My meager math skills fall short of getting this calculation.
I'm pretty sure any old calculator can get this but knowing what to
feed it is whats missing.
I've figured a compound angle to join a 2x4 frame of 16" square. with
the 4 side verticle ... (on edge)
Now to keep the top side parallel to floor...
A quicky ascii art diagram:
Those two angles are not the same:
a= 78.69 and b„.28. You have to imaging the 45 degree mitre
not shown. But when the parts are layed together at a 90, the top
side leans inboard so it isn't parallel to an imagined floor.
These are 2x4 lumber, how can I figure the angle of cut for the
top 2in wide side, so that it ends up parallel to floor?
WWRD? = What would Roy do?
I like your thinking, Art. I often ask myself how my grandfather, a
Danish-immigrant blacksmith, would have done solved a problem. HE never
took trig, that's for sure. And he was the hardware supplier for the area,
for the most part.
Exactly! I was born with a head for math (no fault of mine <g>) and have
successfully vanquished many an equation with enough Greek symbols to start
a library. But in woodworking my bevel gauge is my constant friend. Who
cares how Einstein would have done it? Set the bevel, draw the line, cut
it, and finish it. ;-)
You can safely assume that if we know how to solve the problem adequately
in several acceptable ways that we can only screw up with extreme effort,
that anything 'more elegant' is 'left as an exercise for the students'.
Heck. I have a degree in Economics. One of the classic phrases of that
art is, uttered while waving the left hand in the air, "It can be shown
that....", and proceeding as though truth had been established, without
ever, in fact, proving, or sometimes, even supporting, the contention.
You got at least one good answer. It's worked for years. You want more,
get a hold of a good book on classic Chinese joinery.
I see people are havuing a high old time with my question.
Let me explain a bit:
I've spent 35 yrs as field construction Boilermaker and pipe
fitter/welder. Now retired. I've had plenty of experience with the
`hold it in place and scribe' technique and am well aware of its
uses and benefits.
Now I'm old and partially crippled. I tinker almost exclusively by
myself. I wanted to just set the saw to an angle and start cutting.
No drama, no fuss. I'm pretty sure this angle of cut can be
established before hand with a light weight calculation of some kind.
I'd hoped someone here would know it.
Egad I was making this way to complicated.
Its a no brainer almost if you look at drawing of my frame.
Its just the other end of the known angle.
The Angle I was after is whats left after subtracting the known angle
78.68 dg of slope and the top needs to be cut at 11.32dg to remain
flat when assembled.
Nothing wrong with that. I've had a degree in math/physics for more
years than I can count. What turns my crank is that you can draw an
ellipse with two circles and a straightedge; the art of descriptive
geometry [layout ...the sort of thing being discussed here, but more,
like the tinsmith forming and joining round tin tubes at an angle].
And who doesn't know about "The Carpenter's Square", a book that shows
you how to layout and build spiral staircases?
Has anyone seen that 'simple' table from IKEA? Don't laugh until
you've designed one yourself. It's a rectangular top. Turn the top
90 degrees and fold it open to double the size. Two questions: 1.
Where do you put the pivot point? 2. what ratio of sides so that the
open table has the same shape (but larger) as the original? I can
figure that out easily, I can then tell you easily, and you can do it
easily (likely much better than I could), and don't forget why ...the
math that is needed to figure it out in the first place. But I would
(and do) come here for the experts who can tell me what type of
material goes with which, and which kind of pivot support is best, and
a whole mess of other useful information. I don't knock that. I
absorb it and someday use it.
I like nothing better than applied math. However, don't forget that
is what it is, "applied". So don't knock it completely. As human
beings we are not satisfied with just a little. We want all the
bananas. My background is blue-collar steelworks. It pays to have
both feet on the ground *and* to know the reasons why. Always keep
an open mind.
You have tables of compound angles available, just handed to you. So
use them. There's nothing wrong with that either, and you don't need a
helper with the shakes. You just need to know how to read. My father
was also a highly skilled tradesman, and I listened to him too. It's
called "tricks of the trade", and we learn something every day.
I offered to post one here a while back I did myself as an Excel
spreadsheet, or just the printout if you wanted, but that's frowned
upon. I'll look for some other way. A PDF is fairly tiny but
someone would bitch even then.
Please be aware that many news servers automatically strip any and all
attachments to anything that was posted in a non-binary group. So even if
nobody objected to your posting binaries here, it wouldn't work anyway. It
has nothing to do with the size of the file, and everything to do with the
fact that there are binaries groups for binary posts, and non-binary groups
for text-only posts.
Besides which, there already is a binaries group set up *specifically* for
posting woodworking-related binaries: alt.binaries.pictures.woodworking, or
ABPW for short. The accepted procedure is to post your picture, spreadsheet,
pdf, or whatever to ABPW, and post a note here alerting people to the post in
Doug Miller (alphageek-at-milmac-dot-com)
For a copy of my TrollFilter for NewsProxy/Nfilter,
send email to autoresponder at filterinfo-at-milmac-dot-com
Go to alt.binaries.pictures.woodworking and post away!
That's what it is there for ... binaries don't just limit you to pictures.
Keep in mind that many folks will be skittish about downloading a document,
other than a .pdf, that could contain a virus of some sort.
Look for compangle2.pdf. I didn't double check, and rounded to
nearest 1/4 degree (fair enough?) I hope this is helpful. If you
find anything wrong, write here ...in a new thread titled "Dan doesn't
have a clue"... or something like that.
He can always try: http://www.betterwoodworking.com/compound_miter.htm
Those are 2. There are many more.
"Property is not the sacred right. When a rich man becomes poor it is a
misfortune, it is not a moral evil. When a poor man becomes destitute, it is a
moral evil, teeming with consequences and injurious to society and morality."
Heh, me too. It really prepared me for the world of application
integration and a woodworking hobby :) I have to stop myself from
thinking about the wood commodity market while picking out boards...
Your comment reminds me of an old economist joke:
An economist, an engineer, and a physicist go out camping together.
The day gets long and they start getting hungry, so they get out thier
stash of canned food and realize that they forgot a can opener. They
all think about it for a minute.
The physicist says "I know! we can put the can in the fire. Eventually
heat will build pressure and the can will not be able to hold the
The engineer replies "Yes, but then we'll be covered with cream corn.
How about we bend that sapling over there to create a tensioned lever.
We stap a pointy rock on the end of it and brace the can on a rock on
the ground. Accounting for wind changes and the angularity of the can
to the ground, we precisely release the tension in the sapling causing
the rock to accurately remove the top from the can.
The economist says, "Sounds way to complicated to me. There's got to
be a better solution. (long pause) Okay! I got it....
"Assume you have a can opener..."
Let the booing begin! I'll also be waiting for the "Neander, Normite,
and rough carpenter" version of the tale.
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