The Hyperboloid Burr is a seven-piece burr puzzle made from identical hyperboloid pieces.
A six-piece version was designed by Oskar van Deventer with the help of Naoaki Takashima. A wooden version was made as a limited (sold-out) edition for Naoaki Takashima by the Kanagawa Toy Company in Odawara. While working on the wooden pieces, the manager of Kanagawa Toy found an unexpected 7-piece solution. With Oskar's permission, Two Brass Monkeys has recreated the puzzle in brass.
What was learned along the way:
Brass is heavier than wood Brass has lower friction than wood Brass does not flex nearly so much as wood.
All this means is that the puzzles pieces have been machined to very accurate tolerances. This seven piece assembly is completed with a satisfying "click" and holds together well - it's a fidget toy in it's own right.
It turned out the tolerances for this puzzle were absolutely critical. A mere 0.03mm tighter or looser and the seven piece version of the puzzle either does not assemble or falls apart!
The pictures contain no spoilers; the assembly of the seven piece Hyperboloid burr is not shown and the puzzle ships disassembled.