Three-cornered miter

[David Champney]

How does one go about making a three-cornered miter of 1/4 round moulding?

By three-cornered I mean two pieces in one plane and another vertical to the mitered joint of the first two. I want to put moulding on stairs, including the risers.

How do I figure the angles on the third piece?

[Brice Burrell]

David, I understand a three way miter but I don't know what you're trying to do in your application. I assume you angles aren't 90s. A little better description of what you're doing would help.

[Jeremy Wilcox]

Well this is an interesting question and one i will be interested in as well. I think it will look sharp once done. Now i know there is a mathematical solution to this i am sure but well I suck at math. So what would i do ...Trial and ERROR(s). what i would do is if its 1/4" round molding you would measure widest points /2 and mark and cut coumpound 45's on the parallel peices and on the vertical you need to cut compound 45's on the that piece as well. after typing this you probably already know that stuff but the other solution to this is to Cope the vertical over the parallel 90deg corner.

[russell lusthaus]

I would just cope the vertical piece around the joint between the other two.

[Brandon Weiss]

I think I agree with what russell is saying. IF I understand him correctly that is. The vertical piece would be in the shape of a V at the bottom... Basically instead of having a 45 deg miter, you'll in essence have three of them. Maybe not exactly 45 degrees, maybe so. I guess I'd have to do the math on that one. It depends on what the compound is on the miter of the two in plane pieces. The in planes will meet at a 45 deg angle no matter what. You can make the compound whatever you want it to be. Then the vertical piece will meet the in plane pieces at 90 minus the compound angle. This will put your vertical piece on the top of the intersection of the two in plane pieces. Is that the look you're going for?

[Jeff Bratt]

This is where CAD can be very handy. I did a quick sketch of your 3-way miter of quarter round pieces - and it didn't turn out quite like what I had originally expected. The way I made it work (and there may be other ways, too) all the angles are 45 deg - but the end of each piece is kind of spear-point shaped, because there are two miter cuts on the end of each piece. If you think of two quarter rounds mitered, that's one 45 deg cut. But if the vertical piece has a v-shaped bottom, then each of the other two pieces now needs an additional 45 deg miter cut to join to the vertical piece. Maybe mitering two pieces together and coping the vertical piece onto the top (as Russell suggested) is a good alternative...

133532

[Paul Atkins]

This cracks me up. 3 minutes on the chop saw would have given you the same answer. Now try an outside corner. Same deal.

[phil harold]

time to learn how to cope...

[Quinn McCarthy]

David,

You could make a plinth block that is thicker than your toe moulding and then your moulding would but up against it. I think that would look great.

Hope that helps..

Quinn

[Greg Sznajdruk]

This cracks me up. 3 minutes on the chop saw would have given you the same answer. Now try an outside corner. Same deal.


How can you make an outside corner with quarter round?

Greg

[Paul Atkins]

Like this. Didn't mean to sound flipant, I've just done miles of this stuff. This took 5 minutes because it's plastic and not 90 degrees.

[Brice Burrell]

Here's a SketchUp model that might help. Make the first cut at a 45 degree miter, then the second with a 45 degree bevel. Do this on all three pieces and you'll have a 3 way miter.

[Greg Portland]

Consider taking a cube and make it a corner detail. It may look better and be a lot easier than coping every single moulding joint.

[Stephen Reid]

How can you make an outside corner with quarter round?

Greg
Thats what I was wondering too.With a 90degree back side 1/4 round wouldn't play very nice with an outside corner!I think corner trim is needed.

[Jeff Bratt]

Once you know how to do something, it's always easier. I thought (and maybe others, too) that there might be a way to do this with one miter cut on the end of each piece. Once you realize that two cuts per end are needed, then things become clearer. Took me about 5 minutes to sketch this, since I didn't have any molding to cut up, and it was too late to run noisy machines...