Some time ago there was a link on this newsgroup for a program that helped to determine the angle and blade height use to run a board across a 10" table saw to cut coves for moulding for specific profiles. I had it on another computer but now can't find it.
Are you simply talking of the use of an angled fence w/ a sawblade to cut coves? If so, it's simply the projection of the partial arc at an angle which is relatively straight forward geometry. If someone doesn't come up w/ the already done one, I'll try to find time this evening to cobble something up....but no promises! :)
It is actually 2 parallel partial arcs offset by the width of the blade. Sounds pretty hairy. I'd be looking at making some sort of hefty and stable sled to do this.
Seems like I remember that you entered the wood dimensions (width and thicknes), the blade tilt and height and the angle across the blade and it displayed an image of what the cove actually looked like. It saves a lot of trial and error to get a desired profile. I think you could also enter the rouigh radius and width of the cove and it would give the other parameters (angle, blade heigth and tilt).
Distance across cove [at bottom] = cosine of the angle turned times the distance across the blade. So, set the blade height you need, and measure the distance across showing above the table. Then turn the miter by the angle whose cosine is the required diameter of cut [across the bottom] divided by the measured blade distance.
That is: With blade distance showing as D, and the required distance across the cove being d [the height being already fixed], then the angle is arcos(d/D). use tables, spreadsheet, or calculator [or slide rule?]
Once you know that you can set the angle smaller and nibble your way up to the final cut instead of stressing the blade. Frankly, I'd rather buy the stuff done and get on with the project.
I've never seen the program but I use a simple jig to get the cove width I need. I make an 18" (or so) long hollow rectangle out of scrap with the long sides the same distance apart as I want the cove to be wide. If I want a 2" wide cove my jig would measure 2" inside the rectangle x 18" (or whatever) long. I lay the jig over the blade as if I was going to rip it (long ways) with the blade inside the rectangle. Then I roll the blade up to the final depth I want in the cove. Next, I turn the jig until it touches the front and back of the blade. This gives me the angle I need to make the desired cove width at the final blade height. If you know you need 1" of flat after the cove detail you can make the jig with 1" sides and clamp the fence right against the jig. Remove the jig, roll the blade down and make several passes to get back to the final blade height/cove depth. If you need a jig for many widths of cove you can make the jig so that it pivots at all four corners. This gives you a parallelogram that can be changed to the width you need.
Not really...I've done it numerous times to make large coves. All it takes is a good fence and a sharp blade. Don't try to hog the whole thing out at once.
For really large coves, one marks the outline and makes some preliminary cuts to remove most of the waste and then uses simply one or two angled passes to clean up the profile.
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