Hi Paul O,
I've seen a jig online that can help calculate cove width etc. Of course, I've hunted but can't find it now. So I drew up a crude drawing on MSPaint as a gif image here
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've never used the jig but here's my theory. Anybody...feel free to add or correct if needed.
What you do is take 4 sticks (2 blue and 2 green) and attach them so they fully pivot. A recessed nut and bolt should do the trick. Stick dimension can be 1/2x1/2 or 3/4x3/4, doesn't matter. I would use
1/2x1/2 for mine. I'll explain why later. You'll probably not make a single cove molding any wider than maybe 6 inches so the max width between the two blue sticks will be about 6 inches. So the green sticks will be about 7 inches, giving extra room for attaching the green to the blue. You get the idea.
For your example of a 1/4 inch deep by 4-1/2 inch wide cove, first set the balde height to 1/4 inch. Then open up the jig and position it on the tablesaw as shown in the picture. Bring the blue sticks to the cutting tips of the blade. Next rotate the jig clockwise until the distance between the two blue sticks is 4-1/2 inches. This is the angle you will use. Then proceed with the normal start of making coves on the tablesaw.
I would use blue sticks that are 1/2 in width. Once I have my angle figured out, I'd clamp two straightedges on either side of the jig, then remove the jig. The distance between the two straighedges is 5-1/2 inches. I'll now pass a 5-1/2 inch board to make my cove molding. If
5-1/2 is too wide for the install, no big deal. I can always trim it up to the specs I need after I'm done.
Oh yes, cut more than you need...just in case. :-)
Hope that helps. Woodwork Safely, Jim Barry
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