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Milling insert feed rate and spindle speed
time：
2026-04-22 16:54
source：
Lizhou
Table of Contents
- What are milling feed rate and spindle speed?
- What spindle speed and feed rate?
- What is the difference between these two?
- How is the feed rate calculated for a milling machine?
- DOC and WOC What are they respectively?
- What are the common issues with milling feed rates?
I. What are milling feed rate and spindle speed?
During milling, spindle speed and feed rate are the two most critical cutting parameters in the machining process, directly determining tool life, machining efficiency, and workpiece surface quality. Spindle speed = How many revolutions per minute does the spindle make? The unit can be r/min( Transfer / minute ) Specifically, the higher the spindle speed, the faster the cutting-edge velocity; if the speed is too low, machining efficiency drops, tool adhesion is more likely to occur, and the surface finish becomes rough. Conversely, if the speed is too high, the tool overheats, wears rapidly, and may even suffer thermal damage or chipping of the cutting edge.
II. What are spindle speed and feed rate?
What is rotational speed?
Rotational speed = How many revolutions per minute does the spindle make? Unit: r/min (Repost / minutes)
What is feed rate?
Feed rate = How many millimeters does the worktable move per minute? Unit: mm/min (Millimeters / minutes)
III. What is the difference between these two?
Cutting speed refers to the rotational speed of the tool, while feed rate refers to the machine’s feed rate; one governs rotational speed, the other governs linear feed. This is what we commonly refer to as spindle speed and feed rate.
How many revolutions per minute does the spindle make, in units of: r/min → Determines the cutting speed, temperature, and sharpness of the cutting tool during machining
How many millimeters does the worktable move per minute, in units of: mm/min → Determines the feed rate, machining efficiency, and chip thickness.
The difference is that spindle speed affects whether the cutting tool will overheat, stick to the workpiece, or wear out quickly, whereas feed rate determines machining efficiency and surface finish.
IV. How is the feed rate of a milling machine calculated?
The feed rate commonly used for milling machines is the feed per minute ( mm/min ), many machining centers use highly standardized calculation formulas; next, let’s examine the most commonly used calculation methods:
F: Feed rate, mm/min
Z: Number of cutter teeth (for example, 4 End mill z=4 )
Fz: Feed per tooth (refer to the tool manufacturer’s specifications)
S: Spindle speed , r/min
The most commonly used calculation method: feed rate per minute F= Number of cutter teeth Z* Feed per tooth Fz* Rotational speed S
V. DOC and WOC What are they respectively?
DOC The full name is Depth of Cut In Chinese, this is also referred to as axial depth of cut, which denotes the depth to which the cutting tool penetrates downward—specifically, the vertical depth of penetration into the workpiece. This parameter determines how thick a single pass can be and directly influences the amount of material removed per pass.
WOC The full name is Radial Depth of Cut, In Chinese, this is also referred to as “radial cutting width,” which denotes the width of the cut made by the side of the tool—essentially, the width over which the tool cuts across the workpiece. This determines how much material is removed in a single pass.
VI. What are the common problems with milling feed rates?
Q1: Does a larger feed rate always result in faster machining?
Answer: In theory, yes; however, excessive feed rates can easily lead to chipping, breakage, and tool vibration, among other issues.
Q2: Is too small a feed rate problematic?
Answer: Low efficiency, easy tool friction and heat generation, leading to built-up edge, blackened workpiece surface, and accelerated tool wear.
Q3: Which should be adjusted first: the feed rate or the spindle speed?
Answer: Generally, the spindle speed is first determined based on the cutting tool and the workpiece material.
Q4: Why does the tool still vibrate and produce chatter marks even after the feed rate has been properly adjusted?
Answer: Common causes include excessive tool overhang, insufficient machine rigidity, and excessive depth of cut.
Q5: How should feed rates be selected for roughing and finishing?
Answer: Use a large feed rate for rough machining to maximize efficiency, and a small feed rate for finish machining to achieve surface finish.
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