# CNC Reference Tables & Engineering Conversion Charts

> Engineering reference tables for CNC: hardness conversion, tap drills, Ra/Rz grades, IT grades, steel grade equivalents and torque charts, checked to ISO/ASME/ASTM/DIN.

https://www.sinbo-machining.com/wiki/reference/

---

# CNC Reference Tables & Conversion Charts
The numbers you reach for every day. Every table cross-checks at least two independent sources (usually ISO + ASTM + a national standard like GB or JIS). If a value disagrees across sources we say so, and explain which one to use when. How to use this section. These are look-up pages, not articles. Open one, find your row, take the number. Each page lists its source standard at the top so you can cite it in your own drawing, quote, or report. Hardness & Material Properties - [Steel Hardness Conversion Table HRC, HB, HV, HRB, HRA and tensile strength cross-checked against multiple standards, with the disagreements between sources marked ](https://www.sinbo-machining.com/wiki/reference/hardness-conversion/)
Threads & Fasteners - [Tap Drill Size Chart — Metric and UNC/UNF Tap drill sizes from M1.6 to M48 plus UNC and UNF, with the D−P formula for 75% thread engagement and how pitch class changes the answer ](https://www.sinbo-machining.com/wiki/reference/thread-tap-drill-sizes/)
Source hierarchy. When sources disagree, our order of preference is: ISO → ASTM/ASME → regional (DIN, JIS, GB) → manufacturer datasheet → textbook. We document every disagreement inline so you can decide for your application.