Making the ONI Fire Tool

Some time after creating the X1 leather hardening method in late 2018, it occurred to me that it’s difficult to appreciate the unique properties of this material from photos alone, and I needed to find an easier way to get samples of it into people’s hands. I came up with several designs I plan to implement soon, but I think my very favorite is the ONI Mini Fire Tool, given my fondness for woodland skills and primitive techniques.

This tool combines a bearing for bow-drill friction fires with a mini bellows in a very compact, lightweight device that carries easily on a keychain. The tool is made completely from X1 hardened leather, with a brass spindle bearing inset. The leather is approximately 3.5 mm vegetable tanned cowhide. At this thickness, the hardened material can still be bent by hand, but will retain shape under normal use and can pushed back to form if needed.

This material won’t soften when used near heat like some plastics, won’t transfer heat like metal, won’t snap like wood, and is food-safe and waterproof. In a pinch, you could even lubricate the bearing by scraping some stearic acid off with a blade.

The ergonomics when used as a bow drill bearing are excellent. The bellows tab can be gripped with two fingers, and two stabilize on each side. The curve of the tool places the bearing divot flat and in the center of the palm.

The dimpled brass disc provides plenty of support while drilling, while not warming up uncomfortably. The pointed spindle tip is placed in the divot, and the blunt end of the spindle is placed on the hearth board. Downward pressure is then applied using the fire tool.

The fire bow is then briskly drawn back and forth, and the wrapped string rotates the spindle. As the fire set warms up, downward pressure and bow speed is increased. With practice, one can reliably generate a glowing ember in less than thirty seconds. The ember is then transferred to a light, fluffy tinder bundle, blown into flame, and quickly placed under kindling to start the campfire.

I had originally tested this tool with aluminum from a beverage can, unfortunately it was too thin and failed before I could even achieve the initial burn-in. I then acquired a supply of 0.6 mm thick brass discs, which easily held up to repeated drilling with heavy pressure and showed no signs of failure. There was only slight warming on the back of the bearing block, and I had no trouble getting a coal without the tool becoming close to uncomfortable.

When used as a bellows, the tool is placed against the lips, and air blown through the hole. This allows for aiming a precise and strong stream of air toward your fuel, very handy for precision burning of spoons and bowls, and coaxing damp or struggling tinder to flame. The tool allows a far more accurate air stream than lips alone, and leaves one hand free as opposed to the “four-finger method” which achieves a similar effect but requires holding both hands to the mouth. In testing, I found the mini bellows very effective.

The tool begins by tracing the pattern to a piece of 9-10 oz, vegetable tanned cowhide. The leather is cased (dampened), then a stylus used to make the impression. The shape is then cut out. In the future, I plan to have a custom cutting die made to speed up this step considerably.

I create the divot in the 6 mm brass discs using a grommet setter with a rivet anvil. One solid whack with a hammer, and the resulting impression is just right for a bow drill spindle.

The leather is cased again, and a circle impressed in the middle of the bearing area.

A small wood-carving gouge is used to scoop out a divot of leather in the circled area, about halfway through the thickness.

Once the divot is removed, an Exacto-knife is used to undercut a flap inside the divot, making sure it extends past where the edge of the brass disc will be.

The leather is moistened again, and a modeling spoon used to lift the flap.

The flap is lifted, and ready for insertion of the disc.

The brass disc is carefully coaxed into the hole, the leather being dampened continually to maintain pliability. This took a bit of practice, and is definitely the bottleneck in build time for this item.

With the disc installed, the edge of the divot is lightly burnished, the bellows hole punched, maker’s mark stamped, and the tool allowed to fully dry before hardening.

The next day, the leather has dried fully and is hardened using my X1 method. First, preheated to 150F.

The tool is then immersed in stearic acid molten and cooled to 150F, then the temperature raised to 200F for about thirty seconds. The tool is then removed and wiped of excess while hot. If you look closely, you can see two streams of bubbles from the edge of the brass disc; the preheated leather soaks up stearic acid like a sponge.

The tools are then clamped into a curved shape and allowed to harden. Tools needing slight adjustment can be gently shaped by bending with the hands.

In the freezer for twenty minutes, and the cooled and fully hardened tool is in great shape. A few finishing touches and it’s done.

Edges are beveled to take off the sharp corners.

The edges are then sanded to about 3000 grit.

And the tool is finished! Colors available are natural, black, red, blue, and green. Be aware that the material scratches very easily with normal handling, and will show age quickly and beautifully. In the top photo of this article, on bottom is shown a natural, un-dyed tool after about a week on my key ring. Details have emerged and the leather has taken on a two-tone look I find very attractive. Other colors will change as well, and I’m excited to see what they all look like in a few months.

Back side, simple with clean edges.

Thanks for reading!

Jason F. Timmermans 3/10/2019