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Discussion Starter · #1 ·
Hi everybody,
Just joined the forums and have a couple projects under my belt(adirondack chair & a simple picture frame) so far.

I'm working on another picture frame, but bigger and with a rabbit to hold the glass and everything else. My problem is that I'm having a hard time with lining up my miters. I'm using 1x3 material(doug fir) and I'm cutting 45 degree on the miter saw, but when I put the pieces together, it doesn't line up.

I've been thinking about the Pythagorean equation, but I can't quite figure it out.

And one other question, when using a router to take out material(doug fir), how much at a time should you be cutting? I have a rabbit that is 5/16", and out of safety I've been doing passes of 2/16". Could I increase the rpm on the router and cut 5/16"?

Thank you
 

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When cutting miters, there are lots of things to consider. The first, is to make sure your saw is dead on at 45 degrees in both directions. Then, you need to check the precision of the saw blade coming down to the bed. The blade needs to drop and be at exactly 90 degrees to the table. Cheaper saws are not always accurate and do not have an adjustment for this. Once you are sure the saw is accurate, you need to be sure you have a sharp blade and make sure that it does not wobble as it spins. The slightest wobble will take a divot out of the top of the edge of your miter cut. Here is another tip on that. When you make the miter cut, stop the blade in the down position. If you raise the blade back through the cut while it is spinning, the blade can mess up the cut, again with a divot, which will affect the fit.

Now, we go to the operator awareness. When cutting miters, you have to be aware that the blade wants to pull the board toward the mitered end. If you don't hold the board firmly or clamp it, you can actually see the board slide as the cut is being made. You definitely will not get an accurate fit, then.

Another factor is how fast you lower the saw blade into the wood, especially when it first touches the wood. When the blade touches the wood, a slight shock goes through the blade and can cause a slight divot, even if the blade is perfectly true. It pays to go slow and let the blade do the cutting without being forced. Be aware of how you are holding the saw handle as you lower the head. If you are flexing the head, it will affect the cut, especially on cheaper saws.

Now, for the wood piece. Check the width and thickness of the pieces. If either is different from piece to piece, you won't get a match. Then, check the profile. If the pieces come from different runs, the profile can be different.

If you are cutting pieces where the back side cannot lay flat on the saw bed, where there is a chance that the back can change angle, your cut angle will vary. This especially shows up on moldings like crown moldings.

So, you have a lot to look at and check.

Oh yeah, you need to measure from the short side of your miters and make sure the 2 sides are the same length and the 2 ends are the same length. If your pieces are not the same length, there is no way your miters will fit.

One more thing...Have your short side (inside) of the miter toward you on the saw bed and miter toward the long side. Cutting this way does not tear the wood grain. It is like running your hand from the back of your hair toward the front. Your hair lays down. Going the opposite way makes your hair stand up. Going the opposite way through the wood will make a rough cut and affect the fit.
 

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As for your router question, it is possible to take out 5/16", but sometimes a chunk of wood will tear out ahead of the bit and rip a section of show wood out with it. I usually go around the area to be cut once without full pressure, to take out part of the wood, then go around the final time to clean out the cut. If you do try to do it in one pass you need to go slower which causes burning and will wear out the bit faster. You are better off doing it in steps like you have been.
 

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Discussion Starter · #4 ·
Thank you for the advice. I checked everything for alignment and everything was good. I clamped everything down and let the wheel power down after the cut. The angles came out a lot better, still a hair off, but I'm perfectly fine with it. I'm going to pocket screw it with a Kreg jig, which might pull the gaps closed.

Thank you. Attached is a picture of the dry fit.
 

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