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Wrapping a cone5/18
Does someone know the formula for cutting bendable plywood around a cone?
Jon, I don't think this is going to work as you are hoping, because the grain orientation on bending ply is all on the same axis, so it only wants to bend on a cylindrical plane.
If you want to make cones, your probably going to need to make your own individual single ply wedge shaped veneers that you can lay up over a conical form.
If you want to try that, give a bit more info like dimensions, and I, as well as others here might be able to talk you through it.
In the meantime, if you have a scrap of bending ply laying around, give it a try, and you'll see what I'm talking about. Now having said that, if your talking about a large portion of a conical shape without coming to a point, you might be able to pull that off.
I know the grain will hinder it. There is a formula to use which I can't remember to cut the shape that will wrap the cone. The piece, when cut looks like the pattern of a windshield wiper path.
Click the link below to download the file included with this post.
If anyone on here is using Rhino they can flatten it for you.
I have done this in the past with the veneer laid up on 1/16" mdf.
I got the shape out of Solid Works
There is more info in the knowledge base,where I got the above links.
Well, If you know the radius of each arc, then multiply x pi for the circumference. Then figure out how many times you divide it up into 360 will give you the angle.
You can then measure the distance between the arcs and use the numbers from above to make your pattern.
If you have a good big TS sled, you don't even need to know the actual angle, if you put a fresh piece of 1/4" mdf on and make a cut through with a fine tooth blade. You can then lay the pattern down with one edge along the kerf, then put a stop or fence over on the other edge.
I cut whole stacks up to about 1" on my sleds like this for things like pie cut round tops. You need a good very sharp low hook angle ATB blade, zero clearance support under the veneers, and a weighted 3/4" mdf platen on top to hold them flat.
That will get you the wedges, however, I have no idea how flat or steep you are visualizing. If you brought both of the straight edges of your drawing around by bending, it would be a pretty steep cone. But if you just wanted to have it pretty flat, you'll need to figure the arcs by how far down the axis from the apex those two arcs are for making your bending form.
I know this sounds a bit nebulous. You kinda need to think of the bending form as stations like is used when lofting a boat plan. I hope that helps.
Contributor J gives the formula.
Conceptual understanding of the Cone.
Flat arcs may be bent around a cone. This was common knowledge a hundred years ago before flex trim etc. Commonly used in furnishing crown moldings for radius walls.
A flat but horizontally arched, sprung crown molding, wrapping around a circular wall, is a segment of the cone wall.
The math applies to any sheets, intended to wrap a cone.
A complete cone may also be unrolled and drawn, full size, from its' dimentions Any bendable material is then substituted for the paper.
Ah hell- cut it big and wing it ;-)