4140 Steel · Q&T 35-38 HRC Speeds and Feeds (Milling, Drilling, Turning)
Carbide end mills in 4140 Steel · Q&T 35-38 HRC: 150–350 SFM. Also called 4140 HT, 4140 high hardness. Chart row used: “Steels – High Tensile” (Quenched & tempered).
Starting point: carbide end mills
RPM and IPM use the low end of the published range (150 SFM and the lowest chip load for each diameter range). RPM = SFM × 12 ÷ (π × D); IPM = RPM × flutes × chip load.
| Diameter | Chip load (in/tooth) | RPM | IPM · 2 flute | IPM · 3 flute |
|---|---|---|---|---|
| 1/8" | .0004 | 4,584 | 3.7 | 5.5 |
| 1/4" | .0005 | 2,292 | 2.3 | 3.4 |
| 3/8" | .0008 | 1,528 | 2.4 | 3.7 |
| 1/2" | .0010 | 1,146 | 2.3 | 3.4 |
| 3/4" | .0015 | 764 | 2.3 | 3.4 |
| 1" | .0018 | 573 | 2.1 | 3.1 |
| Diameter | Chip load (in/tooth) | RPM | IPM · 2 flute | IPM · 3 flute |
|---|---|---|---|---|
| 3 mm | .0004 | 4,851 | 3.9 | 5.8 |
| 6 mm | .0005 | 2,426 | 2.4 | 3.6 |
| 10 mm | .0010 | 1,455 | 2.9 | 4.4 |
| 12 mm | .0010 | 1,213 | 2.4 | 3.6 |
| 16 mm | .0015 | 910 | 2.7 | 4.1 |
| 20 mm | .0018 | 728 | 2.6 | 3.9 |
Full published chip-load ranges
- 1/32-1/8": .0004–.0009"
- 1/8-1/4": .0005–.0015"
- 1/4-3/8": .0008–.0018"
- 3/8-1/2": .0010–.0020"
- 1/2-3/4": .0015–.0030"
- 3/4-1": .0018–.0040"
Calculator — prefilled for 4140 Steel · Q&T 35-38 HRC
Results for Milling
- Spindle RPM
- 1,146
- Feed
- 4.6 IPM
- Chip load
- 0.0009 in
- MRR
- 0.17 in³/min
- Power
- — HP
- Torque
- — lbf·ft
- Programmed fz
- 0.0010 in
- Actual SFM
- 150
- Spindle use
- 10%
- Pick a material in the library below to estimate spindle power and torque.
http://127.0.0.1:36217/tools?tool=milling-calculator&op=milling&material=4140-steel-q-t-35-38-hrc&dia=0.5&sfm=150&flutes=4&chip=0.001&ap=0.25
Material library
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
Chip thinning & cutter body
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 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
Speeds by tool material
Published starting ranges for 4140 Steel · Q&T 35-38 HRC by operation and tool material. Rows marked * are estimates.
| Operation | Tool | SFM | Feed | Source row |
|---|---|---|---|---|
| milling | Solid carbide end mill | 150–350 | 0.0010–0.0020 in/tooth | Lakeshore Carbide · Steels – High Tensile |
| milling | Coated carbide (GC4230) | 400–600 | 0.0040–0.0120 in hex | Sandvik milling (large engagement) · CMC 02.2-350 Low-alloy steel, hardened and tempered (350 HB) |
| turning | Coated carbide (GC4325) | 365–670 | 0.0040–0.0310 in/rev | Sandvik turning · CMC 02.2-350 Low-alloy steel, hardened and tempered (350 HB) |
| turning | Cermet (CT5015) | 495–740 | 0.0020–0.0080 in/rev | Sandvik turning · CMC 02.2-350 Low-alloy steel, hardened and tempered (350 HB) |
| drilling | Coated carbide (4234) | 230–425 | 0.0055–0.0146 in/rev | Sandvik CoroDrill 870 · CMC 02.2-350 Low-alloy steel, hardened and tempered (350 HB) |
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 4140 Steel · Q&T 35-38 HRC?
- Lakeshore Carbide – General Purpose End Mill Speeds & Feeds lists 150–350 SFM for carbide end mills in the "Steels – High Tensile" row. Start at the low end and adjust for your machine.
- What chip load for a 1/2" end mill in 4140 Steel · Q&T 35-38 HRC?
- The published range for 3/8–1/2" carbide end mills is .0010–.0020" per tooth. At 150 SFM a 3-flute 1/2" end mill runs about 1146 RPM and 3.4 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 4140 Steel · Q&T 35-38 HRC where a source lists them (LittleMachineShop, Sandvik Coromant).
Sources
- Lakeshore Carbide – General Purpose End Mill Speeds & Feeds — “Steels – High Tensile” row (SFM and chip load per tooth).
- Lakeshore Carbide speeds and feeds charts
- Sandvik Coromant catalogue, Milling cutting data, large engagement, inch values (pp. J482-J485), via BRW
- Sandvik Coromant catalogue, General turning: cutting speed recommendations by MC/CMC group, inch values (pp. A562-A564), via BRW
- Sandvik Coromant catalogue, CoroDrill 870 cutting data, inch values (p. K174), via BRW
Starting values only. Adjust for rigidity, tool manufacturer data and machine.
Put your skills on a free talent profile
Machines, controls, certs and saved calculations in one profile shops can find.
Create free profileBring shift handoffs to your shop
Stop losing job status between shifts. Every station's notes, counts and issues, handed off cleanly.
See shift handoffs