Fabricating a Curved Jamb

Laminating, piecing together, or sawing out of large stock: there's more than one way to build an arched door jamb. April 18, 2015

Question (WOODWEB Member) :
I have a curved jamb to do for an exterior door. Someone told me it's possible to glue many stripes 1/4" thickness in order to easier for bending them and after that, to put veneer on the edge, so the stripes don't show. I think veneer is not going to work for exterior and is better to work with many curved solid pieces, as always the problems are the seams. Does anyone know what the least expensive method is to do this?

Forum Responses
(Architectural Woodworking Forum)
From contributor L:
It depends on your equipment. We've got a band resaw and can saw 3/16", then wide belt and glue up on an adjustable form rack. Just use a board thick enough to get all your strips out of and keep them in order. No need to veneer the edge.

From Contributor O:
One could state that the only low cost way to do these is to make them straight. You basically have three choices: Glue up a huge slab and bandsaw the inside and outside curves and then machine the door rabbet (wasteful), or stack sawn shorter curved segments bricklaid style to make the curves, or laminate several plies of thinner stock.

If you are not familiar with any of those three, then things will not be inexpensive. The lamination of thinner plies implies a springback that may or may not be an issue. If glued correctly, then the edges are fine - they will not show as laminations. The bricklaid method will have butt joints that show on the inside faces and discontinuous grain. If stained, this may be viewed as a problem. If painted, the joints will still telegraph. As popular as they are, there are a lot of curved head doors out there, and some are pretty poorly made. There is more to it than meets the eye, so be careful. The curved jamb is just the beginning.

From contributor C:
It depends on the radius and thickness of the veneers to make the bend, but how will the edges of the thick veneers show under the casing? Maybe one ply will show from the reveal but not much more. It would be a really critical client that would get up and examine the wood in the reveal. Now the casing will be a different story.

From contributor L:
Even on the casing the glue lines simply do not show if done correctly. Rip all laminations from one board, keep in order and use a sturdy form and uniform pressure in gluing. We've tried finger joining, brick lay, and laminating. I'll take the lamination method any day. Pressure is applied with a 3/4" steel banding.

From Contributor O:
Our normal construction is bricklaid segment arches glued up for jamb width, then sawn to the final curve, then a face lamination is added to clean it all up. Either paint or stain, this is the only way to eliminate joints telegraphing. The finished edge - casing reveal is clean and tidy, so is never an issue.

From Contributor B:
I just saw out solid segments and put them together - no bending, facings spring-back whatever. This doesn't take too long.

From Contributor O:
What works is what works, dogmatically speaking. Your method apparently works, and should be good over time. It looks like a method from older shops - the type that are used to working with larger segments of wood. I think the problem with what you illustrate is accurately band sawing out 5" to 7" tall sections of lumber (7" thick x 7" wide x 30" long blanks), and creating the joints. My little bandsaw is limited to 6" jambs - no wider.

Sometimes I see two basic ways to work wood - a large thing cut down to make a smaller thing, or smaller things glued/joined together to make a larger thing - subtractive or additive. Both have their advantages and disadvantages, and some applications may be better than others. Plenty of room for lots of opinion, though. We band saw segments of the curve at the desired inside radius, then add a curved fence to the bandsaw and saw for width. Then we square cut the ends to butt up well, and then stack them on a jig with the radius drawn on it and clamp them to the line. Once dry, the assembly is removed and the facing - usually a 1/8" x a bit over the width - is added with cauls and clamps (per photo above). We have made curved jambs over 12" or wider this way. These can even be fed thru the planer to get to a final width if need be.

Now there are two variations to the above: Sometimes we make our segments over wide and they are roughly sawn to the approximate radius. They are glued up -bricklaid and then the final inside and outside radii are drawn and the assembly goes through the bandsaw again, for final, accurate curves. This is for narrower jamb parts, exterior type with a curve rabbet section and a curved 'fat jamb.' The other method involves the use of the Curvulator - a jig I made for accurate bandsawing of parts, from about 12" radius on up to about 96" radius. This is basically an adjustable center point with two pivoting arms that end in points that will hold the piece as it travels in an accurate arc through the saw. It makes flawless curves with no skill. These can then be bricklaid and faced as in the other methods.