ISO 1832 Codes · APMT / SEKT / RDMT · Carbide, PCD & CBN Grades

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Milling Inserts for Face, Shoulder and Slot Milling

Indexable milling inserts for CNC cutter bodies — square and shoulder, face mill, round, slotting, roughing and wiper geometries in coated carbide, PCD and CBN grades. Square milling inserts in the common APMT 1604 and 1135 sizes, round milling inserts for profiling, and shoulder milling inserts with the corner radius, chipbreaker and grade your cutter pocket takes. Send the cutter body, insert code and workpiece material and we quote the insert, grade and starting cutting data.

Square, shoulder, face mill, round, slotting and wiper insert geometries
Coated carbide, PCD and CBN grades for steel, stainless and aluminum
APMT, SEKT and RDMT families in common IC sizes and corner radii
Negative double-sided and positive single-sided edge geometry
Roughing and heavy-feed chipbreakers through to finishing wipers

Milling Speed & Feed Data

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

How indexable milling inserts work: clamping, edge geometry and grade

A milling insert is a small piece of carbide, ceramic, CBN or diamond, shaped to a cutting geometry and clamped into a steel cutter body. That is the whole idea behind indexable milling: the expensive part is the insert edge and the cheap part is the body, so when an edge wears out you index it to the next corner — or swap the insert — instead of replacing or regrinding a whole cutter. The body decides the lead angle, the rake and the depth of cut the insert will see; the insert decides the edge, the chip and the surface the cut leaves behind.

Edge geometry is where the job is won or lost. A negative insert has no clearance ground into it, so both faces can be used and the edge is strong — ideal for steel on a rigid machine. A positive insert has clearance ground in, cuts more freely and suits thin walls, small machines and soft material. The corner radius then trades finish against strength: a small radius finishes better, a larger one survives interrupted cuts, and the chipbreaker behind the edge decides whether the chip leaves the cut or gets recut under the cutter.

Grade and coating place the insert on the heat and wear map: coated carbide covers the bulk of steel, stainless and iron work, uncoated tough grades hold up in abrasive castings, polished inserts and PCD cut aluminum without pick-up, and CBN or ceramic inserts take hardened material and interrupted surfaces. Choose the geometry for the operation, the radius for the finish, then the grade for the material — and the insert lasts as long as the cutter body that holds it.

Milling Insert Types

Milling insert geometries — square, shoulder, round, slotting and wiper

Square & Shoulder

Square milling inserts, 90° corner

Shoulder and square-shoulder cutters

The workhorse of the pocket: a 90° cutting corner squares up a shoulder and takes the load of a heavy radial cut. APMT and SEKT families cover most cutter bodies, from 6 mm IC for small cutters up to 16 mm IC for production face mills.

Face Mill Inserts

Square, octagonal or round in a face cutter

Facing and flat surfaces

The flat-surface geometry: several edges around a body, one at a time in cut, with a lead angle that thins the chip and spreads the load. Wide cutters with fine-pitch bodies finish a large face in one pass, where a solid end mill would have to step over.

Round Inserts

Full radius, all-direction cutting

Profiling and radius work

Round milling inserts have no corner to break down: the cutting edge is continuous, so the insert survives interrupted cuts, scale and heavy profiling that would chip a square corner. Round milling inserts also leave a strong edge for roughing castings and blasting through hard material.

Roughing & Heavy Feed

Strong edge, high-feed chipbreaker

Stock removal

Roughing is a geometry decision before it is a grade decision: a strong edge geometry with a reinforced corner radius and a chipbreaker that folds the chip takes depth of cut and feed that a finishing insert cannot. Run it hard, then change inserts for the finishing pass.

Slot & Grooving

Narrow width, straight-sided

Slots, keyways and T-slots

Cuts a groove to width in one pass rather than interpolating it: the insert is often double-ended and ground so the sides of the slot stay parallel at depth. Slot milling tools are quoted to the groove width and depth rather than to a nominal insert size alone.

