CBN for HRC 45+ · PCD for Aluminum & Non-Ferrous

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CBN and PCD Inserts for Hard Turning and Aluminum

Superhard cutting inserts for the two jobs coated carbide cannot hold: cubic boron nitride CBN inserts and PCBN inserts turn hardened steel, chilled cast iron and sintered alloys from HRC 45 upward, where they can finish a hardened part in one pass instead of grinding it. Polycrystalline diamond PCD inserts, PCD end mills and PCD milling cutters finish aluminum, copper, plastics and composites at high speed without built-up edge. Send the material, hardness and operation and we quote the grade, edge preparation and starting cutting data.

CBN turning inserts and PCBN inserts for hardened steel above HRC 45
PCD turning, grooving and PCD milling cutters for aluminum and non-ferrous
Edge preparation — chamfered, honed or polished — matched to the cut
Dry and minimum-lubrication cutting for hard turning
Grades for continuous, interrupted and high-speed finishing passes

Convert Hardness Values

Quotes within hours — email or WhatsAppWorldwide shipping from Guangzhou, China

CBN and PCD: two superhard materials, two different jobs

Superhard inserts are made from the two materials next to diamond on the hardness scale, and they exist for the two jobs ordinary carbide cannot survive: cutting material that is almost as hard as the tool itself, and finishing soft, sticky material without the edge wearing or grabbing. Cubic boron nitride — CBN — is a sintered material with a low affinity for iron, which is what makes it the standard tool for hardened steel, chilled cast iron and sintered alloys. Polycrystalline diamond — PCD — is harder still, but reacts chemically with ferrous material at cutting temperature, so it is used on non-ferrous work: aluminum, copper, brass, composites and plastics.

The hardness band is where the decision starts. Hardened tooling, dies, bearings and wear parts typically sit between HRC 45 and HRC 65, and that is the band where coated carbide stops being economic and CBN starts to pay. The superhard premium is real, so the calculation is cost per finished part: a CBN insert that replaces a grinding operation, or that holds a tolerance without re-setting the part, earns its price on the first batch.

That is also why hard turning can replace grinding. A single-point CBN tool reaches surface finishes comparable to a ground surface and holds size and form while it does it, in the same setup the part is already in — no transport, no fixturing, no wheel to dress. The trade is geometry: hard turning follows a tool path, so features that only a formed wheel can produce still belong to the grinder.

Which material for which job

CBN — hardened steel, chilled iron, sintered alloys; HRC 45 to 65.
PCBN — the polycrystalline form: interrupted and high-speed hard turning.
PCD — aluminum, copper, brass, plastics, composites.
PCD milling and end mills — profiling and facing non-ferrous at speed.
Not for steel — PCD reacts with iron; use CBN instead.

Superhard Insert Types

CBN, PCBN and PCD inserts, end mills and milling cutters

CBN Turning Inserts

Solid or tipped CBN, negative or positive

Hardened steel HRC 45+

A CBN turning insert cuts hardened steel in a single pass where a coated carbide insert would fail within seconds — the material is almost as hard as the insert. Supplied in the standard turning geometries so an existing holder takes it, with grades chosen for continuous turning or interrupted cuts.

PCBN Inserts

Polycrystalline cubic boron nitride

Continuous to interrupted

A sintered layer of cubic boron nitride on a carbide base — thermally stable, so the insert takes interrupted cuts and high-speed hard turning, holding hardness at temperatures where any ferrous-cutting carbide has already given up.

PCD End Mills

Solid or tipped PCD cutting edge

Aluminum, composites

A PCD end mill brings diamond-hardness to profiling, slotting and pocketing in aluminum and composites, holding mirror finish and holding size across production runs that would wear a coated carbide tool out weekly.

PCD Milling Cutters

Indexable PCD tips in a body

High-speed finishing

For facing and shoulder milling in non-ferrous work, a PCD milling cutter runs at ultra-high speed with no built-up edge, so the surface comes off clean and the same insert keeps cutting shift after shift.

PCD Turning & Grooving

Diamond-tipped turning and grooving

Fine finish, non-ferrous

The finishing answer for aluminum, copper, brass and composites: the edge stays sharp at speed and does not weld to the chip, so the finish is a function of the feed, not of the tool wear.

Polycrystalline Diamond Tools

Special geometries to drawing

Special and production parts

Polycrystalline diamond tools beyond the standard insert range — special profiles, cut-off forms, grooving and custom geometries ground to a drawing — cover the production parts where a stock insert geometry does not fit the feature.

Diamond-coated solid end mills sit in the solid round tool family rather than here — a coated carbide body with a diamond film — and we quote those alongside the carbide end mill range when the job is graphite, composites or abrasive non-ferrous work.

