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All about drill bits

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Infographic: Types of drill bits

When it comes to drilling holes there is a large diversity of drill bits available but not all of them are the same. They come in different shapes and are made from different materials which correspond the given task. Why is it important to choose the right drill bit? Well the answer is simple, you will ensure that the hole has smooth edges and none of the equipment will be damaged in the process. Obviously, selecting the right drill bit, to a large degree, depends on the material that will be drilled. The best way to determine which one do you require is to get to know the drill bit market. I hope that this guide will be helpful and will leave you informed and ready to purchase drill bits suitable for your needs. Before we start you must know that good quality drill bits are not crazy expensive and with a little maintenance they can last for a very long time. Don’t be cheap and you won’t be sorry.

Check out this infographic: “Different types of drill bits”

 

High Speed Steel (HSS) Bits

HSS-Drill-Bit

This is a general purpose drill bit. It is also known as ‘twist’ drill bits and they are most common ones among all types. They are perfect for drilling through wood, metal, plastics and most other materials. These drill bits are made from “High Speed Steel” and therefore can stand high temperatures.

Titanium Nitride HSS Bits

Ti-Nite-Drill-Bit

These drill bits run cooler, drill smoother and last up to three times longer than standard drill bit set. They are coated with titanium nitride that protects the steel bit for extended performance life. Just like the standard HSS it is used regularly for drilling in wood, metal, plastic and other materials.

Cobalt HSS Bits

Cobalt-Drill-Bit

Cobalt drill bits hold their rigidity and hardness at a higher temperature than standard HSS bits. They are made from cobalt steel blended with a fairly large percentage of cobalt which makes the drill bit incredibly hard and resistant to abrasion. They are used for drilling through stainless steel, cast iron, cast steel, bronze and weld seams.

Reduced Shank HSS Bits

Reduced-Shank-Drill-Bit

These drill bits have the precision crafted from premium high speed steel, also they are hardened and tempered for long life and performance. They are specially designed to fit drills with chucks 3/8” and larger. Ideal for drilling into steel, wood and plastics.

HSS Rivet Bits

Rivet-Drill-Bit

Rivet bits are specifically designed for drilling holes for rivets. Usually they have flutes on both ends and are made to drill shallow holes through thin metal. It is important to know that the hole must be larger than the rivet in order to reduce metal fatigue and allow rivet’s expansion.


Brad Point (Wood) Bits

Brad-Point-Drill-Bit

Also known as dowel or W-point bits. They have a brad point at the end of the bit which allows making clean, straight holes in all types of wood. The bit doesn’t grab because the edges cut through the wood before the center breaks through. These bits sometimes come with depth stops, or small rubber rings that fit around the bit and allow you to choose the depth you would like to drill to.

Masonry Bits

Masonry-Drill-Bit

Used on hammer drills and designed for a variety of masonry surfaces – bricks, concrete, stone. These bits often have tips that are made of extra-hardened material. Certain professional quality bits have a hexagonal shank (rather than a cylindrical one) to stop the bit from slipping in the chuck. They usually tend to heat up quickly when used and this can chip or otherwise damage the tip. When using you should withdraw the bit often in order to clean the flutes as well as use the correct drilling speed.

Multi-Purpose Bits

Multi-Construction-Drill-Bit

These bits have a special diamond ground tungsten-carbide tips and therefore can be used in both rotary and hammer drill mode. They have the ability to drill through almost anything, including wood, masonry, ceramic, plastic and metal. It is recommended to use them on rotary mode, and use masonry drill bits for repetitive masonry drilling.

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Spade Bits

Spade-Drill-Bit

Also known as flat bits, they are designed for rough and ready drilling when the speed rather than the neatness of the hole is important. They can cause splintering of the wood around the entry and exit of the hole. They are available in larger diameters and are ideal for cutting holes in posts and timber supports and joists for cables, wires, pipes and ropes. Also they have a ¼”” hex shank which can be combined with extension shank.

Auger Bits

Auger-Drill-Bit

The design of the auger means that it requires torque rather than a downwards force to move the bit through the wood. The threaded spur acts like a screw and pulls the bit into the wood keeping it on course for very accurate boring. Auger bits are used to make large, deep, accurate holes in dry timber.

Forstner Bits

Forstner-Drill-Bit

The Forstner bit is recognizable by its flat cutting edges which slice through the wood fibers keeping the bit straight during cutting. These specialized drill bits are used for installing concealed hinges which are from 26mm-35mm in diameter. Two types of forstner bits exit: those with a continuous rim which are the best for small holes and make a clean edge; and those with a saw-tooth rim which are better for larger holes and produce rough holes. These bits are commonly used with drill presses.

Countersink Bits

Countersink-Drill-Bit

When there is a need to fit screws flush to, or below the surface of the wood, these are the drill bits for you. They are available with or without pilot drills and have the ability to cut neat conical holes for countersink style screws. There are found in different sizes and different styles for metal and wood.

