter. That 17-degree difference changes how the cutting lips engage the material.

The 118° angle presents a sharper, more acute wedge. It slices in with less axial force, which is why it’s the classic choice for wood, plastic, and soft aluminum. The downside is that sharp point wants to skate on hard, curved surfaces, the classic “drill walking” problem.

The 135° angle is more obtuse. It acts more like a punch than a slicer, requiring more downward pressure to initiate the cut. This flatter geometry spreads the cutting forces over a wider area at the point of contact. That wider contact patch is what gives it better purchase on hardened steel or a curved bolt head, reducing the tendency to walk at the start.

The 135° split point’s self-centering action comes from grinding away material at the very tip to create a small chisel edge. This eliminates the dead spot in the center of a conventional point, so the outer cutting lips engage immediately.

But geometry is only half the story. The “heavy-duty” label on many 135° bits like the NACHI cobalt jobbers or the Chicago-Latrobe 150ASP often signals a second, critical spec: web thickness.

The web is the central column of metal between the flutes. A standard bit has a thin web that gradually thickens toward the shank. A heavy-duty bit has a web that’s thickened much closer to the point. This makes the bit tremendously resistant to bending and breaking under the high torsional loads of drilling tough alloys. It’s also why these bits feel like they need a running start, that thick web at the tip has to be forced through the material before the cutting lips can do their work.

Feature	118-Degree Drill Bit	135-Degree Split Point Drill Bit
Point Angle	Sharper (118°)	Flatter (135°)
Primary Strength	Lower thrust required, cleaner exit in soft materials	Resists walking on hard/curved surfaces, better heat dispersion
Typical Web	Standard thickness	Often a “heavy” or thickened web for rigidity
Best Machine Match	Drill press, milling machine	Handheld cordless/corded drill
Material Sweet Spot	Wood, plastic, soft aluminum, mild steel	Hardened steel, stainless steel, titanium, high-temp alloys

When the 135-Degree Split Point Actually Wins (And When It Doesn’t)

Manufacturer catalogs are clear. The KYOCERA SGS Tool Hi-PERCARB Series 135 is listed for steel up to 45 HRc, stainless, titanium alloys, and hardened steel. NACHI states its 135° cobalt drills are for “heavy-duty operations in high tensile strength, low machinability, ferrous metals, and alloys.” This isn’t marketing fluff. For drilling out a seized grade-8 bolt or putting a hole in a stainless steel sink flange, a 135° cobalt bit is the right tool.

The split point design is key here. By grinding a small notch at the tip, the bit’s theoretical “dead zone” is eliminated. Both cutting lips engage the material instantly, which is why brands like IRWIN tout it for portable drills, you don’t need to hammer a center punch first. This self-centering is real, but it’s not infallible. It assumes the bit is perfectly ground and your drill is held perfectly straight.

The Handheld Advantage

For work where the drill isn’t fixed in a press, the 135° split point’s anti-walking claim holds the most water. Trying to start a hole on the curved shoulder of a pipe or a rounded bolt head with a 118° bit is an exercise in frustration. The 135° bit, with its wider bearing surface and immediate cutting engagement, will bite and start the hole where you want it. This is the single biggest reason to keep a few 135° bits in your portable kit.

The Aluminum Problem

Here’s where the consensus cracks. While a 135° bit will drill aluminum, the result is often uglier than with a 118° bit. The flatter point angle changes the chip formation and exit dynamics.

Where this goes sideways: Using a 135° split point on thin aluminum sheet. The bit tends to “grab” or bite aggressively at the breakthrough point, tearing a burr on the exit side instead of shearing cleanly. This is a documented observation from machinists, not a theoretical flaw.

The issue is chip control and pressure. The 135° geometry can form a tighter, more continuous chip that doesn’t break as easily in soft, gummy aluminum. Right before breakthrough, this chip can pull the bit forward, causing that exit grab. A 118° bit, with its sharper angle, often produces a looser chip that breaks freely, resulting in a cleaner hole with less tear-out. If you’re drilling aluminum on a drill press, the 118° bit is almost always the cleaner choice.

The Hidden Trade-Offs: Walking, Web, and Wear

The common sales pitch is “135° split point for no walking, longer life.” The real performance is more nuanced, governed by physics your drill feels before you see it.

1. Walking Isn’t Solved, It’s Managed

The YouTube test from Edge Precision is telling. He put new 118° and 135° bits head-to-head in aluminum and steel. The visual? Sometimes the 135° walked less. The metrology? The 135° split point drills often produced bell-mouthed, slightly oversized holes compared to the 118° bits. The split point started true, but deflection during the cut, likely due to chip pressure or the bit’s own geometry, caused the hole to open up. The takeaway: a split point improves the start, but it doesn’t guarantee a perfectly straight, on-size hole all the way through if other factors like tool rigidity or feed pressure are off.

2. The Thick Web Demands Thrust

That “heavy-duty” rigidity comes at a cost: feed pressure. A bit like the Chicago-Latrobe 150ASP with a heavy web is a stout little punch. In a rigid drill press or mill, you can lean on it and it won’t bend. In a handheld 18V drill, you might find yourself pushing hard enough to stall the motor or drain the battery prematurely. For handheld use, a 135° bit with a split point but a standard web (like many HSS-G TiN bits from Ares Tools) can be a better compromise, offering easier starts without the excessive thrust requirement.

