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The Magic Cafe Forum Index » » The workshop » » Question on "The Seven Basic Secrets of Illusion Design" (0 Likes) Printer Friendly Version

ClintonMagus
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I love this book, but there are two formulas on page 35 that are apparently incomplete in my book. About 2/3 of the way down the page, in the formulas for calculating bevel and miter, the blanks are empty. It's probably a printing issue, but my book says:

...Sin(__/__)] and
...Cos(__/__)]

Can someone please share with me what should go in those blanks? I know it's some combination of "Rise" and "Run".

ALso, was this book ever printed by anyone other than Illusion Systems?

Thank you...
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EsnRedshirt
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Finally got home and dug out my copy of this book. The text is grey and incredibly faint. On both instances the equation is "(rise/run)". The triangle beside has "rise" going up the side, and "run" across the bottom. Be warned, though, using these formulas may result in you trying to cut a bevel of 37.667 degrees, or some other ridiculously absurd angle to attempt to measure on any standard table saw. When I built a base, I ended up working backwards, starting by rounding off to an angle I could actually cut and measuring the rise and run from there.

I don't know of any other publisher for the material.

-Erik
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George Ledo
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I haven't read the book, but from what you're saying I get the impression that calculating an angle for a woodworking project by using a sine and cosine is major overkill.

Don't know if this will help, but cabinetmakers for many years have worked out precise dimensions and angles by drawing a full-size diagram on paper and going from there. It works beautifully. Woodworking magazines and books occasionally have articles on this.

Basically, you would just start with a large sheet of paper (a roll of cheap tracing paper or something similar), lay out your rise and run in actual size, and then draw the hypotenuse and measure the angles. Or, instead of using a protractor, just take the paper itself, fold it along the angle you want to cut, and use that to set up your table saw. You may end up with an angle of 37.6790876456 degrees, but you'll never know it.

Another option is to use a CAD program to lay out the thing and get the angles. But be warned -- CAD programs don't understand about reality. That angle MAY just measure out to 37.6790876456 degrees. Smile

Again, I haven't read the book, so this may all be in there anyway.
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ClintonMagus
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I disagree that using a formula for calculating miters and bevels is "overkill". Rather, properly using a formula can save a lot of trial-and-error and possible expesnse of wasted material.

If your calculation produces an angle of 37.6790876456 degrees, you use the rounding skills you learned in junior high to make it 38 degrees (or 37.5 degrees, if it needs that kind of accuracy). I'm not familiar with the "large sheet of paper" method, but I also haven't seen many cabinetmakers who utilize a lot of compound angles in their work, with the possible exception of crown or base molding.

I have found several tools online for calculating compound miters. Most are intended for crown molding, but there are several that can be used to calculate the angles necessary for beveled base construction.

I would be curious to know how some other illusion builders on this forum address the issue.
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Thomas Wayne
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Quote:
On 2008-11-16 11:56, George Ledo wrote:
[...]
Another option is to use a CAD program to lay out the thing and get the angles. But be warned -- CAD programs don't understand about reality. That angle MAY just measure out to 37.6790876456 degrees. Smile
[...]


Of course, if you have the CNC routers, milling machines and/or lathes to cut whatever angle your CAD system generates, then you may not bother to even check what the measure of the angle actually is. Just program it and cut it.

That's how I do it, anyway...

TW
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ClintonMagus
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I'm sure that information was helpful to those who had forgotten that they had a CNC machine just collecting dust out there in the garage, but I was looking for information for the remaining 99.999999 percent of us who will have to suck it up and use the old rotating blade method. Smile

Here is a website with a lot of resources for calculating compund cuts:

http://www.compoundmiter.com/

And another useful tool:

http://www.woodweb.com/knowledge_base/_S......ram.html

And maybe the most helpful one (for me, anyway):

http://www.woodweb.com/knowledge_base/Be......xes.html
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EsnRedshirt
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Hmm, those CNC machines would be nice. If I had a hundred thousand dollars to spend on a new workshop.

Fortunately, I'm content in the knowledge that I can knap something that can, in a few blows, destroy your CNC machine beyond repair.

The rest of us use regular power tools.

ClintonMagus- George is right on about full-scale drawings. There's another method for doing the sides that join at corners, once you've got the top and bottom cut to the proper size. You can build a jig to hold the wood in the proper position (i.e. at it's final bevel), and just run it through the bandsaw/tablesaw/etc with a 45 degree setting. Then use a -45 degree setting for the joining piece. The two pieces should then fit tightly together at a 90 degree angle, while retaining the proper rise. And you won't have had to measure any compound mitre cuts.

-Erik
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* = Take any advice from this person with a grain of salt.
ClintonMagus
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Quote:
On 2008-11-17 18:23, EsnRedshirt wrote:
ClintonMagus- George is right on about full-scale drawings. There's another method for doing the sides that join at corners, once you've got the top and bottom cut to the proper size. You can build a jig to hold the wood in the proper position (i.e. at it's final bevel), and just run it through the bandsaw/tablesaw/etc with a 45 degree setting. Then use a -45 degree setting for the joining piece. The two pieces should then fit tightly together at a 90 degree angle, while retaining the proper rise. And you won't have had to measure any compound mitre cuts.

-Erik


That does work, and I have done that way many times in the past, but I would rather calculate the angles and cut them with the oard lying flat on the table or miter saw. I just feel warmer and fuzzier when the board has a solid, flat surface to sit on.
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George Ledo
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Quote:
On 2008-11-17 08:32, ClintonMagus wrote:
...but I also haven't seen many cabinetmakers who utilize a lot of compound angles in their work, with the possible exception of crown or base molding.

Not to go off on a tangent, but a number of periods and styles of furniture (including what we call "colonial") do use a lot of compound angles in the trim and moldings, and the full-size-drawing method is how a lot of those angles are worked out even today when making a custom piece. Maybe I should have specified "furniture makers" instead of using the more generic "cabinetmakers."

I'm all for accuracy, but I've also seen way too many errors made by overthinking a project and rounding up or down incorrectly. In some cases the time required to fix it may not matter, but in my field (theatrical design), where you work with an inflexible deadline called Opening Night, you want to simplify things and minimize errors.
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Mark McDermott
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ClintonMagus,

When you find your angle you like, use a sliding T bevel to set up your table saw and it will go a lot faster.

This is a great tool to have when wood working!

Thomas,

My day job we have a lazer cnc that will hold a 72" x 144" sheet of steel and one can enjoy the beauty of the quality that it does.

good luck,

Mark
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