Inthesameyear1828Mr。Clementbeganthemakingofflutedtapsanddies，andheestablishedamechanicalpracticewithreferencetothepitchofthescrew，whichprovedofthegreatestimportanceintheeconomicsofmanufacture。Beforehistime，eachmechanicalengineeradoptedathreadofhisown；sothatwhenapieceofworkcameunderrepair，thescrew-hobhadusuallytobedrilledout，andanewthreadwasintroducedaccordingtotheusagewhichprevailedintheshopinwhichtheworkwasexecuted。Mr。Clementsawagreatwasteoflabourinthispractice，andhepromulgatedtheideathateveryscrewofaparticularlengthoughttobefurnishedwithitsappointednumberofthreadsofasettledpitch。Takingtheinchasthebasisofhiscalculations，hedeterminedthenumberofthreadsineachcase；andthepracticethusinitiatedbyhim，recommendedasitwasbyconvenienceandeconomy，wasveryshortlyadoptedthroughoutthetrade。ItmaybementionedthatoneofClement’sablestjourneymen，Mr。Whitworth，has，sincehistime，beenmainlyinstrumentalinestablishingthesettledpractice；andWhitworth’sthreadinitiatedbyClementhasbecomerecognisedthroughoutthemechanicalworld。Tocarryouthisidea，Clementinventedhisscrew-enginelathe，withgearing，mandrill，andsliding-tablewheel-work，bymeansofwhichhefirstcuttheinsidescrew-toolsfromtheleft-handedhobs——thereversemodehavingbeforebeenadopted，——whileinshapingmachineshewasthefirsttousetherevolvingcutterattachedtothesliderest。Then，in1828，heflutedthetapsforthefirsttimewitharevolvingcutter，——othermakershavinguptothattimeonlynotchedthem。Amonghisotherinventionsinscrewsmaybementionedhisheadlesstap，which，accordingtoMr。
Nasmyth，issovaluableaninvention，that，”ifhehaddonenothingelse，itoughttoimmortalizehimamongmechanics。Itpassedrightthroughtheholetobetapped，andwasthusenabledtodothedutyofthreeordinaryscrews。”Bytheseimprovementsmuchgreaterprecisionwassecuredinthemanufactureoftoolsandmachinery，accompaniedbyagreatlyreducedcostofproduction；theresultsofwhicharefelttothisday。
AnotherofMr。Clement’singeniousinventionswashisPlaningMachine，bymeansofwhichmetalplatesoflargedimensionswereplanedwithperfecttruthandfinishedwithbeautifulaccuracy。Thereisperhapsscarcelyamachineaboutwhichtherehasbeenmorecontroversythanthis；andwedonotpretendtobeabletodeterminetherespectivemeritsofthemanyablemechanicswhohavehadahandinitsinvention。ItisexceedinglyprobablethatothersbesidesClementworkedouttheproblemintheirownway，byindependentmethods；andthisisconfirmedbythecircumstancethatthoughtheresultsachievedbytherespectiveinventorswerethesame，themethodsemployedbythemwereinmanyrespectsdifferent。AsregardsClement，wefindthatprevioustotheyear1820hehadamachineinregularuseforplaningthetriangularbarsoflathesandthesidesofweaving-looms。Thisinstrumentwasfoundsousefulandsoeconomicalinitsworking，thatClementproceededtoelaborateaplaningmachineofamorecompletekind，whichhefinishedandsettoworkintheyear1825。Hepreparednomodelofit，butmadeitdirectfromtheworkingdrawings；anditwassonicelyconstructed，thatwhenputtogetheritwentwithoutahitch，andhascontinuedsteadilyworkingformorethanthirtyyearsdowntothepresentday。
Clementtookoutnopatentforhisinvention，relyingforprotectionmainlyonhisownandhisworkmen’sskillinusingit。WethereforefindnospecificationofhismachineatthePatentOffice，asinthecaseofmostothercapitalinventions；butaverycompleteaccountofitistobefoundintheTransactionsoftheSocietyofArtsfor1832，asdescribedbyMr。Varley。ThepracticalvalueofthePlaningMachineinducedtheSocietytoapplytoMr。Clementforlibertytopublishafulldescriptionofit；andMr。Varley’spaperwastheresult。*
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