The trapezoidal thread calculator for metric trapezoidal thread dimensions of single and multiple start trapezoidal threaded rods and nuts for different pitch diameter tolerance classes.
ISO metric trapezoidal thread profile is a thread form with 30° angle of thread which is used for lead screws (power screws). Dimensions and tolerances for metric trapezoidal screw threads are defined in ISO 2901:1993, ISO 2902:1977, ISO 2903:1993 and ISO 2904:1977 standards. Gauges and gauging for ISO metric trapezoidal screw thread are defined in the DIN 103-9:1985 standard.
Note 1: See the "Results" section for preferred pitch value for selected nominal diameter.
Note 2: See the "Definitions" section for recommended tolerance classes.
Note 3: The tolerances for multiple start threads are same with single start threads except pitch tolerances. The tolerance values of Td2 and TD2 for single start are multiplied by following factors; Number of start - Factor : 2 - 1.12 , 3 - 1.25 , 4 - 1.4 , 5 - 1.6
Note 1: Preferred pitch value for selected nominal diameter of trapezoidal metric thread.
Note 2: If the length of engagement is larger than this range, length of engagement is classified as long. See the "Definitions" section for preferred pitch diameter tolerances according to length of engagement.
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
Metric Trapezoidal Thread Form
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 metric trapezoidal screw threads are specified in the DIN 103-9:1985 standard. It specifies the features of the types of gauges (thread plug and ring gauges, plain plug and ring gauges, wear check plug and ring gauges etc.) which are recommended for checking trapezoidal threaded rods and nuts.
Lead: The distance that nut advances in one revolution of the trapezoidal threaded rod.
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.
Recommended tolerance classes for Pitch Diameter: For general engineering use, select medium tolerance quality. For cases where manufacturing difficulties exist, coarse tolerance quality can be selected. If the actual length of thread engagement is unknown, use "Normal" length of engagement .
Tolerances for Major and Minor Diameter: The tolerance position for the minor diameter D, and the major diameter D4 of the nut threads is always H, i.e. with zero fundamental deviation. The tolerance position for the major diameter d and minor diameter d3 of the threaded rod is in all cases h, i.e. with zero fundamental deviation, and it is independent of the tolerance position of the pitch diameter.
Tolerances Grades: The following tolerance grades are specified for the features in the ISO standard.
The tolerance grade for the minor diameter (d3) of the threaded rod is always the same as for the pitch diameter (d2).