In finish carpentry the trim wood around doors is called casing. When casing a door you want to try and get the miters as tight as possible. A miter joint is the point where two pieces of casing meet at a corner. At a 90 degree corner where two pieces of casing meet each piece will be cut at 45 degrees to make this 90 degree corner. In theory this should work perfectly every time but little variables and imperfections throw this theory out of whack. Here are some tips and tricks to use to combat these little variables for almost perfect miters every time.
In order to have two pieces of casing cut at 45 degrees to make a 90 degree corner the casing has to be perfectly flat. A lot of times this isn't possible because the jamb of a door either sticks out past the inside sheet rocked wall or doesn't come out flush to the inside sheet rocked wall. This causes the casing to be tipped either inward or outward and when the casing is tipped in or out this will change the degree at the corner because of the distance of the miter to close the gaps. For example; if the casing is tipped inward or outward the miter will be open slightly to the inside or outside of the joint depending on how much it is tipped. Chances are you will run into this problem while doing finish carpentry but there is a solution.
In finish carpentry when casing a door or window always start with the top piece of casing. If the casing will be fairly flat when applied in place go ahead and cut each end at 45 degrees with a slight bevel back at the cut so the face of the casing is just slightly longer then the back of the casing. To get this slight bevel at the 45 degree cut slide a small piece of card board under the casing and close to the blade before cutting to slightly lift the end of the casing up the thickness of the card board. This piece of card board should be about an inch or so wide and the length of the width of the casing.
Another technique to get this bevel is to cut the casing upside down at the saw. If you have traditional type casing the casing will be thicker on the outside edge and go thinner to the inside edge. By cutting the casing upside down you automatically will create a natural back cut or bevel to the 45 degree angle cut.
Now you have the top piece of casing tacked in place with the ends cut at 45 degrees, it's just a bit of trial and error now. Cut a piece of scrap casing at the 45 degree angle and hold it in place. This will show you where the gaps are at the joint and you can adjust the miter saw to the correct degree to close the gap. When you have the correct degree adjusted to the miter saw you are ready to cut the next piece of casing that will be installed and have a nice tight miter. Be sure to apply the bevel technique to each cut.
Always apply glue to your miters before making the joint. Then each miter will be pinned together with a small nail at the outer corner so the nail goes through the miter to hold the two pieces together tightly. I use an 18 gauge nailer for nailing the inside of the casing to the door jamb as well as at the outside miter joint. After everything is pinned with the small gun I will use a 16 gauge gun to solidly nail the outer edge of the casing to the wall. When using the bigger gun to finish the nailing process stay away from the miter joint so you don't disturb the miter.
Finish carpentry has many little tips and tricks and these little tricks can have a big impact to the over all quality and the time it takes to finish a project.
Autor: Pat Fisher
Pat Fisher is a professional carpenter and woodworking craftsman. For more information on finish carpentry and household carpentry projects, visit http://www.finishcarpentryhelp.com - Also available is a comprehensive eBook for building hand railings
Added: April 12, 2009