Can Sketchup give me the right angle?

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I am building lamp shades for craftsman styled lamps. I use 1/4 by 1/2 inch material lap-jointed to form the four panels, which are trapezoidal in shape. I have attached a simple shade shape and I know the angle of the slope to be about 39 degrees. I also know that to assemble the panels, I have to set my table saw to cut a miter at 24.5 degrees. When I use the protractor in Sketch up to find the slope, no problem 38.4 degrees. How do I use Sketch up to find the necessary miter angle between the panels?
 

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  • shade-angles.skp
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Frank, you can get fairly close. I used one side of the shade, gave it some thickness and rotated it around to get edges aligned as I wanted. Based on what you drew, with the base against the miter fence, you could set the miter gauge to about 38.401° and tilt the blade to about 64.461° to cut the miters between the pieces.
 
Dave:
Thanks for the quick reply. Your calculations agree with the real world cuts that I have to do to make this frame; however when I draw this shade and give it a little thickness, one inch as in my attachment, the angle I keep measuring with the protractor is 31.4 degrees, yet I know the real angle is 24.5 degrees. I do just not understand how to use the protractor to see or get the real angle of 24.5.
 

Attachments

  • 1_inch_thick_shade.skp
    12.5 KB · Views: 9
Dave:
Your drawing was just what I needed. It put the piece in the proper perspective, lying on the top of my table saw with the miter gauge set at 38.4 degrees. I think my mistake was trying to measure the angle from within the drawing; I didn’t have the proper perspective. Keep up the good work; I follow your instruction from three different forums.
 
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