Series: Why Drill Bits Fail | Article 10
Keywords: drill bit point angle, 118 vs 135 drill bit, split point drill bit, HSS drill bit, drill bit selection guide
If you sort through enough drill bit inquiries, you notice a pattern. Buyers ask which point angle is "better" — 118° or 135° — as if one is an upgrade over the other. It isn't. Each angle solves a different problem, and the confusion usually comes from marketing copy that treats 135° split point as a universal replacement rather than a specific tool for a specific job.
We manufacture both, in volume, for customers who use them in very different ways. Here is what actually determines which one belongs in a buyer's toolbox — and why.
What Point Angle Actually Changes
Point angle is the angle formed between the two cutting lips at the drill tip. It is usually described as "118° is sharper, 135° is flatter," which is correct but incomplete. What that angle actually controls is three things:
• How much axial thrust is needed to start the cut. A sharper point concentrates force on a smaller area, so it bites in with less push. A flatter point spreads that load across a longer cutting edge.
• How the chisel edge behaves. The chisel edge — the short section at the very center of the tip, where the two flutes meet — does not cut. It pushes material aside. This is the single biggest source of friction and heat at the start of a hole, and it behaves differently depending on point angle.
• Chip formation. At 118°, chip thickness varies more across the cutting edge — thicker at the outer corner, thinner near the center. At 135°, chip thickness is more even, which matters for materials that produce long, stringy chips.
None of this is opinion. It is why the two angles exist in the first place, and why one isn't simply a "better version" of the other.
Why 135° Almost Always Comes With a Split Point
This is worth explaining properly, because it's the part most sourcing guides get wrong or skip entirely.
The chisel edge doesn't cut — it extrudes material. The angle at which it does this (its effective rake angle) gets more negative as the point angle gets flatter. In practical terms: the flatter the point, the more that center section is plowing rather than shearing. A 135° point, left untouched, has a worse chisel-edge problem than a 118° point — not a smaller one.
That's the opposite of what most buyers assume. The logic goes: "135° is flatter, flatter should mean gentler, gentler should mean easier to start." In reality, an un-split 135° point walks more than a standard 118° point, because the geometry that's supposed to make it stable at the outer edges makes the center worse.
Split point geometry exists specifically to fix this. It grinds two additional cutting edges into the chisel edge, turning that non-cutting center section into an actual cutting surface. That's what gives 135° split point its self-centering behavior and its lower starting thrust — not the point angle by itself.
This is also why the two are almost always sold together. A 135° point without split point geometry underperforms in exactly the applications 135° is chosen for — precision holes in hard material, CNC work without a center punch, drilling into curved or slippery surfaces. There's no upside left once you skip the split point step, so very few manufacturers bother offering that combination. It's not a hard rule of geometry. It's that 135° without split point defeats its own purpose.
A common misconception worth correcting directly: split point is not exclusive to 135°. 118° split point exists and is used — mainly where a buyer wants the lower thrust and general-purpose versatility of 118°, but also needs better centering than a standard 118° point provides, without moving to the flatter, more wear-resistant geometry of 135°. It's less common because most 118° applications don't demand that level of centering accuracy in the first place, but it is a real, manufacturable configuration — not a niche curiosity.
Point Angle Isn't the Whole Story — Material Behavior Varies
Treating point angle as the single variable that determines drilling success oversimplifies the problem. A few examples where the "harder material, flatter angle" rule breaks down:
• Aluminum: Point angle matters less here than helix angle and lip relief. A drill with a high helix angle (34°–38°) and generous lip relief clears chips fast enough to prevent built-up edge — the real failure mode in aluminum — regardless of whether the point is 118° or 135°.
• Cast iron: Produces short, granular chips rather than long ones, so the chip-evacuation advantage of 135° matters less here than in materials that produce continuous chips. Many shops run 118° on cast iron without issue.
• Stainless steel: This is where 135° split point earns its reputation. Stainless work-hardens under friction, and the chisel edge's plowing action at the start of a hole is exactly what triggers that hardening. Reducing that friction with split point geometry is not optional if you want consistent hole quality across a production run.
• Plastics and composites: The logic flips entirely. These materials need a blunter, not sharper, point to avoid cracking or splintering as the drill exits the material. Standard metal-drilling point angle guidance doesn't apply.
The pattern here is consistent with what we've seen across every failure mode in this series: a single spec sheet number rarely tells the whole story. Point angle interacts with helix angle, lip relief, and web thickness. Treating it as an isolated decision is how buyers end up with a drill bit that's correct on paper and wrong in the job.
What This Means for Sourcing
If you're specifying drill bits for a mixed-material shop, general-purpose 118° covers most of the routine work at lower cost. If your production runs into stainless, alloy steel, or hardened material — or if your process doesn't allow for a center punch step — 135° split point isn't a preference, it's a requirement for keeping tolerances and cycle times consistent.
The angle stamped on a spec sheet is only useful once you know what problem it's actually solving. A drill bit that walks, skates, or wears out early isn't necessarily a bad drill bit — it may simply be the wrong point angle for what it was asked to do.
About this series
Why Drill Bits Fail is a technical series written by our production team. Each article focuses on one specific factor in drill bit performance — from raw material to packaging. The goal is simple: help buyers understand what they are actually buying, and which questions to ask.
Post time: Jul-28-2026