Need help w/tenons on curved piece

[Ron Corselli]

I'm making a headboard for a bed with an arched upper rail and vertical slats (1-3/4 wide x 3/4" thick). The lower rail is straight. I was going to shoulder tenon the ends of the slats and I have a horizontal mortising machine to cut the mortises. But what is the best method to get the verticals straight into that curvature?

I'm open to other joinery methods to make this easier but durable. Thanks.

[Prashun Patel]

Floating tenons might be easier.

[Jamie Buxton]

Or a different approach is to make the mortise in the upper rail big enough that the whole end of the slat inserts into the mortise. The "tenon" has no shoulders. You only need to rough-cut the upper end of the slat.

[Dave Richards]

On the loose tenon theme, you might try something like this for creating the mortises in the curved rail. You could do it with a drill instead of the Domino.

(note: No affiliation. I just happened to be watching that video moments before reading this thread.)

[Prashun Patel]

Actually, I like Jamie's solution even better than what I said b4. His way you could make all the mortises before bandsawing the curve. The ones on the ends will be deeper than the center one. This will allow you to cut the ends of your slats all to the same length and square ended. Seems much faster, easier, and cleaner.

[Ron Corselli]

No-shoulder tenons do seem best. How about layout and alignment? With 12 verticals, one just a hair off, well, you know how that goes. Any suggestions on how best to transfer that position of the slat end to the curved part?

Much appreciate your advice.

[Shawn Pixley]

If going that way, cutting fillers for the slot between the verticals is the way to go. Some careful layout and shaping will be required. Alternatively, my friend would fasten using glue and a pnuematic pinner from the back side. Still, layout is everything.

[Reed Gray]

If you can, draw it out full scale on a table. This is a really huge help! Been there, done that. If your verticals are going to be round, then you could do a jig for the drill press to support the rounded arch, and drill straight in. No shouldered tenons would be easier. I have seen stair railings done where there is a slot/dado and the tenon end fits into the dado, then the spaces between the ends are filled in with cut offs.

robo hippy

[Alan Caro]

Ron Corselli,

Yes, the situation seems to me to be the mortise angle and horizontal alignment problem. Here's an idea:

Fabricate the tenons on the slats and the arched upper rail to profile. Then, radius the end of the tenons to correspond to the rail arch. Using squares clamped to the bench, align the slat tenons against the rail and scribe the positions-outlines- for the mortises. If the radius is large- a flat arch-you may be able to scribe with the tenons squared or the radius may be approximated to have the surface close enough, as the shape of the ends will be hidden in the mortise. If approximated the transfer will need to be more carefully done to avoid a misalignment if the scribing tool is not projected at an accurate angle onto the radius. Take a a 2 X 4 or what ever size will accommodate the radius of the arch and leave one slide flat. Scribe the radius of the arch onto the 2X and cut that radius into it. Place that piece flat on the bench as a cradle and using squares, clamp so the arched rail will be held in such a way that the mortising machine will cut parallel to the tenons.

Alan Caro

[Gary Rogowski]

The bare faced tenon or unshouldered tenon I think is the easiest way to deal with an arched section. But I would consider lightening up the slat thickness. Even 1/2" is thick for what you're asking the slat to do. Chair makers use bare faced or unshouldered tenons all the time because it eliminates the curved shoulder issue. Just do your glue up in halves so you're not trying to glue up all those slats at both ends at once.

[Shawn Pixley]

I have done these both ways. I did the shouldered mortises with the curved shoulders. Takes some time but really not that bad to pull off. I do it by hand but can see a couple of ways to do it on a machine.

The dado slot with the unshouldered tenons are easier but easy to make a last minute alignment mistake. If you go this route, you could build a construction jig from scrap to hold the slats / tenons in alignment by making dado on identical boards top and bottom to ensure the alignment is equal. All that is required then is to ensure the glue-up is square and doesn't skew to a parallelogram. After glue-up the remaining part of the dado can be infilled or not to your choosing.

[Ron Corselli]

Yes, it's becoming clearer that the unshouldered tenons and spacers matched to a full size layout is the best for this project. Everyone please stay tuned because I'll post up another concern about the upper arch form tomorrow. Thanks for your help.

[Chris Parks]

Why not do the shoulders with a router? Cut the tenons too long so you can trim them to size then make a pivoted board whose end swings in the radius you need. Clamp the router above the board somehow so the cutter is at the required height, place the board that will have the tenon on the pivoted board and swing the whole lot past the router bit. You could cut the shoulders this way before the tenons were done as either way would work.

[Ron Corselli]

Why not do the shoulders with a router? Cut the tenons too long so you can trim them to size then make a pivoted board whose end swings in the radius you need. Clamp the router above the board somehow so the cutter is at the required height, place the board that will have the tenon on the pivoted board and swing the whole lot past the router bit. You could cut the shoulders this way before the tenons were done as either way would work.

I'd probably make a jig for that if it was production work Chris, but this is a one-off project. In effect, as others have suggested, the verticals are like long, exposed loose tenons, spaced and parallel.

[Ron Corselli]

So now the mortise and tenon issue is resolved, my final question is about making the upper curved piece of the headboard. Rather than drawing an arc as in a circle the sweep of the curve should be more like an ellipse or maybe even less curve than that. What is the best way to get that on a template so it is symmetrical?

And what hand tools would you recommend to finalize the shape and dimension after cutting out the piece on a bandsaw?