How many tools should you keep loaded for efficient batch runs?

It depends on part complexity, but 12-18 tools cover most drilling/tapping jobs without constant swaps. Keep duplicates of high-wear items like spot drills, roughers, and taps. A 21-pocket magazine gives breathing room for backup or specialty form tools. Organize by operation sequence to minimize arm travel. Use sister tools for roughing/finishing pairs. The TMC-800L's arm-type changer hits 1.8 seconds chip-to-chip, so even full magazines don't slow you much. Load common drills first, then taps last to reduce wait time on rigid cycles. Shops running lights-out often max out the magazine and use macro programs to skip empty pockets.