How to Make Mitered Cabinet Doors
To make a miter door frames you will need three cutters, 1st left is a bit for cutting the face of the door frame. There is a lot to choose from, this one is one I use the most. 2nd middle is to cut the biscuits; this one is for#10. 3rd is to cut the panel grove for the raised panel to slide into.
When making cabinet doors the first thing I do is cut my lumber to size you can cut it to the width of the cutter or you can cut it oversize so you will have a little hang over on the top and bottom as shown here. Then cut to size on the table saw this is the way I like. Then install the feather boards, you will need one for the top and one for the bottom, this to keep steady pressure on the board to be cut as well as safety. You may want to raise the bottom feather board closer to the center of the piece being cut; it will help keep it from moving when cutting. You will make three passes cutting a little each time until the work piece hits the bearing at the top. I also find it better to cut short (3-4 ') pieces over long (8 '), I have less sanding when finished.
When measuring the size for a full overlay cabinet door, start from outside to center of opening and from outside bottom to center of face frame if a draws is above the doors if no draws then go to the top. You can make these measurements a 1/6 shorter so you will have a little room for adjustments. When it comes to cutting miters I use a miter sled that I had made for the table saw, this allows me to place a block so I can cut the pieces the same size. Use a miter saw if it cuts accurately; always check by cutting scrap first. Remember that it takes 8 cuts to make a miter door frame so even a little off will end up making a big gap and the two sides and the tops and bottoms need to be exactly the same size. If one is a little shorter than the other you will have gaps. If all pieces are the same size and you still have a gap, do not try to cut one piece at a different angle to make it fit. This will take the door out of square so you will have to re cut the correct miter. Remember each time you re cut, the door will be a little smaller and you may need to remake them.
Once all the miters have been cut it is time to cut the biscuits and grove for the raised panel, I prefer to cut the grove first. The grove for the raised panel will 1/4" and will be center. You will cut this in one pass so set your fence so the piece being cut will touch the bearing on the cutter, once you have cut all the frames then change to the biscuit cutter. You need to mark a center location on each side of the fence so you will cut all the pieces the same. If you have a lot of doors and draws to make try to make them at the same time, it is easier when you can have one set up for each step vs reset for each piece.
When making the raised panel for the cabinet door you will measure side of the grove you cut on the frame, you need to allow for expansion and if you are using space balls you need to subtract the thickness for them. When you cut the panel out always check to make sure it is square. There is two ways to setup the shaper or router table, 1st set the fence by placing a straight edge across the fence and move the fence back until it touches the bearing on the cutter then mark the location and set the height. Then move the fence back until a third of the cutter is past the fence and make your first pass. You will make three passes; on the last pass you should have a smooth finish. 2nd set the fence as you did for the first way but instead of moving the fence back, leave it in place. Now attach a 3/4" board the table top with a cut out the same size as the cutter, now raise the cutter though the first cutting height and make your first pass. Instead of moving the fence you will raise the cutter to the height. I can change height within 10 seconds after the shaper has stopped. After the profile is cut lower the cutter and you can do the undercut if you want without moving the fence. Make sure the edge of the panel is no more than 1/4" thick, so it will fit in the grove of the door frame. Do not try the second way if you cannot attach the board the top safely.
After all the panels are cut do a dry fit before you add glue, if everything fits start adding biscuits and glue. When clamping I like to use banding clamps they work well on mitered door frames and some of them are cheap.