# METRIC THREAD DIMENSIONS CALCULATOR

Metric thread calculator to calculate external and internal metric thread dimensions including major diameter, minor diameter, pitch diameter and thread tolerance according to ISO 724 and ISO 965 standards.

There are two calculation options available, general engineering use or custom use.

In general engineering use, calculations can be done by selecting a standard metric thread size in a range from 1.6 mm (M1.6) to 64 mm (M64). Tolerance class can be selected among the alternatives 6e, 6f, 6g and 4h for bolts and 5H, 6H, 7H and 6G for nuts. 6g and 6H are default values and selected class for commercial external threads and internal threads in ISO 965-1:1998. The user shall use 6g for bolts and 6H for nuts unless there is a specific requirement to use other tolerance classes.

In custom use, thread size, pitch and tolerance classes can be independently selected for custom metric thread dimensions calculations.

Some important notes from ISO metric thread standards:

- External Screw Thread Designation: Nominal Diameter x Pitch - Tolerance class for pitch diameter - Tolerance class for major diameter (M10 x 1 5g 6g)

- Internal Screw Thread Designation: – Nominal Diameter x Pitch - Tolerance class for pitch diameter - Tolerance class for minor diameter (M10 x 1 5H 6H)

- If the two class designations for the pitch diameter and crest diameter are the same it is not necessary to repeat the symbols. (M10 x 1 6g)

- According to ISO 1 , standard reference temperature for geometrical product specification is 20  °C.

- Gauges and gauging for ISO general purpose metric threads are defined in the ISO 1502 standard.

- The list of metric screw thread used in general engineering applications are given in the General Purpose Metric Screw Threads Table.

### Metric Thread Calculator:

 INPUT PARAMETERS Calculation Type General Engineering Use Custom Use GENERAL ENGINEERING USE Metric Thread M1.6 x 0.35 M2 x 0.4 M2.5 x 0.45 M3 x 0.5 M4 x 0.7 M5 x 0.8 M6 x 1 M8 x 1 M8 x 1.25 M10 x 1 M10 x 1.25 M10 x 1.5 M12 x 1.25 M12 x 1.5 M12 x 1.75 M16 x 1.5 M16 x 2 M20 x 1.5 M20 x 2 M20 x 2.5 M24 x 2 M24 x 3 M30 x 2 M30 x 3.5 M36 x 3 M36 x 4 M42 x 3 M42 x 4.5 M48 x 3 M48 x 5 M56 x 4 M56 x 5.5 M64 x 4 M64 x 6 External Thread (Bolt) Tolerance Class * 6e 6f 6g 4h Internal Thread (Nut) Tolerance Class** 6G 5H 6H 7H CUSTOM USE Nominal Diameter Pitch 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.6 0.7 0.75 0.8 1 1.25 1.5 1.75 2 2.5 3 3.5 4 4.5 5 5.5 6 8 Bolt Tolerance Class Tolerance Grades Deviations Pitch Diameter Tolerance 3 4 5 6 7 8 9 e f g h Major Diameter Tolerance 4 6 8 e f g h Nut Tolerance Class Tolerance Grades Deviations Pitch Diameter Tolerance 4 5 6 7 8 G H Minor Diameter Tolerance 4 5 6 7 8 G H

Note : * 6g is normally selected for commercial external (bolt) threads. Use this tolerance class for commercial external (bolt) threads. For usage of the other classes, refer to ISO 965-1:1998.

Note : ** 6H is normally selected for commercial internal (nut) threads. Use this tolerance class for commercial internal threads. For usage of the other classes, refer to ISO 965-1:1998.

 RESULTS Parameter Value Note --- Designation -- --- --- Tolerance Class for Bolt -- --- Tolerance Class for Nut -- --- Screw Thread Series -- --- Pitch P --- mm LIMITS OF SIZES FOR EXTERNAL THREADS (BOLTS) Maximum Major Diameter dmax --- mm Minimum Major Diameter dmin --- Maximum Pitch Diameter d2max --- Minimum Pitch Diameter d2min --- Maximum Rounded Root  Minor Diameter d3max --- Minimum Rounded Root  Minor Diameter d3min --- Minimum Root Radii Rmin --- Minimum Truncation Cmin --- Maximum Truncation Cmax --- LIMITS OF SIZES FOR INTERNAL THREADS (NUTS) Minimum Major Diameter Dmin --- mm Maximum Pitch Diameter D2max --- Minimum Pitch Diameter D2min --- Maximum Minor Diameter D1max --- Minimum Minor Diameter D1min --- BASIC DIMENSIONS Basic Major Diameter d , D --- mm Basic Pitch Diameter d2 , D2 --- Basic Minor Diameter d1, D1 --- Fundamental Triangle Height H ---

Note-1: For coated threads, the tolerances apply to the parts before coating, unless otherwise stated. After coating, the actual thread profile shall not at any point transgress the maximum material limits for positions h or H. For external (bolt) threads; The actual root contours shall not at any point transgress the basic profile. Fasteners of property class 8.8 and higher (see ISO 898-1), the root profile shall have a non-reversing curvature, no portion of which shall have a radius of less than Rmin.

### Definitions:

Basic profile: The theoretical profile of a screw thread in an axial plane defined by theoretical dimensions and angles common to internal and external threads

Crest: The surface at the top of the ridge connecting its two flanks.

Gauges and Gauging: Details for the manufacture and use of gauges for checking ISO general-purpose metric screw threads are specified in the ISO 1502:1996 standard. It specifies the features of the types of gauges (Solid/adjustable GO screw ring gauges, check plugs, setting plugs, wear check plugs, screw caliper gauges, plug gauges, etc.) which are recommended for checking external and internal screw threads of workplaces and for the setting and checking of certain of the screw gauges.

Major Diameter: The maximum diameter of a thread which is diameter of the crest of a male thread or root of a female thread.

Minor Diameter: The minimum diameter of a thread which is diameter of the root of a male thread or crest of a female thread.

Root: The surface at the bottom of the groove connecting the adjacent flanks