Artificial bulk “zero-angle” boundaries parallel to thecaxis have been engineered between large melt-processedYBa2Cu3O7−&dgr;(YBCO) grains and observed to carry a transport supercurrent at fields up to at least 5 T at 77 K. The temperature and angular dependencies of the boundary resistance have exactly the same form as those of the grains, which is evidence that the grains are intimately coupled. The limiting mechanism for current transfer across these boundaries is, therefore, not a simple weak link or Josephson effect. This joining technique is extremely promising for production of macroscopic engineering artifacts. ©1998 American Institute of Physics.