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The drills and drilling

The drills and drilling FAQ
An electric drill is likely to be the first power tool that you buy. I exclude wallpaper steamers and heat guns from my definition of power tool as they do not actually *cut* anything. In all probability, the time you buy your first drill will be when you have just acquired your first property. Because of this, my personal recommendation is to buy a drill in the £30 range, as opposed to the £100 range. You can buy the rest of your tool kit with that £70, or put it towards a project like decorating a room. My £30 B&D has lasted for three properties, with over 250 holes into brickwork, plus uncounted ones into wood. When you decide that you really do enjoy DIY, you may want to splash out on a more expensive drill.
The most important thing about a drill for DIY is to be aware that it is a power tool, and as such, if used carelessly it can result in injury to yourself or others. It is also important to be sure that you will not drill into any services. Stud and pipe finders are available at most, if not all DIY outlets. For any work involving drilling into masonry, hammer action is essential, and for some jobs, variable speed is handy. Rechargeable drills are nice, but are best bought as a second drill. My experience is that they go flat two holes before the job is finished.

After you buy a drill, you will need drill bits. These come in a variety of types, and it is important to use the right bit for the job.

Masonry bits:
These are designed for drilling into hard, brittle materials such as stone, brick and concrete. They are the only bits hammer action should be used with, and unless you are drilling into a tile, the hammer action should be used. The hammer action crushes the material in front of the bit, and the rotary action sweeps the fragments out of the hole. Often the dust does not clear out of the hole fast enough and the bit tends to "choke". This wastes the power of the drill, and can result with the bit stuck down the hole, or worse still snapped off in the hole. For this reason, particularly on downward holes ,a "pumping" action should be used. You may wish to have a helper hold a vacuum cleaner hose in a strategic position to catch as much of the dust as possible to make cleanup easy. You may wish to buy a second-hand wreck of a vac for this job, as the abrasive dust may make your nice vacuum cleaner wear out before its time. When the project is finished, you should be able to sell the thing for the same price you bought it. WARNING particularly with masonry the drill bit can become VERY HOT, so be careful not to burn yourself. The tip of these drills is made of tungsten carbide, and needs special sharpening equipment. When the drill becomes blunt, (and it will) it is probably best to buy a new one. Almost all of the masonry drilling I have done is with a 6mm bit, so this is probably the only size you will need at first.

High Speed Steel (HSS) twist bits:
Designed for metal and most plastics, these bits work reasonably well in wood, and if you are on a budget, these are the ones to buy. Most metals and plastics form swarf well, (swarf is the curls of metal or plastic that spiral off during machining) and these travel up the flutes of the drill bit (the helical grooves up the side) fairly freely. Wood, on the other hand tends to form sawdust, and this tends to cause the drill to "choke" with the consequences described above. Hence, it is necessary to use a pumping action with these bits in wood. This is particularly important with the smaller sizes as not only are they easier to snap, but more inclined to choke. If you are drilling metal, the swarf may be very sharp, and the hole edges may be too. You have been warned.

Wood bits:
Designed for drilling wood. (duh)
For 9 out of 10 wood drilling jobs a HSS twist drill will suffice. However, for larger or more accurate holes you will need a wood drilling bit which is specially designed for the purpose. There are three basic types:

