用(yong)內(nei)(nei)卡(ka)鉗(qian)(qian)(qian)測(ce)(ce)量(liang)(liang)(liang)(liang)內(nei)(nei)徑(jing)時(shi)(shi)，應(ying)使兩個鉗(qian)(qian)(qian)腳的(de)測(ce)(ce)量(liang)(liang)(liang)(liang)面(mian)的(de)聯(lian)線正(zheng)好垂直(zhi)相交于(yu)內(nei)(nei)孔(kong)(kong)(kong)(kong)的(de)軸線，即(ji)鉗(qian)(qian)(qian)腳的(de)兩個測(ce)(ce)量(liang)(liang)(liang)(liang)面(mian)應(ying)是內(nei)(nei)孔(kong)(kong)(kong)(kong)直(zhi)徑(jing)的(de)兩端點。因此(ci)，測(ce)(ce)量(liang)(liang)(liang)(liang)時(shi)(shi)應(ying)將(jiang)(jiang)下(xia)面(mian)的(de)鉗(qian)(qian)(qian)腳的(de)測(ce)(ce)量(liang)(liang)(liang)(liang)面(mian)停在(zai)孔(kong)(kong)(kong)(kong)壁上(shang)作(zuo)為(wei)支(zhi)點（圖(tu)1-7a），上(shang)面(mian)的(de)鉗(qian)(qian)(qian)腳由孔(kong)(kong)(kong)(kong)口略(lve)往里面(mian)一些逐漸向外試探(tan)，并沿(yan)孔(kong)(kong)(kong)(kong)壁圓(yuan)周(zhou)方(fang)向擺動(dong)，當沿(yan)孔(kong)(kong)(kong)(kong)壁圓(yuan)周(zhou)方(fang)向能擺動(dong)的(de)距(ju)離為(wei)最小時(shi)(shi)，則表示內(nei)(nei)卡(ka)鉗(qian)(qian)(qian)腳的(de)兩個測(ce)(ce)量(liang)(liang)(liang)(liang)面(mian)已處(chu)于(yu)內(nei)(nei)孔(kong)(kong)(kong)(kong)直(zhi)徑(jing)的(de)兩端點了(le)。再將(jiang)(jiang)卡(ka)鉗(qian)(qian)(qian)由外至里慢慢移動(dong)，可檢驗孔(kong)(kong)(kong)(kong)的(de)圓(yuan)度公差，圖(tu)1-7b 所(suo)示。

      用巳在(zai)(zai)鋼直尺(chi)(chi)上(shang)(shang)或在(zai)(zai)外(wai)卡(ka)鉗(qian)上(shang)(shang)取好尺(chi)(chi)寸(cun)的內(nei)(nei)卡(ka)鉗(qian)去測(ce)量(liang)內(nei)(nei)徑，圖(tu)1-8a 所示(shi)。就(jiu)是比較內(nei)(nei)卡(ka)鉗(qian)在(zai)(zai)零(ling)(ling)件(jian)孔(kong)內(nei)(nei)的松緊(jin)程度(du)。如內(nei)(nei)卡(ka)鉗(qian)在(zai)(zai)孔(kong)內(nei)(nei)有(you)較大的自(zi)(zi)由(you)(you)擺(bai)動時，就(jiu)表示(shi)卡(ka)鉗(qian)尺(chi)(chi)寸(cun)比孔(kong)徑內(nei)(nei)小了；如內(nei)(nei)卡(ka)鉗(qian)放不進，或放進孔(kong)內(nei)(nei)后緊(jin)得(de)不能(neng)自(zi)(zi)由(you)(you)擺(bai)動，就(jiu)表示(shi)內(nei)(nei)卡(ka)鉗(qian)尺(chi)(chi)寸(cun)比孔(kong)徑大了，如內(nei)(nei)卡(ka)鉗(qian)放入孔(kong)內(nei)(nei)，按照上(shang)(shang)述(shu)的測(ce)量(liang)方法能(neng)有(you)1～2mm的自(zi)(zi)由(you)(you)擺(bai)動距離，這(zhe)時孔(kong)徑與內(nei)(nei)卡(ka)鉗(qian)尺(chi)(chi)寸(cun)正好相等。測(ce)量(liang)時不要(yao)用手抓住卡(ka)鉗(qian)測(ce)量(liang)，圖(tu)1-8b 所示(shi)，這(zhe)樣手感就(jiu)沒有(you)了，難以比較內(nei)(nei)卡(ka)鉗(qian)在(zai)(zai)零(ling)(ling)件(jian)孔(kong)內(nei)(nei)的松緊(jin)程度(du)，并使卡(ka)鉗(qian)變形(xing)而產生測(ce)量(liang)誤差(cha)。