territorialmillworks Posted December 9, 2012 Share Posted December 9, 2012 Before posting I went online looking for help...wow, was I ever in over my head. Since this is a blacksmith project (fire pit cap) I'd see if someone on iforge could make it simple LOL I have a plasma cutter and access to a roller but don't know where to start drawing this up. Finished measurements are 36" diameter base, 18" rise and 10" diameter top hole. Thanks, Keith Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted December 10, 2012 Share Posted December 10, 2012 you are trying to hard, get a chunk of cardbaord ( like from an old box) get that where ya like it and you then have your pattern for the steel. much easier to use cold light weight and flexable cardboard, than steel :) Quote Link to comment Share on other sites More sharing options...
Stephen Olivo Posted December 10, 2012 Share Posted December 10, 2012 Hopefully this will help. He deals with laying out a frustum of a cone. Worth watching anyways :D http://www.youtube.com/watch?v=S9vt1qNaoGA&feature=plcp Quote Link to comment Share on other sites More sharing options...
swedefiddle Posted December 10, 2012 Share Posted December 10, 2012 Good Morning, Like Steve says use cardboard for the pattern. 36" diameter = pi x D = 113.10 inches. 10" diameter = pi x D = 31.42 inches. Add for the joint overlap. Make a mark for the center point, draw a verticle line 36" from center, swing an arc from center mark and the 36" mark, measure 56.55" on either side of the center line. That is your length of material for the 36" diameter. Using the same center mark and center line, but at 18" down from center, draw an arc from the center mark and the 18" mark, 15.71" long on either side of center. Draw a line from the end of the 36" arc to the end of the 18" arc. Divide both lines evenly by 20 or 30 with a compass or dividers. Draw lines corresponding to each division joining each radius. This give you your bend lines. Enjoy the math. :) Neil Quote Link to comment Share on other sites More sharing options...
pkrankow Posted December 10, 2012 Share Posted December 10, 2012 You can "cheat" on the math by googling cone calculator Phil Quote Link to comment Share on other sites More sharing options...
Glenn Posted December 10, 2012 Share Posted December 10, 2012 reference: http://www.red-bag.com/engintools/calccone.php I would make one out of paper first just to be sure everything fit before I started cutting metal. Quote Link to comment Share on other sites More sharing options...
doc Posted December 10, 2012 Share Posted December 10, 2012 http://books.google.com/books?id=0V01AAAAMAAJ&pg=PA5&dq=Essentials+of+sheet+metal+work+and+pattern+drafting&hl=en&sa=X&ei=wV7FUJjBBISy0AGDwICgCg&ved=0CDAQ6AEwAA Copy this link and paste in browser. About page 97 will answer your question Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted December 10, 2012 Share Posted December 10, 2012 All the old sheet metal books I have seen cover this job. Quote Link to comment Share on other sites More sharing options...
clinton Posted December 10, 2012 Share Posted December 10, 2012 Any sheet metal pattern can be laid out using triangulation. Like Swedefiddle says use your compass or dividers to mark your bend lines. The closer the bends the smoother your cone will be Quote Link to comment Share on other sites More sharing options...
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