Drill/Countersink Bits

Drill-Countersink-Drill-Bit

These bits are the combination of a High Speed Steel drill bit and countersink bit. They represent the best possible solution for holes made for countersink-head screws. The drill bit is secured to the bit by a small grub screw and it has the option to be adjusted up and down to the desired length. The drills are multi-purpose and will serve the needs of most woodworkers for both hard and soft woods. 2-3/4″ to 4″ long overall.

Self Centering Bits

Self-Centered-Drill-Bit

These bits are designed to make precise pilot holes in hinges and other hardware. This drill bits end is placed in the hardware’s countersunk holes and it mechanically aligns itself to the hole center. When you place pressure the spring-loaded drill bit is pushed out of the metal sleeve into the work which gives you a perfectly centered hole. These bits are identified by the screw size and they usually get the job done right, quickly and easily.

Spear Point (Tile and Glass) Bits

Spear-Point-Drill-Bit

These drill bits have tungsten-carbide tips that are spear shaped. They can penetrate a tile or a piece of glass before enlarging the hole to the diameter of the tip’s base. Also they have a special coating and make up which allows you to drill smooth holes in glass and ceramic surfaces, including porcelain. When using these the speed must be slow and it is preferable to use a coolant such as water, turpentine or kerosene.

Diamond (Tile) Bits

Diamond-Drill-Bit

These bits are used for hard-surfaced masonry as well as on porcelain. When using these you must commence the drilling at a 45 degree angle to stop the drill bit from slipping. As you continue to drill you can slowly straighten the drill. For proper performance the bit needs to be supplied with water constantly and it must be used at a very slow speed.

Special Direct System (SDS) Bits

SDS-Drill-Bit

An SDS drill bit is thought to provide more efficient drilling and hammering action than a regular hammer drill bit does. SDS drill bits are designed for hammer drilling applications on harder materials such as brick, granite and marble. They have to be durable enough to withstand hammering applications while drilling, which is why most manufacturers construct their SDS drill bit models out of tough, durable materials such as tungsten carbide – one of the hardest materials on Earth.

Step Drill Bit

Step-Drill-Bit

Step bits have a staircase profile that runs from a narrow point to a wider base in a nearly conical shape. These are used for making holes in soft materials or for enlarging existing holes. They can also be used for deburring. These bits have a titanium-nitride coating and can achieve multiple size holes. A similar bit without the steps is called a conical bit.

Plug Cutting Bit

Plug-Cutter

Plug cutters are used for making wooden plugs. They come in a range of sizes and are extremely useful for cutting plugs to conceal screw heads or to replace a knot or other fault in a wooden surface. It is advisable that these bits are used in a drill press because they do not have a centre point to keep them steady and aligned.

Saw Bit

Saw-Drill-Bit

Saw Bits have a High Speed Steel drill bit points at the first 15mm or so, but they feature shafts with abrasive patterns. By applying lateral force to the bit enables it to saw holes into wood and metal. You should also know that drill saws are difficult to steer which can lead to the production of inaccurate holes.

Extra Long Bits

As the name above states these are simply bits which have a much longer length. They are ideal for drilling through walls and especially cavity walls.

Maybe this is the solution

Those who do a lot of drilling may prefer to invest in a drill bit set. One should always use the bit that is designed for a particular job as this will increase the lifespan of one’s bits. Some sets contain only one type of bit (for example masonry bits), and some sets contain a variety of commonly used bits (like the common sizes needed for wood, metal, and masonry).

drill bits set

 

Preservation

These few tips might help you to preserve the life of your drill bits:

  • Use slow drilling speed on hard materials and faster drilling speed on soft materials;
  • center punch holes for more precise drilling; when drilling metal apply cutting fluid if you want to achieve better results;
  • always let the drill bit cool naturally;
  • always make sure that the bits are sharp in order to provide less load on the power tool and better cutting results;
  • always apply pressure in a straight line with the drill bit;
  • in order to prevent the material from breaking you need to reduce the pressure and ease the bit through the last part of the hole.

Look out for

When you are buying drill bits you need to consider three things coatings, type of metal and shank. Coatings like titanium-nitride and even diamond particles can extend the life of the cutting edge of the bit by many times. The type of material determines the strength of the bit, how suitable it is for abrasive materials and how long the bit will remain sharp. Most drills feature a standard cylindrical shank for use in hand drills and powered drills. Other drill bits are available with a 1/4″ wide hexagonal shank for use with quick change chucks that offer faster bit change than conventional drill chucks. Consider what you will be using the drill bit for and how often you will be changing drill bits during the project before you select a drill bit.

Conclusion

There is really a great variety of drill bits which can make your search for the right one a bit overwhelming. Standard bits are generally made for wood, metal, or masonry. As long as one remembers that a harder bit can generally be used on a softer material (but not vice versa), finding the right drill bit becomes a great deal easier.

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Steve G.

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