Step 3 of 5
50%
Inspection cadence: what to look for at 1K, 10K, 50K, and 100K hits
A hit-count inspection checklist that tells you what is normal at each milestone of a forge die's life and what is the early warning the operator must not miss.
Step 3 of 550K hits, the decision inspection
At 50K hits a typical H13 forge die has done most of its expected life. The wear is established, the heat-check pattern is mature, and the inspector is making the pull-or-run decision rather than the keep-watching decision. The inspection at 50K is where the next 10-30K hits of die life gets budgeted, and where the recoat or re-nitride decision in Lesson 10 lands.
Normal at 50K. An established heat-check network on the highest-temperature regions of the impression, fine, dense, and uniform under magnification, with no individual crack standing out of the network. Measurable flash-land wear, on the order of 0.03-0.08 mm of dimensional drift from baseline depending on stock and lube. Slight rounding of internal radii, on the order of 0.05-0.10 mm in well-radiused features and more in tighter ones. Surface roughness on the working faces visibly increased from build but not gouged. Lube pattern still even across the engineered spray map.
Red flag at 50K. Cracks propagating beyond the heat-check network, defined as a single crack 2 mm or longer that is deeper than the network around it, or a directional crack pattern (parallel lines, not random network) that follows the mechanical-stress map of the die rather than the temperature map. Either pattern is structural crack growth into the diffusion zone. Adhesive pickup that was not there at 10K means the surface treatment has worn through and the bare H13 is now galling against hot stock. Dimensional drift greater than 0.05 mm on a critical feature, or any drift that puts the part outside the production tolerance band, means the die is hitting its end of useful life regardless of what the heat-check network looks like.
The 50K inspection is also where the pull-now-or-run-more economic call happens. A die showing all-normal at 50K with no propagating cracks can usually be planned through to 75-100K with inspection cadence tightening to every 5K. A die showing any red flag at 50K is a candidate for pull and decision (recoat, re-nitride, weld repair, scrap) per Lesson 10. The economic math is in Lesson 11.
Quick check
A die at 50K hits has a fine heat-check network on the flash land, no cracks coming out of corners, flash-land drift of 0.04 mm, and a single dull-grey area 6 mm across on the impression floor that was not there at 10K. The grey area is not a crack and not pickup. What is it and what do you do?