# Beveled miter on door casing



## ejordan

Hi, 
I'm new to the forum (just browsed in the past), and am hoping someone can help me out of the jam I've created.

I am installing door casing and am using a dual bevel compound miter saw. Based upon the passing recommendation of a friend, I decided to try beveling the miter cut on the legs to get a stealthier join. I had the saw set as follows:

Miter Angle: 45 degrees
Bevel: -10 degrees from 90
Kerf: 0.110

I set the bevel angle with a magnetic digital angle gauge.

Now, as I attempt to cut the head casing, I cannot match the angles. I have tried the complementary cut at 45 degree miter with +10 degree bevel and the fit isn't close. The finished edge of the head casing is far too "short" to match against the finished/facing edge of the leg.

Normally, I would scrap the materials and start from scratch, but these pieces are built-up, glued, and pre-finished, so I'd hate to lose the time (and money) I already have invested in them. I would be very grateful for any help you can provide. Thanks in advance.

Eric


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## DannyT

stop listening to your friend. cut them at 45 and glue the miters.


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## woodnthings

*10 degrees is too much bevel*

If you are going to deviate from a true 90, I would only go 2 degrees or so, maybe less. Both lengths of miter should be equal if your saw is set properly. Make some samples before you chop 'n hack the good stuff to get the fit just right. :yes:


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## chopnhack

A slight undercut (think a few strokes of a handplane) can help in some cases when there is drywall that is proud of the frame, but why would you cut this at a compound miter when the pieces are all in the same plane? You may have very few options to work with here...
You may have to recut the top of the miter at a flat 45 and install a plinth at the bottom..


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## FrankC

10 degrees is way to drastic, 1 or 2 degrees is enough to give some relief to the bottom so the face fits tight. Rather tag tilting the saw, which can get you into trouble if you forget it was tilted for the other side, just lay a flat carpenters pencil on the table next to where the cut will be and rest your board on it.


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## cabinetman

chopnhack said:


> A slight undercut (think a few strokes of a handplane) can help in some cases when there is drywall that is proud of the frame, but why would you cut this at a compound miter when the pieces are all in the same plane?


+1. :yes: Cutting a bevel on the miter will leave a void either on the inside or outside corner or both depending on the profile. If the joint needs to be closed up, a handplane or rasp would be sufficient.








 







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## ejordan

Thanks guys, I appreciate the feedback. Going forward, I will revert to my historical approach of square cuts.

Concerning the problem at hand (as I wish to avoid scrapping the materials and plinth blocks will clash with my other molding), can anyone suggest either a saw setting for the complementary cuts (at least to line up the front-facing profile, I don't mind filling the edges) or at least point me in the right direction?

Thanks again,
Eric


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## woodnthings

*lessee now*

You want to cut it twice and not have it too short? It will take better advice than I have..... :yes:


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## cabinetman

ejordan said:


> Thanks guys, I appreciate the feedback. Going forward, I will revert to my historical approach of square cuts.
> 
> Concerning the problem at hand (as I wish to avoid scrapping the materials and plinth blocks will clash with my other molding), can anyone suggest either a saw setting for the complementary cuts (at least to line up the front-facing profile, I don't mind filling the edges) or at least point me in the right direction?
> 
> Thanks again,
> Eric


Are you looking for a completely different answer? You have been given good advice.


















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## ejordan

I haven't cut the head piece yet; it has about 8" extra length for now. I've been practicing on a scrap.


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## ejordan

cabinetman said:


> Are you looking for a completely different answer? You have been given good advice.
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Not to be ungrateful, but yes. My question relates to finding the complementary angle/saw configuration to cut the head board to match the legs, which I already have cut and fastened to the wall. 

Most of the advice given is great and will help me make better cuts in the future, but don't address the specific problem of cutting this head board to match the already installed pieces. Clearly the approach I took is suboptimal, but I'd like try and make it work.


