mating radii

[swarfrat]

I just discovered the radius dish recently, and some of the howtos on making them got my wheels turning. I think the dish itself is typically used for sanding, the actually carve out a radius, putting the router on rails seems to be the ticket.

But... How do I carve out two mating domed surfaces? I had this crazy idea for a lam top. Take a thicker than normal blank (say 2") , and a thicker than normal top. T(say 1/4-1/2") temporarily stick em together,index them, and rough cut them on the bandsaw.

Split em, dome the tops of the blank and top, dish the bottoms.  (This is why they need to match very closely).  Stick em back together and route to shape. (Jazz Bass with a guitar neck pocket btw).

Shazam! You now have a cool three dimension dished body. Actually this wouild be coolest on a shape like the musiclander, where you might can see the effect a little better.

So in the interest of carving mating surfaces, it seems a good idea to be able to use the exact same form for both operations, but the rails I've seen people make are sort of gravity assisted single sided deals. Anyone seen something like this done using jigs (rather than CNC)

 

[Cagey]

I did it some years back to make seats for some bar stools. It was called a "scooping jig". Worked pretty well. Thing is, they're only good for symmetrical shapes, which you don't have with a guitar top. Tops are asymmetrical in the extreme, so you really need a CNC machine to pull it off.

 

[swarfrat]

This isn't for a traditional carved top. More of a Salvador Dali/Warwick/ jbass left in the car on a hot day. It's still essentially a constant thickness slab on another constant thickness slab, but morphed into a curve. The top would just be like a contact lens, so that whatever the body shape is cut to, it follows the perimiter at a constant thickness.

I'd look at the scooping jig when I can see it on a bigger screen. But it's occured to me that if I make my rails, I can cut the curve twice, then pin the two halves together so the router sled follows a captive track that can be inverted.