A bow drill is most often used for starting a fire – it’s the most efficient fire starting method – but a bow drill can be used for drilling too. A bow drill consists of five basic components – spindle (or drill), board, socket (aka handhold or bearing block), string, and the bow. Here’s how to make and use a bow drill for firecraft and drilling.
Bow drill components and how to make them
Spindle (or drill)
To make the spindle, whittle a 1-foot long round piece of wood or tree branch to a dowel about 1 inch in diameter. Sharpen both ends to points. To ensure the bow drill is as efficient as possible, make sure the entire surface of the dowel is as smooth as possible.
Board (or fireboard)
The board is the base and used to create the embers needed to ignite tinder for your fire.
Begin with a branch about 1 foot long and 3 inches wide. Soft wood such as poplar or cottonwood work best. If a suitable branch cannot be found, you can split a larger branch using an axe or knife to form a flattened board about 1 inch thick.
Cut away any remaining protrusions so you have a flat board (top and bottom). The ideal dimensions for the final board will be 1 foot by 2-3 inches wide by 1 inch thick.
Socket (or handhold or bearing block)
The socket, or bearing block, is the handhold you place on top of the spindle to keep it in stationary while drilling. The spindle must be allowed to rotate within the socket with as little resistance as possible (i.e. we want resistance and friction on the drilling end of the spindle, not the handhold end).
Whittle a 4-5-inch-long piece of wood to form a comfortable gripping surface. On the flattened side of the bearing block, gouge a small hole for the spindle to fit into. The hole should only be about ½ inch deep. Shape the hole to have sloped edges to guide the spindle into the hole during operation.
Note: you can also use bone (look for a naturally socketed piece), shell, or stone for the socket. Some bushcraft knives and sheaths have bearing block holes built into the handle.
String is attached to the bow and wrapped around the spindle. It can also be attached to the spindle using a clove hitch knot and then wrapped around. The best type of cordage is any thick cotton string, leather ribbon, or fibers from plants (formed into cordage if possible). Paracord works great too.
String should be 1 ½ times the length of the bow.
The best bow material will be a straight or slightly bowed green wood branch about the thickness of your index finger. It should be thin enough to be slightly flexible but thick enough to provide adequate strength. The length of the box should be the length of your fingertips to your elbow.
If the bow does not bend well, you can shave away the inside edge to allow inward bending.
Cut slits in both ends about 2 inches deep. The slits will be used to insert the bow string into. Make sure the slits are cut perpendicular to the bend or the string will slip off.
Slide cordage into the slits and tie off.
Preparing the bow drill for operation
Before using the box drill for the first time, the spindle, board hole, and socket hole must be conditioned by burning in the components. Operate the drill as instructed below until smoke begins to form on both ends of the spindle. If only one end smokes, flip the spindle around and continue.
Continue working the drill until the hole in the handhold is smooth.
From this point on, do not reverse the spindle ends. One end will be consistently used for insertion into the bearing block (and lubricated) and the other for insertion into the board hole (to create an ember from friction). Mark the spindle ends if necessary.
Lubricate the bearing block end of the spindle to reduce friction. Facial oil will work if nothing else is available. Fresh green leaves can be stuffed into the handhold hole to help reduce friction.
Place the spindle in the handhold and turn while applying as much pressure as possible. Continue adding lubricant and turning with pressure to harden the handhold end of the spindle and the handhold hole (the wood is hardened by compressing the wood fibers).
Next, make a notch in the board near the spindle hole so ground-off powder can exit without accumulating in the hole. Cut the notch at 45-60 degree angles with the narrow end of the notch beginning on the edge of the hole and widening as it approaches the edge of the board.
Alternatively, you could gouge the spindle hole near the edge of the board so a small section of the hole falls off or gaps at the board edge to allow ground-powder to exit the board into the tinder.
Operating a bow drill
Using a bow drill to start a fire
The technique of starting a fire with a bow and drill is simple, but as with other friction methods, you must exert much effort and be persistent to produce a fire. Still, the use of a socket and bow makes it the most effective friction method.
- To reduce friction between the spindle and the socket we hold in our hand, grease the top of the spindle where our socket will be placed, with any available oil such as hair oil, body oil, soap, etc.
- First prepare the fire lay. Then place a bundle of tinder under the V-shaped cut in the fire board.
- Place one foot on the fire board. If using your right hand to work the bow, put your foot on the left side of the hearth (fireboard).
- Loop the bowstring over the drill, with the arc away from the foot placed on the fire board. The cord is looped around the spindle so that movement of the bow will cause the spindle to spin.
- Place the spindle in the precut depression on the fire board.
- Place the socket, held in one hand, on the top of the spindle to hold it in position.
- Press down on the drill and saw the bow back and forth to twirl the drill.
- Once you have established a smooth motion, apply more downward pressure and work the bow faster. This action will grind hot black powder into the tinder, causing an ember to catch the tinder on fire.
- Blow on the tinder until it ignites.
If the bow drill smokes on the handhold/sprocket end, add lubrication to the spindle on that end. Facial oil works fine. Do not use water! This will cause the wood to expand and create even more friction. You can also add more taper to the end of the spindle (the narrower the spindle end, the less friction) to reduce friction or shoulder the spindle down (whittle the end to reduce the diameter).
If the resulting powder is brown (not enough heat being generated) and fuzzy, you are working the drill too slow (or possibly the wood is too wet). If it is brown and powdery, you are working the drill too slow and not apply enough pressure. The powder created should be dark brown or black.
Using a bow drill to drill holes
Although the technique will remain the same, the wood spindle should be adjusted if you intend to use the bow drill to drill holes. Use a harder wood for the spindle if you intend to drill holes. You may also wrap the string around the spindle multiple times to provide a “rise and fall” action to the spindle.