A Brief Note on Drills and Drill Bits
An electric drill is perhaps the most common and frequently used power tool. The main job of a drill is to make holes in wood, metal, masonry and other materials. Cordless Electric Drills are becoming extremely popular in both the DIY community as well as with the professional usage. The following image shows a typical cordless electric drill along with all its important parts. A drill usually has a handle with good grip to hold the drill, a rechargeable and removable battery, a trigger switch and a chuck. 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. Apart from these, a drill also has a forward/reverse switch, a torque collar to manually adjust the torque. Coming to the Drill Bits, they are the main rotating parts that make the holes in wood (or other materials). Depending on the type of material we are working on i.e., wood, metal, masonry etc., there are different type of drill bits.
Types of Drill Bits
Before diving into Drill Sizes and Drill Bit Size Chart, let us quickly take a look at some of the popular types of drill bits.
Twist Bit: This is perhaps the largest produced drill bit today. These bits come in almost all drill bits kits and you can use them to make holes in wood, metal, plastic, etc. Coming to sizes, twist bits are available from 1/16 inch to 1/2 inch. Spade Bit: This bit has a flat square shape with a point on the end to make wider holes particularly in wood. The point end centers the bit for the hole and the paddle shape part will follow to make a wider diameter. Wood-Spur Bit: Also known as Brad Point Bit, is a type of twist bit that is primarily used with wood. Unlike conventional twist bits, which have a flat end, the Wood-Spur bit has a pointed end, just like a spade bit. Hence, we can consider a wood-spur bit as a cross between twist bit and a spade bit. Masonry Bit: As the name suggests, we use masonry bits to make holes on concrete, bricks, cement and stone. The tip of these bits is wide and is usually made up of tungsten carbide, which is known for its strength. Forstner Bit: We use these bits primarily with drill presses rather than handheld drills. This bit also helps you make wider holes, just like spade bits. But unlike spade bits, Forstner bit make flat bottoms.
Drill Bit Sizes
Just like other gauges, the Drill Bit Sizes are also defined as per different international standards. 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. Defined 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. The Number & Letter Gauge drill bit sizes are very similar to American Wire Gauge (only in the representation but not the actual gauge numbers). 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. After #1, the gauge number end and letters start with ‘A’ all the way up to ‘Z’. Here, A is next largest drill bit size then #1 and the pattern continues with Z being the largest. Metric Drill Sizes are straightforward representation with the drill size (equivalent to gauge number) is same as the diameter of the drill size.
Drill Bit Size Gauge
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. It is usually a rectangular plate with several holes corresponding to different drill sizes. The following image shows a typical drill bit gauge (not to scale). Image You can use such device to easily identify the gauge of your drill bit.
Drill Bit Size Chart
Let us now see the Drill Bit Size Chart. Since there are different standards and representations, we will also have multiple charts, with chart having the diameter both in inches and millimeters.
Drill Size Chart – Fractional Sizes
Drill Size Chart – Wire Gauge and Letter
Drill Size Chart – Metric Sizes
Conclusion
Drill Bits are an important tool as they are the main part of a Drill that make the hole. Different materials need different types of drill bits. Coming to the Drill Bit Sizes, these are the diameters of holes that we want to make and are represented as gauge numbers, fractional inches or just straight forward millimeters. We learned the importance of drill bits, types of drill bits and also standards associated with drill sizes. We also learned different representation of Drill Size Chart and also all the important Drill Bit Size Chart. (in) Comment * Name * Email * Website
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