While most of the tools in the kit of a bone worker are relatively simple affairs, occasionally something a bit more special is called for. The most common of these is a drill of some description. A knife will suffice for many small holes, such as a suspension hole for an amulet or even a stitch hole in a belt buckle, but for certain tasks such as riveting, a regular parallel sided hole is much better. The way to achieve this with any certainty is to use a drill.
The smaller drills used during the period essentially come in two flavours – the pump drill and the bow drill (see below).
Pump drills are very good, but can be quite difficult to make so that they work efficiently, a bow drill however is very easy to make and use if a few particular points are followed.
Parts of the bow drill
Below is my own bow drill setup. It consists the three parts; the bow, the spindle and the cup.
If you have looked at bow drills before or spoken to anyone about the, you may have heard that you need specific wood, or that the spindle should be make from XXX. I will take wild guess here, but if you have been told that then the chances are it is referring to a bow drill used for fire lighting in which case the wood for the spindle and the hearth are very important as they directly affect your chances of it working (incidentally, my own suggestion would be willow/willow or willow/lime for the spindle and hearth of a fire lighting bow drill).
In the case of a bow drill that is to be used for actual drilling of holes, then the choice of wood is much less important. The bow itself should not be too flexible as this can cause the cord to slip on the spindle, but neither should it be too thick and totally inflexible. Also, the bow does not have to be curved; a relatively straight piece will work just as well. Personally I use a piece of ash (cut green) about 3/4″ wide and about 24″ long, and notched approx 2″ from either end. The cord I use is a heavy hemp rope about 36″ long. Some people like to permanently attach the cord to the bow but because of how I use it I prefer to have them separate.
As for the spindle, any decent tool handle wood or hardwood will make a good spindle. Avoid anything soft e.g. cheap pine as it will not grip the drill-bit well enough once pressure is applied. Again, opinions regarding shape differ – some people prefer a roughly parallel sided spindle, but I find that a waisted spindle works best for my style and the thickening at either end prevent the knot travelling up and down the shaft. The drill I normally just wedge into the centre of the spindle, piloting it slightly if it is a larger width.
Finally the cup is simply a large limpet shell from the beach. The smooth inside is excellent for reducing friction against the top of the spindle. If you are working particularly vigorously the shell can heat up quite a lot, so use either two shells on top of each other, or a piece of damp leather between your hand and the shell.
Assembling the bow drill
This is the part that seems especially simple but how you do it can make the difference between a working bow drill and a collection of objects that fail to work together and just generate frustration. I am sure I wasn’t the first and neither will I be the last person who saw someone else assemble and use a bow drill and thought “aha, you wrap the cord around the spindle it works!”
No, it doesn’t. At least not for an effective and efficient drill.
I found the key element to assembling a successful bow drill was how the cord is attached to the spindle. Rather than just wrapping the cord around and hoping for the best, tie the cord onto the spindle. The best knot I have found for this so far is the clove hitch. Here is a quick rundown of how to tie a clove hitch.
1. Make two loops in the cord as shown in picture 1, making sure that in one loop the loose end passes UNDER the middle of the cord and that in the other it passes OVER the middle of the cord.
2. Lay the two loops over each other, with the loose ends coming out from the between the two loops (pictures 2+3)
3. Slide the spindle through the centre of both loops. Centre the loops on the middle (or narrow section) of the spindle.
4. Holding both ends of the cord, pull them tight so that the knot tightens onto the spindle.
Once the clove hitch is tight onto the spindle it should take quite a bit of force to rotate the spindle within the knot. If your cord is separate from the bow (like mine) now is the time to hook it into position. Taking one side of the cord, wrap it below the knot on the spindle, following the direction it is pointing, then repeat with the other side of the cord but above the knot. For example, on picture 5 above, the cord to the left would be wrapped above the knot in a clockwise direction and the cord of the right would be wrapped below the knot in an anti-clockwise direction. The diameter of the spindle, and the length and thickness of the bow and cord will all dictate how many turns you will be able to manage above and below the knot, my own bow will manage 2 in either direction. The number doesn’t matter but try to keep it roughly even e.g. 4/3 not 5/2. The image below shows this. Sometimes the last turn can be quite hard to achieve and I often have to brace the bow and flex it slightly to get the last turn of the cord.
After the spindle is wound with the cord, the drill is ready to use. I find that the drill bit has a tendency to skitter, so I usually start the hole with an awl point to give the bit something to engage with. Place the drill bit in the pilot hole, and holding the cup in your left hand (assuming your are right handed) over the top of the spindle bring the spindle vertical. Use the bow in your right hand back and forth while applying gentle but firm downward pressure on the spindle and you will drill your hole, as in the image below. As the knot holds the cord in one position on the spindle, the winding and unwinding of the cord above/below the knot will cause the bow to rise and fall as you drill.
In addition to drilling holes, this drill can also be used with something like a ring and dot bit to speed up decoration.
Hopefully this will help a few of you to make one of these rather useful tools, as for me I am off to Largs viking festival to eat lots of hog roast and have fun playing a 13th c chap with a big sword! 😀