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What is The Indexable milling cutter

Indexable end mills are advanced multi-edged replaceable insert end mills. Through an indexing mechanism, they allow multi-edge cutting of the inserts, thereby improving insert utilization and prolonging tool life.

Compared with traditional end mills, the biggest advantage of indexable milling cutters is that their inserts are indexable. This means that when one cutting edge gets worn, the insert can be indexed to present a fresh cutting edge for continued cutting, making full use of the insert without frequent replacement.

The geometry of indexable end mill cutter,indexable face milling cutter and indexable insert milling cutter

An indexable milling cutter has one main helix angle and two lead angles, an axial lead angle, and a radial lead angle.

The radial lead angle γf mainly affects the cutting power, while the axial lead angle γp influences chip formation and the direction of axial force, with positive γp producing climbing cuts on the workpiece.

The geometry of Indexable Milling Cutters

Lead angles (rake faces):

Negative lead angle: used for steel, steel alloys, stainless steel, and cast iron.

Positive lead angle: used for adhesive materials and some high-temperature alloys.

Centered lead angle: used for gear cutting, grooving, profile milling, and form cutters.

A negative lead angle should be used whenever possible.

Geometry of Milling Cutters

1. Positive angle–Positive angle

Cutting is light and chip evacuation is smooth, but cutting edge strength is relatively low. Suitable for machining soft materials, stainless steel, heat-resistant steel, plain carbon steel, and cast iron. Should be preferentially selected for small power machine tools, rigidness insufficient process systems, and where built-up edges are likely to form.

Advantages: 1. Smooth cutting 2. Smooth chip evacuation 3. Good surface roughness

Disadvantages: 1. Cutting edge strength 2. Unfavorable for cut-in contact 3. Workpiece detachment from machine table

2. Negative angle–Negative angle

High impact resistance, uses negative inserts, suitable for rough milling of cast steel, cast iron, and high hardness, high strength steel. However, cutting power consumption is high and requires excellent process system rigidity.

Advantages: 1. Cutting edge strength 2. Productivity 3. Pushes workpiece towards machine table

Disadvantages: 1. Greater cutting forces 2. Chip clogging

3. Positive angle– Negative angle

Cutting edge impact resistance is relatively strong and cutting edge is also sharper. Suitable for machining steel, cast steel, and cast iron. Also good for heavy machining.

Advantages: 1. Smooth chip evacuation 2. Beneficial cutting forces 3. Broader application range

Cutter tooth pitch

1. Fine pitch: high-speed feed, larger milling force, small chip space.

2. Standard pitch: conventional feed speed, milling force, and chip space.

3. Coarse pitch: low-speed feed, smaller milling force, larger chip space.

If the milling cutter is not equipped with dedicated wiper inserts, the surface roughness depends on whether the feed per revolution exceeds the width of the wiper face on the insert.

Example: slot milling & contour milling

slot milling & contour milling

Number of teeth:

1. Coarse or standard pitch for slot milling (safety)

2. Fine pitch for contour milling (productivity)

What is an indexable end mill?

The indexable end mill is an end mill that allows adjustment of the cutting-edge angle position of the inserts. By changing the cutting edge angle position of the inserts, multiple cutting edges on the inserts can be utilized for cutting, extending the tool life of the inserts.

What are the common structures of indexable end mills?

Common structures of indexable end mills include indexable shell end mills, indexable bolt-clamping end mills, and indexable collet-clamping end mills. Indexable shell end mills are the most commonly used.

What are the structural characteristics of indexable shell end mills?

The inserts of such end mills are installed on shells with an indexing mechanism. Rotating the shell can adjust the cutting-edge angle position of the inserts. The shells have accurate indexing devices, making insert indexing precise and reliable.

What are the pros and cons of indexable bolt-clamping end mills?

Such end mills clamp inserts directly with indexing bolts, featuring a simple structure but relatively poor repeatability in insert indexing. The advantage is convenient indexability while the disadvantage is inaccurate indexing.

What are the main application scopes of indexable end mills?

Indexable end mills are mainly used in high-precision, high-efficiency machining fields such as mold manufacturing, automotive, and aerospace industries. They can make full use of inserts, extend tool life, and reduce tool change frequency.


Overall, indexable end mills provide economical, long-life, and flexible solutions for a variety of milling operations. The indexability gives versatility and lower tooling costs versus solid-end mills.

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