Andrew Darley

Senior Technical Support

24 years engineering experience, specializing in milling, turning, grinding & EDM wire erosion.

When searching for Hole Making Tools or Drills there are many facets to take into consideration.

Over time we have been asked all sorts of queries from customers who have varying levels of knowledge and experience. I have summarised below some of the most frequently asked questions that I am asked on a regular basis...

What are hole making tools used for?

Hole making tools consist of a wide range of tooling specifically designed and manufactured to create holes into a workpiece, part or component. Hole making processes like drilling and reaming can be performed on a variety of machines, including both milling machines and machining centres (lathes). The process of hole making involves cutting away unwanted material by piercing the surface of the workpiece at a given diameter. Hole making is usually part of a larger machining program or process which may involve milling processes (e.g. slotting, facing, profiling, end milling) or lathe machining (e.g. threading/tapping, boring, grooving, copying). 

Drilling is the process whereby a drill bit (or indexable drill) enters the workpiece (traditionally on the vertical axis but could be horizontally if, for instance, working on a lathe), and penetrates the material at a given drill depth and diameter. These criteria are determined by the geometry and size of the drill. Reaming is a separate hole making operation performed after a hole is drilled. A reamer’s diameter can be accurate up to 3 decimal places; it will give the hole a more accurate diameter and smoother finish. For example, a 9.8mm drill may be used to produce a hole, followed by a 10mm HSS or Carbide reamer to widen the hole incrementally to ensure the hole is to the desired tolerance.

What are drills made from?

Drills can be made from a wide range of different materials, all of which are suitable for different machine types, conditions and cutting data.

HSS, or high speed steel, drills, is probably the most commonly used drill material. This is due to its tough properties, making them hard wearing in situations where vibrations are present. It can also withstand high temperatures without losing its shape. HSS drills can come with cobalt content in them, including 5% or 8% cobalt content.

Powder metal drills are the bridge between carbide and HSS drills. Powder metal is used where carbide is not suitable, such as in unstable machining conditions but you also want the toughness and wear resistance that HSS offers. Powder metal is a tough substrate that can tolerate increased vibrations over carbide, making them ideal for manual machines or CNC machines where set-ups cannot be stable.

Carbide drills are extremely hard, giving carbide tooling increased wear resistance and tool life over HSS and Powder Metal tools. Carbide drills are usually more expensive than HSS drills, but the difference in performance (productivity) and tool life means that, in the long run with the right machining conditions, carbide can offer higher cost efficiency. Different substrates of carbide will affect performance, but manufacturer’s also tailor specific geometries, coatings and flute shapes to different applications and materials; aluminium drills, for instance, feature polished flutes and are uncoated to prevent clogged flutes. A downside of carbide, however, is that these drills must be used in situations where vibrations are minimized, and set-ups are stable. Without these criteria being met, carbide drills are susceptible to chipping or even snapping. Although they are hard, the material is fairly brittle, which affects its toughness to absorb vibrations.

What is the difference between solid and indexable drills?

Solid drills are any drill which consist of a singular substrate throughout both the body and cutting edge. Solid drills can perform a variety of operations, ranging from general-purpose to high-performance. Commonly, solid drills are chosen for small diameter drilling (usually up to 12mm). The practicality of using a solid drill when drilling diameters larger than 12mm means that it makes more sense to use an indexable drill. The main reason is that solid drills are considerably more expensive once you reach sizes over 12mm due to the cost of materials (especially carbide). Solid drills offer material-specific ranges, with features designed to increase tool life and performance in specific machining conditions.

Indexable drilling has a huge cost-saving benefit, mainly when machining larger diameters (above 12mm). Indexable drills consist of a drill body and replaceable inserts. Some systems, such as the Supercut Spade Drill system, allow for multiple diameter holes to be created using the same drill body by replacing the insert, hence improving cost efficiencies. Indexable drills are available to machines from Ø12-114mm diameter. Indexable drills are excellent for roughing operations, but they are also very good for many operations with a looser tolerance. When machining with an indexable drill you may need to use a reamer to perform further passes to achieve a high-quality surface finish as they usually achieve a surface finish at around 40µm run out.

What materials can drills be used on?