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## chopnhack

I don't think that you will be able to cut a complimentary angle to fill in the rest. If this is paint grade, get some 15 minute mud, an old credit card and pack the joint with mud, use the card as a scraper and follow the profile of the molding. Getting a little old world like raking plaster cornices :thumbsup: I have had to do it before on a larger molding that was a three piece corner around a round corner... lasted for years before wood movement finally cracked it, after you pack it with mud, prime it two or three times, this will help some with the cracking. The old timers used to embed lathe in their moldings, if the joint is big enough, consider some fiber of some sort. GL


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## woodnthings

*I'd like to see a photo of what you have*

If the side legs are mitered and the bevel is negative then the head piece must slide down from the top to fit behind the bevels ...unless I don't understand this whole dilemma ..... possibly.... more than likely.... definitely? :blink:


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## ejordan

woodnthings said:


> If the side legs are mitered and the bevel is negative then the head piece must slide down from the top to fit behind the bevels ...unless I don't understand this whole dilemma ..... possibly.... more than likely.... definitely? :blink:


 
You've got it exactly right. The cut shown is the one described in the original post (+10 degree bevel, intended to complement the original -10 degree cut on the right side leg). You'll see that the length of the cut is too short to match that of the leg.

I have also included a side shots.


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## ejordan

chopnhack said:


> I don't think that you will be able to cut a complimentary angle to fill in the rest. If this is paint grade, get some 15 minute mud, an old credit card and pack the joint with mud, use the card as a scraper and follow the profile of the molding. Getting a little old world like raking plaster cornices :thumbsup: I have had to do it before on a larger molding that was a three piece corner around a round corner... lasted for years before wood movement finally cracked it, after you pack it with mud, prime it two or three times, this will help some with the cracking. The old timers used to embed lathe in their moldings, if the joint is big enough, consider some fiber of some sort. GL


 
Thanks for the tip. Unless someone presents a better way, I'll first look way back to my high school geometry days to see if I can calculate the volume of the void and work my way into the correct cut (or close to it). If that doesn't prove successful, mud it is. I'm not familiar, however, with what you mean by lathe..??


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## woodnthings

*how's this?*

Just cut the head piece at a true 90 degree as see if the length matches up better. If so, just mud in behind the negative bevel and let it squeeze out as you press down, clean it up and go home... just sayin'.

metal lath is expanded metal screen used in wet plaster wall and such.

I also wonder if the head piece is from the same stock as the sides...? Is it a cut off?


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## ejordan

woodnthings said:


> Just cut the head piece at a true 90 degree as see if the length matches up better. If so, just mud in behind the negative bevel and let it squeeze out as you press down, clean it up and go home... just sayin'.
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Thanks. The head piece is identical stock. Unfortunately, the true 90 degree cut at 45 degree miter is much worse. It seems that the beveling resulted in an effective miter angle of 47-48 degrees on the leg, hence the longer cut (hypotenuse, I guess?). I'll play with it some more, perhaps experimenting with 90 degree cuts at 42-43 degree miter will help (I'll try that tomorrow...too late for that kind of noise). If no luck, mudding it shall be.


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## Sawdustguy

Best fix is to start with new pieces of molding, if available. When you cut compound angles the miter changes significantly. I am installing crown molding cutting it flat on the miter saw and cutting compound angles. My Starrett digital protractor gives me proper bevel and miter angle for installing crown molding. I know you are not installing crown molding, I am just using this as an example of how the angle changes when you go to compound angle cuts.

Example with 45 degree spring angle crown molding in a perfect 90 degree corner the miter angle is 35.3 degrees and the bevel angle is 30.0 degrees. This makes a perfectly fitting mitered corner joint with this crown molding in a perfect 90 degree corner.

George G


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## FrankC

ejordan said:


> You've got it exactly right. The cut shown is the one described in the original post (+10 degree bevel, intended to complement the original -10 degree cut on the right side leg). You'll see that the length of the cut is too short to match that of the leg.
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Looking at second photo it appears you have extra length in the upright to make another proper 45 degree cut if you remove it.


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## TimPa

ejordan said:


> Thanks. The head piece is identical stock. Unfortunately, the true 90 degree cut at 45 degree miter is much worse. It seems that the beveling resulted in an effective miter angle of 47-48 degrees on the leg, hence the longer cut (hypotenuse, I guess?). I'll play with it some more, perhaps experimenting with 90 degree cuts at 42-43 degree miter will help (I'll try that tomorrow...too late for that kind of noise). If no luck, mudding it shall be.


I am a little confused. if the miter angle is set to 45 degrees, and a bevel is added to "tilt" the blade, why isn't the miter still at 45 degrees? I can't visualize why it will alter the miter angle. guess i'll have to go look at my saw.

fyi i always take away 1/2 degree on the back side of my miters for casings to close up the front, walls and jambs are seldom on the same plane.


