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How to Select the Correct Grinding Wheel for Cutting Tools
September 18, 2026 Mike Xu

How to Select the Correct Grinding Wheel for Cutting Tools

Grinding a cutting tool is not simply a matter of using a grinding wheel that is harder than the tool.

Different cutting-tool materials behave very differently during grinding. A grinding wheel that works extremely well on tungsten carbide may perform poorly on high-speed steel, while a wheel designed for HSS may barely grind carbide at all.

For good grinding performance, the grinding wheel should be selected according to:

  • Cutting-tool material

  • Amount of material to be removed

  • Grinding operation

  • Required surface finish

  • Tool size and geometry

  • Grinding-machine rigidity and spindle speed

  • Dry or wet grinding

  • Type and delivery of coolant

  • Wheel bond and grit size

The most important rule is:

Tungsten carbide → Diamond

High-speed steel and hardened tool steel → CBN or aluminum oxide

1. Tungsten-Carbide Tools

Examples include:

  • Solid-carbide end mills

  • Carbide drills

  • Carbide router bits

  • Carbide inserts

  • Carbide-tipped woodworking cutters

  • Carbide-tipped saw blades

  • Carbide planer and jointer knives

Recommended Grinding Wheel

First choice: Diamond grinding wheel

Diamond is the preferred abrasive for cemented tungsten carbide.

Depending on the grinding operation, common wheel bonds include:

  • Resin-bond diamond

  • Hybrid-bond diamond

  • Metal-bond diamond

  • Vitrified diamond in suitable grinding systems

  • Electroplated diamond for certain profile and form-grinding applications

For general tool sharpening, resin-bond diamond is usually an excellent starting point because it cuts freely and can produce a good cutting edge.

Typical Grit Selection for Carbide

These are general starting ranges rather than universal specifications because wheel manufacturers use different grading systems.

Heavy material removal / rough grinding

Approximately:

80–120 grit diamond

Useful for:

  • Removing substantial carbide

  • Repairing badly damaged tools

  • Rough fluting

  • Major geometry changes

Advantages:

  • Fast material removal

Disadvantages:

  • Rougher surface

  • Larger grinding marks

  • Greater risk of edge chipping if used for the final cutting edge

General sharpening

Approximately:

120–180 grit diamond

Useful for:

  • End-mill relief grinding

  • Drill sharpening

  • Router-bit sharpening

  • Carbide cutter sharpening

  • General-purpose regrinding

This is often a good compromise between stock-removal rate and finish.

Finish grinding

Approximately:

180–320 grit diamond

Useful for:

  • Final cutting edges

  • Small carbide tools

  • Fine finishing

  • Improving edge quality

  • Reducing grinding marks

A finer wheel normally produces a better finish, but it removes material more slowly and can generate additional heat if it becomes loaded or is fed too aggressively.

2. High-Speed-Steel Tools

Examples include:

  • HSS end mills

  • HSS drills

  • HSS-Co / cobalt drills

  • HSS reamers

  • HSS taps

  • HSS woodworking knives

  • HSS moulder knives

  • HSS planer and jointer knives

  • Profile knives

  • Hardened tool-steel cutters

There are two major grinding-wheel choices.

Preferred precision solution: CBN

CBN stands for cubic boron nitride.

CBN is particularly suitable for:

  • High-speed steel

  • Cobalt high-speed steel

  • Hardened tool steel

  • Hardened alloy steel

  • Other hardened ferrous cutting materials

For a professional tool-grinding machine that regularly sharpens HSS tools, I recommend CBN rather than using a diamond wheel intended for carbide.

CBN offers:

  • Efficient material removal

  • Good edge quality

  • Excellent thermal resistance

  • Good wheel life

  • Better chemical compatibility with iron-based materials than diamond

3. Conventional Alternative for HSS: Aluminum Oxide

CBN is not the only option.

Traditional aluminum-oxide grinding wheels are still widely used for HSS tools.

Common choices include:

  • White aluminum oxide

  • Pink aluminum oxide

  • Premium ceramic aluminum oxide

They are particularly suitable for conventional tool grinders and manual sharpening machines.

