tight miter joints (hardwood, install, molding, glue)

[brrrinmass]

Can anyone give some tips on getting tight miteer joints when replacing trim around interior doors and windows. I know that you are supposed to "back" cut the joints but is it just a trial and error kind of thing? Thanks all.

[chet everett]

Better quality finish carpenters will use power miter box with a thin cut saw and also get out a manual coping saw to fine tune the match between pieces. If younare using imported hardwood or something it is worth the extra labor...

[Barking Spider]

Measure twice, cut once!!!!!!!
A good accurate mitre saw is needed.
Accurate measurements are critical.
After you make the 45 degree cut, take a utility knife and trim away some of the waste (on the angle you just cut) on the part that goes against the wall (back side AT THE ANGLE).
As long as you stay away from the finished edge, the mitres should come together without any gaps.

You can also tap in a small finish nail at the top corners to draw the two pieces together. This is a little tricky because you can split the wood and also knock it out of alignment if you are not careful.

[thecoalman]

Originally Posted by Barking Spider

You can also tap in a small finish nail at the top corners to draw the two pieces together. This is a little tricky because you can split the wood and also knock it out of alignment if you are not careful.

I've been doing this with outside corners on the larger crown molding but instead using a small thin finishing screw. Drill a pilot hole first and you shouldn't split anything.

[K'ledgeBldr]

Originally Posted by brrrinmass

...tips on getting tight miteer joints when replacing trim around interior doors and windows.

First and foremost- a very good power mitersaw. Chop type mitersaws are not good mitersaws. Sliding double bevel saws are very good saws.
If you're not in a position to buy one- rent one. You also want out-runners to support the entire length of the trim you're cutting. Without this support the piece can wander making the cut less accurate.
Second- a brand new blade! Let me repeat myself. A brand new blade!!
With at least 80 teeth. The more teeth the smoother and more precise the edge. I emphasize edge because you can still create a bad cut by not allowing the saw to gain maximum rpm's before cutting. When a saw is first engaged, the blade tends a wobble- allowing full rpm's gives the blade time to stabilize, hence a true and accurate cut.

Confirm accuracy of the saw's angle markings using scraps. Once adjustments are made and are correct- you're ready to start cutting.

If all of the above is correct and accurate and you still have problems with tight miters- this is the number one problem;
Surface planes are not even or level.
The jamb is not flush with the d/wall or plaster. Shimming is about the only way to correct this.

Brad nailing a miter together can sometimes work- along with gluing. I generally find it easier to test fit the pieces then lay them on a flat surface and glue and nail. Then install as a unit on the window/door jamb.

"Back cutting" isn't necessary if the equipment is right. Adjusting your angles might be necessary if the jamb isn't exactly plumb, level, and square.