Different types of drill bits – Drilling accurately into wood will be made easy if you use the right equipment. A whole range of bits is available for use with swing braces. hand drills (sometimes known as wheel braces) and electric drills, although swing brace and drill bits are often not interchangeable because of the type of fitting. Each bit is specially shaped to do a specific job. so it is important to check which one you need for the work in hand. Bits are available in a range of sizes, with width measurements in both metric and Imperial.
Used specifically for drilling into wood. the most common auger bits have a clearly defined spiral so the waste is cleared rapidly iron the whole when
drilling. Auger bits with tapered ends must be used exclusively with a swing brace fitted with Alligator type jaws. Straight shank bits can be used with a swing brace fitted with Universal jaws. Two types of auger bit are used with the brace, the Jennings and solid centre pattern bits.
Jennings pattern The most common type, this is particularly suitable for drilling deep holes since the long spiral keeps the hole straight.
Solid centre pattern Although this is not as accurate as the Jennings pattern, it has a slightly faster drilling action.
Often referred to as twist drills, twist bits are the most common drilling tools used by the handyman with either a hand or electric drill. You can buy
them individually or in sets; the usual sizes are 0.8-6mm (* tin). Designed for drilling small holes, they do tend to clog quickly so when drilling
deep holes (especially in hardwood) the bits should be withdrawn regularly to remove the waste.
Warning Take particular care when using the smallest sizes since these bits are thin and brittle. Always hold the drill square to the work and apply only light pressure when drilling.
Depending on the type of work and material used special purpose bits are available, some for use with a brace and some for use with a hand drill or an electric drill.
Expansive bit Suitable for drilling into softwood. it has an adjustable cutting head so you can drill different size holes into wood at least 13mm (]in) thick. However it is difficult to keep straight when drilling deep holes.
Forstner bit Ideal for accurate drilling of flat-bottomed holes. But you will have to apply a lot of pressure when using it.
Centre bit Its use should be restricted to drilling through plywood. Unlike the spiral twist auger bits, this type of head is inclined to wander off course when drilling deep holes.
Countersink bit Different patterns are available for drilling with a brace or hand or electric drill. Its cutting edge funnels out the surface of wood to take the head of a countersunk screw. Once the cutting edge of this bit has worn down you will have to replace it.
Screwdriver bit For use with a brace or hand or electric drill. You must use a multi-speed electric drill since you have to work at very low speeds.
Dowel bit This bit, which drills flat-bottomed holes into wood, must be used with an electric drill at full speed. lt tends to be difficult to control since it drills quickly without the accuracy of an auger bit.
Flat bit Popular for use with electric drills. it is suitable for drilling wider holes in wood. Take care, particularly when working with hardwood, because the bit tends to overheat and blacken along the cutting edge. This indicates the steel has lost its temper and the cutting edge is ruined. Keep the bit as cool as possible by using it only in short bursts.
Power bore bits As long as the cutting face is kept sharp, there is little risk of this bit overheating quickly, therefore making it ideal for deep drilling into wood.
Screw sink bit Available in sets, this type is multipurpose since it drills a pilot hole of the correct diameter for the screw and countersinks for the head of the screw in one drilling operation.
Hole saw bit useful when making large holes in thin gauge material such as plywood. Different diameter holes can be drilled by changing the ring saw around the centre pilot drill.
Spear point bit Used at slow speed for drilling glass. The point should be continually lubricated with turpentine or white spirit during drilling.
Yankee drilling point bit Special small drilling bit available for use with the push drill and Yankee pump action screwdriver. This is ideal for making small holes.
Heavy duty bits
These are designed for drilling into hard materials such as masonry, brick and concrete, because they have specially treated cutting edges.
Masonry drill This type of twist drill. used at slow, speed. is suitable for drilling into masonry and brickwork. It has a tungsten carbide cutting edge which must be resharpened by the manufacturer.
Percussion drill Looks like the masonry drill and also has a tungsten carbide cutting edge. lt is. designed for use with a percussion or hammer drill for boring into concrete. Always use it at a slow speed. The cutting edge will have to be resharpened by the manufacturer.
You can resharpen slightly worn cutting edges on the Jennings and solid centre pattern bits and the expansive bit yourself, using a 100mm (4in) medium cut flat needle file. Work very carefully using the original angle of the steel as a guide until you have formed a keen edge on the bit. The Forstner bit will probably have to be returned to the manufacturer for resharpening. The screwdriver bit can be reground.
Twist bits must always be kept sharp, which used to be difficult because of the problem of maintaining a symmetrical cutting head by hand-filing. There is now an easy-to-use twist drill sharpener which will give most of the twist bits in the range a balanced cutting edge.
Originally posted 2015-07-31 08:08:15.