For high accuracy, clamp down your workpiece and use a drill press. A hand drill may cause precision issues. You can therefore use a brad point drill bit jig to level and increase accuracy. A unibit (often called a step drill bit) is a roughly conical bit with a stairstep profile. [11] Due to its design, a single bit can be used for drilling a wide range of hole sizes. Some bits come to a point and are thus self-starting. The larger-size bits have blunt tips and are used for hole enlarging. The best drill bits for plastic are spur (also known as dowel or Brad point) bits. These bits essentially have a four-point tip, which results in a much neater entry point and a cleaner hole. A countersink is a conical hole cut into a manufactured object; a countersink bit (sometimes called simply countersink) is the cutter used to cut such a hole. A common use is to allow the head of a bolt or screw, with a shape exactly matching the countersunk hole, to sit flush with or below the surface of the surrounding material. (By comparison, a counterbore makes a flat-bottomed hole that might be used with a hex-headed capscrew.) A countersink may also be used to remove the burr left from a drilling or tapping operation.

It is true that you can use Brad point drill bits for all types of drilling work. The function is basically the same, but the difference is that Brad point drill bits will drill straighter and leave less excess room. This makes little difference in drilling standard holes, but it quite important when drilling holes for pins that hold together shelves, cabinets, and the like. Their spiral flute makes it easy to sink into the wood and with the right length and diameters; you can have variable diameter holes as you like. However, there is a limit to widening holes using a brad point bit. Sizes and Diameters Bits are commonly available in sizes from 8–50mm (0.3–2.0in) diameter. Sawtooth bits are available up to 100mm (4in) diameter. Rather than using a Brad point/dowel/spur bit, you can also use a step drill bit to make clean holes in plastic.

It’s also crucial that you use a drill bit designed for plastic, given how difficult it can be to create a clean hole using any other type of bit. At times, you may find the name brad point bits being used in place of these bits and are mainly used for boring small-medium-sized holes in timber. Further, you can also use them to drill holes in plastic since they don’t emit friction which may cause melting. A brad point drill bit is a modified twist drill with a long sharp point at the end of the bit that resembles a brad nail (hence the name). This central point helps to position the drill accurately and prevents the bit from skating. The two spur cutting edges of the brad point bit produce clean holes with very less splintering or tear outs on wood. Hence the brad point drill bits are also known as spur point bits or wood bits.

More gentle bits designed for use with wood will perform a little better, but may not have the right style of tip to make a clean entry into the plastic you’re drilling. Is it worth buying a drill bit set? For sharpening, you could use the drill sharpener, the grindstone jig, or even an oilstone will work.Carbide-tipped: one of the hardest materials on the planet, this drill bit only uses carbide on the tip. It’s suitable for drilling masonry, tiles and concrete. Most brown wall plugs are 7mm in diameter, so to drill a hole for a brown plug, you will need a 7mm drill bit. For sharpening, you can use the regular drill sharpener or a grindstone. Both are efficient at sharpening these bits. This is sort of similar to using a regular bit with a steep angle tip, except step bits will offer more control over your drilling.