Background: The pump-drill is an ancient technology that was used world-wide for at least the last 5,000 years. As most (sometimes all) of the parts are perishable, archaeologists are often limited to conjecture based on a few surviving bits. Despite its immense antiquity, pump drills (and their cousins the bow-drills) maintained their currency in the maker's tool kit well into the Industrial Revolution and, in some places, into the 20th century.
My Experience: I made my first successful pump-drill over 20 years ago from scraps around my workshop and a stone drill bit I made for a flint knapping demonstration. I was so impressed by its efficacy and simplicity I was immediately hooked. It became a hit at every primitive technology demo when I brought it out and the hands-on nature really sparked interest in the genius of our ancestors.
The Technology: In a time before consumer culture, most everything was made for a reason and in response to an actual need. People who build things often have a need to put holes in objects and using a bit of stone or metal with bare fingers is not a very efficient use of time. It probably didn't take long for the first hole driller to put the drill bit on the end of a straight stick and twirl it between his or her palms in the same way they learned to make fire from friction. From this point, a bow was added to the system in order to save the hands and ultimately, the flywheel and pump completed the kit. In essence, the pump-drill takes simple linear motion that is easy for a human to produce and turns it into rotation. The addition of the flywheel not only increases the duration of the spin but also rewinds the cord at the end of every stroke. A true piece of genius.
Step 1: Creating the Pieces
I intentionally did not include dimensions for this project as they are not relevant. This is a primitive tool (primitive meaning from the dawn of time, not simple or backward). The shaft in the photo above is about 14" long if that helps. Before beginning this project, I suggest running an image search for pump drills to get an idea of the variety out there. When you are making your own, remember that a longer shaft allows more rotations per stroke but can become rather unwieldy. The longest I have seen are those used by Japanese bead makers.
The components can be easily gathered around the house or the wood pile. The flywheel, in this case, is steatite, a soft soapstone that is easily carved but has a high mass. Wood or other materials can be substituted if they are more readily available. My first drill, many years ago had a flywheel from a mesquite wood log. I chose it for its relatively high mass and availability. The flywheel doesn't really even need to be round. Many older ones I have examined are just blocks of wood or crossed sticks; anything to give mass. However, the mass needs to be centered or the drill will wobble all over the place and carve oval holes.
Step 2: The Shaft
The shaft -
Hardwood of just about any type about 1/2" or a little wider will do. A 5/8" dowel rod would work as well.
The shaft for this project was split out from some aged oak I had in the shop and worked into a cylinder with a diameter of just over 1/2″ (13 mm). The shaft needs to taper slightly, widest part at the bottom, to keep the flywheel from sliding off. I drill the flywheel hole 1/2″ wide and slowly reduce the shaft size until it finds a snug fit. The “chuck” shown here was created by drilling a small hole lengthwise down the shaft and cross-cutting with a small back saw. This allows a square shaft drill bit to lock in place as the shaft is lashed tight. If in doubt, a little glue or epoxy can save the day later. You will need to drill a small hole at the top of the shaft to run the cord through. Alternatively, you can tie a clove hitch at the top (see the second drill below).
Step 3: Flywheel
Flywheel or spindle whorl -
As noted above, a disk or slab of wood or stone drilled with 1/2" hole will work for this.
The key to the flywheel is that it adds mass and helps the drill bit to continue spinning when you reach the bottom of the cycle. It will then wind the cord back up and continue to cut without your effort. Within reason, the heavier the better. This on is drilled 1/2" and has a "key" cut into it with a triangular file.
I learned long ago that through hard use, the stone will sometimes slip around the wood shaft. Cutting a key slot on the shaft with a corresponding one on the stone will solve this problem with the insertion of a sliver of hard wood or “key.”
Step 4: The Cord
Mine is latigo leather but parachute cord, seine line or other tough material will work fine.
Step 5: Making a Drill Bit
Drill bit -
A modern bit will work fine but is difficult to attach without epoxy. Mine is made from a square masonry nail. To make a bit from a masonry nail, simply heat it until it is cherry red and let it cool naturally in order to anneal it. This makes the metal soft and easily worked with a file, stone, or grinder. The end of this style bit should look like a pointed spade and be sharp on both edges.
After it is shaped the point can be re-hardened by heating the point to a dark cherry red again then plunging it in water to cool. What I didn’t document here is the lashing method. After fitting the bit in the shaft, the chuck was secured using heavy cotton thread coated in pine tar. I think that a long-term solution would benefit from using wire but I wanted to keep these simple. We’ll see if they last. If you aren’t concerned with “primitiveness” then a strong and permanent connection could be made with JB Weld or two part epoxy.
String to bind the bit in place -
I used heavyweight carpet thread. Any heavy thread will work. I covered mine in pine tar to protect from the elements. You will want to really squeeze the bit in place and it may take a little experimentation but you will get there with patience.
Step 6: Testing the Product and Wrapping Up
After assembling the parts, I took it for a test drive drilling more soapstone as that is what it will be used for much of the time. I wasn't empirical but it was about 25 pumps to get through 1 cm of stone.
Sometimes things aren't immediately obvious. The kit breaks down for easy travel by pulling the cross bar over the end of the shaft making it much less awkward. And finally, anything worth doing is probably worth doing twice so I made another along the same lines with only a few minor changes. Note the clove hitches instead of holes for the cord attachment.
The best way to learn, is to get up and out and dive right in. Sketch out a plan, gather the pieces and make yourself something worth while.
Check out more projects like these and other ramblings at Paleotool.
Step 7: Follow-up and Test Run
While preparing materials for a primitive tools class I decided to test the new drill on a piece of slate. This is a little harder than soapstone and more abrasive. I didn't have any lubricant handy (e.g., water) but decided to try it out anyway. It cut like a charm! Just a note to those not familiar with these low-tech drills; the hole is generally cut until is just barely pokes through the other side then the object is flipped over and drill from the rear. This keeps the bit from binding as is comes through.