I have been on a number of forums, including machining forums, three different casting forums, miscellaneous general hobby forums, etc., and it can be tricky to find people who are closely aligned with your interests.
Some forums have terrible software, some have ok software, but still clunky and outdated, and some forums have a very severe limit on how many pictures you can upload at the same time.
This forum has good software, easy to use, easy to load 20 or more photos per post, and some really interesting topics/people.
This forum is by far has been the best model engine forum for me, and also a pretty good casting/foundry forum too.
Great folks here with an incredible amount of skill and knowledge.
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