Advantages

  • Lower wheel cost than CBN

  • Easy to dress

  • Widely available

  • Suitable for HSS

  • Good for manual and lower-volume grinding

  • Wheel shape can often be restored relatively easily

Disadvantages compared with CBN

  • Faster wheel wear

  • More frequent dressing

  • Greater dimensional change as the wheel wears

  • Lower productivity in many production environments

Therefore:

Occasional HSS sharpening

Aluminum oxide is perfectly reasonable.

Frequent or precision HSS sharpening

CBN is generally the better investment.

4. Why We Do Not Normally Recommend Diamond for HSS

A common question is:

"If diamond can grind extremely hard tungsten carbide, shouldn't it grind softer HSS even more easily?"

From a simple hardness perspective, this seems logical.

But grinding performance is not determined by hardness alone.

Diamond has poor chemical compatibility with iron at elevated grinding temperatures. HSS is an iron-based material.

As grinding temperature rises, interaction between diamond and ferrous material can accelerate diamond wear.

Other problems can also occur:

  • Wheel loading

  • Increased grinding heat

  • Loss of grinding efficiency

  • Poor surface finish

  • Excessive wheel wear

  • Possible thermal damage to the HSS cutting edge

The diamond wheel may physically remove HSS, but that does not make it the correct production grinding wheel.

Therefore:

Do not select diamond simply because it is the hardest abrasive.

For HSS:

Use CBN or aluminum oxide.

5. Why Aluminum Oxide Is Not Recommended for Carbide

The reverse situation also creates problems.

An aluminum-oxide wheel designed for HSS is generally unsuitable for grinding cemented carbide.

The wheel may remove a small amount of carbide, but grinding efficiency will be extremely poor.

Typically:

  • The wheel wears quickly.

  • Grinding forces become high.

  • Material removal becomes slow.

  • Heat increases.

  • Tool geometry becomes difficult to maintain.

  • Cutting-edge quality suffers.

For professional carbide sharpening:

Use diamond.

6. Grinding Solid-Carbide End Mills

A solid-carbide end mill may require several different grinding operations:

  1. Flute grinding

  2. Gashing

  3. OD or margin grinding

  4. Primary relief grinding

  5. Secondary relief grinding

  6. End-face grinding

  7. Corner-radius or chamfer grinding

The same diamond-wheel specification is not necessarily ideal for every operation.

Flute Grinding

Fluting removes a relatively large amount of carbide.

Use a relatively aggressive diamond wheel, often with a somewhat coarser grit and a bond designed for high stock removal.

A wheel that is too fine may:

  • Remove material too slowly

  • Generate excessive heat

  • Load more easily

For production flute grinding, specially engineered resin or hybrid diamond wheels are commonly used.

Gashing

Gashing creates space for chip evacuation at the tool end.

Use a diamond wheel with:

  • Good form retention

  • Adequate corner strength

  • Appropriate wheel profile

Common tool-grinding wheel shapes include narrow dish and cup-type wheels.

Primary Relief

The primary relief is immediately behind the cutting edge.

This operation directly affects how the end mill cuts.

A medium-to-fine diamond wheel is generally preferable because cutting-edge quality is more important than maximum stock removal.

The objectives are:

  • Correct relief angle

  • Smooth cutting edge

  • Minimal chipping

  • Accurate geometry

Secondary Relief

The secondary relief removes additional material behind the primary land.

A somewhat more aggressive wheel may be acceptable because the secondary relief does not form the actual cutting edge.

Final Edge

Avoid finishing the cutting edge with an unnecessarily coarse wheel.

Excessively coarse grinding can produce:

  • Edge chipping

  • Large grinding scratches

  • Weak cutting edges

  • Poor workpiece surface finish

7. Grinding HSS End Mills

For HSS end mills, the grinding sequence is similar to carbide:

  • Fluting

  • Gashing

  • Primary relief

  • Secondary relief

  • End-face grinding

  • OD grinding

But the abrasive changes.

Recommended

Professional CNC / production grinder

CBN

Conventional manual tool grinder

White, pink or premium ceramic aluminum oxide

Do not simply install the carbide diamond wheel and continue grinding HSS.