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## woodnthings

*Yup*

I'll betcha that the side casing is not at 45 degrees. Check it with a known accurate guage, preferably a digital miter guage. More than 45 degrees with leave a shorter length bevel, less than 45 degrees will yield a longer leg. I'm thinkin' it's less that 45 by a tad and that's why the head piece won't match up. Just a WAG.... :blink:


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## woodnthings

*any luck yet?*

What did you find out? Are the angles spot on? :blink:


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## cabinetman

*Obviously Not Yet*



woodnthings said:


> What did you find out? Are the angles spot on? :blink:


I wouldn't waste my time with the bevel angles. He was likely slightly off when swinging saw from right to left...or left to right (depending on how he starts). I would cut new pieces.


















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## ejordan

George G said:


> Best fix is to start with new pieces of molding, if available. When you cut compound angles the miter changes significantly. I am installing crown molding cutting it flat on the miter saw and cutting compound angles. My Starrett digital protractor gives me proper bevel and miter angle for installing crown molding. I know you are not installing crown molding, I am just using this as an example of how the angle changes when you go to compound angle cuts.
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> Example with 45 degree spring angle crown molding in a perfect 90 degree corner the miter angle is 35.3 degrees and the bevel angle is 30.0 degrees. This makes a perfectly fitting mitered corner joint with this crown molding in a perfect 90 degree corner.
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From what I can gather, this pretty well describes the situation. I measured the actual angle with my Starrett miter protractor (not digital) and found it to be closer to 47 than 45.


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## chopnhack

It looks like you can hold the head piece high, tack in place and then mud the joint and squeegee the profile into place with the plastic card. If the gap will be larger than expected and no lathe available, find another suitable backing material, even cloth like jeans or canvas may be suitable. I don't think your gap will be more than a quarter inch or so. There is a great article from Fine Homebuilding that might give you some insight on this method. Its worth reading. HTH


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## ejordan

cabinetman said:


> I wouldn't waste my time with the bevel angles. He was likely slightly off when swinging saw from right to left...or left to right (depending on how he starts). I would cut new pieces.
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The original guts were set at positive stops and bevel checked with a Wixey digital gauge, so the initial configuration should have been spot on.


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## ejordan

woodnthings said:


> What did you find out? Are the angles spot on? :blink:


Measured from the inside edge with a Starrett miter protractor (not digital), they're at about 47 degrees, so about 2 degrees shy, explaining the longer edge (just like you pointed out in your diagram). I tried a 43 degree cut at 90 degree bevel...much closer cut length when aligning the pieces, but not wuite close enou to fix with mud. I'll continue to play with it, as I seem to be moving in the right direction.


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## ejordan

*Wish I could explain it...*



TimPa said:


> I am a little confused. if the miter angle is set to 45 degrees, and a bevel is added to "tilt" the blade, why isn't the miter still at 45 degrees? I can't visualize why it will alter the miter angle. guess i'll have to go look at my saw.
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Truly, I'm not exactly sure. Intuitively, I am with you 100%, unfortunately, I have cuts that defy my intuition! Going forward, I think your suggestion of a 1/2 degree sounds like a much better approach, thanks.


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## ejordan

FrankC said:


> Looking at second photo it appears you have extra length in the upright to make another proper 45 degree cut if you remove it.


Thanks, I hadn't even considered this. Since the 45 degree square cut will be "shorter", if I'm careful, I should be able to preserve the length of the legs and recut. Much appreciated!


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## cabinetman

cabinetman said:


> I wouldn't waste my time with the bevel angles. He was likely slightly off when swinging saw from right to left...or left to right (depending on how he starts). I would cut new pieces.





ejordan said:


> The original guts were set at positive stops and bevel checked with a Wixey digital gauge, so the initial configuration should have been spot on.


As I mentioned, if you used your detent stops for your table setting, you moved it right and left (to get both pieces mitered). Unless of course you cut one upside down. You may have to adjust the saw to be more accurate if using them.


















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## ejordan

cabinetman said:


> As I mentioned, if you used your detent stops for your table setting, you moved it right and left (to get both pieces mitered). Unless of course you cut one upside down. You may have to adjust the saw to be more accurate if using them.
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I'm not sure I follow. Prior to this beveling experiment, I have cut dozens of pieces of casing with this saw at the 45 degree detent stops with very good results. I don't have a digital gauge to check the miter angle, however, the resulting cuts seem to be a pretty good indication that they're true. Am I missing something?


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## cabinetman

ejordan said:


> I'm not sure I follow. Prior to this beveling experiment, I have cut dozens of pieces of casing with this saw at the 45 degree detent stops with very good results. I don't have a digital gauge to check the miter angle, however, the resulting cuts seem to be a pretty good indication that they're true. Am I missing something?