3. Sharpening Becomes a Specialist’s Job

Touching up a dull 118° bit on a basic bench grinder is a standard workshop skill. The geometry is simple. Sharpening a 135° split point correctly is a different task. You must maintain both the 135° angle on the primary lips and recreate the small, precise split at the chisel edge. Doing this freehand is difficult; doing it wrong eliminates the self-centering benefit. For most users, a dedicated drill sharpener or a decision to treat 135° bits as consumables is the realistic path.

118 vs 135 Drill Bit: Your Material-Decision Matrix

Stop thinking about “better.” Start matching the bit’s geometry to your material’s personality. This table cuts through the general advice.

Material	Best Point Angle	The Why-Layer & Caveat
Hardwood & Softwood	118°	The sharp point shears wood fibers cleanly. A 135° can crush fibers, leading to splintering on the exit side. For finest work, use a brad point bit.
Plastic & Acrylic	118°	Low thrust prevents melting and grabbing. A 135° requires more pressure, generating heat that can melt and bind the bit.
Aluminum & Soft Metals	118°	Produces a cleaner break-through with less exit burr. Use a 135° only if you must start on a curved surface, and be prepared to deburr.
Mild Steel (< 1/4″)	Either	118° is fine with adequate pressure and cutting oil. 135° split point (like an IRWIN Series 675) makes starting easier for handheld work.
Stainless Steel, Hardened Steel	135°	The flatter angle spreads heat away from the cutting edges, and the split point prevents skating on the hard surface. A cobalt version (e.g., NACHI jobber) is mandatory.
Cast Iron	118° or 135°	Cast iron is brittle, not hard. A sharp 118° works well. A 135° is also fine, but avoid excessive feed pressure to prevent cracking.

What to Buy: Cutting Through the Brand Lists

You need bits that work, not a catalog of every option. Here’s the distilled recommendation based on what the specs actually enable.

For the all-purpose, home-shop drawer: A good quality HSS 118-degree set. It will handle 80% of your drilling in wood, plastic, and mild steel. This is your foundation. When you need to choose a drill bit for an unknown job, start here.

For the “I need to drill this hard thing” moments: Buy individual 135-degree split-point cobalt bits in the sizes you actually use. Start with 1/8″, 3/16″, and 1/4″. The NACHI 135° cobalt jobbers are a benchmark for performance. Their black oxide coating and heavy web are built for the abuse of drilling out bolts and stainless.

For precision metalworking on a drill press: Consider the KYOCERA SGS Tool Series 135. Its 145° notched point is a different beast entirely, engineered for CNC machining where eliminating a spot-drill step saves time. It’s overkill for handheld use, but it represents the high end of what the 135° geometry can do.

Skip the budget 135° HSS sets that promise cobalt performance. If the bit isn’t marked “Cobalt” (often M35 steel), it’s just a standard bit with a different point grind. It won’t last in tough materials. For truly hard surfaces like ceramic tile or masonry, you need a carbide drill bit, not a different point angle on a metal bit.

Frequently Asked Questions

Can I use a 135-degree bit for wood?

You can, but you shouldn’t make a habit of it. The flatter point tends to crush and tear wood fibers rather than slice them, leading to a rougher exit hole and possible splintering. For clean holes in wood, a brad point bit or a standard 118° twist bit is superior.

Why does my new 135-degree bit seem to drill so slowly?

You’re likely feeling the “heavy web” effect. That thickened core near the point requires significant downward thrust to push through the material before the cutting lips fully engage. It’s not drilling slower; it’s demanding more force from you and your drill. Make sure you’re applying firm, steady pressure and using a cutting fluid for metals.

How do I identify a 135-degree split point bit?

Look at the tip. A 135° bit has a noticeably flatter, broader point than a sharp 118° bit. Then, look dead-center at the tip. You should see a small, ground notch or line, that’s the split point. If it’s just a solid, chisel-like edge, it’s a standard 135° point without the self-centering feature.

Is a split point the same as a pilot point?

No. They solve similar problems (walking) differently. A split point grinds material away at the tip’s center. A pilot point (like on some DeWalt bits) features small, stepped spurs that cut a tiny pilot hole before the main lips engage. Both are effective; the split point is more common on industrial-grade bits.

Should I buy a 135-degree bit set for home use?

Only if you regularly drill hard metals. For general DIY, a 118° set is more versatile. Instead, buy a small set of individual 135° cobalt bits for your specific tough jobs. This approach is cheaper and ensures you have the right tool when you need it, without a drawer full of redundant sizes.

Before You Go

The 118 vs. 135 drill bit debate isn’t about finding a universal winner. It’s about matching a tool’s engineered geometry to your specific material and machine. The 118-degree bit is your reliable generalist, perfect for the drill press and softer materials. The 135-degree split point is your specialist, engineered to bite into hard steel and resist walking in your handheld drill.

For most home workshops, the path is clear: build your core kit around a quality HSS 118-degree set. Then, invest in two or three specific 135-degree cobalt bits for the stubborn bolts and stainless projects that inevitably come up. That combination covers the real-world spectrum without overcomplicating your toolbox or your decisions.