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1、WorkshopHintsBAThreads TheBritishHorologicalInstitutehasarchivedandeditedthefollowingfrome-mailssenttotheClock/ClockersmailinglistsontheInternet.TheinformationheredoesnotnecessarilyindicateamethodapprovedbytheBHI,weareonlypublishingthisdigestsothatotherscandecideforthems
2、elveswhetherthemethodslistedbelowwillsuitthem.From:TonyHarrison-Smith,RandolphLee,EliotIsaacsFBHIWaybackinthe1890's,theBritishAssociationforAdvancementofScience(BA)realisedtherewerenoEnglishscrewthreadsstandardsforsmallelectricalandscientificequipment,sotheyproposedtheBA
3、systemlooselybasedontheThurythreadsalreadyinuseinEurope(hencethemetricsizes).TheyquicklycaughtonandrapidlybecamethestandardintheUK.Theyaregoodnews-threadangleof47-1/2degrees(goodforholdinginthinworklikeclockwheels);roundedtipsandcrests(lesspowerneededtocut,lessriskoftear
4、ingthreads,lesswearonthetools);enormousrangeofsizes(0-26BA).Beforeyourushoutandorderafullset,afewusefultips:Hardlyanyoneeverusestheoddnumbers-mostengineersgetbywith2,4,6&8BA.Watchmakerstendtoadd10,12&14BA.Ifyoustickwiththeevennumbers,thenthetappingdrillforonesizebecomest
5、heclearancedrillforthenextsmaller.And,ifyoustillusenumberdrillsinsteadofthenewfangledNapoleonicupstarts,youcanusethe'ruleof4'i.e.,2BATapsize244BAClearancesize24Tapsize346BAClearancesize34Tapsize448BAClearancesize44Tapsize54Notexactlyoptimumsizes,butcloseenoughformostever
6、ydayuse,andsaveshavingtolookuptableseachtime.BATapsanddiesarereadilyavailablefrom'TheTap&DieCo'445WestGreenRoad,LondonN153PL,UK.Tel+44(0)1818881865orFax+44(0)1818884613.TheycarrymassivestocksofthesetapsanddiesaswellasothercuttingtoolsandarehighlyrecommendedThreadTPIMajor
7、Dia.PitchTappingDrill025.46.0mm1.00mmNo.55.1mm128.25.3mm0.9mmNo.144.5mm231.34.7mm0.81mmNo.224.0mm334.84.1mm0.73mmNo.293.45mm438.53.60mm0.66mmNo.313.00mm543.13.20mm0.59mmNo.362.65mm647.92.8mm0.53mmNo.412.30mm752.92.5mm0.48mmNo.452.05mm859.12.2mm0.43mmNo.491.80mm965.11.9mm
8、0.39mmNo.521.55mm1072.61.7mm0.35mmNo.541.40mm1181.91.5mm0.31mm3/64"1.20mm1290.71.3mm0.28mmNo.571.05mm13