I don't know if you are. But it stands to reason if your miter cuts aren't at 45° for each, the detent stops were off. Or, something changed when you included a bevel, i.e., the length of the miter cuts were different.


















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## ejordan

cabinetman said:


> I don't know if you are. But it stands to reason if your miter cuts aren't at 45° for each, the detent stops were off. Or, something changed when you included a bevel, i.e., the length of the miter cuts were different.
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I believe the latter to be true, though I can't necessarily explain the mathematics behind it. George G's earlier message paralleling this to crown molding cuts seems to offer the best explanation.


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## woodnthings

*it may be simple physics*



ejordan said:


> I believe the latter to be true, though I can't necessarily explain the mathematics behind it. George G's earlier message paralleling this to crown molding cuts seems to offer the best explanation.


A miter is made in a vertical plane 90 degrees to the table. When you add a bevel this changes the approach angle of the blade to other than vertical. I can see how this would change the length of the mitered angle as well.


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## cabinetman

ejordan said:


> I believe the latter to be true, though I can't necessarily explain the mathematics behind it. George G's earlier message paralleling this to crown molding cuts seems to offer the best explanation.


Mitering for spring angle is different than a single plane miter, as in door casing, or picture frames, etc. You were not trying to induce a spring angle. For a flat moulding, a 45° miter is 45°.








 







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## ejordan

cabinetman said:


> Mitering for spring angle is different than a single plane miter, as in door casing, or picture frames, etc. You were not trying to induce a spring angle. For a flat moulding, a 45° miter is 45°.
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I don't see much point in arguing with you, but if my detent stops have been (and continue to be) true at 45 degrees for the other 50-60 pieces of casing I've cut in the last few months, it seems highly unlikely that they jump out of alignment only when I change the bevel of the saw blade, and somehow revert when I straighten it. The only variable here is the change in bevel angle, as the cut is otherwise identical in every measurable way to ones I have made hundreds of times. If you can offer a better explanation, I'd truly like to hear it, but to assume operator error simply because you don't understand why this is happening (nor do I, to be clear), isn't helpful.

Thanks to everyone else who has tried to help me solve this. If I ever do figure out the solution, I'll be sure to share the results, even if only to address idle curiosity.


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## Sawdustguy

cabinetman said:


> Mitering for spring angle is different than a single plane miter, as in door casing, or picture frames, etc. You were not trying to induce a spring angle. For a flat moulding, a 45° miter is 45°.


Cabinetman, he did set a bevel which changes the miter, per what I explained previously. He actually cut a compound angle. If you have a miter saw capable of cutting a bevel set the saw for a bevel and a miter and cut a piece of scrap and you will see what I am explaining.

George G


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## cabinetman

ejordan said:


> I don't see much point in arguing with you, but if my detent stops have been (and continue to be) true at 45 degrees for the other 50-60 pieces of casing I've cut in the last few months, it seems highly unlikely that they jump out of alignment only when I change the bevel of the saw blade, and somehow revert when I straighten it. The only variable here is the change in bevel angle, as the cut is otherwise identical in every measurable way to ones I have made hundreds of times.


No need to get huffy. You answered your own question in the above.:yes:


















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## FrankC

George G said:


> Cabinetman, he did set a bevel which changes the miter, per what I explained previously. He actually cut a compound angle. If you have a miter saw capable of cutting a bevel set the saw for a bevel and a miter and cut a piece of scrap and you will see what I am explaining.
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Just had to go down and check this, set my saw at 45 degrees and cut straight down at 90 degrees for a standard miter joint. Then set perpendicular angle to 45 degrees as well, made a cut, placed one board on top of the other and the 45 degree mitres match perfectly.


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## woodnthings

*They should however....*



FrankC said:


> Just had to go down and check this, set my saw at 45 degrees and cut straight down at 90 degrees for a standard miter joint. Then set perpendicular angle to 45 degrees as well, made a cut, placed one board on top of the other and the 45 degree mitres match perfectly.


It's the length of the bevel on a constant width piece that seems to be the issue here. If you don't mind trying that OR if you already know please inform us. This is a mind bender! :blink::blink::yes:


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## FrankC

woodnthings said:


> It's the length of the bevel on a constant width piece that seems to be the issue here. If you don't mind trying that OR if you already know please inform us. This is a mind bender! :blink::blink::yes:


When you swing your miter saw to 45 degrees and bring the blade down it passes through the slot in the table, now tilt the blade off perpendicular, it still passes through the slot in the table the same as when perpendicular only at an angle. 

