What Is a Drill Point Angle?
The point angle of a twist drill bit is the included angle formed between the two main cutting lips (edges) at the tip, measured across the full cone of the point. When you look at a drill bit head-on, the cutting lips form a V shape — the angle of that V is the point angle.
Why It Matters
The point angle is not cosmetic. It directly controls three critical drilling parameters:
- Thrust force (axial force): A sharper (smaller) point angle concentrates cutting force into a smaller area, increasing the force needed to push the drill into the workpiece. A flatter (larger) point angle spreads the cutting action across a wider contact zone, reducing thrust.
- Centering behavior: A sharper point digs in more aggressively but tends to walk (skate) across the surface before engaging. A flatter point with split-point geometry self-centers because the modified chisel edge actively cuts from the first rotation.
- Chip formation: The point angle influences chip thickness and curl. At 118°, chips are thicker at the outer edge and thinner near the center. At 135°, the chip thickness distribution is more uniform, which improves chip evacuation in materials that produce long, stringy chips.
The Two Standards
In the HSS twist drill market, two point angles dominate: 118° and 135°. These are not arbitrary — they represent optimized geometries refined over decades of industrial use. Other angles exist (90°, 130°, 140°) for specialized applications, but 118° and 135° account for over 95% of all HSS twist drill production worldwide.
The 118° Standard Point
The 118-degree point angle is the oldest and most established standard for general-purpose twist drill bits. It has been the default point angle since the modern twist drill was standardized in the early 20th century, and it remains the standard for economy-grade drill bits worldwide.
Geometry
A 118° point forms a relatively sharp cone. At the center of this cone sits the chisel edge — a short, blunt ridge connecting the two cutting lips. The chisel edge is not a cutting edge; it does not produce chips. Instead, it acts as a wedge that pushes material aside through plastic deformation. On a standard 10 mm drill, the chisel edge is approximately 1.2-1.5 mm long and accounts for roughly 50-65% of the total thrust force during drilling.
Cutting Mechanics
When a 118° drill contacts the workpiece, the chisel edge hits first. Because the chisel edge cannot cut, it must be forced into the material by axial pressure. This creates two problems:
- High thrust force requirement: The operator or machine must apply significant downward pressure to push the chisel edge through the material before the cutting lips can begin producing chips. In hard materials, this force can be substantial — enough to cause deflection in light-duty drill presses.
- Walking tendency: On smooth, flat surfaces, the chisel edge tends to skate sideways before penetrating. This is why a center punch is traditionally required when using 118° drill bits on metal — the punch mark creates a small depression that traps the chisel edge and prevents walking.
Advantages of 118°
- Easy to resharpen: The 118° conventional point is a simple conical geometry that can be ground on a standard bench grinder or hand-held drill sharpener. No special jigs or CNC equipment required. An experienced operator can resharpen a 118° point in under 30 seconds.
- Good for soft materials: In wood, plastic, and soft aluminum, the aggressive chisel edge actually helps — it pulls the drill into the material, reducing the need for manual feed pressure. The higher thrust force is not a problem because soft materials offer minimal resistance.
- Lower cost: Grinding a simple 118° conical point is faster than grinding a 135° split point, which requires an additional grinding operation. This translates to a lower unit cost in production.
- Universal availability: Every drill bit manufacturer in the world produces 118° points. It is the default — if a specification sheet does not mention point angle, assume 118°.
Limitations of 118°
- Cannot self-center: Requires a center punch or pilot hole on metal surfaces.
- High thrust force: The chisel edge generates 50-65% of total thrust, which is wasted energy that produces heat rather than chips.
- Work hardening risk: In stainless steel and other austenitic alloys, the chisel edge's rubbing action generates heat without cutting, causing localized work hardening that makes subsequent drilling even harder.
- Poor on curved surfaces: The walking tendency makes 118° points unreliable on pipe, tubing, and curved sheet metal.
The 135° Split Point
The 135-degree split point is the modern solution to every limitation of the 118° conventional point. It combines a flatter point angle with a modified chisel edge geometry that transforms the non-cutting center into an active cutting zone.
Geometry
The split point is created by grinding a notch (or pair of notches) into the chisel edge of the drill. This notch extends the cutting lip geometry through the center of the drill, effectively creating four cutting edges instead of two. The original chisel edge is split — hence the name — and replaced with two small secondary cutting lips that produce chips all the way to the center of the drill.
