---
title: "SFM 转 RPM：公式、对照表与实例"
description: "一步把表面英尺每分钟换算成主轴转速——3,82 简算、1/4 到 4 英寸对照表，以及与公制公式的差异。"
image: "https://nestingcalc.com/og-default.png"
url: "https://nestingcalc.com/cn/guides/sfm-to-rpm/"
locale: "zh-Hans"
---

# SFM 转 RPM：公式、对照表与实例

一步把表面英尺每分钟换算成主轴转速——3,82 简算、1/4 到 4 英寸对照表，以及与公制公式的差异。

## SFM 到底测量什么

SFM——表面英尺每分钟——是切削刃在材料中的速度，以英尺计。4 英寸刀具的刃口每转走过 π × 4 ≈ 12,57 英寸；在 500 rpm 下刃口每分钟约走 524 英尺：524 SFM。SFM 是公制切削速度 Vc 的英制孪生，1 SFM 恰好 = 0,3048 m/min。

## 公式——以及 3,82 简算

rpm = (SFM × 12)/(π × D)，D 单位英寸。由于 12/π = 3,8197，车间常简写为 rpm ≈ 3,82 × SFM/D。例：100 SFM 的软钢用 1/2 英寸立铣刀 → 3,82 × 100/0,5 = 764 rpm。[转速](https://nestingcalc.com/cn/rpm-calculator/) 计算器在两种单位制下都可计算，还显示每秒转数。

## SFM 转 RPM 对照表

直径看行、速度看列：

| 直径 | 50 SFM | 100 SFM | 200 SFM | 300 SFM |
| --- | --- | --- | --- | --- |
| 1/4 英寸 | 764 | 1 528 | 3 056 | 4 584 |
| 1/2 英寸 | 382 | 764 | 1 528 | 2 292 |
| 3/4 英寸 | 255 | 509 | 1 019 | 1 528 |
| 1 英寸 | 191 | 382 | 764 | 1 146 |
| 2 英寸 | 95 | 191 | 382 | 573 |
| 4 英寸 | 48 | 95 | 191 | 286 |

修边机刀头在上排，大面铣刀在最后一排——同一张表，因为几何相同。

## 由转速回到 SFM（与公制）

反向公式可检验给定转速的实际输出：SFM = π × D × rpm/12，简写 SFM ≈ 0,262 × D × rpm。公制：Vc = π × D × n/1000，且 100 m/min ≈ 328 SFM。[nav.cs](https://nestingcalc.com/cn/cutting-speed-calculator/) 计算器并排显示 m/min 与 SFM，公制图纸与英制样本可直接对比。

## 两个经典错误

一是单位混用：3,82 简算只在直径为英寸时成立。把 12 mm 刀具按“12”输入会慢约 25 倍（12 mm = 0,472 英寸）。二是把转速当成全部设定：线速度决定刃口温度，但每齿切屑厚度才决定刀具是切削还是摩擦。[转速与进给基础：RPM 与进给速度公式](https://nestingcalc.com/cn/guides/feeds-and-speeds-basics/) 讲这对参数，[RPM 公式：如何计算主轴转速](https://nestingcalc.com/cn/guides/rpm-formula/) 深入公式——[转速](https://nestingcalc.com/cn/rpm-calculator/) 与 [进给与转速](https://nestingcalc.com/cn/feeds-speeds-calculator/) 工具负责计算。

[转速](https://nestingcalc.com/cn/rpm-calculator/) [打开线性切割计算器](https://nestingcalc.com/cn/linear-cutting-calculator/)

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