Drills are one of the most commonly used engineering tools, used both in specialist machining workshops and in general day-to-day use (e.g. DIY). As such, drills encompass a wide range of styles and sizes designed for different applications and materials. In theory, users can drill whatever materials they like, and there will likely be a drill to achieve it. For instance, drills exist for cutting wood and glass, as well as metal. At Cutwel, our drills are almost exclusively designed for machining metals, however we do offer drills for plastics and composites too.

HSS and Powder Metal drills are available for a wide variety of materials depending on the substrate content, coating and flute geometries. Even the cheapest HSS drills will be able to deal with carbon and some soft alloy steels up to approx. HRc25-HRc30. Most will also handle some malleable cast iron, as well as aluminium (if the drill is uncoated). Adding cobalt (5% or 8%) to the HSS substrate means that these HSS drills could be suitable for some stainless steel and exotic materials (e.g. titanium and Inconel). Premium Superhardened HSS and Powder Metal drills can also machine pre-hardened steels up to HRc45, as well as providing excellent performance on stainless steel and exotic materials.

Basic carbide drills will give good performance across most of the materials HSS and Powder Metal drills will machine including carbon steel, alloy steel, stainless steel, exotic materials, cast iron and aluminium. However, as the quality (fineness) of the carbide substrate increases, the performance on these materials increase and also new materials can be machined.

What tools are used to prepare or finish holes?

Before drilling a hole, it is usually best practice to create a pilot hole in the workpiece. What this does is help centre a drill and prevent either wonky holes or holes which don’t line up with each other. To achieve this, you would use either a spot drill (on a milling machine) or a centre drill (on a lathe). NC spot & centre drills are made from HSS or carbide and are available in 90°, 120° or 142° and have geometries such as long pilot designs, long body, left hand or with different chamfers. Centre drills create an accurate centre and can be used to locate a live centre. Their primary purpose is to spot or start a precise hole, which will also give a chamfer on the hole. Of course, if your drill has self-centring properties (most commonly found in carbide drills), spotting operations are not required.

Once you have machined the hole you would then use a reamer to finish the hole, Reamers are used to produce high tolerance holes and to improve surface finish on a pre-drilled hole. Reamers are available in a wide range of materials including carbide, HSS & HSS 5% cobalt materials. Hand and machine reamers are available depending on the material or operation it is used in.

What tools can be used for large hole drilling or hole making?

When machining large diameter holes (usually 12mm and above), indexable drills are much more cost-effective. There is a wide range of different indexable drills from general purpose to ultra-high performance and precision.

The King Drill is the ultimate high-performance indexable drilling system. The SPMG U-Drill is brilliant for low-cost general-purpose indexable drilling. The TPDC Drill is an Ultra-High performance replaceable carbide head drill for steel, stainless steel, and cast-iron production. The I-One drill is the next generation high-performance drill with replaceable carbide heads for drilling steel and cast iron. The I-Dream drill is high-performance with replaceable carbide heads for production milling of steel, stainless steel and cast iron. Spade drills are the most versatile drilling system in the world – you can drill from 9.5mm to 114mm diameter using 9 different sized holders. Modular boring systems are available for rough and finish boring at a wide range of large diameters

Do Cutwel supply custom hole making tools?

In short, yes.

Cutwel are expert in the supply of bespoke tooling. We work alongside the best global and local manufacturers to provide bespoke and special tools to suit your requirements.

From simple tool modifications to complex hole-making tools, we can help you with concept, tool design through to machining the final part.

Our experienced technical team are available to advise you on the best solutions and they will work closely with our manufacturers to ensure the tool is delivered to you on time and it meets your tooling expectations and needs.

Can drills be sharpened?

Yes. Cutwel supply drill sharpening machines which can be used to grind HSS or carbide drills (using different grinding wheels for each). Cutwel pro drill sharpening machines are available for either 2-13mm drills or 13-26mm drills. The drill sharpening machine has an up & downswing grinding method, which gives the sharpest and most durable drills. The machine has a fast and simple orientation and has a point angle of 90°-135° (generally 118° is suitable).

High speed steel & powder metal twist drills for general and high performance drilling. Ranges for short and deep hole drilling.

Solid carbide twist drills for general, high performance and extreme performance drilling. Ranges for short and deep hole drilling.

Indexable drill holders inserts with multiple cutting edges available in diameters from 12mm.