Project Information
THIS project is making a router jig and and using it to make a template for both a 15 foot and 28 foot radius. The template will be used to sand curved braces for guitars or ukes, and eventually to make radius dishes. The following is confusing, so I will make every effort to answer questions in the comments.
USING the three point method to scribe the arc with a pencil was easy (see LJ "Tooch" Large Radius Arc Jig), but the difficulty was cutting the radius on the band saw and trying to sand to the line. With a base line 30 inches long, and a rise in the curve of only 3/8 inches, staying in the thickness of a pencil line can leave flat spots on the curve of ~6 inches. It took a while to come up with the idea of making a jig for the router to scribe the arc.
THE ROUTER jig is two sided for making a template with both a 15 foot and 28 foot radius. Each channel in the bottom of the jig has two offset straight lines using the three points defining the base line and the center rise of each radius. The jig and template are both 1/2" MDF.
THE TEMPLATE has five "blind" holes for removable dowel pins that serve the same purpose as the nails in the Tooch project. The center pin is common for both radii, and two holes on each side define the end points of each radius. Only two dowel pins are used for any cut - one in the center and one at the end point of the cut. The router depth was set at 3/8" to not cut all the way through the template. The cut in the template was then completed with the band saw, and the edges cleaned up with a flush trim bit on the router table.
THIS PROJECT was very rewarding, but there was a lot of "trial by error" and sleepless nights of consternation. The result met my best expectations for smooth and uniform curves, but keeping track of two curves on both jig and template, which is up and which is down, and which is convex or concave was mind boggling. Now I can get back to work on the two uke's on my workbench.
USING the three point method to scribe the arc with a pencil was easy (see LJ "Tooch" Large Radius Arc Jig), but the difficulty was cutting the radius on the band saw and trying to sand to the line. With a base line 30 inches long, and a rise in the curve of only 3/8 inches, staying in the thickness of a pencil line can leave flat spots on the curve of ~6 inches. It took a while to come up with the idea of making a jig for the router to scribe the arc.
THE ROUTER jig is two sided for making a template with both a 15 foot and 28 foot radius. Each channel in the bottom of the jig has two offset straight lines using the three points defining the base line and the center rise of each radius. The jig and template are both 1/2" MDF.
THE TEMPLATE has five "blind" holes for removable dowel pins that serve the same purpose as the nails in the Tooch project. The center pin is common for both radii, and two holes on each side define the end points of each radius. Only two dowel pins are used for any cut - one in the center and one at the end point of the cut. The router depth was set at 3/8" to not cut all the way through the template. The cut in the template was then completed with the band saw, and the edges cleaned up with a flush trim bit on the router table.
THIS PROJECT was very rewarding, but there was a lot of "trial by error" and sleepless nights of consternation. The result met my best expectations for smooth and uniform curves, but keeping track of two curves on both jig and template, which is up and which is down, and which is convex or concave was mind boggling. Now I can get back to work on the two uke's on my workbench.
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