Pump Drills

In preparation for summer teaching I recently spent some time making a couple new pump drills for demonstrations and hands-on activities.  While some modern tools were used in the production, these are entirely hand-made with no purchased parts or plans.  As I have only made two of these previously I spent a little time perusing images of old pump drills to find good examples to use as models.

Beginning at the end. The first pump drill of the weekend.

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 on the finer points based on a few surviving parts or images available.  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 21st century.

The components of the basic pump drill: shaft, drill bit, flywheel, cross-arm, cord, and flywheel key.

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 “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.

The shaft for this project was split out from some aged oak 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 central hole is “keyed” to keep the weight from sliding around the shaft as it reverses direction.

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.”

My fancy oak key is just a sliver wood. You can literally use a toothpick if you have one in the pantry. Imagine the labor it will save.

Someone could create a nifty GIF animation of this but I think the photos below will assist in understanding how the key works.

A small groove on the shaft holds the key in place while the flywheel is slid over the shaft.

A bit of glue would probably help but I don’t think it necessary if the pieces all fit securely together.

The wheel (or whorl) is slid down the shaft holding the key in place will securely lock both pieces together.

Soapstone is easily worked and can be slabbed, by hand with a hacksaw.  A rasp or an assortment of sandpapers are all that are needed to shape the stone.

 

A simple metal bit can be easily shaped 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.  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.

Anything fun worth doing is worth doing twice. Here are the sibling projects from the weekend.

The second drill, on the left is rigged in a different fashion.  All the connections are made with clove hitches.  We’ll see which we like better.

The rain drove me indoors but it seemed like a good time to take one for a test run. Drilling a block of steatite.
The drill, which hasn’t had it’s final sharpening yet, made it through about 3/8″ of the stone in about 15 seconds.

Spade bits like this one tend to bind as they come through the opposite side so the hole will be finished by flipping the stone over.  Still, the hole is peeking through and ready to finish.

Broken down for storage or easy packing.

Pump drills are an awkward shape to pack when assembled but I discovered early on that they easily disassemble to fit into a very small space.

If you are considering a primitive project as part of your summer “to do” list, give a pump drill a try.  Lots of fun, can be made in a day, and it will impress your not-so-primitive friends.  As a final note, I put an Instructable up based on this post as well.  Have a look if you don’t mind and give comments if you see fit: https://www.instructables.com/id/Primitive-Pump-Drill/

20180529_211322_resized
Follow-up. Drilling slate pendants.

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.

Enjoy…

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