General Information:
Material Group P - Steel
Sub-Group Low Alloy Steel
Hardne259.0 HB
Tensile Strength 890 [N/mm^2]
Machinability57%

Machining Steel 4340

SAE 4340 is Nickel-chromium-molybdenum steel produced with 1.65-2% nickel and 0.7–0.9% chromium content. It has good hardenability, strength, wear resistance, toughness, and ductility. 4340 Steel is used mainly on piston pins, bearings, gears, machine tool arbors, die blocks, and cutting tool shanks.

The hardness of these steels depends on the heat treatment:

  • 215 HB - Anealed.
  • 320 – 365 HB - Normalized.
  • 250 – 360 HB - Quenched

The average machinability rating of 4340 steel is around 55% (Annealed condition).

You can find here a list of machinability Ratings for different Low Alloy Steels.

Summery:

  • For turning operations on 4340, it is best to use inserts with thick CVD coating and medium hardness. For milling, any all-around carbide grade is suitable.
  • For detailed carbide grades recommendations, check the Below Chart, or use the Grades Wizrad.
  • Recommended Cutting speed range for turning at stable conditions is 710 - 950 [SFM] / 215 - 290 [m/min].
  • Recommended Cutting speed range for milling with stable clamping and short overhang is 430 - 590 [SFM] / 130 - 180 [m/min]
  • For detailed cutting speed recomendations, check the Below Table, or use our Speed and Feed Calculator.
  • Equivalent International Designations for Steel 4340

    Standard Name
    sae4340
    wnr1.6582
    din35CrNiMo6
    bs817M40
    ss2541
    anfor35NCD6
    uni35NiCrMo6(KB)
    unfF.1280

    Chemical Composition for Steel 4340

    Element Amount
    Nickel (Ni)1.65-2.00%
    Chromium (Cr).70-.90%
    Manganese (Mn).60-.80%
    Carbon (C).38-.43%
    Molybdenum (Mo).20-.30%

    Cutting Speeds Recomendations for Steel 4340

    * Click on the speeds below for higher precision in specific conditions!

    ApplicationVc (m/min)Vc (SFM)
    Turning215-290710-950
    Milling130-180430-590
    Parting100-140330-460
    Grooving120-160390-520
    Drilling85-115280-380

    Important! The speed estimation is given for an ideal situation:

    • Most suitable carbide grade
    • Stable tool clamping
    • Stable workpiece clamping
    • Good quality raw material
    • A short overhang of the cutting tool.
    • Nominal hardness of the material.
    • etc.
    Click on the speeds in the above table to get better precision for specific parameters
    Or use our Speed and Feed Calculator


    Recommended Carbide Grades for Steel 4340

    * If you don't understand the below table? Read This Explanation to make the most out of it!

    Grade for Turning

    Grade for Parting Off

    Grade for Grooving

    Grade for Milling (Indexable)

    Recommended Insert Cutting Edge Geometry for Steel 4340

    Honing Size:0.05-0.08 mm / 0.002-0.003"
    Rake Angle:11° -13°
    Land Angle:Positive
    Land Width:0.20-0.30 mm / 0.008-0.012"

    Learn more about carbide inserts Cutting-Edge Geometry Parameters.

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