Cutting Adjustable Concaves

Tom R

Needed to cut some concave radii out of the back of some tapered lengths of Azek so they could straddle tight onto my 8" round, tapered columns and yet form plumb casings.

I did it by setting a (make-shift) fence at a diagonal angle to my 10" cabinet saw blade and then running the tapered-side down as it veered diagonally into the 'sides' of the blade-teeth.

By setting your fence at the right angle, - - and your blade to the correct depth, - - you can cut an arc of absolutely any radius you want that's 5" or less (or whatever the radius of your blade size).

The more parallel your fence is with the blade, - - the smaller you can make your radius.

The more perpendicular you put your fence with the blade, - - the closer your radius will be to your blade size (radius).

Azek's much softer and easier to cut than wood, - - so I was able to comfortably make this cut-out with just one pass. If I was making the same cut with wood I wood have made the first pass with the blade set a little lower.

Keep in mind, of course, - - that you can take more of a 'swipe' in a single pass with a smaller radius than with a larger one, - - because your material will be headed more 'into' the blade than 'across' it . . .

Careful now, - - experienced only need apply . . .

Here's a few pics . . .

Tom R

Oh, - - and you can also use this same method to make your Azek (or wood) bend very easily to a nice, tight radius, - - rather than cutting visible kerfs, - - or wrestling with those god-awful methods of trying to heat the material to several hundred degrees . . .

ron schenker

You lost me at "Azek" but I enjoyed the pretty pictures

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dkillianjr

Thats a great idea Tom Ill tell ya what you seem to always come up with new tricks. I will deffinetly keep that one in mind.


Dave

kklick

I've made some crown molding like that before. I was trying to match up some crown from a really old farm house. Worked out really well. Just keep a sharp blade and alot of sandpaper.

I'm a big fan of azek for exterior work. I've made a few really nice arched head pieces and some raised panel shutters out of it. One of the best projects was a rounded reception desk. We "engineered" our own heat box to be able to bend 14 foot lengths of 1x12. It definitely was a learning experience on that one.

Bone Saw

very sweet, wonder if it'll work with a skilsaw and a modified miter gauge in lieu of rip fence?

Tmrrptr

Good rabbet trick!

Bone Saw beat beat me to the 77... Ha!

...You gotta lay the 77 on it's side, drag the table towards you along the board while tipping it and it's NOT safe, NOT very controllable, and eats up one side of the blade pretty quick. Get R dun!

I musta done that in another life. table saw looks a lot better!
r

Tmrrptr

BTW Tom, nice shop & fine selection of tools.
It sure help do the best work.
I suspect you won't be trying a skilsaw anytime soon!
r

reveivl

I've used a similar technique for the profile on panels for cabinet doors.

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Tom R

Right, - - that's what I first used this method on years ago, - - profiling the edges of raised panels (essentially an arc cut in half) . . .

WNYcarpenter

I was doing s search on a different subject and stumbled on this...I've read about this in "Fine Woodworking", but never tried it.

The pics are great, but better is pulling this out of your bag of tricks.

How long and how much scrap did it take to get what you were looking for?

Tom Struble

very nice Tom thanks for the pics,how do you mean it works for radius?It will work for circle tops?

Leo G

I would use this method mostly for making cove molding. The biggest cove I made had a 5" radius. I pushed the board 90º to the blade.

Here is one of the moldings that I made using this method. It has 4 parts. The top thumbnail bead, the cove, a 1/4" bead and a molding on the bottom.

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Tom R

If I'm understanding what you're asking, - - I mean it works for lateral bending, - - the same as if you cut a bunch of kerfs on the back-side of the piece, - - except you don't have see the kerfs exposed on the edges. You can get away with it because azek is so much more flexible than wood to begin with.