In my woodworking career there have been numerous times I needed to scribe an arc or a complete circle, usually full size. For example, scribing the trim for a 6' wide circle head window with a 3' radius or making a template for rounding off the corners of a curved archway.
A handy idea to use for a large woodworking compass in the field, is to make a compass from a length of 1x2 or a similar size ripping. Yes, the yuppies use what they call trammel points, a point attached to a block and a pencil attached to a block with a specific sized stick of wood, or beam between them. The adjustment is made by sliding the ends along the beam to arrive at the correct radius. Well, although I have a pair of trammel points it's often faster to pick up one of the rugged and ever present sticks laying around a woodworking site. I measure the correct radius from the square end and drive a nail through it at this point. With my pencil always at the ready, I scribe the arc while the nail holds the center point fast into the piece of wood or plywood onto which I want the circle or arc drawn.
Here is a drawing of a simple woodworking compass:
Dave(Ask Dave) (About Dave)
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