mathmatical formulas


If I have a piece of timber 3' long and I want to make a 45 degree cut so one face is 12" long, how do I work out the length of the timber if the final cut leaves the one side longer than the 12" origanal measurement?
Hope that makes sense.
Is there a website for all these woodworking formulas?
Many Thanks
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Try this:
http://www.sizes.com/numbers/triangles.htm
Somewhere in here you should find what you are seeking.
-- PDQ
--
| If I have a piece of timber 3' long and I want to make a 45 degree cut | so one face is 12" long, how do I work out the length of the timber if | the final cut leaves the one side longer than the 12" origanal | measurement? | | Hope that makes sense. | | Is there a website for all these woodworking formulas? | | Many Thanks |
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I don't know of any website and there may be an easier way, but at least with a 45 degree cut it's not too difficult. All you need to do is add the width of your board to 12" and that will be the length of the long side. This is because if you were to draw a 90 degree line across the board from the edge of your 45 degree cut you would then have a right triangler with the 45 degree cut being the long side, the width of the board being one leg and the distance from the line you drew to the far edge of the cut being the other leg. If the angle were anything other than 45 degrees it would involve some trigonometry using sine and cosine, but fortunately for 45 degrees it works out that both legs are exactly equal, so since you know the width of your board you automatically know the length of the other leg and since the distance you are looking for is 12 " plus the length of that far leg you can now just add the width of the board to twelve inches and that will give you the distance you are looking for. I wish I could draw you a picture that would make it more clear, but unfortunately I'm better with math than I am computers. I hope this helps. Good Luck BC
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wrote:

If I am seeing what you are seeing, it depends on the width. The additional length [added to the 12" smaller one] will be the width. So you'll have 12 + w.
12 ........... . . . . Cut Angle = 45 . Width . . . ............................ 12 + W
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TrailRat wrote...

A 45-degree triangle always has equal-length legs. So, if your timber is, say, 3-1/2" wide with the other end cut square, then the difference between the lengths of the two sides will be 3-1/2" inches. If both ends of the workpiece have (opposite) 45-degree angles -- as in one edge of a mitered picture frame -- then the outside edge will be longer than the inside edge by twice the width of the material.

Rather than a woodworking formulas reference, you might try looking for one with common geometry and trigonometry formulas.
Good luck,
Jim
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"TrailRat" wrote in message

If I am understanding you correctly, just another viewpoint garnered from much practical experience:
Good woodworking practice generally precludes using mathematical formula's for this type of cut.
Just a couple of reasons are kerf waste and the fact that not all measuring devices are created equal, so not only trial and error is generally required for the first cut, but repeatability also becomes an issue.
The very best method is to make one initial 45 degree cut on the workpiece; then measure and mark your desired distance from that cut on the face in question, using your project measuring tape/ruler; then line up your saw blade to cut to that mark, first setting a stop block in the appropriate place on the fence for precise repeatability if required.
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TrailRat (in snipped-for-privacy@o13g2000cwo.googlegroups.com) said:
| Is there a website for all these woodworking formulas?
This is just an ordinary geometry/trig problem. I've put up a web page at http://www.iedu.com/DeSoto/CNC/trig.html that may help out.
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/solar.html
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wrote:

Hmmmmm.... Textbook, but a bit overboard [a woodworking term?] for your average woodsmith.
[You have an A in the tan(x/2) function you might want to correct.]
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Guess who (in snipped-for-privacy@4ax.com) said:
| On Tue, 10 Jan 2006 10:35:18 -0600, "Morris Dovey"
| || This is just an ordinary geometry/trig problem. I've put up a web || page at http://www.iedu.com/DeSoto/CNC/trig.html that may help out. | | Hmmmmm.... Textbook, but a bit overboard [a woodworking term?] for | your average woodsmith.
Yuppers. The page was (is) primarily intended for CNC types who didn't get it all down in high school (I was /so/ sure that I'd never have any use for this stuff.)
| [You have an A in the tan(x/2) function you might want to correct.]
Urk! You're absolutely right. Not only that, I just gave myself a C- for consistancy in variable naming.
Thanks! (I'll fix it)
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/solar.html
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The TrailRat entity posted thusly:

The 45 degree angle becomes the diagonal of a square whose sides are equal to the thickness or width of the board, depending on which way you make the cut. It's a special case of the general application of the Pythagoras Theorem. (the square of the hypotenuse is equal to the sum of the squares on the other two sides).
Example: a board 1" by 6"
Tilt your saw blade to 45 degrees, and make a right angle cut across the width of the board. The height of the cut is 1" (because the board is 1 inch thick). The length of the board on one face is 1" less than the length on the other face (because the 45 degree angle dictates that the 'top' of the square must match the side of the square)
or: With your saw blade vertical (90 degrees), angle the board to 45 degrees and make a cut across the width of the board. The length of the board on one edge will be 6 inches less than the length on the other edge.

We don' need no steenkin' formula for this one,!
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Look around in second hand book shops for a copy of the Mathematical tables from the Handbook of Chemistry. They're as common as dirt. With one of those and a $10 scientific calculator, you can calculate anything you want simply by reading the mensuration tables. Bugs
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Go here for what seems to be a major reference for just about any technical field. They have 21,000 + calculators on line. You could spend hours and hours browsing through this site. I found it by accident just a couple of days ago, and haven't been able to even begin to explore it all. Lots of good info, some of it woodworking related. Heck, there are several articles on the physics of baseball.
http://www.martindalecenter.com /
Regards, Roy
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Brilliant - thanks very much.
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Cool thanks for that, Neat little site.
TR
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... snip

Thanks for the post. That one's been bookmarked.
+--------------------------------------------------------------------------------+ If you're gonna be dumb, you better be tough +--------------------------------------------------------------------------------+
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