Out of square miters

[Lynn Reid]

Hi...I am installing wainscoting in the kitchen of a 100 year old plaster walled house. I am using 1/2" MDF for the rails and stiles...leaving the original baseboard and will use poplar for the handrails. The rails and stiles are, of course, like a picture frame into which I glued 1/8" hardboard. All of this worked fairly well except that due to bulges and generally out of square/plumb everything. I plan to put molding to line the inside of the "frame" created by the rail/styles. The miters are not going to be exact 45's...I am wondering if there is a good way to make the miters fit well on all 4 corners?
My thinking was to take the angle from where the stile and rail meet...divide it by 2...and cut that angle on my table saw...I don't have a miter saw. Then theres the question of the other end of the stick...all the way around the frame. Help would be appreciated!!
Lynn

[Jerry Miner]

Hi Lynn---You are entering the world of "Finish Carpentry"---a world i have lived and worked in for many years. You know now that square corners make mitering much easier, but out-of-square corners are what finish carpenters deal with all the time.

Your instinct is correct---to get a good miter you should divide whatever angle you have by two. In a square frame the opposite sides would be identical in length and the miters would all be 45 degrees. In an out-of-square frame you have to deal with what's there. Lengths will vary and angles will vary. A chop saw (aka miter saw) is the best tool for this, but it can be done by hand or on the table saw.

For table saw, I would make a sled with a 45 degree miter fence, then adjust the cuts with shims to make the cuts fit the angle. Use some scrap to test the miter cuts before you cut the actual piece to length.

Small adjustments can be made with a sharp block plane.