How to choose the right end mill

When selecting an end mill, we recommend following three steps:

1. What do you want to mill – a slot, a general profile, or do you need to rough the material?
2. What material are you machining?
3. What tool diameter and dimensions do you need?

The first two points determine which of the four design ranges to choose. Only then do you select the specific size.

You need to mill a slot

For producing slots, use the 2-flute slot drill DIN 327.

The two cutting edges leave more space between the flutes for chip evacuation, and the design is specifically intended for slot milling. The cutter is centre-cutting, so it can also cut with its end face and is suitable when you need to start a slot within the surface of the material.

When is it the right choice?

• you are milling slots from solid material,
• you are producing, for example, a keyway,
• you need a tool designed primarily for slot milling,
• you need the cutter to engage with its end face.

If slot milling is not the main requirement and you need to perform various general milling operations, a general-purpose type N end mill is more suitable.

You need one cutter for general milling operations

For general milling, use the general-purpose end mill DIN 844 type N.

It is suitable where neither specialised slot milling nor intensive roughing is the main task. It can be used for general machining of edges, surfaces, shoulders and other standard milling operations.

When is it a good choice?

• you are looking for a general-purpose end mill for regular workshop work,
• you switch between several types of milling operation,
• you do not need a special geometry for aluminium,
• the result should not be only a rough preliminary material removal stage.

A general-purpose end mill can also perform some operations that overlap with the use of a slot drill. The difference is therefore not that one can mill a slot and the other cannot. The 2-flute slot drill is specifically designed for this operation, whereas type N is more versatile.

You need to remove a larger amount of material quickly

If the main objective is roughing, choose the roughing end mill DIN 844 type NR.

A roughing end mill is designed for preliminary material removal. Its purpose is not to produce the finest possible finished surface in a single pass, but to prepare the workpiece efficiently for subsequent machining.

When is it the right choice?

• you first need to remove a larger amount of material,
• you manufacture a component in several machining operations,
• roughing will be followed by a finishing operation,
• material removal is more important than the final surface quality after this operation.

If the same cutter is mainly intended for more precise general milling and a better finished surface, type NR is not automatically the best choice.

You are machining aluminium or soft non-ferrous materials

For aluminium, the range includes a dedicated end mill DIN 844 type W.

The reason is not only the tool material itself, but especially the geometry adapted to machining soft and ductile materials and to evacuating the resulting chips. Chip formation and chip evacuation are among the important differences between milling aluminium and machining steel.

When should you choose it?

• you are machining aluminium,
• you work with aluminium alloys and other soft non-ferrous materials,
• you want to use a geometry designed specifically for this type of machining.

Unlike the first three groups, this range is supplied uncoated. The other three current OREN ranges have a TiAlN coating.

Only then choose the diameter

Once you have selected the correct type of end mill, choose the specific diameter according to the required size of the machined surface, slot or other feature.

The diameter alone therefore does not replace the need to select the correct cutter design. Two cutters with the same diameter can be intended for very different work.

Where and how end mills are used in practice

End mills are used mainly in machining workshops, metalworking, toolrooms, maintenance departments and CNC production. These are tools for machine cutting, not rotary burrs intended for hand-held use in die grinders.

One-off and small-batch production

In smaller machining workshops, end mills are used to manufacture and modify individual components. Depending on the operation, you can for example:

• produce a slot,
• machine an edge or shoulder,
• machine part of a surface,
• remove excess material before finishing,
• manufacture or modify an aluminium component.

Practical example:
You need to produce a keyway on a shaft or another component. For this operation, choose a 2-flute slot drill. If you need to carry out several general milling operations on another component, the general-purpose type N is more suitable.

Manufacturing components in several operations

When removing a larger amount of material, it may not be appropriate to try to achieve the final shape and surface in a single operation.

You can first use a roughing end mill to remove the required amount of material and then change to a tool intended for finishing or more precise machining.

This approach is typical where fast material removal needs to be separated from the requirements for final dimensions and surface finish.

Machining aluminium components

Aluminium components are used, for example, in mechanical engineering, equipment construction, fixture production and one-off component manufacture.

For machining these parts, it is important to select a cutter with suitable geometry. This is why the range includes a separate type W. It is not simply another general-purpose cutter in a similar design, but a range intended specifically for aluminium and other soft materials.

Maintenance and toolrooms

End mills are not only tools for CNC series production. They are also suitable for:

• manufacturing a replacement part,
• adjusting the dimensions of an existing component,
• manufacturing fixtures,
• repairing machine components,
• modifying slots or other design features.

For a smaller manufacturing company or maintenance department, it is therefore important to distinguish whether you need a general-purpose, slotting, roughing or material-specific design.

How to work with end mills

The end mills in this category are intended for milling machines and CNC machining centres with a suitable tool holder. All four current OREN ranges have a Weldon shank to DIN 1835 B.

Tool holding

A Weldon shank has a flat clamping surface against which a clamping screw acts in the corresponding holder. The tool must therefore be used in the correct holder for the shank diameter.

Before starting work, always check:

• the correct holder size,
• that the tool is clamped correctly and securely,
• the condition of the cutter and its cutting edges,
• that the selected cutter is suitable for the material and the intended operation.

These end mills are not intended for use in a standard hand drill or cordless screwdriver.

Cutting conditions are not selected solely according to cutter type

Speed, feed and depth or amount of engagement depend on several factors at the same time:

• cutter diameter,
• material being machined,
• type of operation,
• tool holding method,
• machine capabilities.

It is therefore not correct to use one universal spindle speed or feed value for the entire category. Cutting conditions must be adapted to the specific tool and operation.

Distinguish between roughing and finishing

When working with a roughing end mill, remember that its main purpose is material removal. If you need a finer finished surface or an accurate final dimension, another operation with a suitable tool may follow.

This is an important difference from a situation where you are looking from the outset for a cutter for general or finishing machining.

When slot milling, pay attention to cutter design

For milling a slot from solid material, this range includes a 2-flute slot drill. It is centre-cutting and its design allows cutting with the end face.

However, axial plunging capability cannot automatically be assumed for every end mill simply from its appearance or diameter. With a different design, always follow the intended use of the specific tool.

Typical mistakes when selecting and using end mills

• selecting a cutter only by diameter without considering the operation,
• using a general-purpose geometry where an aluminium cutter would be more suitable,
• expecting a finished surface after a roughing operation,
• incorrect or insufficiently secure tool holding,
• using an unsuitable machine,
• using the same cutting conditions for different diameters, materials and operations.

Choosing the correct end mill therefore always starts by clarifying what you are machining, which operation you want to perform and which machine you will use.

How is the range divided?

The current OREN end mill range is divided into four groups according to the main application and the material being machined:

• Slot drills – 2-flute DIN 327 cutters intended mainly for producing slots. The centre-cutting design allows cutting with the end face and is suitable where slot milling is the main operation.
• General-purpose end mills – DIN 844 type N end mills for general milling operations. They are a suitable choice if you need a more versatile tool for machining steel materials and do not require special roughing or aluminium geometry.
• Roughing end mills – DIN 844 type NR end mills intended for roughing and preliminary material removal. Choose them when material removal is the main objective and a finishing operation may follow.
• End mills for aluminium – DIN 844 type W end mills with geometry intended for aluminium and soft non-ferrous materials. This range is uncoated; the other three current ranges have a TiAlN coating.

After selecting the correct type of end mill, choose the specific variant mainly according to the required diameter and tool dimensions.