Deep Hole Drill Bits: What They Are and What They're For

In the toolbox of a maintenance professional, construction, or any sector that involves the use of drills, deep hole drills cannot be missing. It must be said that, generally speaking, it is especially the construction, automotive, and carpentry sectors that call for these very specific tools. In fact, professional ones.

A DIY enthusiast will hardly need deep hole drills, but it's always useful to be aware of what we're talking about, what the technical characteristics are, and the uses of a good set of tools dedicated to very deep and long holes.

What Are Deep Hole Drills?

With this term we mean drills designed for drilling of great depth on any type of material, from stone to wood. Clearly, coring and soil drilling activities are excluded, activities specific to sectors other than ours.

We remain in the classic definition of drills for deep holes to be applied to drill presses: in most cases – and we will also see some exceptions – we are dealing with drills that have structures similar to those we already know.

But they have technical characteristics capable of guaranteeing maximum performance when you need to make very long and deep holes even on particularly hard materials such as concrete, stone, or solid construction wood.

The Technical Characteristics of These Drills

Regardless of the parameters of the types of deep hole drills, 2 fundamental aspects must be remembered that characterize the structure of the tools in question: the need to eject chips in depth and resistance to high temperatures.

A deep hole presents considerable operational difficulties in getting the waste material out, which must not remain as an obstacle to the drilling of wood or stone. Furthermore, a drill used for these activities must be able to withstand high stress and consistent temperatures. Not surprisingly, the issue is supported not only by the type of drill but also by the material used.

Better HSS or Cobalt for the Drills in Question?

Clearly, the starting point is always a good HSS drill, high-speed steel. That is, high-speed metal that has excellent heat resistance properties. But for more demanding activities, it's better to choose hardmetal in tungsten carbide, perfect for durability and resistance to high temperatures. All this without forgetting that TiN coatings and TiAlN (titanium aluminum nitride) extend lifespan and improve efficiency in demanding applications. Like very deep holes.

What Are the Types of Deep Hole Drills?

The first point to consider is that there are drills for deep drilling that are similar to normal ones, only longer and with specific characteristics for this task. These are the drills you also find in the Krino catalog: they have a ground structure, cross-sharpened point, and a reinforced tip to achieve specific results on long and deep operations.

Not surprisingly, these drills are HSS-co (cobalt) at 5%. A condition that allows working with alloyed steels with resistance up to 1200 N/mm2. There are also other very specific solutions such as, for example, gun drills with a single cutting edge and a channel for the coolant passage. This solution is considered ideal for small diameter holes, while for larger holes BTA drills (Boring and Trepanning Association) can be used, which are more robust.