Sandviks CNMM 644-PR 4425 CNMM 19 06 16-PR 4425 Carbide Turning Insert CNMM 190616 Sandviks CVD Coated 80 Degree Diamond R1.6 Roughing Insert for Steel CNC TOOLS

Overview
The CNMM 644-PR 4425 — ISO designation CNMM 19 06 16-PR 4425 — is a heavy-duty turning insert for roughing steel on large, rigid machines. Its 19.05 mm inscribed circle and 6.35 mm thickness put it in a different class from the 12 mm inserts used for general turning: more carbide under the edge, more heat capacity, and far greater resistance to impact.

The insert is single-sided: the chipbreaker is on one face only, giving two effective cutting edges. That is a deliberate design choice for roughing, where the priority is a thick, supported edge rather than the lowest cost per edge. If your operation needs four or six edges, a double-sided CNMG or TNMG is the correct family — this insert trades edge count for strength.

PR is sandvikss's roughing geometry. Its land and groove are proportioned for heavy feeds and depths of cut, including cuts through casting or forging skin where the edge meets interrupted engagement. R1.6 adds further edge strength at the corner, which is where roughing inserts usually fail first.

Grade 4425 is GC4425 — sandvikss's current-generation P25 steel grade, CVD-coated with TiCN + Al₂O₃ + TiN and built on second-generation Inveio® technology. It balances wear resistance against toughness across a wide application range, which suits heavy roughing where both flank wear and edge breakage are live risks.

• 19.05 mm IC, 6.35 mm thick — heavy section for high depth of cut and impact resistance.
• Single-sided, 2 cutting edges — chipbreaker on one face; strength is prioritised over edge count.
• PR roughing geometry — designed for high feed and deep cut, including skin and scale.
• R1.6 corner radius — strong corner for roughing; not intended for tight profiles.
• GC4425 (P25), CVD TiCN + Al₂O₃ + TiN — current-generation grade, second-generation Inveio® coating.
• 80° rhombic, 0° clearance — rigid clamping, 100° corner strength for facing and OD roughing.
• Cylindrical central hole — secure, repeatable clamping on heavy cuts.
• ISO 13399 dimensioned — IC ±0.10 mm, thickness ±0.13 mm, edge position ±0.15 mm.

Both designations describe the same insert. Buyers in North America usually quote 644, while European and Asian buyers quote 19 06 16 — check both when matching a requirement.

PR is for metal removal rate, not surface finish. The geometry opens the chip groove and thickens the land so the edge survives high feed per revolution and deep cuts.

• depth of cut is large and constant, typically on forged, cast or pre-machined blanks;
• the first pass must cut through skin, scale or an interrupted surface;
• machine power and rigidity allow feeds in the roughing range;
• the priority is removing volume quickly before a finishing pass with another insert.

• the operation is finishing — the edge radius and land will smear rather than cut cleanly;
• the part is slender or the setup is weak — roughing forces will deflect it;
• the machine lacks power or the fixture lacks rigidity;
• the material is stainless, cast iron or aluminium — different geometries apply.

GC4425 is sandvikss's current P25 steel grade, not a legacy grade. Three things follow from that for a buyer:

• Availability — it is the grade sandvikss actively positions for P25 steel turning, so supply and lead time are more predictable than older generations.
• Coating — second-generation Inveio® CVD with TiCN + Al₂O₃ + TiN; the documented benefit is more uniform crystal orientation in the alumina layer, which raises wear resistance.
• Range — P25 sits between finishing (P15) and tough roughing (P35), which is why GC4425 is used across mixed roughing and medium turning rather than one extreme.

sandvikss positions GC4415 (P15) alongside it for higher heat resistance and GC4405 for the hardest, most heat-intensive cuts. If the application is at either extreme, those grades are the correct neighbours — not a different make of insert.

• Heavy roughing of large steel shafts, rolls, axles and hubs
• Forging and casting blanks where the first pass cuts skin and scale
• Railway wheels and heavy transport components
• Large flanges and rings on horizontal lathes
• Interrupted OD and facing cuts where edge strength decides tool life

• small parts, light finishing and tight profile work — use a 12 mm IC insert with a finishing geometry;
• low-power or low-rigidity machines — the insert will not reach its feed range;
• non-steel materials — select the matching grade and geometry.

Reference feed ranges for the CNMM 190616 geometry in alloy steel at average stability, from a public insert database:

These are geometry-level reference values, not a sandvikss recommendation for grade 4425. They also assume adequate machine power and rigidity — a 19 mm IC insert at 1 mm/rev demands both. Confirm vc and final feed against the actual material, machine and Fixture before production, and treat the first part as a trial cut.

CNMM 190616 inserts require holders with a 19-size seat (insert IC 19.05 mm), from families such as MCLNR/L and MCMNN. Heavy-duty holders for this insert size normally use 32 mm or larger shanks. Confirm the exact holder code, approach angle and hand before ordering — the insert alone cannot be mounted, and an undersized holder will not survive the feed range this insert is designed for.

• Order by ISO designation: CNMM 19 06 16-PR 4425, or ANSI CNMM 644-PR 4425
• Always state the chipbreaker (PR) and grade (4425) — CNMM 644-PR 4405 and CNMM 644-QR 4425 are different items.
• Packing quantity varies by channel; confirm against the actual packing list before publishing a quantity.

How many cutting edges? Two. This insert is single-sided — the chipbreaker is on one face only.

Why single-sided instead of double-sided? For heavy roughing the edge needs a thick, fully supported section. A single-sided design allows that; the trade-off is fewer edges per insert.

Is CNMM 644 the same as CNMM 19 06 16? Yes — 644 is the ANSI (inch) description, 19 06 16 is ISO. Same insert.

What is the difference between PR and QR? Both are roughing-oriented geometries but they are different items with different edge preparation and chip control. Specify PR if PR is what the process was set up for; do not substitute without a trial.

Is 4425 an old grade? No. GC4425 is sandvikss's current-generation P25 steel grade, introduced with second-generation Inveio® coating.

Can it be used for finishing? Not recommended. Use a smaller IC insert with a finishing geometry for the final pass.