NEWS

I. Basic Concepts of the Anterior Angle

The rake angle is the angle between the rake face and the base plane of a cutting tool, and it is one of the core geometric parameters affecting the cutting performance of the tool. On solid carbide helical end mills, the rake angle is mainly divided into the following two types:

• Rake angle of the peripheral cutting edge (side cutting edge): The rake angle on the helical cutting edge, measured in the normal plane.

• End face rake angle: The rake angle on the end face cutting edge.

Furthermore, in cutting theory, the helix angle of a spiral end mill is essentially the axial rake angle at the outer circle of the tool, and the two have equivalent physical meanings.

II. Functions and Influences of the Anterior Horn
Front corner size

Effect on cutting

The larger the front angle

The lighter and faster the cutting, the smaller the chip deformation, the lower the cutting force, the smoother the chip removal, and the sharper the cutting edge.

smaller front corner

The greater the strength of the cutting edge and tool tip, the better the heat dissipation and the stronger the impact resistance.

Test data shows that when milling aluminum alloys at high speed, the cutting force decreases by about 1% for every 10° increase in the rake angle.

III. Recommended value for the front corner
3.1 Select according to the material being processed
processed materials

Recommended front angle of the blade

illustrate

aluminum alloy

15° 20° (up to 20° 30°)

A large rake angle reduces cutting forces and avoids built-up edge.

Carbon steel/alloy steel (180~380HB)

10°~15°

Standard Recommendation

Stainless steel/high temperature alloy

9°~12°

A larger front angle facilitates chip removal.

cast iron

5°~8°

Brittle materials must ensure the strength of the cutting edge.

Hardened steel HRC 28~32

Approximately -5°

The higher the hardness, the smaller the rake angle, and it can even take a negative value.

Hardened steel HRC 30~40

Approximately -10°

A negative rake angle subjects the cutting edge to compressive stress, leveraging the compressive strength advantage of cemented carbide.

Hardened steel HRC 40~50

Approximately -15°

Same as above

Titanium alloys/difficult-to-machine materials

9°~12°

A common combination is a smaller rake angle and a larger helix angle.

Pure copper/copper alloy

15°~20°

Larger front angle

3.2 General Design Values for Solid Carbide End Mills
Part

Recommended front corner

Front angle of the circumferential cutting edge (side cutting edge)

Around 15°

end cutting edge rake angle

Around 8° (balancing sharpness and strength)

The orthogonal rake angle (radial rake angle) used in the standard end mill life test is 12°±3°.

3.3 Select according to processing nature
Processing type

Front corner strategy

roughing

Choose a smaller rake angle (e.g., 9°~12°) to ensure cutting edge strength and withstand greater cutting resistance.

finishing

A larger rake angle can be used to reduce cutting forces and improve surface quality.

Intermittent cutting/impact conditions

The front angle should be appropriately reduced, and negative chamfering reinforcement should be used if necessary.

IV. The Coordination Between Rake Angle and Helix Angle
The helix angle has a significant impact on the actual rake angle, which is an important characteristic that distinguishes helical end mills from straight flute end mills.

Actual front angle calculation formula

In the formula: - γ_f: rake angle - β: helix angle - γ_x: actual rake angle

Calculation example (anterior normal angle γ_n = 6°)
Helix angle β

Anterior face angle γ_f

Actual rake angle γ_x

20°

6°23’

12°5' (approximately twice γ_n)

30°

6°55’

19°10' (approximately 3.2 times γ_n)

40°

7°49’

28°20' (approximately 4.7 times γ_n)

Key conclusion: Increasing the helix angle significantly increases the actual rake angle of the end mill, resulting in a sharper cutting edge and a decrease in cutting force. When the helix angle of a carbide end mill is increased from 20°/25° to 30°, the main cutting force can decrease by 10%-15%.

V. Special Forms and Reinforcement Measures of the Front Corner
To resolve the contradiction of "sharp but weak large front angles, and strong but not sharp small front angles," the following reinforcement design is adopted in engineering practice:

5.1 Front corner with chamfer
Grind a narrow negative chamfer on the rake face with the following parameters: - Chamfer width: 0.2~1mm - Chamfer rake angle: -5°~-15°

Function: Enhances the strength of the cutting edge, improves heat dissipation, and allows for a larger rake angle without chipping.

Applications: Roughing and interrupted cutting with carbide tools.

5.2 Front corner type
The rake face has a negative rake angle, and the cutting tool is under compressive stress.

Functions: Impact resistant and good heat dissipation.

Applications: Machining hardened steel (HRC 50+) and high-strength materials.

5.3 Curved surface type (with chip groove)
The rake face is ground to form a curved surface or chip groove.

Function: Forces chips to curl or break, improving chip removal.

Applications: For processing plastic materials (such as stainless steel and copper), the rake angle can be increased to 25°~30°.

VI. Core Principles of Front Angle Selection
1. The lower the strength/hardness of the workpiece material, the larger the rake angle (e.g., 20°~30° for aluminum alloys).

2. The higher the strength/hardness of the workpiece material, the smaller the rake angle, even to a negative value (e.g., -5° to -15° for hardened steel).

3. Machining plastic materials → Use a larger rake angle (to reduce tool sticking and built-up edge)

4. When machining brittle materials, use a smaller rake angle (to avoid chipping).

5. Rough machining/intermittent cutting → Reduce the rake angle or add chamfer (to ensure strength)

6. Finishing → The rake angle can be appropriately increased (to reduce cutting force and improve surface quality).

7. Increased helix angle → increased actual rake angle; the synergistic effect of both must be considered during design.

VII. Summary Table of Technical Parameters
Parameter Items

Typical value range

Rake angle of the circumferential cutting edge (general design)

Around 15°

End-edge rake angle (general design)

around 8°

Standard radial rake angle

12°±3°

Aluminum alloy machining rake angle

15°~30°

Rake angle of hardened steel

-5°~-15°

For every 10° increase in rake angle, the cutting force decreases.

Approximately 1% (high-speed milling of aluminum alloys)

The effect of increasing helix angle on cutting force

The main cutting force decreases by 10% to 15% when the angle changes from 20° to 30°.