Start a fire with air

Step 5 Cut the hollow and the seat

On the very end of the piston a hollow is cut using a rounded or squared end drill bit. The hollow may also include 1mm or 1/16" hole, drilled in the center for a total depth of no more that 1mm or 1/16" to help hold the char cloth or twine better. Commercial versions may use a slightly deeper (3/16") hollow with no center hole and with the O-Ring set back behind it for practical use in the field.

For construction of this firepiston I just wanted to see if it the limits of the science and technology that might keep it from working. I tried several other configurations. You can experiment with all sorts of arrangements, including a double O-Ring configuration. Feel free to experiment and learn everything you can in case you ever really need to make one of these out in the field!

I cut the seat for the O-Ring next by placing the other end of the piston in a 1/4" power drill and using a hack saw blade, glass file and the threads of a bicycle wheel spoke as lathe chisels.

The O-Ring is and seat are next lubricated and the O-Ring is slid on and the O-Ring fitted to the inside diameter of the cylinder.