Sliding door cornice

[Richard Hutchings]

My daughter wants me to make these for her 2 sliding doors leading out to the deck. I'm basically following https://www.thisoldhouse.com/windows/21016601/how-to-build-a-window-cornice . My concern is cutting the 45s on these 1x10x80 poplar boards with hand tools. I'm going to make a miter box for the moldings so that shouldn't be an issue. Any tips, I've never done anything like this before. I'm considering rabbit joints if there isn't a good solution for the miters which I prefer even though they'll be painted.

[Jim Koepke]

Are the miters on the long dimension?

I've done something like this with a plane held in a vise and guides to keep the board steady at a fixed angle. Kind of like an inside out shooting board.

Do you have an edge plane? Mine has holes in the fence edge so an angled fence can be attached to make angled cuts.

Also if you can keep the two boards together and offset you could plane them at as close to 45º as you can. If it isn't exact the boards should still match up to a closed corner as long as you don't have hills and valleys.

jtk

[Richard Hutchings]

The meters are on the 10" dimension.

[Jim Koepke]

The meters are on the 10" dimension.

You could rig up something like a miter jack. A temporary shooting board to hold the plane at 45º to the board so the board could be held flat.

jtk

[Richard Hutchings]

That sounds like good idea.

[James Pallas]

I would approach it this way. The first thing is to see if the existing opening is plumb and level. The two sides may be different. It doesn’t take much to make things difficult but not impossible. You may have to adjust the angles of the 45* to something else to make it work. Whatever angle you end up with split it and that will be what you need to cut. Mark the angle on one board and saw to the line. Trim with a plane gently to true it up. Mark your other board from the first and saw to the line and clean up with a plane. Do not cut to length on the floor side until you get your miters. You would be lucky indeed if that opening was plumb and square enough to have everything match up to use a 45* cut at both corners. Typical everyday world of a finish carpenter.
Jim

[Richard Hutchings]

I would approach it this way. The first thing is to see if the existing opening is plumb and level. The two sides may be different. It doesn’t take much to make things difficult but not impossible. You may have to adjust the angles of the 45* to something else to make it work. Whatever angle you end up with split it and that will be what you need to cut. Mark the angle on one board and saw to the line. Trim with a plane gently to true it up. Mark your other board from the first and saw to the line and clean up with a plane. Do not cut to length on the floor side until you get your miters. You would be lucky indeed if that opening was plumb and square enough to have everything match up to use a 45* cut at both corners. Typical everyday world of a finish carpenter.
Jim

I guess I need a better description of what I'm doing. It's a box around the top of curtain rods on sliding doors. There's no fit up. The box, enclosed on the top will have crown moldings at the top of it and some smaller moldings at the bottom. It's the box that needs the miters.

[Richard Hutchings]

This is what I think I need to build. Then, it's just hand planing.

[James Pallas]

Easier. Make sure your material doesn’t have a cup in it or you will cut a curve. If there is just clamp a straight edge to it if it’s no too bad. Mark your cut on the show side. I than mark the 45* slightly a degree or two obtuse to open the back a bit. Saw to the line going into your finished side. Use a plane to clean up if needed. Don’t be tempted to use the off cut from your first ccut for the other side, remember the angle and the cut may be ragged on the edge from cutting out. When you do the other end of the face piece take your time. You won’t be able to recut much if you err on it. You’ll need to use a panel saw for the cut. Make sure it’s sharp. I’d make a test cut just to get a feel for it. Do the test like you mean it. You may get lucky and have it turn out beautiful. Be a shame to waste a great cut. Good luck.
Jim

[Jim Koepke]

This is what I think I need to build. Then, it's just hand planing.

That looks like the tool for the job.

All it needs is support for the work at the far. A clamp or two might be good to secure the work.

jtk

[Richard Hutchings]

Mark the face, transfer that at 45 degrees, then saw from the back to the front? With the board laying flat or do you mean with the edge up?476775 But from the back like this.

[James Pallas]

That’s it. Check for that cup. You can support it as needed. When you make the cut you’ll soon see why you cut that way. You may want to knife that front side. Like I said make a practice cut.
Jim