The 135° included angle means the point cone is flatter than a 118° point. Combined with the split-point modification, this geometry produces dramatically different cutting behavior.
Cutting Mechanics
When a 135° split point drill contacts the workpiece, the modified center begins cutting immediately. There is no dead zone, no chisel edge pushing material aside without cutting. The result:
- 20-30% lower thrust force: Because the center is cutting rather than extruding, the wasted force component is eliminated. This is measurable on a dynamometer and significant in practice — operators report noticeably easier drilling, and thin workpieces are less likely to deform or dimple.
- Self-centering: The four cutting edges engage the workpiece symmetrically from the first rotation. The drill does not walk — it starts cutting exactly where placed. No center punch needed. This is particularly valuable when drilling on curved surfaces, angled surfaces, or existing holes that must be enlarged.
- Reduced work hardening: Because the entire point is cutting (not rubbing), the heat generation at the center is lower and more evenly distributed. In stainless steel, this is the difference between successful drilling and a glazed, work-hardened surface that no drill can penetrate.
Advantages of 135° Split Point
- Self-centering: No center punch or pilot hole required on any surface, including metal, curved pipe, and sheet metal.
- Lower thrust force: 20-30% less axial force required. Reduces operator fatigue, improves accuracy on thin stock, and extends machine bearing life in production drilling.
- Better chip formation: Uniform chip thickness across the entire cutting diameter produces cleaner, more consistent chips that evacuate more reliably.
- Mandatory for stainless steel: The elimination of the rubbing chisel edge prevents work hardening — this alone makes 135° the only acceptable point angle for austenitic stainless steel.
- Reduced walking on curves: The self-centering action makes 135° split point drills reliable on pipe, angle iron, and curved sheet metal where 118° points would skate.
Limitations of 135° Split Point
- Harder to resharpen: The split-point geometry cannot be recreated on a simple bench grinder. It requires a specialized split-point grinding jig, a Darex-style sharpener, or a CNC tool grinder. Many workshops lack this equipment, meaning a dulled 135° split point drill is either sent out for professional resharpening or discarded.
- Higher initial cost: The additional grinding operation to create the split point adds 10-20% to the manufacturing cost compared to a simple 118° point.
- Less aggressive in wood: The lower thrust force and self-centering action mean 135° drills do not pull themselves into soft materials as aggressively as 118° points. In wood, this is rarely a problem — but in green or wet wood with high resistance, some operators prefer the more aggressive bite of 118°.
Side-by-Side Comparison Table
The following table provides a direct comparison of 118° conventional and 135° split point drill bits across the parameters that most influence purchasing and application decisions.
| Parameter | 118° Conventional | 135° Split Point |
|---|---|---|
| Chisel Edge | Full chisel edge — does not cut | Split — converted to cutting edges |
| Number of Cutting Edges | 2 | 4 (2 main + 2 secondary) |
| Thrust Force | Higher (chisel edge pushes, not cuts) | 20-30% lower (center cuts actively) |
| Self-Centering | No — needs center punch on metal | Yes — starts cutting where placed |
| Walking Tendency | High on smooth/curved surfaces | Minimal — reliable on all surfaces |
| Stainless Steel | Not recommended — causes work hardening | Mandatory — prevents work hardening |
| Wood / Soft Materials | Excellent — aggressive self-feeding | Good — less aggressive pull-in |
| Sheet Metal | Poor — walks, punches through | Good — controlled entry, less deformation |
| Resharpening Ease | Easy — bench grinder, 30 seconds | Difficult — needs jig or CNC grinder |
| Manufacturing Cost | Lower (one grinding operation) | 10-20% higher (additional split grind) |
| Standard HSS Grades | entry-level HSS, M2 | M2, M35, M42 |
Which Angle for Which Material
The point angle decision is ultimately driven by the workpiece material. This section provides definitive guidance for the most common materials encountered in professional drilling.
Wood (Softwood, Hardwood, Plywood, MDF)
Recommended: 118°. Wood is soft and fibrous. The aggressive chisel edge of a 118° point helps the drill self-feed into the material, reducing the need for manual pressure. Walking is not an issue because wood is soft enough for the point to dig in immediately. A 135° split point works in wood but offers no meaningful advantage — save it for metal.
