Reference guide
Sources and Methodology
How this site stores chart values, checks assumptions, and separates reference values from job-specific engineering decisions.
How chart values are handled
The site keeps drill, tap, clearance, and pilot-hole values in a central data model instead of scattering numbers through page copy. That makes corrections easier and reduces the risk that one page is updated while another page keeps an old value.
Reference hierarchy
For the static launch, values are treated as practical reference values cross-checked against commonly published drill and tap charts. Production work should still be verified against the drawing, a recognized standard, or the tooling supplier. Future updates should record exact source documents and revision dates beside each data family.
Why assumptions are shown
A tap drill answer changes when percent thread, material, hole depth, coating, cutting tap versus forming tap, and fit class change. The pages state those limits because a fast answer is useful only when the user knows where it stops being enough.