# MachinistCharts

> Free shop-floor reference for bolt tightening torque and tap drill sizes. Every value is calculated from published standards (ISO 898-1, SAE J429, ASME B1.1, ISO 724, ISO 273) and each page shows the working. Updated 2026-10-05.

Cite as: MachinistCharts, https://machinistcharts.com/ . Values are general starting points for steel fasteners in steel; when a manufacturer publishes a torque, theirs takes precedence.

## Charts
- [Bolt torque chart](https://machinistcharts.com/bolt-torque/): metric M4–M36 in class 8.8, 10.9, 12.9 and inch 1/4–1 in SAE grade 2, 5, 8, dry and lubricated
- [Tap drill chart](https://machinistcharts.com/tap-drill/): metric coarse and fine M1.6–M48, UNC and UNF #0–1 in, with thread percentage

## Page patterns
- Metric bolt torque: https://machinistcharts.com/bolt-torque/m10/  (m4, m5, m6, m8, m10, m12, m14, m16, m18, m20, m22, m24, m27, m30, m33, m36)
- Inch bolt torque: https://machinistcharts.com/bolt-torque/1-2-inch/  (1-4, 5-16, 3-8, 7-16, 1-2, 9-16, 5-8, 3-4, 7-8, 1)
- Metric tap drill: https://machinistcharts.com/tap-drill/m8/ (coarse), https://machinistcharts.com/tap-drill/m10x1-25/ (fine)
- Inch tap drill: https://machinistcharts.com/tap-drill/1-4-20/, https://machinistcharts.com/tap-drill/10-32/
- Every page has a Markdown version: append index.md, e.g. https://machinistcharts.com/bolt-torque/m10/index.md

## Data (CC BY 4.0)
- [Bolt torque CSV](https://machinistcharts.com/data/bolt-torque.csv) and [JSON](https://machinistcharts.com/data/bolt-torque.json): 108 rows
- [Tap drill CSV](https://machinistcharts.com/data/tap-drill.csv) and [JSON](https://machinistcharts.com/data/tap-drill.json): 80 rows
- [Everything in one file](https://machinistcharts.com/llms-full.txt)

## Calculators (accept URL parameters)
- [Bolt torque calculator](https://machinistcharts.com/calculators/bolt-torque/): ?sys=metric|inch&size=M12|1/2-13&grade=8.8|10.9|12.9|2|5|8&k=0.20&pct=75&unit=nm|ftlb|inlb
- [Thread percentage calculator](https://machinistcharts.com/calculators/thread-percentage/): ?unit=mm|in&d=8&p=1.25&drill=6.8&want=75 (p is pitch in mm, or TPI when unit=in)

## Method
- Torque: T = K x F x d. F (target clamp load) = 75 % of proof load. Proof load = proof stress x tensile stress area. Proof stress: ISO 898-1 (8.8: 580 MPa up to M16, 600 MPa above; 10.9: 830 MPa; 12.9: 970 MPa), SAE J429 (grade 2: 55 ksi to 3/4 in, 33 ksi above; grade 5: 85 ksi to 1 in; grade 8: 120 ksi). Stress area: metric As = pi/4 x (d - 0.9382 p)^2; inch As = 0.7854 x (D - 0.9743/n)^2. K = 0.20 dry, 0.15 lubricated.
- Tap drills: Cut-tap drill sizes. Thread percent = (D - drill) / (0.01299 x P), equivalent to 76.98 x (D - drill) / P for metric; for inch threads P = 1/TPI.

## Optional
- [About the data](https://machinistcharts.com/about/)
- [Disclaimer](https://machinistcharts.com/disclaimer/)