Need Help with Miters from Sawmill Creek
The woodworker who began this discussion was having problems measuring miter cuts on the ends of his picture frame boards. - Editor
"How do I measure a board if I am cutting angles on the ends? It's easy enough to measure for a 90 degree angle -- just measure out from the blade and cut -- but I cannot figure an easy way to measure for a 45 degree angle. In other words, if I want to make a picture frame, what is the procedure for measuring the boards and cutting them? If I am missing some minor thing here, please forgive me for being so thick. By the time I get through trying to get these cuts right, my picture is like half the size I started to make." - Bruce G.
Some draw them out, either by hand or in a CAD program. - Editor
"There are different ways. The simplest is to just draw it out full-scale if you are having trouble wrapping your head around it. Otherwise, you need to know the rebate [rabbet] size desired, the internal size, and the width of the stock. Geometry from there." - Steve R.
"Either draw it in SketchUp, et al, or lay it out full size on a piece of paper. From there it's 'just' a matter of cutting 2 boards each to the same exact length with 8 perfect 45's. - John T.
The length of the outside edge is the length of the inside edge plus 2 X the width of the piece. For example. If I want to make a picture frame for an 8 X 10 picture. The pieces I am cutting are 2" wide. I will use a 3/8" rabbet for the picture to sit in the frame. I will need two pieces 13 1/4" (10" - (2 X 3/8") + 4") and two pieces 11 1/4" (8 - (2 X 3/8") + 4") - Mike C.
Some use the actual physical pieces in determining their measurements. - Editor
"I run my rabbet first. Then, using two pieces of stock laid back to back (rabbets facing out on both pieces), place tape measure on the inside edge of rabbet with actual size of desired opening, plus 1/8th inch. Where the tape meets the rabbet on the other piece gives me the exact length to cut pieces." - Bruce W.
"Do you already have the picture mounted? You could work directly off that. The critical dimension is the 'shorter' side of the miter that meets the picture. I would start with one of the longer dimensions, first. If you make a mistake, it could be cut down for one of the smaller pieces. Take the framed artwork and place it on a stable, flat surface. Trace around the outside. Put the original art safely away. Each molding will have a relief cut away (the side that holds the picture) that is a fixed distance in from the inner dimension - 1/4" or more. Inside the tracing made of the mounted artwork, trace a second line that distance in from the template line. That's where your molding should line up, when properly fitted.
"I cut with a miter box, by hand. I cut the first three, fitting to the actual mounted artwork or cover glass. I leave the last two pieces long, and overlap them at the final corner. I cut directly through these last two for the final joint, to correct for alignment errors." - Jim M.
The original woodworker came back and said he'd traced the root of his problem to a measurement he'd forgotten to consider -- and that he appreciated everyone's advice. - Editor
"Thanks to everyone for the good advice.I think I figured out what I was doing wrong. My problem was more like I just didn't where to start cutting even once I knew what lengths I wanted. After seeing everyone's formulas and such, I got to thinking. And I just now realized that I was not allowing for the width of the kerf when I made the cut." - Bruce G.
Do you have any tried-and-true methods for measuring your miters? - Editor
Backer Board for Crown Molding from WoodCentral
The original poster in this thread asked for advice on a backer board he'll be installing behind some crown molding in his daughter's home -- half a country and a different climate away. - Editor
"I'll visit my daughter in Virginia next month, and she's asked me to install some crown molding in her townhome. I have a sample of the molding and will make backer board to go behind the molding. I'll rip some 2x4s for the backer board. I live in Colorado (dry climate) and as I mentioned, she's in Virginia (humid climate). So, my question is whether or not I should flatten the 2x4s on the jointer prior to ripping them. That, should they be flattened at all? or should they be flattened here then taken to a more humid environment? Is this even worth worrying over?" - Andy Z.
He received suggestions for trying a different size of lumber, or cutting down his 2x4s. - Editor
"A 1 by 4 might be cheaper and would already be dried. Remember to let your wood acclimate to the house before installing." - Brian
"Unless it's some fantastically huge crown molding, a 2x4 ripped into a wedge shape will be flexible enough to pretty much follow the wall and ceiling. What you want to make sure you do, however, is to rip the 2x4 smaller than the cross-sectional gap between the crown and the wall-ceiling intersection. Ideally, you'd leave at least a 1/8" gap between the backer and the crown to allow for variations in the wall and ceiling, and to allow a little fudging on the placement of the crown." - Jason R.
Or, some thought he might try plywood instead. - Editor
"Why not plywood? Even common construction stuff is likely to be straighter and more stable than 'good' modern 2X4s." - John M.
"When I put up 3-1/2" crown in my living room, I put up 1-1/8"x 1/4" ply on the ceiling and wall, nailed and glued with construction adhesive. It's been up three yrs now with no problems. You don't need to fill the whole cavity behind the molding, just have to get something to hold some nails." - Fred
The original poster left the discussion with considerations of the different lumber sizes, as well as the fasteners he planned to use. - Editor
"Thanks, everyone, for the answers and advice. I'll consider the plywood, as was suggested. Also, I will install the backer with screws -- McFeely's square drive, the most convenient fasteners I've encountered -- which should make it a bit easier to pull everything flat." - Andy Z.