Carpentry and Woodworking - Mitered cuts...help!

I'm fixin' to cut the moldings around windows and doors. I know the cuts are 45 degrees (more or less), but I was told to add 1/4 inch to the length. Is this right?

I never heard of such a thing. Just remember to keep straight whether you are measuring the inside length or outside length. Also don't asume it's 45 around a window. Measure, measure, cut.

The 1/4" was probably for an 1/8" reveal on each side.
Anthony

Looneyfarm,
The miter cuts will (should be) 45 degrees.
We'll assume too, that the window was mfg at 45 degrees.
Problems come with the opening, which may be slightly off.
That's okay, cuz YOUR 45s will fix(hide) any minor problems. Adjustments (lengths) are made after the first installed piece, but all your cuts are still 45's.

fred

What I find to be handy is have a scrap piece approximately 12-24" in length and use this to get the perfect angles. Cut your first piece at 45s both ends with extra length to account for 1/4" (I usually use 3/16") reveal. Then put the scrap piece up with a precut 45. Now temp set this at your reveal and see if the 45 will fit.
The reason I say to change from the 45 is usually it looks pretty crappy when you have different sized reveal around a window or door.

For instance, your inside dimensions are 24" and you want a reveal of 1/4" all the way around the opening (this is between the trim and the inside "frame" of the window...therefore you would cut your first piece at 24-1/2" short point to short point. Set your scrap piece...change angle if needed and go on around for the rest of the pieces.

Just my .02

Here is the way I do trim around a door. I don't use any ruler. I do use a combination square that has had the depth set to the reveal that I want. I go around the perimeter and mark the reveal in several places to give me a guide to align the trim. When I get to the corners, I make sure to have the reveal lines cross. I cut the first 45 degree angle and put it at one of the intersections. I then go to the next intersection and mark it on the piece of trim. I then repeat this on the other side. When it gets to the top piece, I cut the first 45 angle and then flip the piece over and match the two points of the 45 together and then just mark the new piece at the point of the other. I can then cut the 45 and put the piece in and it fits every time.

Excellent technique... but this assumes that the door frame was installed square. If you do the work yourself you know how it was installed. But if reworking some trim on a door that someone else put in, sometimes you can't be so lucky.