In 1997 I fabricated a cone mandrel that is still in use. At the time I hadn't come across a real cone mandrel yet but latter found two good ones. I did have two small cone mandrels. One was long and skinny and the other squat and wide. Both seemed awkward to use in the anvil hardy holes. I wanted a better base, taller and stable and something I could cobble together in a week.
I drew up some plans and took them to a fabrication shop which cut and bumped the halves of the frustrum on their break. I MIG welded them and placed and welded a centered square tube which fitted the mandrel tangs. A circular 4.5" end plate was welded with the center square cut out. This made a watertight hollow form which, when turned upside down, could be filled with concrete. A piece of rebar was place in the central opening and driven into the ground to hold the vertical position. I used Sakrete High Strength Concrete Mix and don't recall the exact amount but I think it just a bit more than one 80 pound bag. The entire volume was concrete filled. The finished base was left in place outdoors for about a week while the concrete set and dried.
The project was finished by welding a circular base plate which aids the smoothness and rapidity of travel when the cone is tipped and rolled into position. I painted it black and put it to work.
This has been one of the most satisfactory tools I have constructed. It has served its' primary purpose as a base for the mini mandrels and the base was used to form larger radius elements until the real cone mandrels were acquired. It cost less than $100 and was quite simple to make. It might not hold up to heavy use especially if it was used for cold work.
This experience led directly to making concrete filled bases for other shop equipment. I'll describe some of those applications in the next post.