If the machine regularly processes both carbide and HSS, it is much better to keep separate wheel sets.

8. Grinding Carbide Drills

For solid-carbide drills:

Use diamond.

Operations may include:

  • Point sharpening

  • Primary clearance

  • Secondary clearance

  • Web thinning

  • Chisel-edge correction

  • Margin work

  • Flute grinding

For ordinary resharpening, a medium or fine resin-bond diamond wheel is a good starting point.

For significant geometry changes, use a coarser wheel first and then finish with a finer wheel.

9. Grinding HSS and Cobalt Drills

For:

  • Standard HSS drills

  • M2 drills

  • M35 cobalt drills

  • M42 cobalt drills

Use:

CBN

or

Aluminum oxide

Cobalt-containing HSS such as M35 or M42 is still an iron-based high-speed steel. The addition of cobalt does not turn it into carbide.

Therefore, it should still normally be ground with CBN or a suitable aluminum-oxide wheel, not a carbide diamond wheel.

10. Grinding HSS Planer and Jointer Knives

For HSS straight knives:

Recommended

Aluminum oxide

or

CBN for higher production and precision

These knives have long straight cutting edges, so overheating is particularly important to avoid.

Use:

  • A sharp, properly dressed wheel

  • Controlled feed

  • Light finishing passes

  • Proper coolant when the machine is designed for wet grinding

Do not allow the cutting edge to turn blue, purple or brown from excessive heat.

Visible heat discoloration is a warning that the grinding process may have overheated the steel.

11. Grinding Carbide Planer and Jointer Knives

For solid-carbide or carbide-tipped knives:

Use diamond.

Carbide is brittle compared with HSS, so excessive grinding pressure should be avoided.

A fine diamond wheel is generally preferable for the final cutting edge.

If substantial stock must be removed:

  1. Rough grind with a coarser diamond wheel.

  2. Finish with a finer diamond wheel.

This approach is usually better than trying to perform the entire job with an extremely fine wheel.

12. Grinding HSS Moulder/Profile Knives

Profile knives create another challenge because the grinding wheel must reproduce the required profile accurately.

For HSS profile knives:

Use aluminum oxide or CBN.

The wheel must also be properly shaped and dressed to reproduce the desired profile.

Important factors include:

  • Profile accuracy

  • Wheel form

  • Cutting angle

  • Clearance angle

  • Knife balance

  • Matching knives in a cutterhead

When multiple knives operate in one cutterhead, they must be ground consistently so that each knife follows the intended cutting circle.

13. Grinding Carbide-Tipped Saw Blades

For carbide saw teeth:

Use diamond.

Typical grinding operations include:

  • Tooth face grinding

  • Tooth top grinding

  • Side grinding

One important point:

The carbide tooth and the steel saw body are different materials.

The diamond wheel should perform the grinding primarily on the carbide tip.

Do not unnecessarily grind the steel plate with the same diamond wheel.

Professional saw sharpeners therefore use wheel geometry and machine movements specifically designed for carbide teeth.

14. Grinding Carbide Router Bits

For carbide-tipped and solid-carbide router tools:

Use diamond.

The cutting face is commonly reground rather than randomly removing material from every surface.

Incorrect grinding can change:

  • Tool diameter

  • Cutting angle

  • Relief

  • Profile

  • Balance

This is particularly important with matched profile cutters.

15. Grinding Carbide Inserts

For conventional cemented-carbide inserts:

Use diamond.

A relatively fine diamond wheel is normally used for the final edge.

Important considerations include:

  • Edge geometry

  • Surface finish

  • Edge radius

  • Chipping

  • Flatness

Some inserts are intentionally edge-honed rather than ground razor-sharp.

The final edge preparation should therefore match the application rather than simply creating the sharpest possible edge.

16. PCD Tools Are Different

PCD means polycrystalline diamond.

PCD tooling should not be treated as ordinary tungsten carbide.

PCD is extremely hard and requires specialized processing.