Lip and Spur (aka dowel bits) are like twist drills but have a single sharp centre point and two outer cutting spurs. The point means they can be positioned very accurately and the spurs give a a very clean hole. They are especially useful for doweling work where precision is essential. They are available in sizes from 3mm up to 30mm diameter but the big sizes are extremely expensive. The smaller sizes are often available in kits of dowels and come with an adjustable collar so that the hole depth can be easily gauged.
Flat Bits have a centre point but a flat cutting edge and look a little like a small spade. A sharp flat bit will rapidly cut a pretty clean hole and it is possible to resharpen with a file after a little practice. Because of their simple construction they are relatively cheap. They are available in sizes of 6mm up to 38mm. They have a tendency to wander when drilling thick timber and a pumping action is needed to remove the waste sawdust. Some flat bits have a screw thread instead of the centre point and this helps the drill pull itself through the timber.
Auger Bits look a bit like corkscrews. They have a wide chisel-like cutting edge which lifts the waste from the workpiece, and one outer spur which cuts into the timber just in front of the main cutting edge to produce a very clean hole. The deep spiral groove means that waste is removed quickly and the centre screw thread helps the drill to pull itself into the material. They are generally slower than Flat Bits but produce a much cleaner hole, and the length of the spiral means that the hole is more accurate. They are available in standard lengths of at least 100mm, 150mm, 200mm, 300mm and 450mm, with diameters of 4mm up to 30mm. Short augers are especially useful for drilling in awkward positions - like drilling holes in joists. Again, these bits can usually be resharpened with a file and a bit of practice.
There are more exotic types like Forstner and Sawtooth cutters, as well as adjustable boring bits, but these are less likely to be used by the amateur DIYer. Note, you should protect your investment in these drill bits by
storing them in a soft leather tool roll.

Glass bits:
Specialist bits, fairly tricky to use. If you are buying a mirror, it is better to have the holes done by the supplier, and if they crack the mirror it is their problem.

Coring bits:
These are a hollow tube with a bronze-diamond composition at the end, and cut concrete etc. fairly rapidly. They go up to quite large diameter (150mm) sizes, but need a water feed down the middle for cooling and debris removal. Normally these would be hired complete with a suitable drill.

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There are also some accessories which fit drills:

Wire brushes:
OK for light work, but drills are not really designed for off-axis loads, and the wire brush can snatch, so make sure you are out of it's likely path. Eye protection is ESSENTIAL with powered wire-brushing. If you intend to do a lot of wire-brushing use an angle grinder with an appropriate brush, or get a wire-brushing tool. Makita do one such tool, and probably other manufacturers.

Sanding discs:
Most of the comments about wire brushes apply, including the fact that there are specialized power tools for the job. It is almost impossible to avoid making gouges with these discs.

Polishing bonnet:
Good for work on car paintwork, especially for T-cutting a car that has gone dull.

Paint stirrers and mortar mixers:
These can be very tough on a small drill, but one of the bigger ones is fine for the job.

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What do I do if my drill bits are blunt?
The general consensus is that sharpening drills is a difficult art to learn, so the best thing is to buy new ones. Drill bits are much cheaper from ironmongers rather than the sheds.

How do I stop my drill bit from slipping in the chuck?
You could get an SDS drill. This is a system where the bit just pushes into the chuck and clicks into place. The torque is transmitted by splines, so slippage simply cannot happen. However the bits are appreciably more expensive than standard ones, as are the drills. Alternatively, put the bit into the chuck, and tighten it finger tight. Then use the chuck key in all three holes in turn tightening firmly. The extra vibration from the hammer action makes chucks much more likely to back off. You may have seen a "professional" simply grip the chuck and turn the drill on to grip a drill bit, but that is because he dropped his chuck key off his horse. If there is not a keeper for the chuck key built in to the drill, you can keep it in the chuck.

Are there any other tips?
DON'T force the drill. Use about 15lbs. (7kg) force and let the drill do the work. Using too much force will greatly shorten the life of the drill, so don't brace yourself against the ceiling and put your full body-weight on the poor thing. Remember the more force you apply, the worse will be the accident should something give way. To achieve a clean exit hole, particularly in wood, drill through into an offcut of similar material. There is also the rag trick for drilling metal in the uk.d-i-y "Miscellaneous" FAQ.
If your drill has been used a lot, it may become intermittent, work only in some orientations, or give up completely. in this case, it is quite possible that the flex has developed a broken conductor in the flex. Almost certainly this will be in the last foot or so of cable where it enters the drill, often at the end of the strain relief. Cutting off the last foot of cable and rewiring the drill could save you the price of a new drill.

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Last updated 18th. Apr 2000

Thanks to Clive E for his input.

Copyright John Schmitt john49@mdx.ac.uk

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