ISO METRIC PLUG, RING AND CALIPER THREAD …

1 ISO METRIC PLUG, ring AND CALIPER THREAD GAUGESG auges for testing ISO metricscrew threads to BS 3643:1981, andBS 919:Pt 3 3643comprises two parts. Part 1provides information and data on thebasic principles, and is based on ISO 965/1 and ISO 965 2 tabulates diameters of coarse,constant and fine pitch series threads,and is based on ISO 965 919: Pt3: 1968contains therecommended gauging system forchecking ISO METRIC threads inaccordance with BS 3643. It is based onISO 1502. The basic profile of the ISOthreads is shown gauge comprises a Go elementwhich tests that the Major andEffective diameters are not too small(maximum material limit). It also testsfor pitch or flank errors in the productthread.

2 The Not Go element tests onlythat the Effective diameter is not toolarge (minimum material limit). TheMinor diameter of the internal threadcan be checked separately using adouble ended plain plug testing external product threads Goand Not Go ring gauges or calipergauges having Go and Not Go anvilsmay be used. 4D = major diameter of internal threadd = major diameter of external threadD2= pitch diameter of internal threadd2= pitch diameter of external threadD1= minor diameter of internal threadd1= minor diameter of external threadP = pitchH = height of fundamental triangle= P/2tan30 BS 3643 Pt1 and Pt2specifies thefundamental deviations and tolerancesfor 5H, 6H, 6G and 7H for internalthreads, and 4h, 6g, 6e, 8g for 6H/6g are regarded as medium fit.

3 The nut and boltdeviations and tolerance zones areillustrated 919 Pt3: 1968specifies the limitsfor gauges for testing the productthread. The basis for determining thegauge limit is the magnitude ofthe product tolerance. larger the producttolerance, the larger thegauge limit regardless ofdiameter. The gaugesrecommended to be used are asfollows:-For testing internal productthreads a double ended screwplug gauge (Style E) may be g e4866576hH H/h = zero = basic sizeProduct tolerance: 8 > 6 > 5 etcPP/860 3/8 HH/4H/890 P/430 D,dAxis of screw thread5/8 HHP/2D1,d1D2,d26G 101036_CG Catalogue 2004/5 22/1/04 8:48 am Page for testing products in the pre-plating condition can be supplied.

4 Forinternal threads class 6G may be usedas a pre-plating condition for 6H afterplating. For external threads class 6emay be used as a pre-plating conditionfor 6g after plating. Class 6g may alsobe used as a pre-plating condition for4h after plating. When orderinggauges for other plating conditions it ishelpful to advise either the effectivediameters required, or the amount ofplating to be applied. Coventry Gauge Limited have a fully equipped calibration laboratory, withUKAS accreditation, capable ofcarrying out calibrations ofscrew and plain gauges, andancillary PITCHThe regular checking of gauges inconstant use is important. Pluggauges should be checked by directmeasurement of the Major andEffective diameters, using a FloatingCarriage Measuring Machine orsimilar specialised equipment.

5 Ringgauges may be checked by directmeasurement, or preferably by usingGo check and Not Go Wear checkplug gauges, as specified in BS 919:Pt3: practicable, externalproduct threads should be tested bymeans of ring gauges as theseprovide a full functional test of allthread features: pitch, angle, threadform and PITCH 0002 SCREW PLUGSSCREW RINGSCALIPERSGONOGO E GONOGOROLLERKNIFEC lass of fitClass of fitClass of fitClass of fitSIZE6H6H6H6g6gANYANY101036_CG Catalogue 2004/5 22/1/04 8:48 am Page 5