General Information for Steel 4340
| Material Group |
P-Steel |
| Hardness |
259.0 HB |
| Sub-Grou |
Low Alloy Steel |
| Tensile Strengt |
890[N/mm^2] |
| Machinability |
57% |
MACHINABILITY OF 4340 STEEL
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:
251 HB - Anealed.
320-365 HB - Normalized.
250-360 HB - Quenched.
The average machinability rating of 4340 steel is around 55% (Annealed condition).
SUMMARY:
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 table below.
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 recommendations,check the table below.
Equivalent International Designations for Steel 4340
| Standard |
Name |
| SAE |
4340 |
| WNR |
1.6582 |
| DIN |
35CrNiMo6 |
| BS |
817M40 |
| SS |
2541 |
| ANFOR |
35NCD6 |
| UNI |
35NiCrMo6(KB) |
| UNF |
F.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
| Application |
Vc (m/min) |
Vc (SFM) |
| Turning |
215-290 |
710-950 |
| Milling |
130-180 |
430-590 |
| Parting |
100-140 |
330-460 |
| Grooving |
120-160 |
390-520 |
| Drilling |
85-115 |
280-380 |
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.
Recommended Carbide Grades for Steel 4340
Grade for Milling (Indexable)
Recommended Insert Cutting Edge Geometry for Steel 4340
| Honing Siz |
0.05-0.08 mm / 0.002-0.003" |
| Rake Angl |
11° -13° |
| Land Angl |
Positive |
| Land Widt |
0.20-0.30 mm / 0.008-0.012" |
