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"The course has been great for me, first step towards electronic drawing. Here's what a recent student on the course, Cady Dodds, a carpenter designer/maker who runs Perfect Space Carpentry, had to say in an email to me: The marker works for boards up to 4″ wide.Once you have learned the basics in CAD drawing, you will have a skill that will last you a lifetime.
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To mark a centerline, snug the bars up to your stock. Drill holes on these marks just large enough to admit the point of a sharpened pencil. Close the bars together and mark holes in each link directly above the line formed by the bar’s inner edges-this is the precise center of the links, end-to-end. Leave the screws a little loose so the links can pivot. Drill pilot holes for the screws that are 1″ and 5″ from the end of each piece. (The holes should be just barely large enough in diameter to let the screws slip through.) Stack the two links together and drill the holes using a drill press.
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Scribe a line down the exact center of one link and mark two holes with an awl, 1/2″ in from each end. To build the marker, you’ll need two hardwood bars 3/4″ x 1″ x 12″, two Plexiglas links 1/4″ x 3/4″ x 4-1/2″ and four #6 pan head screws 3/4″ long. It doesn’t require any measuring or trial-and-error adjustments. There are many ways to draw a centerline, for example, but this method is very clever. Sometimes it’s fun to build a gadget just because it’s a neat idea.
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