How do I figure out this angle?

[Kyle Iwamoto]

No framing (house frames) carpenters? I would imagine that would be the same process to figure out what angles to cut the corner facia on the roof eaves..... Usually the roof slope is the "other way" but the theory is the same. I think. I have no clue.....

[David Winer]

I'm getting close to finishing this tv frame and I'm at the point where I'm attaching the trim that runs the perimeter of the frame. I can't figure out what angle and or bevel I need to set my saw at make the cut. The two columns are angled at 10 degrees. The backside of the molding on the front of the column has been bevelled at 10 degrees as well so that the top of the profile isn't angled down when applied. I've tried to figure this out through trial and error but I'm getting to the point where my trim stock is getting low. Any help would be appreciated.

I'll take a stab at this too. Years ago I worked out a program in BASIC that computes saw angles for multi-sided constructions that slant from their bases. I plugged in your 10 degrees and 4 sides to arrive at this result:

Miter angle = 80.1 degrees
Blade tilt angle = 44.1 degrees

I would set the miter angle at 44.1 degrees and the blade tilt angle at 80.1 degrees in your situation.

This applies for a table saw, radial arm saw, or a miter (chop) saw. I suggest that you try these settings on some scrap. If it doesn't work I would be surprised, but no guarantees!

[Russell Tribby]

I'll take a stab at this too. Years ago I worked out a program in BASIC that computes saw angles for multi-sided constructions that slant from their bases. I plugged in your 10 degrees and 4 sides to arrive at this result:

Miter angle = 80.1 degrees
Blade tilt angle = 44.1 degrees

I would set the miter angle at 44.1 degrees and the blade tilt angle at 80.1 degrees in your situation.

This applies for a table saw, radial arm saw, or a miter (chop) saw. I suggest that you try these settings on some scrap. If it doesn't work I would be surprised, but no guarantees!

Thanks David I'll give it a shot. I felt like a real idiot not being able to figure this out yesterday. I'm not feeling so bad anymore since it's thrown more people than me for a loop. I've already back bevelled the molding that runs along the face of the cabinet and columns, I'm wondering now if I should have waited to cut the miters first before doing that
I've included some more pics of the cabinet to give you guys a better idea of what I'm looking at.

[bill mullin]

Hi Russel.

Have you applied the crown already? It looks to me like you would have the same issue with it.

[David Winer]

... I felt like a real idiot not being able to figure this out yesterday. ...

This setup actually requires quite complicated geometry and trigonometry to calculate the proper saw angle settings. A I recall I first saw the equations in a copy of Fine Woodworking and thought these would make a good learning project for me to apply BASIC language, which I was learning at the time. I worked out a user interface in DOS--which is crude compared to Windows that we have all gotten use to by now. But it worked. I have used the program, which I named "Staves.exe," several times over the years to make bird houses, flower boxes, and the like of multiple sides. It should work for moldings just as well.

Yesterday I took a picture of a four sided flower box that has the same angles as your trim: four sides at ten degrees slant. See attached. The open miter is from several years of weather, not poor fitting.

[bill mullin]

There are no compound mitres to be cut. This is difficult to explain, but I will try.

The columns to be trimmed only have the angle on the front, not the sides. So I'll start there.

The trim will lay flat on the side of the column. That means the back of the trim(cove mold) will be straight up and down; vertical, plumb. Therefore, the top of the cove will be 90* to the back; horizontal, level. And, it will be applied level from front to back, parallel to the top. I'll call this condition "square to the world".

Okay, now the trim on the front is to be applied the same way, top of cove level to match the side cove. But, he bevelled the back of the cove for the front of the column. Forget about that for now. That piece has to be applied as if the front of the column is straight up and down, not angled. Again, "square to the world". That is the only way all of the shapes and facets of the cove will match at the mitres. Look at figure 1 of my crude drawing. This would leave a gap (fig. 1) at the bottom of the front piece of cove.

There is one, and only one, type of cut to be made here-- 45* outside mitre.

Now, back to the bevel. Look at figure 2. Since he bevelled the back of the front piece of cove to match the 10* angle, the short point of the mitre will be moved back by the amount of material removed at the top of the cove. This will remove the gap shown in fig.1. Only one way to do this, look at figure 3.

He should have cut the front pcs. of cove long, held them up to the front face of the column, marked the two mitres, bevelled the back between the two marks, then cut the mitres. This would leave the little triangles, shown as A on fig. 3, moving the short point of the mitre back as previously mentioned. The shaded portions on figs. 2 and 3 show the material removed for the bevel.

As it is, he has already bevelled the cove, so those triangles will be missing, leaving a triangle shaped gap at the top corners of the cove.

I simply cannot see any type of compound cut working here. If all three sides of the column were angled, and the cove applied flat to those faces so that the top of the cove angle down accordingly, then, yes, a compound mitre would be correct.

I gave it my best shot. Hope it's not too confusing.

[johnny means]

There is no way to make that piece fit if you are using the same thickness molding in the front. You will have to mill a piece with the added thickness of the gap created by tcolumns bevel. Then you would 45 miter to leength. After that you bevel the piece on the back edge to fit.

[bill mullin]

There is no way to make that piece fit if you are using the same thickness molding in the front. You will have to mill a piece with the added thickness of the gap created by tcolumns bevel. Then you would 45 miter to leength. After that you bevel the piece on the back edge to fit.

Yes. If he wants to make his own trim, that will work fine.

[Chaz Alexopoulos]

I ran into a similar situation when putting crown moulding on a vaulted ceiling. After much trial and error, the only way I could get the sides to match up was to leave a little gap on the bottom that I filled with caulking before painting. You can't even tell it's there. If you can get a compound mitre to match up without a gap, you are a much better carpenter (woodworker) than me. Good luck. I hope it works.

[David DeCristoforo]

It's not that hard! You have to make the front piece of trim so that the width of the top is equal to the width of the side piece. But the bottom will be wider because you need to bevel the trim as shown here:
trim_2.jpg
Line "A" represents the face of your mantle. Line "B" represents the "Short point of the miter. The small triangle they form is where you need to make a triangular notch in "face" piece so that dimension "C" is the same on both pieces.

No trig is needed. Basically you just need to create a plumb "short point" on the mitered ends of the face trim.

[Russell Tribby]

Well, I didn't set out to stump anyone but it looks like this may have been a good learning experience for some, myself included. I ended up getting a good fit on the trim piece. The outside corners were easier than the inside corners. The fit for the crown was more of a challenge. Among other things l learned that if I run into this again that I won't rip all the moulding to the same thickness before I start cutting the joints. It would have made things a lot smoother if I had some extra thickness to work with. I'll post some pics tomorrow.

[Russell Tribby]

I'm a little behind on the posting of pics. I installed the frame a couple of weeks ago and it turned out alright. The miters were tight on the bottom of the joint but if you were able to look at it from the top down then you can see the difference in thickness of the stock. Thanks for everyone's help.

[Bill White]

I have a HEAD ACHE. .1 degrees on a miter saw? How'djadodat?
Bill