Difference Between HSS and Black Oxide Drill Bits

When it comes to CNC machining, not all drill bits are created equal — and this is especially true for High-Speed Steel (HSS) drill bits. With precision, repeatability, and durability being critical in CNC operations, choosing the right HSS drill bit can make a significant difference in tool life, cycle time, and surface finish.

In this article, we’ll dive into what to look for when selecting HSS drill bits for CNC applications, supported by industry standards, real-world feedback, and cross-sell product suggestions to help you choose wisely.

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Why HSS Drill Bits for CNC?

HSS remains one of the most widely used materials in CNC drilling due to its excellent combination of toughness, heat resistance, and affordability. Unlike brittle carbide tools, HSS bits can tolerate minor flexing and vibrations — common in CNC setups with less rigid workholding or lower-end machines.

According to the Tool and Manufacturing Engineers Handbook by SME, HSS is preferred for jobs requiring moderate cutting speed and tool resilience, especially in drilling medium-hardness materials.

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Key Features to Look For in CNC-Compatible HSS Drill Bits

1. Material Grade (M2 vs. M35 vs. M42)

Not all HSS is the same. For CNC use, you’ll want to match the bit’s alloy grade to the material being machined:

Grade	Composition	Best For
M2	Standard high-speed steel	Mild steel, aluminum, plastic
M35	HSS + 5% cobalt	Stainless steel, harder alloys
M42	HSS + 8% cobalt	High-tensile steel, titanium alloys

Tip: Cobalt-enhanced HSS bits (M35/M42) are ideal for CNC setups that run longer cycles and need better heat resistance.

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2. Point Angle (118° vs. 135° Split Point)

• 118° Standard Tip: General-purpose drilling; good for soft to medium materials

• 135° Split Point: Self-centering, minimizes walking, ideal for CNC machines with automated peck drilling or spot drilling

CNC operators often prefer 135° split points for faster, more accurate drilling without pilot holes — especially on metals like stainless steel.

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3. Coating Type

While raw HSS performs well, coated HSS drill bits provide significant performance advantages:

• Black Oxide: Reduces friction, improves chip flow

• TiN (Titanium Nitride): Increases hardness and wear resistance

• TiAlN / AlTiN: Best for high-speed and dry machining

As tested by the Fraunhofer Institute for Production Technology, TiN-coated HSS bits lasted up to 2.5x longer in continuous drilling of low-carbon steel.

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4. Shank Type (Straight vs. Reduced vs. Weldon)

For CNC machines (especially vertical machining centers or CNC routers), shank compatibility is key:

• Straight Shank: Standard, fits most ER collets and drill chucks

• Reduced Shank: Allows larger diameters to fit into standard collets

• Weldon Flat Shank: Common in milling/drilling centers with set-screw holders

Choose the shank that matches your CNC’s spindle or tool holder system to avoid runout or slippage.

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5. Coolant Holes or External Cooling Compatibility

In production environments, coolant-fed or externally lubricated HSS bits reduce heat buildup, improve chip evacuation, and extend tool life. For long holes or metals like stainless, this is crucial.

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Recommended HSS Drill Bits for CNC Applications

Here are a few products we manufacture that meet CNC-grade standards:

M35 Cobalt HSS Twist Drill Bits

• Ideal for stainless steel and high-strength alloys

• Long life and fast penetration

• Compatible with CNC milling centers and turret drills

Black Oxide HSS Drill Bits – Straight Shank

• Cost-effective for CNC batch work on carbon steel, aluminum

• Suitable for general-purpose CNC setups

Jobber-Length HSS Drill Bits – Bright Finish, M2(HSS6542) Grade

• Designed for CNC routers and table-top mills

• Best for soft materials and non-ferrous metals

Please contact us to obtain the product catalog to explore all variations, or contact us for OEM branding or bulk orders.

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CNC Use Case: What Professionals Say

A CNC sheet metal manufacturer in Malaysia replaced their standard HSS bits with our TiN-coated M35 cobalt HSS drill bits and saw:

• 30% increase in tool life

• 15% reduction in machine idle time

• Consistent hole tolerance in stainless sheet up to 3mm thick

"The split-point TiN drill bits eliminated pilot holes in most of our operations. Definitely helped with throughput," — Plant Manager, Johor Bahru

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Conclusion

When selecting HSS drill bits for CNC machines, you must go beyond the price tag. Focus on:

• The right alloy grade (M35/M42 for tough materials)

• Proper tip geometry (135° split for auto-centering)

• Durable coatings (TiN, AlTiN)

• Shank compatibility and coolant support

A well-chosen HSS drill bit can extend tool life, reduce scrap rates, and improve part consistency — all of which translate into real operational savings.