What SFM should I use for 41L40 Steel?

Lakeshore Carbide – General Purpose End Mill Speeds & Feeds lists 200–400 SFM for carbide end mills in the "Steels – Med Carbon" row. Start at the low end and adjust for your machine.

What chip load for a 1/2" end mill in 41L40 Steel?

The published range for 3/8–1/2" carbide end mills is .0015–.0035" per tooth. At 200 SFM a 3-flute 1/2" end mill runs about 1528 RPM and 6.9 IPM.

Are these values for HSS tools, drilling or turning?

The end mill chart covers carbide end mills. The "Speeds by tool material" table adds published HSS, turning-insert and drilling rows for 41L40 Steel where a source lists them (LittleMachineShop, Sandvik Coromant).

41L40 Steel Speeds and Feeds (Milling, Drilling, Turning)

Carbide end mills in 41L40 Steel: 200–400 SFM. Also called leaded 4140, 41L42. Chart row used: “Steels – Med Carbon” (Annealed).

Starting point: carbide end mills

RPM and IPM use the low end of the published range (200 SFM and the lowest chip load for each diameter range). RPM = SFM × 12 ÷ (π × D); IPM = RPM × flutes × chip load.

41L40 Steel — inch end mills
Diameter	Chip load (in/tooth)	RPM	IPM · 2 flute	IPM · 3 flute
1/8"	.0005	6,112	6.1	9.2
1/4"	.0006	3,056	3.7	5.5
3/8"	.0010	2,037	4.1	6.1
1/2"	.0015	1,528	4.6	6.9
3/4"	.0020	1,019	4.1	6.1
1"	.0025	764	3.8	5.7

41L40 Steel — metric end mills (inch chip-load range the size falls in)
Diameter	Chip load (in/tooth)	RPM	IPM · 2 flute	IPM · 3 flute
3 mm	.0005	6,468	6.5	9.7
6 mm	.0006	3,234	3.9	5.8
10 mm	.0015	1,940	5.8	8.7
12 mm	.0015	1,617	4.9	7.3
16 mm	.0020	1,213	4.9	7.3
20 mm	.0025	970	4.9	7.3

Full published chip-load ranges

1/32-1/8": .0005–.0010"
1/8-1/4": .0006–.0018"
1/4-3/8": .0010–.0025"
3/8-1/2": .0015–.0035"
1/2-3/4": .0020–.0040"
3/4-1": .0025–.0050"

Calculator — prefilled for 41L40 Steel

Results for Milling

Spindle RPM: 1,528
Feed: 9.2 IPM
Chip load: 0.0014 in

MRR: 0.34 in³/min
Power: — HP
Torque: — lbf·ft
Programmed fz: 0.0015 in
Actual SFM: 200
Spindle use: 13%

Pick a material in the library below to estimate spindle power and torque.

Operation Type

Milling

Turning

Material library

Auto-adjust cutting data

Material & condition

Cutting tool material

Tool coating

Tool & coating guidance

Grade, edge geometry and coating determine usable cutting data. Sharp polished edges can suit nonferrous work; substrate and geometry still govern. Coated vs uncoated carbide changes turning data only; no coating speed multiplier is inferred.

Tool & cut parameters

Manual values

SFM (Surface Feet/Min)

Cutter Diameter (in)

Number of Flutes

Axial depth of cut (in)

Feed per Tooth (in)

Machine RPM limit

Chip thinning & cutter body

Cutter body

Chip-thinning compensation

Radial engagement (% of diameter)

Entering angle KAPR (°)

Radial factor ×1.09Angle factor ×1.00Programmed fz 0.0015 inMax chip hex 0.0014 in

Fixed-angle peripheral estimate: hex = fz × radial factor × sin(KAPR). No radial correction at ≥50% engagement. Not a centered face-milling or ball-nose model. Sandvik geometry reference

Insert styles, guidelines & formulas

RPM = (SFM × 12) / (π × D) | Feed = RPM × programmed fz × effective zc | MRR = WOC × DOC × feed | HP = Kp × C × MRR × 1.1 ÷ 0.8 (Machinery's Handbook)

Milling Insert Styles

Square (SEMT/SNMG)

General purpose, 90° lead angle

Round (RPMW/RCKT)

Ramping, 3D contouring, high feed

Triangular (TPMX)

Light cuts, finishing

Octagonal (ONMU)

Face milling; HFM suitability is body-specific

Milling Guidelines

Start at 70% of max SFM, increase gradually
Chip load too low → rubbing & heat buildup
Use climb milling when machine rigidity allows
Radial engagement >50% → reduce feed per tooth
Round inserts: best for ramp-in and 3D surfaces

Open in the full calculator workspace

Speeds by tool material

Published starting ranges for 41L40 Steel by operation and tool material. Rows marked * are estimates.

41L40 Steel — speeds by tool material
Operation	Tool	SFM	Feed	Source row
milling	Solid carbide end mill	200–400	0.0015–0.0035 in/tooth	Lakeshore Carbide · Steels – Med Carbon
milling	Coated carbide (GC4230)	610–920	0.0040–0.0120 in hex	Sandvik milling (large engagement) · CMC 02.1 Low-alloy steel, not hardened
milling	Cermet (CT530)	800–980	0.0040–0.0080 in hex	Sandvik milling (large engagement) · CMC 02.1 Low-alloy steel, not hardened
turning	Coated carbide (GC4325)	710–1500	0.0040–0.0310 in/rev	Sandvik turning · CMC 02.1 Low-alloy steel, not hardened
turning	Cermet (CT5015)	1050–1550	0.0020–0.0080 in/rev	Sandvik turning · CMC 02.1 Low-alloy steel, not hardened
drilling	Coated carbide (4234)	260–460	0.0055–0.0146 in/rev	Sandvik CoroDrill 870 · CMC 02.1 Low-alloy steel, not hardened

Machinist tips

Chip thinning: At light radial engagement (under half the cutter diameter) the real chip is thinner than the feed per tooth. Raise the feed to keep the chip at the chart value, or the tool rubs and wears.
Climb vs conventional: On a rigid CNC, climb mill so each tooth starts thick and exits thin. Use conventional milling on machines with backlash or on hard scale skins.
Coolant: Flood coolant or mist controls heat. Coated carbide (such as AlTiN) handles steel heat better than uncoated.

Common questions

What SFM should I use for 41L40 Steel?: Lakeshore Carbide – General Purpose End Mill Speeds & Feeds lists 200–400 SFM for carbide end mills in the "Steels – Med Carbon" row. Start at the low end and adjust for your machine.
What chip load for a 1/2" end mill in 41L40 Steel?: The published range for 3/8–1/2" carbide end mills is .0015–.0035" per tooth. At 200 SFM a 3-flute 1/2" end mill runs about 1528 RPM and 6.9 IPM.
Are these values for HSS tools, drilling or turning?: The end mill chart covers carbide end mills. The "Speeds by tool material" table adds published HSS, turning-insert and drilling rows for 41L40 Steel where a source lists them (LittleMachineShop, Sandvik Coromant).

4130 Steel · Q&T speeds and feeds 4340 Steel · Q&T 36-40 HRC speeds and feeds 4140 Steel · Q&T 35-38 HRC speeds and feeds