Mild Steel (A36, 1018, 1020, Q235)
Recommended: Either — 135° preferred. Both angles work well in mild steel. The 118° point requires a center punch for accurate positioning but cuts efficiently once engaged. The 135° split point eliminates the center punch step and reduces thrust force, making it the more productive choice in production environments. For hand-drill use where a center punch is impractical, 135° is strongly preferred.
Stainless Steel (304, 316, 430)
Mandatory: 135° split point. There is no debate here. The chisel edge of a 118° point rubs against the stainless surface without cutting, generating heat that causes immediate work hardening. Once the surface work-hardens, even the cutting lips struggle to penetrate. The 135° split point eliminates the rubbing zone entirely, allowing continuous chip production from the center outward. Combined with M35 cobalt steel, this is the only geometry that reliably drills austenitic stainless steel.
Sheet Metal (Thin Gauge, Under 3mm)
Recommended: 135° split point. Thin sheet metal is particularly challenging because the drill punches through the bottom surface before the full diameter has engaged the top. A 118° point's high thrust force exacerbates this — it pushes the sheet downward, creating a large exit burr and deforming the workpiece. The 135° split point's lower thrust produces a cleaner breakthrough with less deformation. For sheet metal thinner than 1 mm, consider a step drill bit instead.
Cast Iron (Gray, Ductile, Malleable)
Recommended: 135° preferred. Cast iron produces short, fragmented chips rather than long spirals. Both point angles work, but the 135° split point's lower thrust is beneficial because cast iron workpieces are often complex castings that cannot tolerate high clamping forces. The self-centering is also valuable when drilling cast surfaces that may not be perfectly flat.
Aluminum and Copper Alloys
Recommended: 118°. Soft, non-ferrous metals do not cause work hardening and generate manageable thrust forces at either angle. The 118° point's more aggressive engagement is an advantage in aluminum, which can be gummy and tends to build up on the cutting edge. The slightly higher thrust helps the drill cut cleanly rather than smearing. Use bright (uncoated) bits — TiN coating promotes aluminum galling.
| Material | Recommended Angle | Reason |
|---|---|---|
| Wood / MDF | 118° | Aggressive self-feeding, low cost |
| Mild Steel | 135° preferred | Self-centering, lower thrust |
| Stainless Steel | 135° mandatory | Prevents work hardening |
| Sheet Metal (<3mm) | 135° | Lower thrust, cleaner breakthrough |
| Cast Iron | 135° preferred | Lower thrust on castings |
| Aluminum | 118° | Better chip clearing in gummy material |
| Copper / Brass | 118° | Aggressive entry, soft material |
| Hardened Steel | 135° mandatory | Minimum thrust, prevents glazing |
Resharpening Considerations
Tool life does not end when the cutting edge dulls — resharpening can restore performance and extend the useful life of a drill bit by 3-5 cycles. However, the point angle geometry significantly affects how easy or difficult resharpening is.
Resharpening 118° Points
A 118° conventional point is one of the simplest tool geometries to resharpen. The requirements are minimal:
- Equipment: A standard bench grinder with an aluminum oxide wheel (60-80 grit for HSS) or a dedicated drill sharpening jig (Drill Doctor, Darex, or similar).
- Technique: Hold the drill at approximately 59° to the grinding wheel face (half of 118°) and rotate evenly to grind both lips to equal length and angle. Check with a drill point gauge.
- Time: 20-60 seconds per bit for an experienced operator.
- Skill level: Moderate. The main challenge is maintaining equal lip lengths — if one lip is longer than the other, the drill will cut an oversized hole and wear unevenly.
Resharpening 135° Split Points
Resharpening a 135° split point is substantially more difficult because the split-point modification is a secondary grinding operation that must be precisely reproduced.
- Equipment: A split-point grinding jig, a Darex XT-3000 or similar professional drill sharpener, or a CNC tool grinder. A standard bench grinder cannot create the split-point notch — it can only grind the conical point.
- The common workaround: Many workshops resharpen only the conical point (restoring the 135° angle and lip symmetry) without recreating the split-point notch. This produces a 135° conventional point — better than a dull split point but without the self-centering and reduced thrust of the original geometry.
- Professional resharpening: Dedicated tool regrinding services can fully restore split-point geometry using CNC grinders. Cost is typically $1-3 per bit, which is economical for M35 cobalt bits priced at $5-15 each but not cost-effective for economy M2 bits.
