I need to figure out the taper angle on a piece of wood. Can someone help me out?? The piece is 18 7/16" long. The top is 1 11/16" wide and the bottom is 2 3/16" wide. What angle would I need to cut that?
Thanks
Looks like 1.5534 degrees. Note that it's often easier to build a jig with the 1/2" offset than to accurately set your saw to 1.5536 degrees.
Are you sure you really need the actual angle? Most times a job on a long-'n-thin piece is done with reference to the dimensions you gave; not the angle. For one thing, there's far too much margin for error trying to set such an angle; any error is magnified dramatically over the length of the work piece.
Also, using a bevel gauge and transferring the angle with it yields good results, too, if you're trying to fit an adjoining piece.
- - LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
Doesn't anybody know how to do simple trig anymore?
Basically you have a 1/2" taper (2 3/16 - 1 11/16") over 18 7/16" long piece
inv cosine (.5/18.4375) =88.44 deg.
or 1.56 deg, depending on how you want to measure it.
I am bulding a Guitar Neck so I need that exact angle. I was going to cut it on my table saw.
snipped-for-privacy@yahoo.com wrote:
someone
I believe that would be arctan(0.5 / (18 7/16) ) But I am curious why you need to know the angle. You can cut it from the measurements you have.
Seriously for a piece like that, I would simply measure where I wanted it, mark it and cut by hand w/ the bandsaw (or a skill saw if didn't have the bandsaw) and then just bring to the line on the jointer...
Of course, if it's a repetitive operation, a sled for the TS w/ a 1/2" offset is worth the time...
I've never seen a table saw with a tilt scale worth a damn.
make a test cut, nudge the saw, repeat.
Unfortunately, no. (At least, not I.) For some things I was never smarter than the day I graduated HS/college/grad school.
Sounds like you would need 1/4" offset on each side to keep the grain straight with the neck, otherwise the grain will be parallel to one side.
"The angle of the piece"
Anything else is trying to calculate an angle from measurements, which are necessarily imprecise, doing icky decimal arithmetic, which is also imprecise.
Instead what you do is say, "Who CARES what the *expletive deleted* angle is? I'll just set my taper jig so that it matches the workpiece."
Or the sliding bevel or whatever measuring tool is right for the job.
VERY small errors magnify greatly over the length of your piece. Measure direct and save your hair.
[2 3/16 - 1 11/16] / [18 7/16]is the tangent of the angle. But do as thet say, and make a jig: Nail a crosscut runner strip to plywood and cut through the saw. Lay out the piece to be cut with markings along the new cut plywood edge. Tack more runner strips to hold it in place, and run through the saw. Ain't no way I'm trying ASCII art.
If you use a taper jig you don't need to figure out the angle. See:
IMHO, you can't get there from here by trying to adjust some cutting tool to an angle guide.
Suggest the following:
1) Lay out the angle with a straight edge and a pencil. 2) Trim away any waste in excess of about 1/4"-1/2". 3) Clamp on a straight edge and clean up with a router and a pattern or bottom bearing, trim bit.(I do it both ways)
HTH
Lew
Case in point, drilling a hole through a plane tote. I tried to use an absolute angle instead of just whatever in between angle the actual thing was supposed to be. I whined about the result on some other thread. Right through the side of a piece I had spent hours shaping.
Doesn't anybody know how to do simple trig anymore?
Apparently some one does the second post of this thread already figured out the angle.....
The trig isn't the problem.
It's setting a taper guide to the angle I get when I crunch the numbers.
If I were setting up a machine to make the part, I'd calculate it, though I'd probably adjust my dimensions so the angle came out a round number.
This is reproducing the angle on another part, so the actual number doesn't matter so much as "getting it right."
A diagram would certainly clarify, but depending on the interpretation of the "long" measurement given two calculations are provided.
For a trapezoid of height 18 7/16", the angle between the sloped sides is
(tan-1(0.25/18.4375))*2 ~= 1.5536886 degrees
For a trapezoid of side length is 18 7/16", the angle between the sloped sides is
(sin-1(0.25/18.4375))*2 ~= 1.5538314 degrees
If you wanted to get really fussy, you might have included the diagonal? You raise a good point, but I'm pretty sure he meant the perpendicular distance.
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