If you’ve got a power drill, then you probably have a set of accompanying drill bits of various size and shape. When it comes to carrying out a DIY task, it’s not always clear which bit to use - each drill bit is designed for different materials. Here’s a basic guide to understand which to use for each job.
Wood drill bits
Wood drill bits can be identified by a pointed tip. These bits are suitable for all types of wood and come in a range of sizes and lengths. There are generally three types of wood drill bits:
- The brad point, which is specially designed to drill and bore clean, straight, and accurately sized holes in hard and soft woods.
- The Auger drill bit which can cut large, deep, accurate hole. Characterised by a spiralling shaft that comes to a fine, threaded point. Carbon-steel bits are best and can be re-sharpened.
- Flat bits, which have, as the name would suggest, a flat head. The pointed top begins the hole, and the paddle-shaped blade bores a larger, wide hole. They come in a range of sizes and the mm sized diameter hole is marked on the flat head.
Wood drill bits are perfect for rapid drilling through various types of wood. For more accurate work use the brad point drill bit as they tend to be smaller and easier to control.
Metal drill bits
These are known as HSS bits as they are manufactured from high speed steel and often produced by a hot roll-forged process which gives them flexibility and break resistance. They are ideal for drilling steel, cast iron, non-ferrous metal, and plastic. Often characterised by their black colour, no sharp tip but spiral design.
Masonry drill bits
Masonry drill bits are ideal for impact drilling into concrete, brick, and most masonry materials. The shaft spirals up to a tip that is often composed of an extra-hardened material such as chrome alloy steel – perhaps a chrome-vanadium shaft and a tungsten-carbide tip. Sometimes the bit may be a different colour to the shaft due to the hardened coating. The shaft tends to have a fast helix flute for rapid spoil removal, because masonry material will clump into the drill bit.
Other drill bits
Wood, metal and masonry bits are classed as standard drill bits, but there are other drill bits available for specific tasks, or for a particular type of chuck. For instance:
- SDS bits are made specifically to fit an SDS chuck mechanism and won’t work with any other. The end that fits into the chuck has a fluted appearance; the drilling part of the shaft is normal.
- Countersunk drill bits can work to enlarge a hole’s opening so that a screw can fit through.
- Plug cutters cut wooden plugs to cover screw heads and disguise them.
- Hinge cutters have a tungsten-carbide tip which cuts holes for kitchen unit door hinges.
- Tile and glass drill bits have a spear headed tungsten-carbide tip that penetrates a tile or piece of glass, then enlarges the hole to the diameter of the tip’s base.
- Flexible drill shafts attach to the chuck and allow a drill to be used in tight spaces. It has an ultra-long flexible shaft with a small hole at each end that allows you to string a wire in after drilling and pull through.
Hole cutters or holesaws can be used for cutting hardwood, soft woods, plywood, laminates, and some metals. They have a steel cutting edge which provides a long life and variable pitch teeth to enable fast, easy cutting. They can be used with other drill bits to initially bore a pilot hole and to prevent slipping. They come in a range of diameters and depths for the perfect hole size.
Also in your drill bit case…
You’ll also find a few extra pieces in your drill bit case, such as a magnetic bit holder which holds the bit that is inserted into the chuck, and a hex nut driver, which is there to tighten nuts or coach bolts.
A standard drill bit selection may also contain a variety of screwdriver bits such as flat-head, Philips and Pozidriv which are short, come in a variety of sizes and can be easily switched into a standard bit holder. It may also contain a range of Allen bits, replacing the Allen key or Hex Key. Always consider how much strength you need when tightening screws or Allen headed bolts as generally these need a softer touch and an electric drill may be overkill.