用鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)尺(chi)(chi)(chi)研(yan)磨鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)板(ban)(ban)(ban)時盡(jin)可(ke)能選用橋型(xing)平(ping)(ping)尺(chi)(chi)(chi)，因其結(jie)構牢(lao)固，不(bu)易(yi)變形，且較重，拖(tuo)研(yan)時能緊貼鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)板(ban)(ban)(ban)，使接(jie)觸斑(ban)點(dian)真實可(ke)靠。且橋型(xing)平(ping)(ping)尺(chi)(chi)(chi)較寬，與平(ping)(ping)板(ban)(ban)(ban)接(jie)觸面(mian)積(ji)較大，有(you)(you)利于刮研(yan)鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)板(ban)(ban)(ban)的(de)(de)修(xiu)理。橋型(xing)平(ping)(ping)尺(chi)(chi)(chi)的(de)(de)選擇時盡(jin)可(ke)能選用分別比鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)板(ban)(ban)(ban)的(de)(de)對角(jiao)線、長邊(bian)、短(duan)邊(bian)稍長一(yi)點(dian)的(de)(de)三把(ba)鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)尺(chi)(chi)(chi)，太長太短(duan)均不(bu)利于鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)板(ban)(ban)(ban)的(de)(de)修(xiu)復，太長會(hui)在拖(tuo)研(yan)時兩(liang)頭(tou)下沉使鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)板(ban)(ban)(ban)變凸，太短(duan)會(hui)使鐵(tie)(tie)(tie)(tie)平(ping)(ping)尺(chi)(chi)(chi)重復在平(ping)(ping)板(ban)(ban)(ban)研(yan)刮而使平(ping)(ping)板(ban)(ban)(ban)變凹。鑄(zhu)(zhu)(zhu)鐵(tie)(tie)(tie)(tie)平(ping)(ping)尺(chi)(chi)(chi)只要能確保(bao)應有(you)(you)的(de)(de)直(zhi)線度，而對外觀質(zhi)量并無嚴(yan)格要求。
平(ping)(ping)(ping)(ping)板(ban)研(yan)(yan)磨(mo)時(shi)，拖(tuo)研(yan)(yan)距離(li)不(bu)宜(yi)太長，一(yi)般(ban)不(bu)_過(guo)100mm，如果選用(yong)鑄(zhu)(zhu)鐵(tie)(tie)平(ping)(ping)(ping)(ping)尺(chi)(chi)的(de)長度明(ming)顯大(da)于(yu)所拖(tuo)研(yan)(yan)的(de)平(ping)(ping)(ping)(ping)板(ban)截(jie)面，則(ze)(ze)拖(tuo)研(yan)(yan)距離(li)不(bu)要縮小。研(yan)(yan)磨(mo)平(ping)(ping)(ping)(ping)板(ban)時(shi)，不(bu)應在(zai)平(ping)(ping)(ping)(ping)尺(chi)(chi)上向(xiang)平(ping)(ping)(ping)(ping)板(ban)外(wai)加(jia)壓力(li)，而應以(yi)鑄(zhu)(zhu)鐵(tie)(tie)平(ping)(ping)(ping)(ping)尺(chi)(chi)自身(shen)重量緊(jin)貼鑄(zhu)(zhu)鐵(tie)(tie)平(ping)(ping)(ping)(ping)板(ban)，在(zai)平(ping)(ping)(ping)(ping)行平(ping)(ping)(ping)(ping)板(ban)方向(xiang)上施力(li)拖(tuo)拉鑄(zhu)(zhu)鐵(tie)(tie)平(ping)(ping)(ping)(ping)尺(chi)(chi)，以(yi)便產(chan)生真實可靠的(de)接觸斑點。如果刮研(yan)(yan)鑄(zhu)(zhu)鐵(tie)(tie)平(ping)(ping)(ping)(ping)板(ban)短邊(bian)(bian)方向(xiang)直(zhi)線(xian)(xian)度誤差明(ming)顯大(da)于(yu)長邊(bian)(bian)方向(xiang)直(zhi)線(xian)(xian)度，則(ze)(ze)在(zai)修(xiu)(xiu)復(fu)對角線(xian)(xian)直(zhi)線(xian)(xian)后應先(xian)修(xiu)(xiu)復(fu)短邊(bian)(bian)直(zhi)線(xian)(xian)度，再修(xiu)(xiu)復(fu)長邊(bian)(bian)直(zhi)線(xian)(xian)度，這樣(yang)更為(wei)合理。
