Hello all,
I’m formulating plans for a fairly simple toy box for my son. I want to use this project howere to hone my hand tool skills and learn some new things as well.
My question is how to calculate the angle cuts for the sides of the box. They will be compound angles as the box is rectangular (I guess that part doesn’t matter) but the the base will be smaller than the top. For example say the bottom is 16″x26″ and the top is 20″x30″.
To add to that I want to dovetail all four sides. Perhaps I’m overthinking this but just wanted to ask in case I could avoid a lot of smoke coming from my ears and possibly some wasted wood.
Replies
Are you familiar with trigonometry? If so, draw a diagram, one or more, of your project. Use trig to solve for the unknowns in the appropriate triangles until you have your answer. If you are not familiar with trig, find a good friend who is. In my experience, this is not an easy problem to figure out for the first time. I am pretty good at trig and geometry, and yet I have struggled with compound angles. There are probably some seasoned pros out their who have simpler processes that will work well. A search in FWW.com might turn up something also.
If you haven't cut dovetails before, I would recommend you practice on a rectangular box first.
Good luck, Tom.
Thanks Tom,
I actually used to be very good at geometry and trig but I fear I'm a little rusty but I my be able to muscle through it. I guess the problem is a can only visualize one of the triangles but not the other. Perhaps with dovetails I only need the one angle and not the other. I guess I'm speaking of the angled cut in reference to the cross-section of the board not the angle across the face of the board.
I thought maybe someone would have a basic woodworkers formula.
gcg,
In FWW Oct. 2002 #158 they illustrate a solution for what your trying to do.."Compound Angles Without the Math". Basically, Steve Brown shows how he makes a template of the angles with chunk of wood and then uses the template to set up the tilted TS blade and miter guage to replicate those angles on his stock...for either butt joins or dovetails on all four sides.
An excel spreadsheet compound angle calculator:
http://www.popularwoodworking.com/new/calc.xls
gcg,
If you can't find your copy of the Oct. 2002 FWW article BG mentioned in 33894.4, it's also on line as a pdf at
http://tinyurl.com/yr2864
(which is really http://www.taunton.com/finewoodworking/SkillsAndTechniques/
SkillsAndTechniquesPDF.aspx?id=2807)
Dan
Since you know the angle the sides will slope which is 4" from the bottom of the box to the top. Draw this line on the ends of all the pieces.
Then take your adjustable bevel and set it to the line you just scribed. You now rip the top and bottom edges of the box sides to this angle.
Lastly make a sled for the table saw and line up the scribe cut with the blade, this is the miter angle. Now set a square so that it is resting on the beveled edge you ripped on the top or bottom edge. Now tilt the saw blade so that it lines up with the leaning square. This is the bevel angle.
It is hard to describe but simple and makes sense when using this method. Plus no math. Or you could do the math just to have it as a back up. I like empirical measurements myself. Just easier to understand.
If you need some clarification just let me know.
Good luck.
J.P.
PS. You can do the same thing with a circular saw if you don't have a table saw.
Before you go running off to the math store, you are not dealing with compound angles because you have chosen to dovetail the corners. Compound angles are only applicable if you were going to miter the corners.
The base of each side is a standard bevel rip, and the sides of each side is a standard miter cut. Solving these angles can be done in 2-dimensions, whereas compound miters require 3-dimensional trig to solve.
I've attached a rough sketch of the box with a 12" height (there are two pages). The angle is 80.5 degrees.
Tim
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