Do You Know About Rougher Milling vs. Indexable Milling?
Rectified milling and indexable milling are two different methods of milling used in machining operations.
Each method offers advantages and suits specific applications, but manufacturers consider factors such as the material, required accuracy, workpiece complexity, and cost when choosing between them.
What is Hard Milling?
Whole hard milling involves the use of a single-piece cutting tool made of a carbide material, usually high speed steel (HSS) or carbide.
The tool has cutting edges that remove material as the tool rotates. Solid carbide milling cutters come in a variety of shapes and sizes, including end mills, flute milling cutters, round nose milling cutters, and more.
What Are the Advantages of Integral Hard Milling?
Rigidity: Integral milling cutters are typically more rigid than indexable cutters, which can result in better surface finish and dimensional accuracy.
Accuracy: Integral milling cutters are ideally suited for applications requiring high precision and tight tolerances.
Smaller diameters: Integral milling cutters are best suited for smaller diameters, and are more efficient for diameters up to Ø16mm.
Operators replace or resharpen the entire tool when the cutting edge wears out, and resharpening reduces its diameter.
Versatility: Rougher milling cutters are available in a wider range of geometries than indexable ones, such as corner rounding cutters, round nose milling cutters, roughing cutters, etc.
Suitable for low power machine tools: Some Rectified Milling cutters with low performance, such as those for machining HSS or powder metallurgy materials, are suitable for low power or manual machine tools.
What Are the Drawbacks of Rougher Milling?
Higher costs for larger diameters: In larger diameters (usually above Ø16mm), Rougher Milling cutters can be more expensive, with higher tool change costs.
More frequent tool changes: When the cutting edge wears out, operators replace the entire tool or resharpen it, which reduces its diameter.
Fragile: Integral carbide milling cutters are fragile and prone to chipping or breaking, especially when machining harder materials or when machining conditions are unstable. This can lead to unexpected tool failure and potential damage to the workpiece.
What is Indexable Milling?
Indexable milling involves milling cutter bodies with replaceable carbide inserts. These inserts have a plurality of cutting edges mounted on the body. When cutting edges dull or wear, machinists easily replace the inserts (or rotate them to a fresh edge), avoiding any need to resharpen the tool.
What Are the Advantages of Indexable Milling?
Manufacturers make the cutter body from cheaper steel and produce the insert from carbide. This makes the cutter body more cost effective at larger diameters. There is no need to replace the entire tool, only the worn insert.
Machining larger diameters: The indexable milling cutter body enables indexable face milling up to Ø315 mm in diameter.
Saving time: Changing inserts is faster than resharpening a complete hardened cutter, thus reducing downtime.Engineers fit the inserts with multiple cutting edges, allowing operators to index them and minimize insert changes.
Better for heavy cutting: Indexable milling cutters can withstand greater loads and interruptions, which allows them to perform heavier machining applications.
INSERT GRADES: Manufacturers offer interchangeable carbide inserts in different grades to match various materials. When you switch materials, you simply change the inserts, whereas solid carbide cutters force you to replace the entire tool.
What Are the Disadvantages of Indexable Milling?
Limited rigidity: Indexable cutters can be slightly less rigid than a solid carbide cutter, which in some cases can affect surface finish and accuracy.
Reduced accuracy: Cutter bodies typically have looser tolerances than carbide, resulting in lower accuracy.
Application limitations: While indexable tools can be general purpose, some specialized, complex or high precision applications may require the use of a solid carbide tool.
Unsuitable for smaller sizes: Indexable tools usually only start at Ø10mm and are therefore unsuitable for machining smaller diameters.
Not suitable for low power machines:Low power machines may not have the capacity to carry larger indexable cutters. Operators must check the required cutting data before purchase.
What Are Interchangeable Head Milling Cutters and What Are the Benefits?
Interchangeable head milling cutters, also known as modular milling cutters or interchangeable head milling cutters, consist of a separate cutter body and interchangeable cutting heads or inserts. These cutters combine the benefits of both rectified hard milling and indexable milling, combining the rigidity and precision of rectified hard milling cutters with the cost-effectiveness and convenience of indexable cutters.
Interchangeable head milling cutters let operators replace only the worn or damaged cutting head or insert, cutting tool consumption costs compared to replacing the entire tool. Engineers can also mount different cutting heads or inserts on the same cutter body, giving them versatility to machine various materials and applications. Modular milling heads are particularly suitable for applications with large machining lengths and different thread adaptations for different lengths.
For whole hard milling Indexable Milling Materials/Grades
In indexable milling, inserts are often available in a variety of grades and chipbreaker designs for different materials and machining applications. This increases their versatility because in some multi-material machining systems, you can use the same cutter body for each material, reducing overall tooling costs.
However, in whole hard milling, especially high-end applications, end mills tend to be about material detail. This improves their performance at the expense of material versatility.
Indexable Milling Applications/Compared to Whole Hard Milling
When dealing with operations that require heavy cutting, usually roughing or semi-roughing, indexable tools are the recommended choice due to their large cutting forces and power consumption.
However, if the operation involves fine cutting that demands precise accuracy and a smooth surface finish, operators should use a rectified hardened tool.
What Shanks Are Used for Indexable Milling?
Face milling cutters: Face milling cutter shanks are designed to hold face milling cutters, which are large diameter tools used to mill surfaces. They usually have a flange that provides stability and support for larger cutters.
End mill shanks: End mill shanks can also be used for indexable milling, especially when using end mill indexable cutters. These shanks provide good rigidity and accuracy for various milling operations.
Operators pair threaded shank adapters with shanks to secure threaded screw-in milling cutter shanks, leveraging the adapters’ extended dimensions for large-length applications.
Hydraulic shanks: Hydraulic shanks utilize hydraulic pressure to provide secure clamping on the tool. They have excellent rigidity, vibration damping properties yet, suitable for high speed and precision milling applications, maintaining end mill type indexable milling cutter bodies.
What Shanks Are Used for Complete Hard Milling?
Some common types of shanks used for Rectification Milling include:
ER Collet Shanks: Collet shanks are versatile and widely used for general Rectification Milling applications. They offer good runout accuracy of 10 microns and are suitable for light to medium milling operations. They are popular and come in a variety of sizes to accommodate different shank tool diameters.
End Mill Shanks:The most conventional shanks for clamping weld shanks on rectified hard milling cutters. End mill shanks, also known as side locking shanks, are common in the shop.
Hydraulic shanks: Hydraulic shanks utilize hydraulic pressure to provide secure clamping on the cutter. They offer excellent rigidity, vibration damping, and 3 micron tool runout accuracy, making them suitable for high speed and precision milling applications.
Heat Shrink Toolholders:Heat shrink toolholders use thermally induced expansion and contraction to securely clamp tools. They provide high clamping forces and are typically used in high speed machining and long reach applications to minimize tool vibration.
What Shanks Should I Use for Milling Applications?
Choosing the right clamping solution for milling is the hard part of CNC toolholder selection. When choosing a toolholder for milling, you need to realize that they can all have different amounts of take-off, rigidity, clamping torque and balance. Higher performance clamps will be more accurate at faster speeds, ultimately increasing productivity, but the initial investment will be greater.