Bion, Nicolas, Traité de la construction et principaux usages des instruments de mathématique, 1723

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        <div xml:id="echoid-div286" type="section" level="1" n="125">
          <p>
            <s xml:id="echoid-s2806" xml:space="preserve">
              <pb o="87" file="101" n="101" rhead="DE DIFFERENS INSTRUMENS. Liv III. Ch. II."/>
            il eſt fait; </s>
            <s xml:id="echoid-s2807" xml:space="preserve">ſa conſtruction ne differe en rien de celle des autres com-
              <lb/>
            pas, ſi ce n'eſt qu'il eſt rond, & </s>
            <s xml:id="echoid-s2808" xml:space="preserve">qu'ily a une vis au-deſſous de ſa
              <lb/>
            tête, pour le monter dans le Porte craïon. </s>
            <s xml:id="echoid-s2809" xml:space="preserve">Ladite vis ſe fait par le
              <lb/>
            moyen d'une filiere double, puis on la repaſſe enſuite dans une fi-
              <lb/>
            liere ſimple, afin de ne pas forcer les charnieres des compas en les
              <lb/>
            taraudant, car c'eſt à quoion doit bien prendre garde.</s>
            <s xml:id="echoid-s2810" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2811" xml:space="preserve">On trace ordinairement ſur les pans de ce Porte craïon les lignes
              <lb/>
            qui ſe mettent ſur le compas de proportion. </s>
            <s xml:id="echoid-s2812" xml:space="preserve">On les prend ſur une
              <lb/>
            regle d'égale longueur, que l'on a diviſée ſuivant les methodes ex-
              <lb/>
            pliquées pour le compas de proportion, & </s>
            <s xml:id="echoid-s2813" xml:space="preserve">que l'on tranſporte ſur
              <lb/>
            chacun des pans. </s>
            <s xml:id="echoid-s2814" xml:space="preserve">L'uſage en eſt à peu près le même, ſinon qu'il ſe
              <lb/>
            faut toûjours ſervir de la même grandeur; </s>
            <s xml:id="echoid-s2815" xml:space="preserve">car ſi, par exemple, ils'a-
              <lb/>
            git de tracer un angle de 40 degrez ſur une ligne donnée, on prend
              <lb/>
            avec le compas commun l'étenduë depuis le premier point de divi-
              <lb/>
            ſion de la ligne des cordes juſqu'au point marqué 60; </s>
            <s xml:id="echoid-s2816" xml:space="preserve">de cette ou-
              <lb/>
            verture on fait un arc ſur la ligne donnée; </s>
            <s xml:id="echoid-s2817" xml:space="preserve">& </s>
            <s xml:id="echoid-s2818" xml:space="preserve">enſuite on prend avec
              <lb/>
            le même compas la diſtance du premier point de diviſion juſqu'au
              <lb/>
            point 40, laquelle on tranſporte ſur l'arc tracé, & </s>
            <s xml:id="echoid-s2819" xml:space="preserve">de ſon centre on
              <lb/>
            tire une ligne qui fera avec la donnée un angle de 40 degrez, & </s>
            <s xml:id="echoid-s2820" xml:space="preserve">
              <lb/>
            ainſi des autres lignes.</s>
            <s xml:id="echoid-s2821" xml:space="preserve"/>
          </p>
          <p>
            <s xml:id="echoid-s2822" xml:space="preserve">On ſait auſſi de ces ſortes de porte craïon à compas qui ſont
              <lb/>
            ronds, & </s>
            <s xml:id="echoid-s2823" xml:space="preserve">ſur leſquels on marque les pouces, dont on diviſe un en
              <lb/>
            douze lignes.</s>
            <s xml:id="echoid-s2824" xml:space="preserve"/>
          </p>
        </div>
        <div xml:id="echoid-div288" type="section" level="1" n="126">
          <head xml:id="echoid-head202" style="it" xml:space="preserve">Conſtruction du porte-craïon a couliſſe.</head>
          <p>
            <s xml:id="echoid-s2825" xml:space="preserve">CE Porte-craïon eſt rond en dedans & </s>
            <s xml:id="echoid-s2826" xml:space="preserve">tourné en dehors; </s>
            <s xml:id="echoid-s2827" xml:space="preserve">on les
              <lb/>
              <note position="right" xlink:label="note-101-01" xlink:href="note-101-01a" xml:space="preserve">Fig. C.</note>
            fait auſſi quelquefois à pans, & </s>
            <s xml:id="echoid-s2828" xml:space="preserve">on y marque les pouces & </s>
            <s xml:id="echoid-s2829" xml:space="preserve">li-
              <lb/>
            gnes par des traits fins qui ſe font par le moyen du tour. </s>
            <s xml:id="echoid-s2830" xml:space="preserve">On prend
              <lb/>
            une lame de laiton ou d'autre matiere de la longueur & </s>
            <s xml:id="echoid-s2831" xml:space="preserve">largeur qu'-
              <lb/>
            on veut faire le porte-craïon, puis on la contourne autour d'un ar-
              <lb/>
            bre ou verge de fil d'acier bien rond, bien droit & </s>
            <s xml:id="echoid-s2832" xml:space="preserve">égal de groſ-
              <lb/>
            ſeur par tout. </s>
            <s xml:id="echoid-s2833" xml:space="preserve">On ſoude enſuite la jointure de ladite lame, qu'on
              <lb/>
            nomme la charniere ou corps du porte-craïon, qu'il faut tirer & </s>
            <s xml:id="echoid-s2834" xml:space="preserve">fai-
              <lb/>
            re paſſer dans une filiere à trou rond par le moyen d'un banc; </s>
            <s xml:id="echoid-s2835" xml:space="preserve">on tire
              <lb/>
            ladite charniere juſqu'à ce qu'elle preſſe l'arbre d'acier partout é-
              <lb/>
            galement, afin que le dedans foit bien rond & </s>
            <s xml:id="echoid-s2836" xml:space="preserve">égal, puis après l'a-
              <lb/>
            voir tourné comme la figure le montre on le fend juſqu'à environ
              <lb/>
            demi-pouce des bouts, & </s>
            <s xml:id="echoid-s2837" xml:space="preserve">on le perce aux extremitez de la ſente & </s>
            <s xml:id="echoid-s2838" xml:space="preserve">
              <lb/>
            au milieu, d'un petit trou rond, pour y recevoir le bouton. </s>
            <s xml:id="echoid-s2839" xml:space="preserve">La figu-
              <lb/>
            re D eſt le dedans du porte-craïon; </s>
            <s xml:id="echoid-s2840" xml:space="preserve">aux deux extremitez on y place
              <lb/>
            </s>
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