Uncoated Carbide Inserts

Uncoated carbide inserts are cutting tools made from cemented carbide that do not have any additional coatings applied to them. They are used for machining applications such as turning, boring, grooving, and cutoff operations.

Overview of uncoated carbide inserts

Uncoated carbide inserts provide good wear resistance and machining performance for many applications. They are more economical compared to coated carbide inserts but may not achieve the same level of tool life or performance in very demanding cutting operations.

Advantages of Uncoated Carbide Inserts:

  • More economical than coated inserts
  • Sufficient tool life and cutting performance for many applications
  • Can withstand high cutting speeds and temperatures
  • Good all-around inserts usable for roughing and finishing

Disadvantages of Uncoated Carbide Inserts:

  • Not as wear-resistant as coated inserts in very tough machining
  • May experience crater wear, edge breakdown in continuous cuts
  • Limited suitability for light depths of cut below 0.5mm

Key Properties:

  • Made of cemented tungsten/titanium carbide
  • Hardness of 86 to 93.5 HRA (Rockwell A scale)
  • Withstand high temperatures up to 1000°C
  • Heat resistance, wear resistance properties

Uncoated carbide is ideal for interrupted cuts and medium to heavy machining at low speeds where high edge strength is needed. For very high-speed machining or finishing passes, coated carbide often performs better.

Types of Uncoated Carbide Insert Grades

There are several uncoated carbide grades used for inserts, classified by material composition and application:

GradeDescriptionKey PropertiesApplications
C1 to C5Straight tungsten carbidesToughness, shock resistanceInterrupted rough cuts
P10 to P50Mixed/medium grainsBalance of strength and toughnessGeneral machining
M10 to M40Fine micrograin carbidesVery wear-resistant, heat resistantFinishing to semi-finishing

The grain size typically decreases from C to M grades while hardness and wear resistance increases. Finer grains improve surface finish but are more prone to chipping.

ISO Standard Grades

Many uncoated carbide inserts conform to ISO standardized grades based on composition and application area:

ISO GradeDescription
ISO C720For steel turning, medium resistance, interrupted cuts
ISO C750For steel/cast iron, good resistance, larger depths
ISO K10High hardness/toughness for hard materials
ISO K20Very high heat/wear resistance grade
ISO P10-P50Universal/general machining grades
ISO M10-M40For finishing operations requiring good surface finish
uncoated carbide inserts

Uncoated Carbide Insert Geometry Options

Uncoated carbide inserts come in many different standard shapes, sizes, and geometries to suit various machining needs:

Insert Shapes:

  • Triangle – General purpose shape, 3 cutting corners
  • Square – Gives strength, used for feed heavy apps
  • Round – Used for heavy depths, extra strength
  • Rhombic – Combination of square and triangle shape
  • Special shapes – Trapezoid, parallelogram, polygon etc.

Chipbreaker Geometries:

  • Flat face – General machining, light finishing
  • Grooved face – General machining, medium depths
  • Wiper face – Finishing cuts, good surface finish
  • Special chipbreakers – Hi-feed, hi-speed, hi-positive etc.

Nose Radii Options:

  • Sharp – Used for feeds below 0.006” per rev
  • Moderate – 0.008”-0.016” feed rates
  • Large radii – Above 0.020” feed per rev

Choosing optimum insert geometry is vital for effective metal removal, good tool life, and desired component finish. The interrelationships between nose radius, feed rates, and cutting speeds must be balanced.

Applications and Suitable Materials

Uncoated carbide performs well for machining harder materials like:

  • Alloy steels, tool steels
  • Cast iron and hardened cast iron
  • Hardened steels, up to 45 HRC
  • Nickel/Cobalt based superalloys
  • Titanium alloys up to Ti-6Al-4V

Carbide grades and insert geometry must match workpiece hardness characteristics and desired surface finish.

Typical components machined with uncoated carbide tooling:

  • Shafts
  • Bushes, sleeves
  • Automotive parts
  • Aerospace components
  • Molds, dies, tooling

Materials NOT Suitable for Uncoated Carbide

  • Non-ferrous materials like Aluminum – require special insert geometries and dedicated carbide grades to prevent insert wear
  • Hard ceramics/composites – require extremely wear-resistant inserts like PCD or CBN

Uncoated Carbide Insert Specifications

Uncoated carbide inserts have established specifications covering inserts dimensions, tolerances, seating platform details etc. to ensure compatibility across tool holders from different manufacturers.

Standard Insert Designations

Inserts follow ISO/ANSI/national standards for the numbering system indicating shape, size, tolerance, hole details etc. Some examples:

Insert DesignationMeaning
CNMG 432C = Shape Code, N = Nose radius, M= Tolerance, G = Thickness, 432 = Inscribed Circle Diameter
DNMX 11 04 08 – PMShape, IC size, Insert thickness, Hole dia & posn, Special feature

Standard Dimensional Tolerances

Insert tolerance grades dictate permitted variations in critical dimensions like thickness, bore diameter/position, seating plane etc.

