Demotech, design for self reliance

Search for

All Designs

Print this manual.

On this page you can find an explanation on the construction of some of our designs. We're currently in the process of constructing and digitalizing more of our manuals. If you do not encounter the information you are searching for please contact us.

Copyright & Open Source

Creative Commons License
This work is licensed under a Creative Commons Attribution-Share Alike 3.0 License.

Please refer to our work and provide us with usefull feedback and comments on our design initiatives.

Liability clause

We cannot be held accountable for injuries incurred during construction or usage of our designs and construction manuals.

Back to Make it!
Back to A three weeks course with farmers in Guatemala

Harvesting Sheet Metal

To teach a practical person this method for cutting and folding sheet metal will take only a few minutes, even if this person is totally strange to this approach.

Back to "Make It" Manual Index page

Freeing sheet metal from a drum
The smart trick is to drive the sharp point of an axe along a line marked on some piece of sheet metal. Only the sharp point has to cut through. To let the blade sink deeper in the cut spoils the work.
The line can be straight, can make curves or sharp angles. It only takes a little practice to follow the line with the sharp front end of the cutting edge. Fast but light hammer strokes on the flat side of the axe force the cutting.
The edge of the cut sheet bends inwards. This can be flattened, by folding it over some more, then flattening the double layer, this makes the edge stiffer, and soft and safe for handling.
A drum has strong edges made to shape the connection between bottom and cylinder. Good use of this reinforcement is made by cutting close to the edge. Cutting with the axe is easier when the sheet metal does not bend away from the cutting.
But cutting free suspending sheet metal is also easily possible by driving the axe with more horizontal hammer blows at the same time inserting the tip of the axe at a sharper angle to the surface of the sheet metal.
Flattening sheet metal
When an 200 liter oil drum is used to recuperate the sheet metal, the cylindrical shaped side part has to be flattened. This works well by pounding it with a log as shown in the picture. Start in the middle and then works towards the ends.
Folding sheet metal
Folding sheet metal is easy using almost the same method as with cutting. Hammering the axe along, but prevent to make a cut, only make a linear sharp dent in the sheet. Bend over the part that has to be folded. Sometimes it helps to fold over an edge, but with some practice just applying some force and hammer blows does the job.
A nice property of this method of folding is the accuracy of the place where the sheet folds. You get it exactly at the line that is dented with the axe.