Depending on the tool and equipment, PCD tools may be processed using:

  • Specialized diamond grinding

  • Electrical-discharge processes where applicable

  • Laser processing

  • Dedicated PCD sharpening equipment

A standard carbide-sharpening setup should not automatically be assumed suitable for PCD tooling.

17. Rough Grinding and Finish Grinding Should Be Treated Differently

One of the most common mistakes in tool sharpening is expecting one grinding wheel to perform every operation perfectly.

A coarse wheel removes material quickly.

A fine wheel produces a better finish.

These requirements conflict.

A better approach for substantial regrinding is:

Step 1 — Rough grinding

Remove damaged or unwanted material efficiently.

Step 2 — Semi-finish

Establish the required geometry.

Step 3 — Finish grinding

Create the final cutting edge and surface finish.

Trying to perform heavy stock removal with a very fine wheel can increase cycle time and heat.

Trying to create a precision cutting edge with a very coarse wheel may produce unacceptable chipping and grinding marks.

18. Wheel Grit — Coarser Is Not Always Better

The general relationship is:

Coarser grit → faster stock removal

Finer grit → better surface finish

But extremely fine wheels are not automatically safer.

A fine wheel has less chip space and may generate additional heat if:

  • Feed is excessive

  • The wheel is loaded

  • Coolant is inadequate

  • The wheel is not dressed properly

Therefore, wheel selection must balance:

Material-removal rate + surface finish + edge quality + heat generation

19. Wheel Bond Is Just as Important as Abrasive Type

Selecting "diamond" or "CBN" is only the beginning.

The abrasive grains must be held by a bond.

Common superabrasive wheel bonds include:

Resin bond

Good cutting action and widely used in tool grinding.

Common for:

  • Carbide sharpening

  • HSS tool sharpening

  • Finish grinding

Vitrified bond

Can provide excellent form control and dressing characteristics in suitable applications.

Metal bond

Very strong bond and good form retention.

Useful for certain high-wear or profile applications, but it may not be the best choice for every sharpening operation.

Hybrid bond

Combines properties intended to improve productivity, profile retention and grinding performance.

Frequently encountered in modern CNC tool grinding.

Electroplated

A single layer of abrasive is bonded to the wheel form.

Excellent profile retention for appropriate applications, but unlike many bonded wheels, the abrasive layer cannot simply be dressed repeatedly in the same way.

20. Dressing the Grinding Wheel Is Critical

A grinding wheel does not remain sharp forever.

During use:

  • Abrasive grains become dull.

  • Swarf fills spaces between grains.

  • The wheel face can become glazed.

  • Wheel geometry can change.

A loaded or dull wheel stops cutting freely and begins rubbing.

Rubbing creates heat.

Heat can damage the cutting tool.

Therefore, proper wheel maintenance is essential.

Truing

Truing restores:

  • Wheel geometry

  • Concentricity

  • Correct profile

Dressing

Dressing restores:

  • Cutting ability

  • Grain exposure

  • Chip clearance

The correct dressing method depends on the abrasive and bond.

Always use the dressing method recommended for the particular wheel.

21. Coolant Is Extremely Important

Coolant does more than simply make the tool feel cold.

It helps:

  • Remove grinding heat

  • Flush grinding swarf

  • Keep the wheel open

  • Reduce loading

  • Improve surface finish

  • Control dimensional accuracy

The coolant must actually reach the grinding zone.

A large amount of coolant aimed in the wrong direction may be less effective than properly directed coolant delivered directly into the wheel/workpiece interface.

Coolant condition also matters.

Contaminated coolant containing carbide or steel grinding particles can adversely affect finish and machine components.

22. Avoid Thermal Damage

Grinding generates significant heat.

Excessive heat can cause different problems depending on the tool material.

HSS

Overheating can affect the hardened structure close to the cutting edge and may reduce tool life.

Warning signs can include:

  • Blue discoloration

  • Brown discoloration

  • Burn marks

  • Cracks

  • Rapid edge failure after sharpening

Carbide

Carbide does not suffer from tempering in the same way as HSS, but excessive thermal stress can contribute to:

  • Microcracking

  • Edge chipping

  • Thermal damage

  • Poor cutting-edge quality

Therefore, overheating should be avoided with both materials.

