Thread Designation | Types and Applications | Tolerance Class chart

This is for Engineers and Machinist who are looking for reference to know about Bolt thread terms and standards.

The whole article contains details about JIS(Japanese Industrial Standard) Thread specifications, although these specifications are based on JIS still they can also apply to ISO and DIN Thread types.

You will learn about following things:

Exterior Features of Thread ridge - Basic designation(description) of threads explained here like definition of flank angle,height of thread,thread overlap,Threaded portion,Length of engagement etc.

Fig: Bolt specification and Thread terms explanation

Thread types and its applications (Symbol,Profile,Equation to calculate thread designation)  - This includes Metric screw thread

Thread Type	Standards
Metric screw thread	JIS B0205(coarse), JIS B0207(fine)
Unified screw thread	JIS B0206(coarse),JIS B0208(fine)
Parallel pipe thread	JIS B0202
Taper pipe thread	JIS B0203

Thread Tolerance -

Fig: Thread tolerance table for external and internal threads

The reason for defining tolerance in threads are:

To ensure compatibility

Limit the quality within a given range

Factors which effect quality of screw thread mainly due to following:

Material - Type,Heat treatment,Surface processing etc

Shape - Root radius,roundness etc.,

Detentions - major diameter,pitch diameter and minor diameter.

Definition of angle error and pitch error (pictorial examples)

ISO and JIS standards for Pipe threads-

Fig: Pipe thread standards,types and symbols

courtesy: maryland metrics (copyright protected)

You can these details in the following URL mdmetric.com.

This is an excellent site to bookmark for yourself, this would help engineers to have quick reference guide on Bolt types,standards,Tolerance table,Pipe thread standards and so on.