Title: Traceability of thread measurements : Expert report DKD-E 4-1
Authors: Krause, Marlen, Physikalisch-Technische Bundesanstalt (PTB), Fachbereich 5.3, Koordinatenmesstechnik
Wedmann, Achim, Physikalisch-Technische Bundesanstalt (PTB), Fachbereich 5.3, Koordinatenmesstechnik
Stein, Martin, Physikalisch-Technische Bundesanstalt (PTB), Präsidialer Stab (PSt)
Contributors: HostingInstitution: Physikalisch-Technische Bundesanstalt (PTB), ISNI: 0000 0001 2186 1887
Resource Type: Text / Technical Requirement
Publisher: Physikalisch-Technische Bundesanstalt (PTB)
Rights: https://creativecommons.org/licenses/by-nc-nd/3.0/de/
CC by-nc-nd 3.0
Relationships: IsVariantFormOf: DOI 10.7795/550.20220914
Dates: Available: 2023-07-18
Created: 2022-09
File: Download File (application/pdf) 2.09 MB (2191916 Bytes)
MD5 Checksum: b24254e5d7c70c408f13979ac83d998a
SHA256 Checksum: 888d57c00f47cf3a513ceb7efdf1318c0a8e0ba467bc8bc93e6cfa7ab86ab8a7
Keywords: DKD Expert Report ; thread measurands ; pitch diameter ; virtual pitch diameter ; major diameter ; minor diameter ; pitch ; lead ; thread angle ; flank angle
Abstract: Metrology plays an essential role in the quality assurance of thread production.. While the testing of workpiece threads is typically carried out by means of gauges, the plug and ring gauges used must be previously calibrated, using suitable measuring methods. In Germany, the calibration of thread gauges is currently carried out by 47 calibration laboratories accredited for thread measurement by the German Accreditation Body (Deutsche Akkreditierungsstelle or DAkkS for short). By means of reference standards, these laboratories establish the traceability of their measurements to national standards of the Physikalisch-Technische Bundesanstalt (PTB) or other National Metrology Institutes (NMI), which are directly linked to the metre, the unit of length in the International System of Units (SI), via primary measurement procedures. Over the past decades, the ever-growing demand from industry for a more precise measuring technology to increase the quality of production with ever smaller manufacturing tolerances has led to the development of innovative measuring methods in thread measurement. Established methods such as the three-wire or two-ball method are now frequently supplemented by profile methods (stylus instrument procedures) and coordinate measurements. And there are other approaches using optical or other kinds of non-contact sensors. The variety of available measuring methods requires harmonisation because it must be ensured that different methods provide comparable measuring results. The difficulties already start with the definition of the fundamental quantities (thread parameters). These parameters must be unambiguous and accessible for all measurement methods. The basic metrological principles and test instructions for cylindrical threaded plug gauges and rings are described in the guidelines VDI/VDE/DGQ 2618 Part 4.8 and 4.9:2006-04. A detailed description of the procedure for determining the pitch diameter with the three-wire or two-ball method according to Berndt and Kochsiek and Lerch can be found in the European guideline EURAMET cg-10:2012-12. The application of these guidelines is limited explicitly to cylindrical threads. Besides, these guidelines rather focus on the technical details of measuring and calculating the determining parameters and not so much on providing basic statements on how to realise a reliable and task-specific traceability. This report is applicable to single and multiple-threaded cylindrical or tapered plug gauges and ring gauges, with straight flanks and positive flank angles. This report is intended to provide an in-depth overview of the requirements necessary for reliable and traceable thread measurements to ensure comparability both between different laboratories and when using different measuring methods.
Citation: Expert report DKD-E 4-1 Traceability of thread measurements, Edition 09/2022, Revision 0, Physikalisch-Technische Bundesanstalt, Braunschweig and Berlin. DOI: 10.7795/550.20230717