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Discussion Forum

More CM IV lessons: crown mold calcs?

| Posted in Construction Techniques on January 14, 2005 01:28am

Okay….I want to impress Frank with my advanced calculator abilities.

Is there a way to calculate the angle and bevel of standard 4” crown mold. We wil be installing it on an octogonal bay, as well as some square corners….and a 12/12 gable and I want to use a sliding compound mitre saw and lay the materials flat.

I know I’d be able to quickly figure out the angles and cuts using trial and error, but I want to prove to him that the calculators “aren’t crap” like he told me they are.

Any mathematical geniuss’ want to crack this egg?

Another coupla houses with this crown mold stuff and I’m turning in my rough tools and buying some trimming stuff!

blue

Just because you can, doesn’t mean you should!

Warning! Be cautious when taking any framing advice from me. There are some in here who think I’m a hackmeister…they might be right! Of course, they might be wrong too!

Reply

Replies

  1. User avater
    SteveInCleveland | Jan 14, 2005 01:48am | #1

    Calculator?  Calculator?  We don't need no stinkin' calculator.

    Just print out these handy Excel spreadsheets and laminate them.........

     

     

     

     

     

    1. blue_eyed_devil | Jan 14, 2005 04:10am | #3

      Thanks steve-o! Too bad I can't interpret them! i did print them out though.

      blueJust because you can, doesn't mean you should!

      Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

    2. blue_eyed_devil | Jan 16, 2005 04:00am | #5

      Steve-O.....HELLLLLLPPPPPPPPPP!

      Would it be possible for you to explain what 38/52 mitre and 38/52 bevel means?

      blueJust because you can, doesn't mean you should!

      Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

      1. User avater
        dieselpig | Jan 16, 2005 04:17am | #6

        That's the spring angle of the crown Blue.  The most common is the 38/52 crown, also popular is 45/45 crown.  It's the angles the crown forms between the ceiling and wall with the crown being the hypotenuse of the right triangle.  Measure your crown with your speed square (har, har, har) to determine the spring angle of the crown supplied.

        That will tell you which column of the chart to use.  The rest is cake and pie although I prefer to cut  crown standing it against a sub fence.  Less head scratching for me and less time standing there in front of the chop saw with my eyes closed, my arms straight in the air, and a piece of crown in each hand.

        1. MikeSmith | Jan 16, 2005 04:29am | #8

          i can see it now brian...

          <<<standing there in front of the chop saw with my eyes closed, my arms straight in the air, and a piece of crown in each hand.>>>

          "posing for holy cards ", as sister mary joseph uster sayMike Smith Rhode Island : Design / Build / Repair / Restore

          1. User avater
            dieselpig | Jan 16, 2005 04:32am | #9

            LOL....

            Like you've never been there?  

        2. blue_eyed_devil | Jan 16, 2005 03:42pm | #13

          Thanks Diesel. I had a feeling that the numbers represented different types of crown, but I just didn't know how they are derived.

          Now that I'm looking at them, I notice that they add up to 90degree, which gives me a clue.

          You have to forgive me, I've spent a lifetime relating to pitches and angles in terms of ratio (12/12, 7/12, 12,17, etc) and I really don't know much about degrees.

          I do know that the crown we are using has a 2.75/3.625. I'm not entirely sure about that 2.75 number, because I only mark the bottom which is 3.625. I've been using a pattern that is about 7.7/12 for the mitre angle (I think I'm on track here). According to the chart I should be marking 31.61 which I suppose is close enough. I've also been beveling at 32 degrees..the chart shows 33.86.

          I suppose I could run up north and get my mitre box...but that would be too easy. I'll just continue on with my framing square and power saw!

          thanks again.

          blueJust because you can, doesn't mean you should!

          Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

          1. Snort | Jan 16, 2005 08:44pm | #14

            Blue,Geeze, does Gabe know you're boogerin trim now? I use this, and a cheap scientific calculator...and then it's still trial and error<G> Don't worry, we can fix that later!

          2. blue_eyed_devil | Jan 17, 2005 05:19am | #15

            Bucksnort.....shhhhhh! I thought we were buddies.!

            Don't tell Gabe I'm hacking my way through this exterior crown mold job!

            The funny thing is...everyone is trying to teach me and all I really want is two simple numbers. I think Ive learned that the numbers I seek are called the mitre and the bevel..but I'm not really sure.

            I think, I'm going toss out a huge milkbone challenge. I'll call out the most prominent trimmer and tell him that the proper angle are 7.5/ 12 on a 32 degree. I'll be especially obnoxious and tell them that their crazy and they don't know what they aredoing and their reading the wrong books and, and, and that they are neo cons!

            Then, to show me up, they'll actually give me the right answers...then I'll be happy!

            Oh well, back to trial and error.

            blueJust because you can, doesn't mean you should!

            Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

          3. blue_eyed_devil | Jan 17, 2005 05:58am | #17

            Hey BB,  I think the second picture will be good enough. I printed it out, it's a bit blurry but readable and I'm sure Frank will be able to figure it out. I'll have to bring him a calc that can do the degree thing.

            thanks...I'd study it, but I don't want to know that much...I just wan't the number for a 90 degree corner and a 45!

            blueJust because you can, doesn't mean you should!

            Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

          4. Snort | Jan 17, 2005 06:25am | #18

            Okay, but it's time to pull out Frank's speed square...LOL...31 and a fat 1/2° for the miter, mark it across the face of the crown. Set the bevel on Frank's sidewinder (the one with the guard!) to a light 34°, put two pcs together on yer boogerin' table, adjust if necessary. I'm just guessing, never even thought about cutting crown with a circular saw...you are so out of the box<G>10 buck cheapo solar casio scientific will do those trig formulas, just plug in what Frank reads off your manly framing square...ha, ha, ha!Oh yeah, good luck ;-) Don't worry, we can fix that later!

          5. blue_eyed_devil | Jan 17, 2005 06:54am | #19

            Bucksnort, we already did two house with our saws! I'm just trying to give the "precise numbers". Also, we trial and errored the joints in the gable trim and I'd like to be able to intelligently calculate it. I think the pictures you gave me along with Joe Fuscos site will be enough to actually educate myself to some degree of rookieship.

            I don't want to become a crown mold expert...

            blue

             

             Just because you can, doesn't mean you should!

            Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

  2. gdavis62 | Jan 14, 2005 02:05am | #2

    I am not a trim carp, but I know my math, and when he tries to transition from running level around all the corners (no matter what angles), he'll have to get real creative with crown mold when making the joint that turns up the inside gable.

    Two photos snipped from Gary Katz's website, <photo galleries>, <crown molding>

    View Image

    View Image



    Edited 1/13/2005 6:13 pm ET by Gene Davis

    1. blue_eyed_devil | Jan 14, 2005 04:14am | #4

      Gene, I understand the challenge, if the crown runs level, then has to transition up on the rake angle. Fortunatly, that is not going to happen on our job. Our rake crown dead ends onto a "Queen Ann" hip return. It does meet at the peak though, but that is simply another 90 degree turn...except that the rise and run of the moldings is oriented differently than if we were turning a corner on the level.

      I think.

      Crown mold expert I ain't!

      blueJust because you can, doesn't mean you should!

      Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

      1. User avater
        goldhiller | Jan 16, 2005 09:39am | #12

        The chart at the bottom of this page may be helpful to you. It's for cutting on the flat.If it ain't, at least you didn't pay anything for it. <G>http://www.dewalt.com/us/articles/article.asp?Site=woodworking&ID=2Knowledge is power, but only if applied in a timely fashion.

  3. Joe_Fusco | Jan 16, 2005 04:27am | #7

    Blue,

    If you want to use a SCM saw to cut crown and lay it flat you can you this chart. http://www.josephfusco.org/Articles/Crown_Moulding/CrownChart.html

    That chart will give you the miter and bevel settings for any 52/38° or 45/45° crown.

    If you have a crown with a different angle you can use this calculator.
    http://www.josephfusco.org/Articles/Crown_Moulding/crownscript.html

    1. blue_eyed_devil | Jan 17, 2005 05:24am | #16

      Joe, I went to the site and I must admit, it is impressive.

      Now, please don't take offense to this...but I'm curious, as well as kinda glad.....I was reading the thread about roof bull session and I saw FramerT refer to you as Joe Fusco, which would surprise me because if that is really you, I'd want to know why you are being helpful to me.

      I'm thankful for your help...and I'm sorry I didn't take the time to check out the site before when you mentioned it.

      blueJust because you can, doesn't mean you should!

      Warning! Be cautious when taking any framing advice from me. There are some in here who think I'm a hackmeister...they might be right! Of course, they might be wrong too!

  4. User avater
    G80104 | Jan 16, 2005 06:39am | #10

    Blue,

         Go to http://www.compoundmiter.com Buy the book $20 & you will never have any question about crown after you educate yourself with this book.

    1. chills1994 | Jan 16, 2005 08:48am | #11

      yeah, and along with buying that book you have to buy the clear plastic protractor gizmos.

      i just prefer to cut upside and backwards, even with a SCMS.  i've got some pics of crown and my method, one of these day's i'll get around to posting them.  if a piece needs a little trimming i just it "slide" up or down the fence (more vertical, or more horizontal) and cut.

      but all that stuff in the book  and spreadsheets only pertains to crown that is 32/58, and you're assuming both corners are 90 degrees.

         there was an article in an old FHB that was later reprinted in a "best of"  book.  the author of that article got together with a math professor and they figured out the trigonometric formulas for cutting crown flat.  you gotta have a scientific calculator with sin, cos, and tan on it.  but it does work.  i've had to cut crown on a table saw and adjusted the blade's tilt and the miter gauge angle to give me perfect corners.

      a couple weekends back  i shelled out about $60 for the new Starret miter protractor thingey.  works great!!! measure any angle between two walls and it gives you what the angle for the chop saw needs to be.

      one of these days i'd like to also get the Nobex miter divider.  another neat gadget.

      of course if you're on a really tight budget a carpenter's sliding (T) bevel will work to for figuring out angles.  but for setting the saw to same angle you need a bevel that has a flush tightener lock the Veritas one or a tightener on the end like the Shinwa.

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