Beveled miter on door casing - Page 2 - Woodworking Talk - Woodworkers Forum
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post #21 of 50 Old 09-04-2013, 03:02 PM
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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....
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post #22 of 50 Old 09-04-2013, 08:56 PM
where's my table saw?
 
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any luck yet?

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

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #23 of 50 Old 09-04-2013, 09:16 PM
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Obviously Not Yet

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What did you find out? Are the angles spot on?
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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post #24 of 50 Old 09-04-2013, 09:56 PM Thread Starter
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Originally Posted by George G View Post
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.

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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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post #25 of 50 Old 09-04-2013, 10:03 PM
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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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post #26 of 50 Old 09-04-2013, 10:21 PM Thread Starter
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Originally Posted by cabinetman View Post
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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post #27 of 50 Old 09-04-2013, 10:21 PM Thread Starter
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Originally Posted by woodnthings View Post
What did you find out? Are the angles spot on?
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.

Last edited by ejordan; 09-04-2013 at 10:22 PM. Reason: Typo
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post #28 of 50 Old 09-04-2013, 10:28 PM Thread Starter
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Wish I could explain it...

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Originally Posted by TimPa View Post
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.
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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post #29 of 50 Old 09-04-2013, 10:31 PM Thread Starter
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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.
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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post #30 of 50 Old 09-05-2013, 06:45 AM
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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.
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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post #31 of 50 Old 09-05-2013, 07:48 AM Thread Starter
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Originally Posted by cabinetman View Post
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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post #32 of 50 Old 09-05-2013, 08:00 AM
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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?
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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post #33 of 50 Old 09-05-2013, 08:03 AM Thread Starter
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Originally Posted by cabinetman View Post
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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post #34 of 50 Old 09-05-2013, 08:17 AM
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it may be simple physics

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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.
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.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 09-05-2013 at 08:29 AM.
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post #35 of 50 Old 09-05-2013, 08:17 AM
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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.
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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post #36 of 50 Old 09-05-2013, 05:36 PM Thread Starter
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Quote:
Originally Posted by cabinetman View Post
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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post #37 of 50 Old 09-05-2013, 06:37 PM
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Quote:
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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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post #38 of 50 Old 09-05-2013, 07:47 PM
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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.
No need to get huffy. You answered your own question in the above.






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post #39 of 50 Old 09-05-2013, 08:54 PM
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Quote:
Originally Posted by George G View Post
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
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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post #40 of 50 Old 09-05-2013, 09:11 PM
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They should however....

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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.
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!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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