Technical Specifications

Superhard Grade Selection Guide — CBN vs PCD, Edge Prep and Cutting Process

CBN for Hard Turning

HRC 45 upward — one pass instead of grinding

Hardened steel, chilled cast iron, sintered alloys and hard coatings all cut cleanly with CBN at speeds and feeds a grinding wheel could only match at a fraction of the cycle time.

PCD for Aluminum and Non-Ferrous

Diamond edge, ultra-high-speed finishing

Aluminum, copper, brass, plastics and fibre-reinforced composites finish at high speed with no built-up edge, holding Ra and size across long production runs.

When Not to Use Superhard

Carbide, cermet or ceramic may do the job for less

Below about HRC 45, coated carbide turns the part more cheaply. Above it, ceramic or coated carbide can still be viable in continuous cuts — CBN and PCD are the tools for hardness, speed and finish that others cannot hold, not a default upgrade.

Parameter	Technical Details / Standard Values
CBN or PCD — the material decision	CBN cuts ferrous material: hardened steel, chilled iron, sintered alloys and hard coatings, because it has a low affinity for iron. PCD is harder still but reacts chemically with iron at cutting temperature, so it is used on non-ferrous work — aluminum, copper, brass, composites and plastics — and never on steel. The workpiece material decides the family before any geometry question is asked.
Hardness band and cutting data	Hardened steel from HRC 45 to about HRC 65 — the band where hardened tooling, dies and bearings usually sit — is CBN territory. Below HRC 45, coated carbide usually turns the part more economically; the superhard premium only pays where the material defeats the cheaper tool. Cutting speeds run several times higher than carbide, with light depths of cut: hard turning is a finishing process, not a stock-removal one. PCD on aluminum and composites runs at very high speed with fine feeds, where edge sharpness and finish are the specification.
Edge preparation — chamfer, hone or polish	CBN edges are normally chamfered or honed: a tiny negative land and a controlled hone remove the fragile sharp edge that would chip on a hardened surface, at the cost of some cutting force. PCD edges are kept sharp and polished for aluminum so the chip does not weld to the edge. The right preparation depends on whether the cut is continuous, interrupted, or a finish pass where surface integrity matters.
Dry cutting or coolant	Hard turning with CBN is normally run dry or with minimal lubrication: the heat leaves with the chip, and a coolant shock can crack the edge instead of cooling it. PCD on aluminum is the opposite — flood coolant or a strong air blast keeps the chip moving and the edge cool. Match the process to the material rather than to habit.
Machine rigidity and setup	Superhard inserts cut at hardness levels where any vibration shows up immediately as chipping: the machine must be rigid, the setup short and the tool holder tight. A CBN insert run on a loose setup will not outlast carbide — the insert is capable, but it cannot absorb the movement a soft tool would tolerate.
Life, regrinding and economics	A CBN or PCD insert is a premium tool, so the calculation is cost per finished part: if it replaces a grinding operation or keeps a dimension without re-setting, it usually wins. CBN and PCD inserts can be reground a limited number of times, and the usable edge count and regrind policy are worth agreeing before a production order is placed.

Hardness alone does not pick the grade — the operation, the interruption and the finish requirement do. Send the material, hardness, operation and drawing and we quote the CBN or PCD grade, the edge preparation and starting cutting data.

Applications

Where CBN and PCD inserts earn their cost

Hardened Steel above HRC 45

Dies, bearings, hardened tooling and wear parts in the HRC 45 to 65 band: CBN turns them in one pass, holding the finish a ground surface used to be the only way to get.

See Application

Chilled Cast Iron

Chilled and hardened cast iron defeats most insert grades at the skin: a CBN grade with the right edge preparation takes the chilled layer in the same pass as the softer body behind it.

See Application

Aluminum, Copper and Composites

PCD edges stay sharp and chemically inert in aluminum, copper, brass, carbon fibre and plastics — mirror finishes at high speed without the built-up edge every other grade suffers.

See Application

Send the material, its hardness and the operation — continuous or interrupted — and we reply with the grade, edge preparation and starting cutting data rather than a catalogue page.

Grades & Sizes

CBN and PCD insert families, edge preparation and hardness bands

Insert family	Edge & hardness band	Common size	Typical application
CBN turning inserts	Chamfered or honed edge, HRC 45–65	Standard turning geometries (CNMG / DNMG / VNMG / WNMG forms)	Hardened steel finishing and hard turning instead of grinding
PCBN inserts	Polycrystalline CBN layer on a carbide base	Standard turning geometries, to holder and feature	Interrupted and high-speed turning of hardened material
PCD turning and grooving inserts	Sharp, polished diamond edge	Standard turning and grooving forms	Aluminum, copper, brass and composite fine finishing
PCD end mills	Diamond edge, high positive rake	To the cutter and workpiece feature	Profiling, slotting and pocketing in aluminum and composites
PCD milling cutters	Indexable or tipped diamond edges	To the cutter body and face width	High-speed facing and shoulder milling in non-ferrous work
Special polycrystalline tools	Ground to drawing	To drawing — profiles, cut-off and special forms	Production parts where a stock geometry does not fit

Superhard inserts follow the same ISO 1832 designation positions as other indexable inserts; the grade and the edge preparation are appended by the tool maker for the material and the cut.

