Monday, March 10, 2014

Can'T Figure Out The Angles For Crown Moulding



Hello.
I'm trying to install some crown moulding in a bathroom and it's making me insane. I've tried about a thousand combinations of angles and can't get the pieces to line up. It's composite, so I'm not doing any coping joints, I just want the two pieces to butt up against each other with their mitered edges touching. Roughly, they should meet at a 45 degree angle (but I know this isn't the actual angle I need to cut). This is the result I'm looking for:
The room corners are a perfect (or very close to) 90 degrees. The crown spring angle, as best I can figure is 45 degrees. Here's a drawing of the dimensions of the moulding I have (not to scale and ignore the handwriting and that I didn't spell wall correctly...been a long day).
I've tried every possible bevel and mitre angle and couldn't get it right. Can someone help me? What am I missing?
Thanks in advance,
JMR

If your using an older regular miter saw [not compound] like mine - you need to turn the crown mould upside down to cut it. Rest the top edge on the saw plate and the bottom edge on the back guide. Basically the opposite of how it sits on the wall/ceiling.

I'm using a compound miter. I have cut everything with the finished side up, not down following some instructions I've read. So, for right inside, place the bottom here, make this cut (miter plus bevel), use left cut (I forget details, but general idea). However, in every case, the moulding was finished side up. Sometimes with bottom of the moulding towards the top of the saw and sometimes top towards the top. I didn't think turning it over would make a difference.

I'm not a carpenter and don't have a compound miter saw. I know that changes how you cut them. Keeping checking in, we have some good carpenters that will give you the info you need as soon as they get time.
almost forgot welcome to the forums!

JMR,
There are 2 ways to cut crown moulding. 1). upside down and backwards and 2). on the flat. A third method uses a cutting jig, but I won't even get into that.
I'll tell you do it the first way, since I think it's easier. Doing it this way, you only change the miter, and you never change the bevel.
First, it's critical how you position the crown moulding on the miter saw. If you are using the first method mentioned above, it HAS to be upside down (bottom edge facing up, finished side toward you) every time you make a cut. You also need to put it in position on the saw. Imagine that the fence on your saw is the wall, and the table of the saw is the ceiling. (that's the upside down part) You square the crown moulding up, nesting it in the corner of your miter saw. It often helps to mark the front of the crown (on the table of the miter saw) with a fine pencil line. You can use this pencil line as a reference so that you are always holding the crown moulding at the same spring angle each time you cut. (you can easily make a 1/16 mistake every time if you don't make a reference line, so the pencil line helps you hold the pieces at the same spring angle each time you cut.)
An important thing to remember when doing crown upside down and backwards is that when you cut, the right side of the piece (as it sits on the saw) will be the left side of the piece once you flip it back the right side up, and then flip it end for end to install it.
It's the way I learned and it isn't too hard once you put up a few pieces.
If you have some extra trim, make yourself a mockup for each inside and outside corner. You can hold these up on the wall to check your corners for square, and also to make a few reference lines on the wall and ceiling.

Even composite (PVC, MDF, Poly) can be coped...it makes things soooooo much easier..esp if they will be painted. And most times makes a better joint.

Xsleeper forgot the second way. On the flat you want the bottom towards the fence. It can be cut face up or down. I found this link to figure out your miter and bevel settings: install crown molding photos tips and the math

LOL, I didn't forget... I just don't like the charts and changing the bevel and miter all the time.

Use the detents on the miter saw for right and left and bevel on the rotation axle, lay the crown flat and cut it. I have mentioned before, I always cut a couple of sacrificial pieces to fit inside corners and outside corners, marking them LI, RI for inside and LO, RO for outside corners. I use them next to the saw to help me remember that I am cutting a certain angle.

Okay, using the in position method, I've finally got it. Turns out that only some of my corners are 90 degrees. Is there an inexpensive tool I can use to measure the angle of inside corners? Everything I see are fancy $100 items, which won't work for my budget.
Regarding coping v. mitering...I think coping makes sense, but I've tried about 10 different practice pieces and always seem to damage the detail on the edges. The MDF I have is a little less than 1/2 inch thick (closer to 1/4, but trying to do from memory as I don't have it with me). So, there's not much to cut off. However, the slightest little error and I'm breaking off pieces of the decorative elements at the end. Am I trying to cut off too much? Any other tips for doing this better?
Thanks for all the help.

Coping saws cut on the up stroke, so make sure your blade is in the saw correctly. Cut slowly and at a back angle to your cut. Don't fret the small stuff, you will be caulking and painting anyway, I hope. You can use one of these. I forgot what it cost, but it measures and divides your angles for you in one step. http://i76.photobucket.com/albums/j3...angleguide.jpg

Originally Posted by hess411
Is there an inexpensive tool I can use to measure the angle of inside corners?
A sliding t-bevel is usually less than $10, and is similar to what Chandler linked to, but not as fancy. Once you gauge the corner, you can set it on your miter saw and turn the angle to match. If it reads 2 degrees (obtuse corner), you add that to 90, for a 92 degree corner, take 180-92= 88, so you would cut two 44 degree angles and miter them together.
IMO, coping is a waste of time when you are going to caulk and paint anyway.
Only hint I would have is to use PL polyurethane construction adhesive to join your miters together. Wipe any that oozes out, and clean with paint thinner before it dries.






Tags: figure, angles, crown, moulding, upside down, crown moulding, finished side, inside corners, pencil line, spring angle