PCD Milling

Polycrystalline diamond tips

Aluminum and non-ferrous

Diamond hardness applied to aluminum and non-ferrous work: mirror finishes at high speed, no built-up edge, and tool life measured in months rather than edges. Used on cylinder heads, gearbox housings and any aluminum part where the finish is a specification.

Finishing & Wiper

Small radius, wiper flat

Surface finish

A ground flat behind the corner radius irons the machined surface at the same feed per tooth, so finishing passes reach a lower Ra without slowing the cycle down. Pair it with a fine-pitch body and keep the depth of cut shallow.

Cutter Bodies

Shell, arbor and end mill bodies

Insert pocket and clamping

Inserts only work in the geometry they were designed for: the cutter body sets the axial and radial rake, the lead angle and the clamping that holds the insert. We match cutter bodies and inserts as a pair — shell mills, arbor-type face mills and indexable end mills — so the pocket and the insert code agree.

Body and insert are one system: shell mills, arbor-type face mills and indexable end mills each take their own pocket geometry, and the safest way to replace an insert is to match the code and the pocket rather than the shape alone. Send the body reference with the order and we check the pairing.

Technical Specifications

Milling Insert Selection Guide — Geometry, Code, Grade & Cutting Data

Steel & Alloy Steel (ISO P)

Coated carbide, negative double-sided

A TiAlN or AlCrN coated P-grade insert on a double-sided negative geometry gives the cheapest edge per corner on steel; use a strong chipbreaker for roughing and a wiper for the finishing face.

Stainless & Titanium (ISO M / S)

Positive edge, sharp, AlTiN

Stainless and titanium want a sharp positive edge and a hard coating: less rubbing, less work hardening, and a geometry that shears instead of pressing the material into the flank.

Cast Iron (ISO K)

Tough K-grade, uncoated or TiCN

Cast iron is abrasive and the cut is interrupted, so a tough grade with a strong edge survives scale and sand where a hard coated insert would chip.

Aluminum & Non-Ferrous (ISO N)

Polished positive edge or PCD

Soft metal needs edge sharpness and rake: an uncoated polished insert runs clean and a PCD milling cutter holds mirror finish and edge life at production speed.

Roughing to Finishing

Geometry change, not speed change

A roughing chipbreaker at depth of cut removes the stock, then a wiper or fine-radius insert finishes the face at the same feed per tooth. Changing inserts costs less than fighting one geometry through both jobs.

Hardened & Interrupted Cuts (ISO H)

CBN or ceramic, rigid setup

Hardened steel and interrupted surfaces load a milling edge differently: CBN and ceramic inserts hold the hardness, with a rigid setup and shallow depths keeping the edge from breaking down.

Parameter	Technical Details / Standard Values
Insert code and what each position means	First letter — shape: A parallelogram (85°), S square (90°), R round, T triangle, W trigon. Second letter — clearance angle: N 0° for a negative insert, P 11°, C 7°, B 5° for positive geometries. Third letter — tolerance class: M is the pressed standard and G is precision ground (needed when the corner must repeat between indexings). Fourth letter — clamping and chipbreaker: T for a hole with a chipbreaker on one face, G for a hole with chipbreakers both sides. The number group then gives IC size, thickness and corner radius, in metric or in the ANSI B212.4 inch form used by US catalogues.
Edge geometry — negative or positive	A negative insert (second letter N, zero clearance) is double-sided: more usable corners per insert and a stronger edge, but it cuts with a higher force and needs a rigid setup. A positive insert has clearance ground in, cuts freely and suits thin-walled parts and smaller machines — at the cost of one face and fewer corners.
Corner radius and what it changes	The corner radius is the finish-versus-strength dial: R0.4 gives a better surface finish on a finishing cutter, R0.8 is the general-purpose choice, and R1.2 to R2.0 strengthen the corner where the cutter takes interrupted or heavy cuts. Match the radius to the operation, not to what happens to be in stock.
Chipbreaker geometry	The chipbreaker is what makes a chip break instead of snaking across the table: a narrow groove and a high land for steel, a wider open form for aluminum and stainless so the chip leaves the pocket instead of recutting. It is part of the insert designation, not a separate choice — but tool makers append their own suffix for it.
Cutter body, lead angle and pitch	A 45° lead angle thins the chip and moves load along the edge; a 90° shoulder cutter squares the wall but loads the corner more. Fine pitch puts more inserts in the same body for higher feed at a smaller depth of cut, coarse pitch does the opposite. Pocket size fixes the insert family, so quote body and insert together.
Depth of cut and feed per tooth	Milling inserts are rated for a chip thickness, and the entry angle decides how much of the feed per tooth each edge actually sees — which is why the same insert runs hard on a 45° cutter and more carefully on a 90° shoulder mill. Start conservative, then push feed rather than depth when the machine allows it.
Climb or conventional milling	Climb milling feeds the cutter into the material so the tooth starts thick and ends thin: less rubbing, better finish and longer edge life on rigid machines with backlash-free drives. Conventional milling reverses that and is used when the machine or the setup cannot take climb. On a CNC, climb is the default; on a worn manual machine it often is not.
Cooling and dry milling	Coated carbide tolerates dry milling on steel and cast iron, which avoids the thermal shock that can crack an edge. Aluminum wants flood coolant or strong air to clear chips; stainless and titanium want coolant aimed at the cutting zone; PCD and CBN prefer a clean, well-cooled or deliberately dry process according to the operation.
Indexing and edge life judgement	An insert is finished when the wear land widens across the corner, the surface finish drops off or the power draw climbs — index it then, before it breaks and takes the cutter pocket with it. Keep the used edges and the batch reference: if a batch wears out of pattern, the evidence is what fixes it.

