zztool About ISO Metric Threads
ISO metric threads are standardized by ISO 261/262, using metric units with a 60° thread angle. They come in coarse (standard pitch) and fine (smaller pitch) variants. Coarse threads are for general use, while fine threads provide higher precision and strength for demanding applications.
Terminology
The outer diameter of the thread, measured at the crest
The axial distance between adjacent thread crests
The diameter at the thread root, used for strength calculations
The hole size to drill before tapping, approximately d - P
FAQ
What is the difference between coarse and fine threads?
Coarse threads have larger pitch, are easier to manufacture, and suit general purposes. Fine threads have smaller pitch, better self-locking, and suit precision machinery and vibration-prone applications.
How to choose tap drill size?
Tap drill diameter is approximately nominal diameter minus pitch (d - P). Select the closest standard drill size available.
What is the difference between M8 and M8×1?
M8 indicates coarse thread (standard pitch 1.25mm), M8×1 indicates fine thread (pitch 1mm). Coarse threads typically omit the pitch designation.
What standards does this data follow?
This chart follows ISO 261 (basic dimensions) and ISO 262 (preferred sizes) international standards.
Essential for mechanics!
Accurate thread specs.
Great reference tool.