![]() Please note that BS 328 sizing only applies to twist drill bits. There are a variety of standards used to define drill sizes, the most common one in the UK is the British Standard BS 328 set which includes twist drill bit sizes between 0.2 mm and 25 mm.īS 328 drill sizes are defined as shown in the drill size chart below: ø0.2 to 0.98 mm: Metric drill sizes are used primarily in Europe and use metric units to measure the drill bit diameter. To get an accurate measurement, use Vernier callipers, but be aware that depending on the quality of the drill bit, there could be a tolerance error of between 5 and 15 thousandths of a unit. Since there are different standards and representations, we will also have multiple charts, with chart having the diameter both in inches and millimeters.To measure the diameter of a drill bit, it’s best to measure the cutting edge rather than the shank (the shank is the part that is held by the drill chuck). ![]() You can use such device to easily identify the gauge of your drill bit. The following image shows a typical drill bit gauge (not to scale). It is usually a rectangular plate with several holes corresponding to different drill sizes. If you are familiar with the wire gauge (the circular tool that helps you identify the diameter of a wire), there is also a Drill Size Gauge or Drill Bit Size Gauge. Metric Drill Sizes are straightforward representation with the drill size (equivalent to gauge number) is same as the diameter of the drill size. Here, A is next largest drill bit size then #1 and the pattern continues with Z being the largest. The largest gauge number (for example #107) indicates the smallest drill bit size and as the numbers decrease (#1), the drill bit size also increases.Īfter #1, the gauge number end and letters start with ‘A’ all the way up to ‘Z’. The Number & Letter Gauge drill bit sizes are very similar to American Wire Gauge (only in the representation but not the actual gauge numbers). In the U.S., Fractional Inch and Wire Gauge & Letter are very common whereas in the rest of the World, the metric drill bit sizes are predominant.ĭefined in the ANSI B94.11M-1979 Standards, the fractional inch drill bit sizes start from 1/64 inch and scale up all the way to 1inch with 1/64inch increments. Just like other gauges, the Drill Bit Sizes are also defined as per different international standards. But unlike spade bits, Forstner bit make flat bottoms. This bit also helps you make wider holes, just like spade bits. Forstner Bit: We use these bits primarily with drill presses rather than handheld drills.The tip of these bits is wide and is usually made up of tungsten carbide, which is known for its strength. Masonry Bit: As the name suggests, we use masonry bits to make holes on concrete, bricks, cement and stone.Hence, we can consider a wood-spur bit as a cross between twist bit and a spade bit. Unlike conventional twist bits, which have a flat end, the Wood-Spur bit has a pointed end, just like a spade bit. Wood-Spur Bit: Also known as Brad Point Bit, is a type of twist bit that is primarily used with wood.The point end centers the bit for the hole and the paddle shape part will follow to make a wider diameter. Spade Bit: This bit has a flat square shape with a point on the end to make wider holes particularly in wood.Coming to sizes, twist bits are available from 1/16 inch to 1/2 inch. These bits come in almost all drill bits kits and you can use them to make holes in wood, metal, plastic, etc. Twist Bit: This is perhaps the largest produced drill bit today.Types of Drill Bitsīefore diving into Drill Sizes and Drill Bit Size Chart, let us quickly take a look at some of the popular types of drill bits. ![]() Depending on the type of material we are working on i.e., wood, metal, masonry etc., there are different type of drill bits. Speaking of chuck, it has two parts: metal jaws that hold shank of a drill bit and a plastic part that rotates to tighten or loosen the jaws.Īpart from these, a drill also has a forward/reverse switch, a torque collar to manually adjust the torque.Ĭoming to the Drill Bits, they are the main rotating parts that make the holes in wood (or other materials). A drill usually has a handle with good grip to hold the drill, a rechargeable and removable battery, a trigger switch and a chuck. The following image shows a typical cordless electric drill along with all its important parts. ![]() Cordless Electric Drills are becoming extremely popular in both the DIY community as well as with the professional usage. The main job of a drill is to make holes in wood, metal, masonry and other materials.
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