DURALUMINIUM MATERIALS AND DRILLING INTO THEM

Dural is one of the most widely used aluminium alloys in mechanical engineering, aerospace, the automotive industry and the manufacture of structural components. Compared with pure aluminium, it offers significantly higher strength while maintaining low weight, making it a popular engineering material. To achieve accurate holes without unnecessarily damaging either the workpiece or the drill bit, it is important to use the correct drilling technique and choose the right drill bit.

What Is Dural?

Dural is a collective term for heat-treatable aluminium alloys whose primary alloying elements are copper, magnesium, manganese and silicon. Their specific properties vary depending on the alloy composition and heat treatment.

The Main Advantages of Dural

• Low weight
• High strength-to-weight ratio
• Good machinability
• Good thermal conductivity

Its excellent machinability makes dural suitable for drilling, milling and thread cutting. However, some alloys produce long chips and, if incorrect cutting conditions are used, the material may tend to adhere to the cutting edges of the drill bit.

Choosing the Right Drill Bit

Twist drill bits designed for metalworking are most commonly used for drilling dural. Both the quality of the drill bit material and its geometry are important.

The most common options are:

• High-speed steel (HSS) drill bits for standard applications,
• Cobalt drill bits (HSS-Co) for higher loads or machining stronger aluminium alloys,
• Solid carbide drill bits, particularly in production environments where high productivity, precision and long tool life are required.

For machining aluminium alloys, drill bit geometries designed for efficient chip evacuation are particularly advantageous. Professional manufacturers therefore often use drill bits specifically developed for non-ferrous metals.

Correct Drilling Technique

The quality of the hole depends not only on the drill bit itself but also on the drilling process.

We recommend:

• clamping the workpiece securely,
• using a sharp drill bit in good condition,
• selecting the correct spindle speed and feed rate according to the drill diameter, alloy and machine capabilities,
• ensuring smooth chip evacuation,
• when drilling deep holes, interrupting the drilling process and withdrawing the drill bit regularly to clear the chips.

When drilling thin-walled sections or sheet material, it is advisable to support the workpiece adequately to prevent deformation or burr formation as the drill exits the material.

Lubrication and Cooling

Aluminium alloys generally do not require as intensive cooling as many steels, but suitable lubrication can significantly improve machining quality.

Cutting fluid or an appropriate lubricant helps to:

• reduce friction,
• prevent material from adhering to the cutting edges,
• improve the surface finish of the hole,
• extend drill bit life.

When manually drilling a small number of holes, lubrication is not always essential. However, for more demanding applications or production work, it is an important part of the machining process.

Common Mistakes When Drilling Dural

Although dural is easy to machine, using the wrong drilling technique can reduce hole quality or cause rapid tool wear.

The Most Common Mistakes Include:

• using a dull drill bit,
• incorrect spindle speed or feed rate,
• insufficient chip evacuation,
• drilling without securely clamping the workpiece,
• using an unsuitable drill bit for the specific application.

The right combination of a high-quality drill bit, suitable cutting conditions and careful drilling technique makes it possible to produce accurate holes with an excellent surface finish while extending tool life.

Choose the Drill Bit for Your Specific Application

When selecting a drill bit for dural, the hole diameter is not the only consideration. The type of aluminium alloy, material thickness, required accuracy and machining method are equally important. For occasional workshop use, high-quality HSS drill bits are often sufficient, while production environments frequently use specialised drill bits with geometries optimised specifically for machining aluminium alloys.

The right drill bit combined with the correct machining technique will help you achieve clean drilling, high accuracy and long tool life.