Dumb question about compound miters

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Forum topic by juanabee posted 05-17-2012 03:49 AM 1656 views 0 times favorited 5 replies Add to Favorites Watch
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113 posts in 4299 days

05-17-2012 03:49 AM

Topic tags/keywords: miter compound bevel trim skill question angles corner

I would like to know the answer to what seems like a simple question about compound mitering, but I feel a bit dumb having to ask it. I have checked the faqs on compound miters but cannot find anything but information about crown molding, which isn’t my issue. If you know of a good reference source that will answer my question, please post it here. Your responses are appreciated.

Here’s the question:
When two pieces of trim meet at a corner in a parallel plane, a simple 45º miter will suffice to make a clean corner with no gaps. but if the two pieces are not in a parallel plane, one mitered surface will be longer than the other and will never match up. However, I was in a church on Sunday and saw some trim on the walls, some corners of which were mitered out-of-plane, and the mitered ends still met exactly square. How do they do this.

I’m not building a church, just a scrap bin with a beveled lid. I want to put a strip of trim around the carcass just under the lid on three sides (not the hinge side), but I haven’t figured out how to make these corners match up. Someone out there must know how. Help, please!

...or does it work only in churches?

-- "Life's nonsense pierces us with strange relation." Wallace Stevens

5 replies so far

View cabmaker's profile


1745 posts in 4100 days

#1 posted 05-17-2012 03:57 AM

There is not a compound cut for what your describing. There is however matching milled profiles to join a pitch to the horizontal. The pitch needs to be known to the miller and knives are machined to make the match. When you change the plane of the horizontal molding to a vault you will not obtain more than two, maybe three points of contact staying in profile. Not a new problem. Transition blocks are an easy solution. JB

View waho6o9's profile


9110 posts in 3868 days

#2 posted 05-17-2012 04:48 AM

That is not a dumb question. This might be of some help:

I think they had an article describing exactly what you need done, but I can’t seem to find it. I remembered
they used hand tools and it turned out perfect.

Good luck.

View Cato's profile


701 posts in 4603 days

#3 posted 05-18-2012 10:54 AM

I think the situation you describe is when you have to cope the joint by scribing a line on the piece you want to match up to the existing mitered piece and using a coping saw to cut to the line to make it fit.

Pretty much the same as when you say are installing the trim on a floor to ceiling bookcase and the straight side of the cabinet does not fit flush with an uneven wall so you scribe the trim piece to the wall and cut it to fit the bulges and waves in the wall.

There are others on here that are way more skilled at this than me, so please step in and correct me if I am not answering his question to the fullest. I am not a big fan of scribing and coping but I have done some and think that maybe this is what he is asking.

View juanabee's profile


113 posts in 4299 days

#4 posted 05-18-2012 08:45 PM

Thanks all for your thoughtful replies.

cabmaker, I can see why you recommended corner blocks. Thanks for the clear explanation and advice. I had some fun making some corner blocks that solved the problem.

This treatment is, of course, extreme overkill for a scrap bin made from OSB. But I was experimenting and thought this was a harmless way to learn some basics. My family will have some fun teasing me about my OSB and pine Taj Mahal , but what the heck, it looks GREAT!

-- "Life's nonsense pierces us with strange relation." Wallace Stevens

View cabmaker's profile


1745 posts in 4100 days

#5 posted 05-18-2012 09:55 PM

Good for you and let em make fun of you ! Enjoy

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