Tolerance GradeTolerance in mm
IT7 (Precision)Up to 0.013mm
IT8 (High precision)0.018mm to 0.036mm
IT90.036mm to 0.072mm

Tighter tolerances improve seating, performance consistency but increase cost. Standard IT9 tolerance allows acceptable seating for most applications.

Comparative Analysis

Comparison between various uncoated carbide insert types for steel turning applications:

ParameterC6 MicrograinC2 Medium GrainM35 Ultra-fine Grain
CompositionMixed MC+WC94% WCSubmicron WC+TiC+TaC+NbC
Hardness1600 HV1760 HV1830 HV
ToughnessVery HighMediumLow
StrengthMediumVery HighMedium
Thermal ConductivityLowMediumHigh
Tool LifeLongMediumShort
Insert WearAbrasionChippingPlastic Deformation
Finish AchievableMediumMedium-GoodVery Good
Price LevelLowEconomicalHigh
Best Suited ForInterrupted CutsGeneral MachiningFinishing Cuts

For steel turning, the medium grain C2 grade provides the best balance between wear resistance and toughness properties like edge line chipping resistance. M35 ultra-fine grade gives an excellent finish but lacks robustness for interrupted cuts. C6 is sufficiently robust but does not give a comparable finish.

uncoated carbide inserts

Uncoated Carbide Insert Suppliers

All major cutting tool manufacturers offer uncoated carbide inserts under their product range. Some leading uncoated carbide insert suppliers are:

CompanyGrades OfferedInsert Style OptionsEstimated Price Range
Sandvik CoromantC2, C6, M35, P25, K20Triangle, Square, Round, Rhombic$8 – $50 per insert
KennametalKC850, KC925, K313Triangle, Square, Parallelogram$6 – $40 per insert
WIDIACC650, CC625DVTriangle, Round$5 – $30 per insert
IscarIC8150, IC907, IC908Triangle, Square, Round, Rhombic$10 – $60 per insert
Kyocera UnimercoCB20, CB30Triangle, Square$15 – $100 per insert

Prices vary hugely based on insert grade, size, geometry specifics. Bulk order quotes offer considerable cost savings versus individual/small orders.

Uncoated vs. Coated Carbide Inserts

Coated carbide inserts use additional treatment like CVD/PVD TiN, TiCN, TiAlN, AlCrN coatings to impart higher heat/wear resistance.

ParameterUncoated CarbideCoated Carbide
Base CompositionTungsten/Titanium CarbideSame as uncoated
Coating TechnologyNo coatingCVD/PVD TiN, TiCN etc.
Coating ThicknessNA3-5 um typical
Hardness86 to 93.5 HRA92 to 96 HRA
ToughnessVery goodGood
Heat ResistanceUp to 1000°CUp to 1100°C
Oxidation ResistanceMediumVery Good
Tool LifeShorterLonger

At very high cutting parameters, the coated insert’s extra heat protection gives notably longer tool life. However, uncoated carbide has sufficient wear resistance for many general machining applications at lower cost. The choice depends on work material, operating conditions, and finish needs.


Q: What is the typical hardness range for uncoated carbide inserts?

A: Most grades used for uncoated carbide inserts have a hardness range of 1600 to 1900 Vickers, equivalent to ~86 to 93.5 on Rockwell A scale. Finer micrograin compositions can reach higher hardness levels exceeding 2000 Vickers.

Q: How are uncoated carbide inserts secured into tool holders?

A: Nearly all inserts use a clamping system, secured via a top clamp or screw. The insert’s underside/seating platform matches the subtle angle and platform geometry of the tool holder pocket. Proper seating ensures insert stability, accuracy, and safety.

Q: Can uncoated carbide inserts machine aluminum effectively?

A: Uncoated carbide can chemically react with aluminum at high cutting temperatures, causing severe aluminum buildup/welding and rapid insert failure. Aluminum-grade inserts with special geometries and dedicated insert grades/compositions are necessary.

Q: What causes inserts to crack or break during machining?

A: Excessive feeds/depths inducing high cutting forces coupled with inadequate insert toughness/bending strength for the cutting conditions leads to chipping or fractures. A less sharp cutting edge and increased edge prep/honing improves edge line toughness.

Q: How many times can an insert be safely reused by indexing to a fresh cutting edge?

A: Insert geometries with 3 usable corners like CNMG/DNMG can often be indexed at least twice for reuse so long as all edges are evenly worn and cutting parameters remain unchanged between cycles. Beyond second reuse may risk uneven loading.

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