Making Curved Doors

[cabinetman]

Making round doors or panels that are to be laminated with a Formica type product or veneer, is fairly easy. "Bending ply" can't be used for doors as there is no way to keep it in a curve. I use a variety of plywoods in 5/8" to 3/4" thicknesses.

You first need to have a form for the curve, such as a cabinet front or a made up form. Using a "tailors tape measure" or anything that will take the curve, like 1/8" masonite, measure for the inside length of the curve. Measure for the desired height, less the thickness of two pieces of the laminate or veneer to be used.

Orient the plywood so the face grain runs horizontally, and cut out the door. You will be cutting saw kerfs in parallel vertically. They will be of a depth just short of the face veneer of the plywood, or at least leave 1/16" or more. The grain running horizontally will help prevent cracking of the face. The spacing between kerfs will be determined by how tight the arc of the curve will be. This should be tested first. For very tight curves, the kerf will be deep and very close together. For very gradual curves, the kerfs may not be so deep, and may be further apart.

You should wind up with some flat on the two vertical ends to end the lamination. Once kerfing starts, the panel will become flimsy and you have to handle it carefully. Tack nail with small finish nails to the form (kerfs being on the outside/front), along the top and bottom edges nailing through the flats between the kerfs. Leave some nail head protruding so you can get it out easily.

Carefully fill the kerfs with a Bondo type mixture. You can't mix up too much at once as it kicks off pretty quick. With a putty knife, force the bondo into the kerfs as deep as you can get without breaking through. When the total area has been filled, and cured, remove from the form, and block sand the face smooth.

I make a block sander from using 3x21 sanding belts. I cut stock from 5/8" or 3/4" ply, MDF, or melamine, 3" wide and just long enough to force the belt over the block to stretch it tightly. I wind up with a two sided hand sander that is 3" wide and somewhere about 9" long, depending on whether you use 5/8" or 3/4".

You can then laminate with your choice of material. As for drilling hinge cup holes, make a mark on the inside of the curve where they go. Using a DP, carefully drill the hole after the door has been wedged at the correct angle, to the minimum depth needed. It's wise to laminate the outside of the door after the hinge holes have been drilled because you may break through if you've drilled too deep.

This method is for an outside curve. For inside curves, the backside of the door gets kerfed and filled as above.

This technique can be seen in this thread.
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[sdk1000000]

Hi Cabinet Man,

Just trying to understand the procedure:

"Once kerfing starts, the panel will become flimsy and you have to handle it carefully. Tack nail with small finish nails to the form (kerfs being on the outside/front), along the top and bottom edges nailing through the flats between the kerfs."

. . .

"Carefully fill the kerfs with a Bondo type mixture. You can't mix up too much at once as it kicks off pretty quick. With a putty knife, force the bondo into the kerfs as deep as you can get without breaking through. When the total area has been filled, and cured, remove from the form, and block sand the face smooth."

So are you saying to attach the kerfed plywood to the curved forms first and then just force bondo into the kerfs from the top and bottom, but not the back of the kerfed plywood (which is covering the form)? Is the Bondo just to hide the kerfs on both ends or to strengthen the now curved plywood? It seems that if it is just on the two ends the curved plywood would not be very strong once removed from the form.

Thanks!

[cabinetman]

Hi Cabinet Man

"Carefully fill the kerfs with a Bondo type mixture. You can't mix up too much at once as it kicks off pretty quick. With a putty knife, force the bondo into the kerfs as deep as you can get without breaking through. When the total area has been filled, and cured, remove from the form, and block sand the face smooth."

Lets say you have kerfed, the panel on one side, and the application is for an outside curve. You take the panel and attach it to the form/cabinet with the kerfs outside. The smooth side is on the inside. The kerfs will be grooves from the top of the door to the bottom, and could be 3/8" to 1/2" wide flats in between. The whole outside will be grooves. Fill ALL the grooves. The bondo will adhere to the inside of the grooves and hold the shape of the door. When sanded, the outside will be smooth. It should be sanded to the flats so the surface is smooth. You will be sanding mostly all just the excess bondo build-up.
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When cured, remove the door from the form and laminate with Formica, or veneer.

[atgcpaul]

Making round doors or panels that are to be laminated with a Formica type product or veneer, is fairly easy. "Bending ply" can't be used for doors as there is no way to keep it in a curve. I use a variety of plywoods in 5/8" to 3/4" thicknesses.

I don't understand your above statement. I personally have done this with
bending ply and I have seen another project on another forum do this with
great success. Using a urea formaldehyde glue, I got zero springback.

As to cost and time, I'd say kerfing has bending ply beat, though.


Paul

[cabinetman]

I don't understand your above statement. I personally have done this with
bending ply and I have seen another project on another forum do this with
great success. Using a urea formaldehyde glue, I got zero springback.

As to cost and time, I'd say kerfing has bending ply beat, though.

Paul

Bending ply works great in situations where it can be directly mounted to the form. As for using thin layers and laminating up for the desired thickness, I found difficulty in maintaining full contact of all the layers. I've also run into the problem of clamping up the curve without leaving marks or flats of some sort. The lamination doesn't seem as stout as with kerfing. Another problem I've run into with using bending ply is getting a door thickness that matches exactly to a flat door it may butt against. There always seems to be some differential. On those occasions I've had to use some intermediary material to laminate before the mica or veneer to get the right thickness.

With kerfing if I start with 5/8" for the curved door, I'll use the same substrate for any flat doors next to it. The kerfing method works pretty good and for someone just experimenting or just for the fun of it, will likely produce good results the first time.

Another method I've used in fabricating curves is coopering, which is the most difficult and time consuming of any method.
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