Gumball Machine Gum ball Machine Free Project PlansBuild your own gumball machine using a jar with a 2 3/4 inch diameter mouth. Children will love to get this as a gift. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Published by Jim Creator of FreeWoodworkingPlan.com, online since 1998. View all posts by Jim