A simple compass for large radii with your own hands. From the scraps that are often in the workshop.

Sometimes there are tasks to draw a circle or an arc with a large radius, but there is no suitable compass at hand.

You can solve such problems in just a couple of minutes and this is not a nail with a string, because the strings are often stretched, although for some situations this may work.

It will be about making a template from scraps of thin strips.

On a suitable rail, you need to make two marks: one for the center, the other for the arc.

For the center, a mark is made at the edge of the rail and in the middle of its width.

The second mark is placed at a distance equal to the radius of the required circle.

Further, with the help of a drill or screwdriver and a drill with a large pencil diameter, indentations are made along the marking. I did it with a countersink with a diameter of 12 mm.

The first hole is made shallow so as not to split the rail when tightening the screw. In order not to split exactly, you can make a through hole with a thin drill.

The depth of the second hole must be controlled and stopped when the tip of the pencil can be inserted into it.

Next, a self-tapping screw is screwed into the first. This self-tapping screw will be the center of the desired circle.

A pencil is inserted into the second hole and that's it - you can use a compass.

This rail can serve as a template for several radii, it is enough to make markings and holes for a pencil at different distances from the center.

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Alexander.

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