CRAZYFROG 302 #1 Posted August 10, 2022 I finally now have the rare tombstone 6 4 Share this post Link to post Share on other sites
Handy Don 12,174 #2 Posted August 10, 2022 Congrats! Make a mold from it, and start casting replicas! 3 1 Share this post Link to post Share on other sites
ri702bill 8,296 #3 Posted August 10, 2022 2 hours ago, Handy Don said: Congrats! Make a mold from it, and start casting replicas! But not in fiberglass!!! 1 Share this post Link to post Share on other sites
Pullstart 62,812 #4 Posted August 10, 2022 2 hours ago, Handy Don said: Congrats! Make a mold from it, and start casting replicas! I learned that replicas from existing castings are generally a bit smaller from the casting cooling. Makes sense! 3 Share this post Link to post Share on other sites
Handy Don 12,174 #5 Posted August 10, 2022 2 hours ago, Pullstart said: I learned that replicas from existing castings are generally a bit smaller from the casting cooling. Makes sense! It does, kinda sorta. I bet @ri702bill knows how much cast iron shrinks from pour (liquid) to cool (solid)? I'll bet there is some way to enlarge a mold made from the original product but if the difference isn't great maybe it doesn't matter? I wonder if there is a way to have a CNC-like machine make the sand cast, that way the programming can make sure the mold is correctly sized? Share this post Link to post Share on other sites
wallfish 16,988 #6 Posted August 10, 2022 Brrly did some repops of the tombstone a while back. Had them done in cast steel and some done in aluminum. Share this post Link to post Share on other sites
lynnmor 7,302 #7 Posted August 10, 2022 Cast iron will shrink about 1/8" per foot,. If you use the original for a pattern, add about 1/16" to the top, bottom and side surfaces. If you want to spend some serious money, have the weight scanned and then add 1.04%. With the resulting file, cut a solid block of wood on a CNC mill. Another option is to do some fancy wood carving. 1 Share this post Link to post Share on other sites
Pullstart 62,812 #8 Posted August 11, 2022 Another option… is to make a hanging weight… 1 Share this post Link to post Share on other sites
ri702bill 8,296 #9 Posted August 11, 2022 (edited) 14 hours ago, lynnmor said: Cast iron will shrink about 1/8" per foot,. If you use the original for a pattern, add about 1/16" to the top, bottom and side surfaces. If you want to spend some serious money, have the weight scanned and then add 1.04%. With the resulting file, cut a solid block of wood on a CNC mill. Another option is to do some fancy wood carving. It is my understanding that the parts from all molding processes shrink a bit, and that bits is dependent on both temperature and material. Last job we had a lot of injection molded parts - had to specify the max amount of regrind allowed to be added to the virgin material prior to shooting the parts. Too much changes the shrink rate!! Similar problem with the colorant added to nylon. Natural uncolored nylon has a rather unappealing color similar to candle wax. Plastics are colored black by adding carbon - too much and the parts become electricly conductive. This happened to us on a switch housing - molder changed to a formuation with less carbon - surprize! shrink rate changed too!! Scanning - I worked at Brown & Sharpe for a while calibrating new CMM's (Coordinate Measuring Machines), They offered a contract service to customers to scan and digitize their complex shaped parts - like the nondescript conical volcano shape of a washing machine aggitator. Once digitized, that info can be used to genereate a file for CNC machining an exact copy, or as @Handy Don mentioned, a percentage offset could be used to "grow" the part in all directions, say 1.04% ... Edited August 11, 2022 by ri702bill 1 Share this post Link to post Share on other sites