- Time: 2-5 minutes per bit on a jig or professional sharpener.
- Skill level: High. Incorrect split-point grinding can create an asymmetric point that causes the drill to cut oversize or wander.
The Economic Calculation
For economy M2 straight-shank drill bits (DIN 338, sizes 1-13 mm), the cost of professional resharpening often exceeds the cost of a replacement bit. In this case, 118° points have an economic advantage because the end user can resharpen them in-house with minimal equipment.
For premium M35 cobalt drill bits and taper shank drills (DIN 345), the replacement cost is high enough that professional resharpening is economically justified even for 135° split points. In this segment, resharpening ease is not a decisive factor.
Why Cobalt Drills Always Use 135°
If you examine the product catalogs of any major drill bit manufacturer — Dormer, Guhring, Nachi, or Zhonghuan — you will notice that M35 and M42 cobalt drill bits are almost universally offered with 135° split point geometry. This is not a marketing convention. It is a technical necessity dictated by the materials cobalt drills are designed to cut.
The Physics of Cobalt + Stainless
M35 cobalt drill bits exist primarily to solve one problem: drilling stainless steel and other austenitic alloys that work-harden under the cutting tool. The cobalt content (5% in M35, 8% in M42) provides the red hardness needed to maintain a sharp cutting edge at the elevated temperatures generated by stainless steel's low thermal conductivity.
But cobalt alone is not enough. The point geometry must also be optimized for the specific challenges of stainless steel:
- Stainless requires continuous cutting. Any pause in chip formation — any moment where the tool rubs instead of cuts — triggers work hardening. The chisel edge of a 118° point creates exactly this condition: a rubbing zone at the center of the drill that generates heat and hardens the surface. The 135° split point eliminates the rubbing zone completely.
- Stainless generates high cutting temperatures. The low thermal conductivity of austenitic stainless (approximately 16 W/mK versus 50 W/mK for carbon steel) means heat concentrates at the cutting edge instead of dissipating into the workpiece. The 20-30% thrust reduction of the split point directly reduces heat generation at the center of the drill, where cooling is poorest.
- Cobalt drills are harder and more brittle. M35 at HRC 65-67 has less toughness than M2 at HRC 63-65. The higher thrust force of a 118° point means higher mechanical stress on the cutting edges. Combined with the thermal stress from stainless steel's heat retention, a 118° cobalt drill is at higher risk of edge chipping or catastrophic fracture than the same drill with a 135° split point.
- Self-centering prevents false starts. When drilling stainless, there is no second chance. If the drill walks across the surface, it work-hardens a track that the drill cannot subsequently penetrate. The self-centering of the 135° split point ensures the drill engages immediately and correctly on the first attempt.
The Manufacturer's Perspective
From a manufacturing standpoint, applying the 135° split point to cobalt drills is a small additional cost (the split-point grinding operation) that prevents a far larger problem: customer complaints and returns from users who cannot drill stainless steel because the wrong point geometry was supplied. Every responsible manufacturer grinds cobalt drills with 135° split point as the default — it is an engineering requirement, not an upsell.
Can You Get 118° Cobalt Drills?
Some manufacturers offer M35 cobalt drills with 118° conventional point as a special order. These are typically requested by buyers who want cobalt's heat resistance for applications other than stainless steel — for example, drilling hardened mild steel or high-temperature alloys in a lathe where a center drill is used first. However, for the general market and for any application involving stainless steel, 135° split point is the universal standard for cobalt drill bits.
At Zhonghuan, all M35 and M42 cobalt twist drills — both straight shank and taper shank — ship with 135° split point as the standard geometry. We do not offer 118° cobalt drills as a standard catalog item because we believe supplying a suboptimal geometry for the intended application does not serve our customers' interests.
Related Procurement Programs
If you are sourcing this product line for a distributor, importer, or private-label channel, these OEM and wholesale programs cover the procurement questions buyers usually ask next.
- HSS Twist Drill Bits Wholesale & OEM Supply for Metalworking Channels — HSS twist drill bit wholesale and OEM supply for importers, industrial distributors, and private-label brands: M2, M35 cobalt, DIN 338, DIN 345, black oxide…
- Metalworking and Sheet Metal Drilling Matrix — A procurement matrix for steel fabrication, electrical panels, HVAC sheet metal, and automotive sheet repair: HSS twist drills, M35 cobalt, taper shank drills…