Secrets to Long Miter Joints
The average woodworker doesn’t always use the best looking method to join two pieces of wood – he or she is happy just to get the face frame stuck to the cabinet side. That’s why these folks are “average”. The “above average” woodworker thinks about visual details and takes extra steps to ensure that the finished work looks like it grew that way.
To the left is a picture I snapped at a job site about 25 years ago. This is a mahogany bookcase/lateral file in a home office. The home was built in the 1920s and the existing work was first rate. When I built the cabinets I paid attention to what piece of wood went where, and how those parts join each other. The three raised panels came from the same board, and they are in the same sequence they were in originally. The picture isn’t the best, but it’s an easy way to make a good looking piece look even better.
The other visual detail is the joint between the face frame stile and the left stile of the panel assembly. The wood grain wraps neatly around the corner. If this a simple butt joint there will be a stripe of edge grain alongside a nice piece of face grain. There are a lot of situations where the long miter looks good, in casework it’s a nice way to join a veneered plywood panel to a solid frame piece. In furniture it’s a great way to make a glued-up leg look like a single piece. In my class last week at Marc Adams School of Woodworking, we made the legs of our Stickley Bridal Chests this way.
The picture at right shows the set up we used. The blade of the table saw is tilted away from the fence at a forty five degree angle. That big gizmo attached to the tall fence is the world’s best hold-down, devised by the late Dr. Roger Cliffe and used extensively at the school. That holds the work down firmly to the table. There is a featherboard just to the left of the operator’s hand, just before the blade. That keeps the work tight against the fence almost all the way through the cut.
As the workpiece nears the end of the hold-in, the saw operator uses a push shoe to move the last few inches of the wood past the blade. The push shoe is held at an angle to keep pressure against the fence as the cut is completed. One of the most important steps to making this cut is preparing the stock. If the leg blanks are as straight as possible the wood goes willingly through the machine set up.
If there are any bows, bends or twists in the material, or if the work isn’t held securely to both the fence and the saw table, a neat joint isn’t possible. There are people who will tell you you can’t make this kind of cut on the table saw and glue the cut parts together straight from the saw. These are “average” woodworkers who don’t know the importance of stock preparation, or how to set up and use the saw. You shouldn’t need to plane the angled surfaces or machine them any further. At most, you might need to run a sanding block along the edge.
A big issue with holding mitered joints together is clamping. Most of the clamps we usually use cause angled surfaces to slide around rather than come together. So, we need a different type of clamp and a slightly different strategy. If we clamp before we apply glue we solve the sliding issue. My clamps consist of a roll of “Tear By Hand” packing tape. As the name implies you don’t need a dispenser or a knife to get a piece off the roll. Great stuff, but for some reason I can only find it online, not at any local stores.
On a flat surface, lay the two pieces face up with the pointy edges touching. They should meet in a nice straight line. If the work is smiling or frowning at you the finished piece will have a gap either at the ends or the middle. This indicates that the piece was bowed or bent before machining, or it somehow crept away from the fence or above the table as the cuts were made. If it looks good, place a piece of tape across the joint every 6-8 inches.
Then place one long strip of tape along the length of the joint. If you have a tiny gap you might be able to pull it closed with the tape, but if you have to do that the tape will most likely pop off in the next step. If you need to make a correction work carefully so you don’t make the situation worse.
These two pieces were cut from a single wide board. The red marks (two legs of a triangle) make it possible to quickly put the parts together in their original orientation. There are eight pieces (to make four legs) so I add additional legs to the triangle rather than number or letter the parts.
I like big, bold, simple marks with a lumber crayon so I can easily tell if I’m about to do something stupid like mix up the matching pieces or run the wrong edge over the saw. With the two pieces taped, flip the parts over on the bench so the outer faces are down.
I spread glue across one of the angled faces. People who like to fool around and not get anything done will put glue on both faces and spread it evenly with a brush. With the glue on one face, close the joint by hand, then open it back up and take a look. If you use the right amount of glue you will see it evenly spread on both surfaces. In the photo at left, I used a bit too much glue. My goal is to have the glue almost squeeze out so I don’t have much of a mess to clean up, and I don’t waste any glue.
When you’re finished worrying about the right amount of glue, fold the two pieces closed and wrap tape across the open corner. I usually start in the middle and work out to the ends. I space the tape about every 6-8 inches and stretch it tight. That provides plenty of pressure and you can reach the inside corner to clean up the glue squeeze-out before it dries. You can take the tape off in an hour or two, but give the glue six to eight hours to thoroughly cure.
This photo is from one of my student’s pieces. At this point he hadn’t done anything but scrape off the glue and put a slight bevel down the length of the joint with a block plane to take off the sharp corner. I’m always pleased when the students in my class produce work that looks better than mine. This looks fantastic before any sanding or finishing. It will look spectacular when everything is silky smooth and a finish is applied.
This particular student started off the class telling me that he was a beginner and I shouldn’t expect much from him. He left the class proud of how his piece looked and with a warning to not call himself a beginner anymore. While this class involved a bunch of mortise and tenon joints, selecting which piece of wood for a particular place (and keeping track of that over a week of work) was just as important.
Other “in-process” photos can be seen in this post and on Facebook in this photo album posted by the school.
I’ll be back at MASW for two weekends over the summer. On July 22-23 the class is “SketchUp For Today’s Woodworker” On August 26-27 we’ll be making the “Gamble House Garage Medicine Cabinet”.
At the moment there are still a few spots available in each of these classes, I hope you can join me.