A compound miter at 45 degrees will still have four corners that form a square or rectangle, they just don't sit flat when joined.


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## woodnthings

*Thanks, but not what I had in mind ...*

I'm seeing the bevel as a pivot of the saw and motor on some shaft
that's horizontal with the table. Where the center of rotation is located "may" affect the length of the leg on a miter...I donno? I would not think at least on the saws I'm familiar with, that the blade plane is the center on which it rotates, rather offset from the blade by some amount. This I believe, is what causes a bevel miter to change it's leg length over a straight down 90 degree miter....again, I donno? My degree is in ART/Design not engineering. :laughing: My trigonometry expertise is very faded after all these years. 

Any engineers listening to all this? WillemJM ?:blink:


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## chopnhack

Sigh..

Geometry is complicated without pictures! I will give it a go 










Ok, so what we see above is a 45 degree cut across the width of the piece of wood, as it lies flat on the bed of the cms. The first vertical line with the square attached is a perpendicular cut to the width, i.e. saw set at no bevel, 45 degree miter. This is your typical miter setting on baseboard, casing etc. 

The next vertical line with the attached arc shows a 10 degree from vertical pitch. This would create a void on the back side of the molding, similar to what the OP stated. Notice how the lengths on top do not change :no:. On crown, the lengths would change, but that is because they are held in position. This means you are working with a compound miter being cut on an angled piece of wood and that is what changes the lengths of crown miters as the angle settings change.

Clear as mud? :yes:


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## woodnthings

*OK, now we're getting closer..*

But this is a theoretical explanation. I would like to see the same thing in real wood using a real saw. I see what you are saying that the bevel angles don't change and we knew that way back in the thread. 
But there must be a reason the legs are different lengths in the photo. 
My explanation is also theoretical, since I can't prove it ...yet.... :laughing:



Maybe I'll have to do it myself to show me if my theory is correct or all wet. :yes:


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## FrankC

It is possible for the board to move during a compound miter cut, which could be a reason for the long cuts that are not at 45 degrees, I usually use the hold down on my saw when doing them.


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## chopnhack

I'm just clarifying because there seemed to be some discussion in previous posts to the contrary: <<A miter is made in a vertical plane 90 degrees to the table. When you add a bevel this changes the approach angle of the blade to other than vertical. I can see how this would change the length of the mitered angle as well.>>

But going back the OP mentioned that the reason for longer lengths was a 47 degree instead of a 45 degree miter.

I also noticed that there was some room behind the molding between the wall. You may be able to rock the molding forward for a better fit, shim and nail. Rock forward meaning rotate down and towards you, away from the wall.


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## ejordan

chopnhack said:


> I'm just clarifying because there seemed to be some discussion in previous posts to the contrary: <<A miter is made in a vertical plane 90 degrees to the table. When you add a bevel this changes the approach angle of the blade to other than vertical. I can see how this would change the length of the mitered angle as well.>>
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To clarify, I made the cuts from 45 degree positive stops, the effective cut is closer to 47 degrees, hence the longer edge and the basis for the original post.

You noted gaps between the wall. On the left side (near side in the pictures), what you actually are seeing is a small gap where the back band (glued, nailed, and painted) doesn't quite cover the casing profile, leaving a 3/16 gap which I will caulk later. On the right (far) side, you see a combination of that and a gap where the drywall is not flush to the door frame. The piece is supported by 1/8 - 3/16 strips and caulked, just not caulked at the joint yet.


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## chopnhack

Don't forget to post finished pics to see how this turned out :thumbsup:


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## ejordan

chopnhack said:


> Don't forget to post finished pics to see how this turned out :thumbsup:


Will do - that will be Sunday's project. 

Unless I am able to figure out the angle/bevel needed to complement what's already there, I likely will try Frank C's recommendation of re-cutting the boards. After looking closely, he is correct in the, since the effective cut is a steeper angle, the error was on the long side, leaving enough stock for a square 45 degree cut. See pic showing 45 degree cut. See pic with 45 degree cut shown.

Given how extreme this particular back cut is, there may not sufficient material on the back side, but the front should align and I will just fill the back with mud.


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## TimPa

i believe that a complimentary angle does not exist, that will provide the profile matching and the same miter length (as your last pic clearly shows), when the original side angle is not close to 45 degrees. re-cut would be way to go.


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