23. Never Increase Grinding Pressure Just Because the Wheel Is Not Cutting

If grinding suddenly becomes difficult, the natural reaction is often to push the tool harder against the wheel.

This can make the problem worse.

Poor grinding may indicate:

  • Incorrect abrasive

  • Dull wheel

  • Loaded wheel

  • Incorrect wheel bond

  • Insufficient dressing

  • Incorrect spindle speed

  • Poor coolant delivery

  • Excessive depth of cut

Increasing pressure creates more heat and grinding force.

Correct the cause rather than simply applying more force.

24. Keep Separate Wheels for Carbide and HSS

A professional sharpening shop processing both materials should ideally maintain separate grinding wheels.

Carbide wheel set

Diamond

HSS wheel set

CBN and/or aluminum oxide

This provides several advantages:

  • Better grinding performance

  • Predictable wheel life

  • Better edge quality

  • Reduced wheel contamination

  • Better surface finish

  • Easier process control

Trying to use one universal wheel for every tool material usually sacrifices grinding performance.

25. Quick Grinding-Wheel Selection Chart

Cutting Tool Tool Material Recommended Abrasive
End mill Solid carbide Diamond
End mill HSS CBN / aluminum oxide
End mill Cobalt HSS CBN / aluminum oxide
Drill Solid carbide Diamond
Drill HSS CBN / aluminum oxide
Drill M35/M42 cobalt HSS CBN / aluminum oxide
Reamer Carbide Diamond
Reamer HSS CBN / aluminum oxide
Tap HSS CBN / aluminum oxide
Router bit Carbide Diamond
Planer knife HSS CBN / aluminum oxide
Planer knife Carbide Diamond
Jointer knife HSS CBN / aluminum oxide
Jointer knife Carbide Diamond
Moulder/profile knife HSS CBN / aluminum oxide
Moulder/profile cutter Carbide Diamond
Saw tooth Tungsten carbide Diamond
Carbide insert Cemented carbide Diamond
Hardened tool-steel cutter Tool steel CBN / aluminum oxide
PCD cutting tool PCD Specialized PCD grinding/process

26. Simple Rule to Remember

If you remember only two lines from this guide, remember these:

CARBIDE = DIAMOND

HSS / HARDENED STEEL = CBN

Aluminum oxide remains an economical and effective conventional alternative for many HSS grinding applications.

27. Recommended Setup for a Shop Grinding Both Carbide and HSS

For a shop that regularly sharpens different cutting tools, a practical wheel inventory would be:

Set A — Carbide rough grinding

Coarser diamond wheel

Purpose:

  • Repair

  • Heavy material removal

  • Major geometry correction

Set B — Carbide finish grinding

Medium/fine diamond wheel

Purpose:

  • Cutting edges

  • Relief

  • Final sharpening

Set C — HSS rough/general grinding

CBN or suitable aluminum-oxide wheel

Purpose:

  • Stock removal

  • General sharpening

  • Geometry correction

Set D — HSS finish grinding

Fine CBN or appropriate fine aluminum-oxide wheel

Purpose:

  • Final cutting edge

  • Fine finish

  • Precision sharpening

This is much more effective than attempting to grind every tool with one wheel.

Final Recommendation

The grinding wheel should always be selected first according to the tool material, then refined according to the grinding operation.

For most professional tool-grinding applications:

Tungsten carbide: Diamond

High-speed steel: CBN

HSS on conventional/manual grinders: Aluminum oxide is also an excellent option

After choosing the abrasive, select the appropriate:

  • Grit size

  • Bond

  • Wheel shape

  • Concentration

  • Wheel hardness

  • Grinding speed

  • Feed rate

  • Coolant

according to the specific machine, tool geometry and grinding operation.

There is no single grinding-wheel specification that is optimum for every tool.

Finally, grinding-wheel operating speed, mounting, guarding, dressing and coolant requirements must always follow the grinding-machine and wheel manufacturer's specifications. Never exceed the maximum operating speed marked on the grinding wheel.

Filed in: grinding-wheel-selection
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