20 April 2020
Whether it’s wood or brass, quite often you’ll need to make a hole in a piece of work when making something. From small holes for handrails to large openings in chimneys, the methods will differ depending on the material you plan on cutting through.
One essential is a set of good quality drill bits, while a mini-drill is also a good investment. Here's our top tips.
Modellers will need a selection of tiny bits, often under 1mm diameter, and these are easily available in graduated plastic boxes. Be warned, not all packs are created equal. The cheapest versions are made down to a price and can contain lots of bits with badly cut points. I've bought boxes for £5.00 where half the tiny bits are useless. Spending a bit more will usually guarantee a full set of useful ones – ask the advice of the trader. Eventually, you will break several of the bits and rather than have half-empty boxes littering the bench, you’ll put the leftovers into a small mixed box for times when a hole roughly large enough will do.
For really small bits, the correct tool is a pin vice. Available in several sizes, these hold the drill bit in a set of jaws and then the vice is twisted between your fingers. Try to have as little of the bit sticking out of the nose as possible, because this will minimise flexing and reduce the chances of breakage.
A useful trick to stop the drill bit wandering is to place a piece of masking tape over the spot and starting the drill on this. Start the drilling slowly as the moving bit can chew up the tape.
If your hole isn't big enough, it can be opened and kept round by using a tapered reamer. Using one of these tools is simple – insert it in the hole and rotate while pushing it gently in. If a precise size is required, keep checking as you work as these things can eat up material very quickly.
A more subtle way of opening a hole is to use a broach. Like the reamer, they are twisted and worked into a hole to enlarge it, but as the taper is very gentle, the action is more controllable. Kit builders will use these to open up axle bearings to ensure friction-free running, handrail knobs where the original hole isn't perfect or holes in etched parts that are too small.
For really large holes in thin plastic sheet, you can't drill, but you can cut using a compass cutter. Either buy a proper tool (these aren’t expensive) or for more modest holes, an ordinary pair of compasses fitted with points in both arms will work. Rotate the tool many times rather than trying to go through in one go. Don’t forget the removed circles, either. These are very useful for making balance weights for steam locomotive driving wheels, when cut to shape.
If you’d like some more advice, take a look at the BRM Techniques page for all our latest guides and advice articles.