Drilling is one of the most important processes in manufacturing, enabling holes of different shapes and sizes to be made in a variety of materials. However, drilling machines vary considerably, as they are designed to carry out different jobs, so it’s essential to understand which type is most suited to your production needs.

If you’re planning an engineering project in which you’ll need to drill holes into metals, it’s essential to choose the most suitable method of drilling to achieve the optimum results. Drilling and trepanning are two options, but it’s vital to understand the difference, and the advantages, to make an informed decision.

Trepanning is a machining technique for drilling large diameter holes in materials, particularly where there is a requirement to retain the solid core or when tolerances are not particularly tied up.

Trepanning is basically deep hole boring with a difference in that it leaves a core. It is an efficient method for drilling deep large deep holes that is more cost-effective than deep hole boring.

The most common use for trepanning is cutting a core out of a larger solid leaving two pieces. The removed material is not reduced to swarf as with drilling but remains a solid billet. The most common example is a solid billet that is left with a hole bored through from end to end and a second smaller round bar that is excised by cutting around it. It can be intended as a roughing operation, destined to be machined further or honed to a finer finish. Alternatively, trepanning alone is sometimes adequate for the job in hand. In fact, people often ask for trepanning when all they want is a deep hole or process bore.

This is a part that has been trepanned.