Running a cutter body with a pocket outside the common families, or need a corner radius the catalogue does not list? Send the body reference and the drawing — inserts, spare screws and bodies can be quoted as one package, in trial quantities first.

Applications

Which milling insert for which material

Steel & Alloy

Coated carbide inserts in a negative geometry cover mild to alloy steel at every depth of cut: rough with a strong chipbreaker, finish with a wiper, and change the insert rather than the process.

See Application

Stainless & Titanium

A sharp positive edge with an AlTiN coating and coolant aimed at the cut: stainless and titanium work-harden under a rubbing edge, so the geometry that shears cleanly is the one that lasts.

See Application

Cast Iron & Non-Ferrous

Tough K-grades handle the abrasive, interrupted cut of castings; for aluminum and non-ferrous, polished positive inserts and PCD milling cutters hold finish and edge life at speed.

See Application

Send the cutter body, the insert code you run now and the workpiece material — we reply with the insert, chipbreaker and grade that fit, plus starting cutting data instead of a catalogue page.

Insert Codes & Sizes

Milling insert codes, sizes and corner radii — ISO 1832 and ANSI B212.4

Insert family	Code & edge geometry	Common size (IC · radius)	Typical application
Square & shoulder (APMT, SEKT)	A / S shape, P 11° or N 0° edge, M or G tolerance	APMT1135 IC 6.35 mm · APMT1604 IC 9.525 mm (thickness 4.76 mm)	90° shoulders and general square-shoulder milling
Face mill inserts	S or O shape, negative double-sided	IC 12–16 mm, corner radius 0.8–2.0 mm	Facing large flat surfaces in one pass
Round inserts (RDMT, RCMT)	R shape, full radius edge	IC 10–16 mm, round edge	Profiling, radius work and interrupted cuts
Roughing and high feed	Strong edge, deep chipbreaker	IC 12–16 mm, radius 1.2–2.0 mm	Heavy stock removal ahead of the finishing pass
Slot and grooving inserts	Narrow width, parallel sided	Groove width and depth to drawing	Slots, keyways and grooves in one pass
Wiper and finishing	Small radius with a wiper flat	IC 12–16 mm, radius 0.4–0.8 mm	Surface finish at production feed rates
PCD milling inserts	Diamond-tipped positive edge	To the cutter body and workpiece feature	Aluminum and non-ferrous, high-speed finishing
CBN and ceramic inserts	Hard-material tip or solid ceramic	To the cutter body and workpiece feature	Hardened steel and interrupted hard surfaces

ISO 1832 gives the seven mandatory designation positions; ANSI B212.4 is the inch equivalent used by US catalogues. IC = inscribed circle. Rows marked to the cutter body are supplied against the pocket geometry.

