用內卡鉗(qian)測(ce)(ce)量(liang)(liang)內徑(jing)時(shi)，應使兩(liang)個(ge)鉗(qian)腳(jiao)(jiao)的(de)(de)(de)(de)(de)測(ce)(ce)量(liang)(liang)面(mian)(mian)的(de)(de)(de)(de)(de)聯線正(zheng)好垂直(zhi)相交于內孔(kong)(kong)的(de)(de)(de)(de)(de)軸線，即鉗(qian)腳(jiao)(jiao)的(de)(de)(de)(de)(de)兩(liang)個(ge)測(ce)(ce)量(liang)(liang)面(mian)(mian)應是內孔(kong)(kong)直(zhi)徑(jing)的(de)(de)(de)(de)(de)兩(liang)端點。因此(ci)，測(ce)(ce)量(liang)(liang)時(shi)應將(jiang)(jiang)下面(mian)(mian)的(de)(de)(de)(de)(de)鉗(qian)腳(jiao)(jiao)的(de)(de)(de)(de)(de)測(ce)(ce)量(liang)(liang)面(mian)(mian)停在孔(kong)(kong)壁(bi)上(shang)作為支點（圖(tu)1-7a），上(shang)面(mian)(mian)的(de)(de)(de)(de)(de)鉗(qian)腳(jiao)(jiao)由孔(kong)(kong)口略往里面(mian)(mian)一些(xie)逐漸向(xiang)外試(shi)探，并沿孔(kong)(kong)壁(bi)圓周(zhou)方(fang)向(xiang)擺動，當沿孔(kong)(kong)壁(bi)圓周(zhou)方(fang)向(xiang)能擺動的(de)(de)(de)(de)(de)距離為最小時(shi)，則表示內卡鉗(qian)腳(jiao)(jiao)的(de)(de)(de)(de)(de)兩(liang)個(ge)測(ce)(ce)量(liang)(liang)面(mian)(mian)已處(chu)于內孔(kong)(kong)直(zhi)徑(jing)的(de)(de)(de)(de)(de)兩(liang)端點了。再將(jiang)(jiang)卡鉗(qian)由外至里慢慢移動，可檢驗孔(kong)(kong)的(de)(de)(de)(de)(de)圓度(du)公差，圖(tu)1-7b 所示。

      用(yong)巳在鋼(gang)直尺(chi)上或(huo)在外卡(ka)(ka)(ka)鉗(qian)(qian)上取好尺(chi)寸(cun)的(de)內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)去測(ce)量(liang)內(nei)(nei)徑(jing)，圖(tu)1-8a 所示。就是比較內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)在零(ling)件孔(kong)(kong)(kong)(kong)(kong)內(nei)(nei)的(de)松(song)(song)緊(jin)程(cheng)度。如內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)在孔(kong)(kong)(kong)(kong)(kong)內(nei)(nei)有較大的(de)自由擺動時(shi)，就表示卡(ka)(ka)(ka)鉗(qian)(qian)尺(chi)寸(cun)比孔(kong)(kong)(kong)(kong)(kong)徑(jing)內(nei)(nei)小了(le)(le)；如內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)放不進(jin)，或(huo)放進(jin)孔(kong)(kong)(kong)(kong)(kong)內(nei)(nei)后緊(jin)得不能(neng)自由擺動，就表示內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)尺(chi)寸(cun)比孔(kong)(kong)(kong)(kong)(kong)徑(jing)大了(le)(le)，如內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)放入孔(kong)(kong)(kong)(kong)(kong)內(nei)(nei)，按照上述的(de)測(ce)量(liang)方法能(neng)有1～2mm的(de)自由擺動距離，這時(shi)孔(kong)(kong)(kong)(kong)(kong)徑(jing)與內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)尺(chi)寸(cun)正(zheng)好相等。測(ce)量(liang)時(shi)不要(yao)用(yong)手(shou)抓住卡(ka)(ka)(ka)鉗(qian)(qian)測(ce)量(liang)，圖(tu)1-8b 所示，這樣手(shou)感就沒有了(le)(le)，難以(yi)比較內(nei)(nei)卡(ka)(ka)(ka)鉗(qian)(qian)在零(ling)件孔(kong)(kong)(kong)(kong)(kong)內(nei)(nei)的(de)松(song)(song)緊(jin)程(cheng)度，并(bing)使卡(ka)(ka)(ka)鉗(qian)(qian)變形而(er)產(chan)生測(ce)量(liang)誤(wu)差。