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Help with a shape

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I am trying to make a shape and I need some help.  I want to make a trapezoid, but with the sides curved in.  Yesterday I cut four sides to make the trapezoid.  They were four inches on the bottom and two inches at the top.   Then I placed them in the forge to get them to temperature.  Once they were hot, I hammered them into my swage block.  After they were cool, I tried to fit them up and nothing fit.  Does the original shape need to be more like an hourglass instead of a true trapezoid side?

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We need more information and drawings.

What is the starting material and dimensions? Solid or hollow? How long? etc. What does the ending shape look like? How much curve and on what sides?

Edited by Glenn
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As I understand your description, ... you're trying to create a "truncated pyramid" shape, ... with 4 concave sides.

I suspect the problem stems from 2 possible issues.

First, ... the concave curve of the 4 sides, needs to inscribe a "decreasing radius" as it transitions from the wide end, to the narrow end of the trapezoid.

The tapering Horn of a London Pattern Anvil would be much better suited for this, than the "constant" radius, of a Swage Block.

Second, ... due to the decreasing radius, ... the angled "sides" of the trapezoid will need to start out with a slight radius, ... in order to compensate for the decreased cross-section, brought about by the concave curvature.


A piece of paper, cut to the desired shape, would be useful in "visualizing" how that all works in 3-dimensional space.

Obviously, ... the trusty AutoCAD makes it easy to just "draw" the shape, and then let the "dimension" function, to tell you the lengths, angles and radii.


I do this ALL THE TIME, ... and am always gratified by the ease of assembly, ... of complex 3-dimensional shapes,  ... facilitated by the accuracy this process engenders.


Hope I correctly understood your project, ... and Good Luck.






Edited by SmoothBore
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