Insert sizes are quoted as an inscribed circle and a corner radius, and the two together set what the insert can do: an APMT1604 at 9.525 mm IC with an R0.8 corner is the general-purpose square milling insert for shoulder and face work, an APMT1135 at 6.35 mm IC suits smaller cutters and lighter cuts, and the round and octagonal families trade corner strength for finish. Metric and inch sizes are both stocked — a 3/8 in insert and a 9.525 mm insert are the same pocket — so tell us the code on the insert you run now and we match it, including the chipbreaker suffix.

Machining reference tools

Why Buyers Work With InsertCore

Sourcing, verification and support around your milling insert programme

Insert code, grade and coating as quoted

Every batch arrives with the insert code, corner radius, chipbreaker and grade that were quoted. Dimensional reports and material certificates are available on request for incoming inspection.

Cutter bodies and custom inserts

Non-standard corner radii, special chipbreaker forms, cutter bodies to a drawing and insert-and-body packages are quoted together — including trial quantities before a production order.

Sourced and QC-verified supply, one contact

We are a trading operation, not a production plant: milling 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

Insert code, geometry and cutting data questions, answered

What is climb milling and conventional milling — which should I use?

Climb milling feeds the cutter so each tooth starts at maximum chip thickness and thins as it exits: less rubbing, better finish, longer edge life, but the machine needs a backlash-free drive and a rigid setup. Conventional milling is the reverse and is what a worn manual machine or a loose setup needs. On a modern CNC, climb is the default for almost every insert.

Shell mill or face mill — what is the difference?

Both are indexable bodies that present inserts to a flat face; a face mill is the general family and a shell mill is the arbor-mounted form of it, with a bore that slides onto a stub arbor and a drive key taking the torque. The practical question is which body your spindle and arbor take, and how wide a cut you need in one pass — the inserts are usually shared between them.

Face mill or end mill for a flat surface?

An end mill cuts a narrow width with the side and end of a solid tool — good for pockets, shoulders and edges, and it can plunge and ramp. A face mill covers a wide flat area in one pass with indexable inserts, at a lower cost per edge once the surface is large. Use the end mill for features, the face mill for faces.

How do I read an insert code such as APMT1604?

Four letters then numbers. A is the shape (a parallelogram with an 85° corner), P is the clearance angle (11°, a positive insert), M is the tolerance class (pressed, the standard class) and T is the fixing and chipbreaker position (a countersunk hole with a chipbreaker on one face). The numbers give the size: 16 is the IC size class (9.525 mm inscribed circle), 04 the thickness (4.76 mm) and the trailing figure the corner radius, usually 08 for R0.8.

Roughing or finishing — do I need two different inserts?

Yes, in most production work. A roughing insert carries a strong edge and a deep chipbreaker to take depth of cut and feed, while a finishing insert — a small corner radius or a wiper geometry — delivers the surface at the same feed per tooth. Fighting one geometry through both jobs either breaks the finishing edge or leaves a rough surface; changing inserts costs seconds.

Where do round inserts make sense?

Wherever the edge is at risk or the cut is interrupted: round inserts have no corner to chip, the load distributes along a continuous edge, and the same insert profiles, ramps and faces. Castings, scale, hard spots and heavy profiling suit round inserts; a square or shoulder geometry wins when the feature needs a defined 90° corner.

How do you control milling insert quality?

Milling inserts are sourced from vetted tooling partners and inspected before dispatch. Insert code, corner radius, chipbreaker, grade and coating 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 milling insert quote?

The cutter body reference or its pocket specification, the insert code you run now (or a photo of the insert and the pocket), the workpiece material and hardness, the operation and depth of cut, and the quantity. With those five points we can quote the insert, chipbreaker and grade that fit the body, rather than a near-match that needs the pocket modified.

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 — inserts, cutter bodies and a spare set of screws on one PO — are both welcome.

Get your milling insert quote within hours

Send the cutter body, the insert code you run and the workpiece material — you get the insert, chipbreaker, grade and starting cutting data, with pricing and availability.

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