About ThreadChart
Your free, comprehensive thread and fastener reference
What is ThreadChart?
ThreadChart is a comprehensive, free online reference database for thread and fastener specifications. We provide instant access to detailed technical data for the most commonly used thread standards including ISO metric, UNC, UNF, NPT, and BSP.
Whether you're designing machine parts, selecting fasteners, or need quick reference data for your project, ThreadChart gives you accurate specifications at your fingertips — no PDF downloads, no paywalls, no hassle.
Who is ThreadChart for?
ThreadChart serves a wide range of technical professionals and enthusiasts:
- Mechanical Engineers — Quick reference during design work and calculations
- Machinists & CNC Operators — Drill and tap size specifications for thread production
- Manufacturing Engineers — Fastener selection and specification verification
- Students & Educators — Learning tool for manufacturing and mechanical engineering courses
- Makers & Hobbyists — DIY projects requiring proper thread specifications
- Maintenance Technicians — Thread identification and replacement part selection
What Data Do We Provide?
ThreadChart covers 157 thread specifications across 9 international standards:
ISO Metric Threads
M1 to M100, coarse and fine pitch variants per ISO 68-1
Unified Threads (UNC/UNF)
#0 to 4", coarse and fine pitch per ASME B1.1
Pipe Threads (NPT/BSP)
1/16" to 6" per ASME B1.20.1 and ISO 228/ISO 7
For each thread, we provide:
- Major diameter (nominal diameter)
- Pitch (thread spacing)
- Pitch diameter
- Minor diameter (external and internal)
- Recommended tap drill size (75% thread engagement)
- Tensile stress area
- Thread height
How is Data Generated?
All thread dimensions in ThreadChart are calculated algorithmically using official formulas from international standards. We don't manually enter data or scrape from other sources — everything is generated from first principles.
Our calculation engine implements formulas from:
- ISO 68-1 — ISO general purpose screw threads — Basic profile
- ASME B1.1 — Unified Inch Screw Threads
- ASME B1.20.1 — Pipe Threads, General Purpose (NPT)
- ISO 228/ISO 7 — British Standard Pipe (BSP) threads
This approach ensures consistency, accuracy, and zero maintenance — the data doesn't need annual updates because the formulas don't change.
Why is ThreadChart Free?
Thread specifications are based on publicly available international standards. We believe this fundamental engineering data should be freely accessible to everyone — students, professionals, and hobbyists alike.
ThreadChart is supported by non-intrusive advertising. We keep ads minimal to maintain a clean, fast user experience. No registration, no subscriptions, no paywalls.
Additional Tools
Beyond the main thread database, we provide useful reference tools:
- Drill & Tap Chart — Quick reference for tap drill sizes and thread percentages
- Torque Specifications — Recommended tightening torques by thread size and grade
- Bolt Grade Reference — Strength classifications for metric and imperial fasteners
- Thread Conversion — Cross-reference between metric and imperial equivalents
Important Disclaimer
While ThreadChart strives for accuracy, this data is for reference purposes only. For critical applications, always verify specifications against official standards documentation. ThreadChart is not liable for any consequences resulting from the use of this data. See our Terms of Service for full details.
Get in Touch
Have questions, feedback, or found an issue? We'd love to hear from you! Visit our Contact page to get in touch.