Sizes are quoted against the holder and the feature rather than from a single stocked list, because superhard inserts are specified by hardness band, edge preparation and geometry together: a CNMG-form CBN insert for continuous hard turning and a PCBN insert for an interrupted surface may share dimensions but not a grade. Tell us the insert code you run now, or the holder and the feature, and we match the family, the preparation and the grade — including special polycrystalline forms ground to a drawing where a stock geometry does not reach the feature.

Machining reference tools

Why Buyers Work With InsertCore

Sourcing, verification and support around your hard turning programme

Grade, edge prep and hardness band as quoted

Every batch arrives with the grade, edge preparation and geometry that were quoted for your hardness band. Dimensional reports and material certificates are available on request for incoming inspection.

Special superhard geometries

Non-standard edge preparations, special profiles, cut-off and grooving forms in CBN and PCD are quoted to your drawing or 3D model — including trial inserts before a production order.

Sourced and QC-verified supply, one contact

We are a trading operation, not a production plant: superhard inserts are sourced from vetted tooling partners and checked before dispatch, and the same contact stays with your programme from quote to delivery.

Quote turnaround

Within hours

Channels

Email + WhatsApp

Shipping

Worldwide, tracked

Quantities

Trial to bulk

Questions Buyers Ask

Hard turning, grade and edge preparation questions, answered

CBN, ceramic or coated carbide — which one for hardened steel?

Below about HRC 45, coated carbide turns hardened steel more cheaply than any superhard grade. Between roughly HRC 45 and HRC 55 a ceramic insert can be the economic middle ground in continuous cuts, and CBN takes over where the material is harder, the cut is interrupted, or the finish and dimensional control have to be held without a grinding operation. The practical test is cost per finished part, not insert price.

When should I use PCD instead of CBN?

When the workpiece is non-ferrous. PCD is harder than CBN but reacts chemically with iron at cutting temperature, so it is the wrong tool for steel — even soft steel — and the right tool for aluminum, copper, brass, plastics, carbon fibre and other composites, where it finishes at high speed without built-up edge.

Can hard turning replace grinding?

In many hardened parts, yes. CBN turning reaches surface finishes comparable to grinding while holding size and form, and it does it in one setup on the lathe — which removes the transport, fixturing and wheel dressing that a grinding operation carries. The limits are the geometry: hard turning follows a single-point tool path, so features a wheel must generate by form may need a different approach.

Should I cut dry or with coolant?

Hard turning with CBN is usually run dry or with minimal lubrication: the chip carries the heat away, and coolant applied to a hot CBN edge can shock and crack it. PCD on aluminum is the opposite — flood coolant or a strong air blast clears the soft chip and keeps the edge cool. Follow the process rather than the habit.

Where does the HRC 45 figure come from?

It is the practical entry point where the hardened-material premium starts to pay: hardened tooling, dies and bearing components typically sit in the HRC 45 to 65 band, and that is where coated carbide starts to fail and superhard grades take over. Hardness alone is not the whole answer — an interrupted cut at HRC 50 is harder on the edge than a continuous cut at HRC 55 — which is why we ask for the operation as well as the hardness.

Does the cutting edge need a chamfer or a hone?

A CBN edge usually does: a small chamfer or hone removes the fragile sharp edge that would chip on a hardened surface, and it is the standard preparation for hard turning. As the cut becomes more interrupted, the preparation gets stronger. PCD edges stay as sharp and as polished as possible for aluminum and composites, because there the risk is adhesion, not chipping.

How do you control superhard insert quality?

CBN and PCD inserts are sourced from vetted tooling partners and inspected before dispatch. Grade, edge preparation, geometry and dimensions are confirmed against the quotation, dimensional reports and material certificates are supplied on request, and each shipment is packed for transit. If a batch does not perform as confirmed, send the batch reference and your measurements and we will put it right.

What information should I send for an accurate CBN or PCD insert quote?

The workpiece material and its hardness (in HRC or HB), the operation and whether the cut is continuous or interrupted, the machine and the holder, the geometry or insert code you run now, and the quantity. With those points we can quote the grade, edge preparation and geometry instead of a near-match that fights the cut.

How fast can I get pricing, and how are orders shipped?

Quotations are normally issued within hours during business hours — email and WhatsApp reach us directly. Orders ship worldwide from Guangzhou, China with tracking, and payment terms are stated on the quotation. Trial quantities and mixed-item orders are both welcome, which matters with superhard inserts where a grade trial de-risks the production order.

Get your CBN or PCD insert quote within hours

Send the material, its hardness, the operation and the holder — you get the grade, edge preparation and starting cutting data, with pricing and availability.

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