Carpentry and Woodworking - crown modling mitre joints driving me crazy

I'm building a bookshelf and I cannot figure out how to make the correct mitre cuts with my mitre saw. It is driving me insane and I am almost out of wood, so I can't screw up again. It is a slightly unusual cut because it is an outer corner

http://img205.imageshack.us/img205/1669/shelf001.th.jpg (http://img205.imageshack.us/my.php?image=shelf001.jpg)

http://img205.imageshack.us/img205/1002/shelf002.th.jpg (http://img205.imageshack.us/my.php?image=shelf002.jpg)

http://img145.imageshack.us/img145/5357/shelf003.th.jpg (http://img145.imageshack.us/my.php?image=shelf003.jpg)

As you can see from the images, the top of the bookshelf is 2" longer on each side than the main case, which allows room for the molding. The front cut looks okay, but I can't figure out the side cut to match it. Can anyone point me to a good web site for determining the right cuts to make? Do I need to buy a protractor to measure the outer angle? Thanks a lot!

Looks as though it's going to be a compound miter cut; yes a protractor might be of help.

Some reading:

How to Cut Crown Molding With a Compound Miter Saw | eHow.com (http://www.ehow.com/how_4867458_crown-molding-compound-miter-saw.html)

Cutting Crown Molding with DEWALT Miter Saws, DEWALT.com (http://www.dewalt.com/us/articles/article.asp?Site=woodworking&ID=2)

These may or may not match the molding you are using.

It looks to me that you are using the wrong type of trim for what you have. Crown moulding sits on an angle. You either need smaller crown or a different type of trim.......but I'm just a painter - the carpenters will be along later:D

It looks to me that you are using the wrong type of trim for what you have. Crown moulding sits on an angle. You either need smaller crown or a different type of trim.......but I'm just a painter - the carpenters will be along later:D

I want the crown to rest on an angle. You probably can't see it from the picture, but the crown is at about a 45 degree angle, and sits the way it would if I was installing it on a ceiling.

If I'm seeing it right...the top sides overlap the case by more than the front? I don't think you can ever get a miter cut to match up if you want them all at the edge of the top. Not with that size crown in any case. And even with smaller stuff, to get the joint tight on the corners, the top will still extend past the top of the crown on the sides.

If you cut 2 small pieces like they were going on a ceiling, you might see what I mean.

No trim carpenter...just an opinion.

I'm with Marksr, I don't see any crown molding. Maybe we don't have the correct pictures. The links provided by TG are excellent. Today's compound miter saws (better ones anyway) have detents to provide proper bevel and miter, allowing you to lay your crown flat on the bed.

The piece of crown moulding that you are trying to install looks like it may be too big for what you are using it for.

Crown moulding has a predetermined spring angle. If it is a 45 degree spring angle, you can place a square on the back of it and determine what the "rise and run" is supposed to be.

My guess is that you are either:

dropping the bottom edge of the crown down too low, which is screwing up your miter...

or, you are not placing the crown upside down on the miter saw as you cut the miter. (and additionally, you must hold the crown against the fence at the correct spring angle... usually so that both edges are equally "flat" against both the base and fence at the same time.)

Upside down and backwards!!

I am with the others. Don't see any crown moulding. However, if the sides and top overhang the bottom, the crown can be installed just like on a ceiling. It fits two flat surfaces at a 90 deg. angle from/to one another. If the front and sides do not overhang the same amount, and you are wanting the crown to come to the edge, you have a problem!

Most cabinets/bookcases that have crown under the top, have it recessed a little. In order to fit properly, the crown will have to be of the same size. Place a square on the back side of the crown(along the two flat surfaces) and you can see how much they will protrude when placed on a 45 deg. angle, which is the way crown is applied.

Good luck!

Am I the only one looking at this picture (http://img145.imageshack.us/my.php?image=shelf003.jpg)?

No, you aren't alone! it either looks to me like crown laid flat or at not enough of an angle. I may be just a painter but it looks like the wrong moulding for the job.

Yeah, I think judging by the size of the crown moulding shown laying on top of the cabinet in this pic (http://img205.imageshack.us/my.php?image=shelf002.jpg), and the amount of overhang that the top has, the crown moulding looks too big for the job, like gunguy said.

It's hard to get a sense of whether or not the crown is laying at the right angle, (it does look like it is laying flat, Marksr!) and the miter is definitely not being bisected. It looks like it got laid flat on the miter saw, and then got cut at a 15 degree angle.

It is definately not being positioned on the saw upside down as it is being cut, it is not being cut at a 45 degree angle (in order to bisect the 90 degree corner), and as it is being cut it is not being held at the correct spring angle to make the top and bottom ends of the miter line up where needed.

Wow, sorry for the delay in replying! A death in the family put this project on hold but now I am ready to have it finished (after five years!). I just re-measured. The front overhangs 1.75". The sides overhang about 1mm less than that (they are not perfectly even). I just held the crown up flat on both sides, and it definitely doesn't lay flat without extending past the top of the shelf, so I'm assuming the crown is too big, or my overhang is too small.

Using a square on the crown, the rise is about 2 1/4, and the run is a little over a 1 3/4. The UPC on the back of the crown says "crown 2-3/4," which I assume is the width of the entire crown. So if I lay the crown perfectly flat, it will extend 3/4" or so past the top of the overhang. My problem is, I really like the size of the crown when looking at the bookshelf. That is because the crown is going to be viewed from head on, rather than from the floor, like it would be if I was installing this on my ceiling. The wider the crown molding the better it looks.

I also agree that I am not cutting the molding correctly on the saw. I am pretty sure I was not holding it upside down and backwards, and was laying it flat against the fence and cutting it. Would it be better for me to buy new crown molding that is smaller (if they make one that is just slightly smaller in width it might still look okay). Or would it be better for me to replace the top shelf with one that is a little bit bigger so it will allow the crown to fully rest evenly? Only problem with the latter option, is that I think the board is a standard size, and it would be a pain to find a new top shelf that is larger and cut it. Thanks for all the great help and here are some better pictures of the angle (crown is laid flat in the very last picture):

http://img171.imageshack.us/img171/2926/case002.th.jpg (http://img171.imageshack.us/i/case002.jpg/)

http://img84.imageshack.us/img84/4345/case005.th.jpg (http://img84.imageshack.us/i/case005.jpg/)

http://img508.imageshack.us/img508/503/case008.th.jpg (http://img508.imageshack.us/i/case008.jpg/)

I'd look for some smaller crown.

In all your latest pictures above, you are holding the crown upside down. The cove detail should be on the bottom.

Oops. Pretty much forget everything I said in my last post then. I then my measurements are correct afterall then, since when I turned it right side up,. it does fit flush:

http://img30.imageshack.us/img30/1002/shelf002.th.jpg (http://img30.imageshack.us/i/shelf002.jpg/)

http://img89.imageshack.us/img89/5357/shelf003.th.jpg (http://img89.imageshack.us/i/shelf003.jpg/)

I did what everyone suggested and finally got the angles cut correctly, after turning the crown upside down and backwards. I did have a small gap, but just filled that in with wood putty. Thanks so much!