Material speeds and feeds answer

Cast Iron (gray): 50–90 HSS · 200–400 carbide SFM

These are the HSS and carbide starting ranges stored in the ShopCalc material library. The RPM table applies the site’s SFM-to-RPM formula to each range.

HSS starting range: 50–90 SFM
Carbide starting range: 200–400 SFM
1/4″ end-mill chip load: 0.003 IPT

Cast Iron (gray) RPM table

RPM is computed at the low, midpoint, and high end of both stored SFM ranges. Diameter is the cutter diameter for milling or cutting diameter for turning.

Tool diameter	HSS RPM			Carbide RPM
Tool diameter	Low · 50 SFM	Mid · 70 SFM	High · 90 SFM	Low · 200 SFM	Mid · 300 SFM	High · 400 SFM
1/8″	1,528	2,139	2,750	6,112	9,167	12,223
1/4″	764	1,070	1,375	3,056	4,584	6,112
3/8″	509	713	917	2,037	3,056	4,074
1/2″	382	535	688	1,528	2,292	3,056
3/4″	255	357	458	1,019	1,528	2,037
1″	191	267	344	764	1,146	1,528

Cast Iron (gray) SFM to RPM

The existing SFM-to-RPM calculator is preset to Cast Iron (gray), a 1/2-inch tool, and the 70 SFM HSS midpoint. Change any input to recalculate.

Material preset

Surface speedSFMDiameterin

Result

535 RPM

Related material starting points

Ductile IronHSS 50–80 · carbide 180–350 SFM Mild Steel (1018)HSS 80–110 · carbide 300–600 SFM Alloy Steel (4140)HSS 60–90 · carbide 250–500 SFM Tool Steel (D2)HSS 30–50 · carbide 150–300 SFM Tool Steel (H13)HSS 32–55 · carbide 162–329 SFM Tool Steel (S7)HSS 32–55 · carbide 162–329 SFM SFM CalculatorFull interactive calculator

Questions about this answer

What SFM should I use for Cast Iron (gray)?

The stored starting range is 50–90 SFM for HSS tooling and 200–400 SFM for carbide tooling.

What RPM is 200 SFM with a 1/2-inch tool in Cast Iron (gray)?

200 SFM with a 0.500-inch tool calculates to 1,528 RPM using RPM = SFM × 12 ÷ (π × diameter).

What is the 1/4-inch end-mill chip load for Cast Iron (gray)?

The material library stores 0.003 inch per tooth as the 1/4-inch end-mill starting chip load.

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Reading the spec sheet

Tool diameter	HSS RPM	Carbide RPM
1/8″	1,528	2,139	2,750	6,112	9,167	12,223
1/4″	764	1,070	1,375	3,056	4,584	6,112
3/8″	509	713	917	2,037	3,056	4,074
1/2″	382	535	688	1,528	2,292	3,056
3/4″	255	357	458	1,019	1,528	2,037
1″	191	267	344	764	1,146	1,528

Tool diameter

HSS RPM

Carbide RPM

Low · 50 SFM

Mid · 70 SFM

High · 90 SFM

Low · 200 SFM

Mid · 300 SFM

High · 400 SFM

1/8″

1,528

2,139

2,750

6,112

9,167

12,223

1/4″

764

1,070

1,375

3,056

4,584

6,112

3/8″

509

713

917

2,037

3,056

4,074

1/2″

382

535

688

1,528

2,292

3,056

3/4″

255

357

458

1,019

1,528

2,037

1″

191

267

344

764

1,146

1,528

Questions about this answer

What SFM should I use for Cast Iron (gray)?

The stored starting range is 50–90 SFM for HSS tooling and 200–400 SFM for carbide tooling.

What RPM is 200 SFM with a 1/2-inch tool in Cast Iron (gray)?

200 SFM with a 0.500-inch tool calculates to 1,528 RPM using RPM = SFM × 12 ÷ (π × diameter).

What is the 1/4-inch end-mill chip load for Cast Iron (gray)?

The material library stores 0.003 inch per tooth as the 1/4-inch end-mill starting chip load.