ISO 16239 pdf download Metric series wires for measuring screw threads
hislnternationa Standard specifiesthe material,metric series nominal diameters. diametertolerancesand designation for screw thread measuring wires.
This International Standard is applicable to the measurement of the pitch diameters of ISO generaourpose metric screw threads (M), Unified screw threads (UN), Whitworth pipe threads (G, R), andSO metric trapezoidal screw threads (Tr) with standard pitches. These wires are intended for use onscrew threads with a small lead angle, less than 5% and are mainly used to calibrate the pitch diametersofthread plug gauges.
2 Normative references
The following documents,in whole or in part, are normatively referenced in this document and areindispensable for its application. For dated references, only the edition cited applies. For undatedreferences, the latest edition of the referenced document (including any amendments) applies.
SO 1, Geometrical Product Specifications (GPS)– Standard reference temperature for geometrical productspecification and verification
ISO 5408, Screw threads – Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 5408 and the following apply.
wire that would touch an imaginary thread of zero lead angle at the pitch cylinder
Note 1 to entry: For symmetric threads, the diameter of a best-size wire is equal to P/(2 cos a/2), where Pis thepitch and a/2 is the flank angle.
4 Reference temperature
in accordance with ISO 1, the dimension of the wire shall be related to the standard referencetemperature of 20C.
Material, hardness, and surface finishThe wires shall be made from alloy tool steel that has been stabilized to ensure dimensional stability.The wires shall be free from cracks and other detrimental defects.The hardness shall be (760 50) HV5 over the measuring surface.The roughness shall not exceed 0,4 um Rz over the measuring surface.
6 Nominal diameters of best-size wires
6.1 Wires for ISO general purpose metric screw threads (M)
The nominal diameters of best-size wires and the allocation of pitches are given in Table 1.