鑄鐵平(ping)臺(tai)在鑄造環節要(yao)留下加(jia)工(gong)(gong)(gong)(gong)量，加(jia)工(gong)(gong)(gong)(gong)時要(yao)從毛(mao)坯上(shang)切(qie)去(qu)的那層(ceng)金屬的厚度，稱為(wei)鑄鐵平(ping)臺(tai)的加(jia)工(gong)(gong)(gong)(gong)余(yu)(yu)量。加(jia)工(gong)(gong)(gong)(gong)余(yu)(yu)量又可分(fen)為(wei)工(gong)(gong)(gong)(gong)序余(yu)(yu)量和(he)總(zong)余(yu)(yu)量。工(gong)(gong)(gong)(gong)序中需要(yao)切(qie)除的那層(ceng)金屬層(ceng)厚度，稱為(wei)該工(gong)(gong)(gong)(gong)序的加(jia)工(gong)(gong)(gong)(gong)余(yu)(yu)量。從毛(mao)坯到成品總(zong)共需要(yao)切(qie)除的余(yu)(yu)量，稱為(wei)總(zong)余(yu)(yu)量，等(deng)于(yu)相應表面各(ge)工(gong)(gong)(gong)(gong)序余(yu)(yu)量之和(he)。
在鑄鐵平臺上(shang)留(liu)加(jia)工余量的目的是為了切除上(shang)一道工序所留(liu)下來(lai)的加(jia)工誤差和表(biao)(biao)(biao)(biao)面缺(que)陷，如鑄件表(biao)(biao)(biao)(biao)面冷硬層、氣孔、夾砂層，脫碳層、表(biao)(biao)(biao)(biao)面裂紋(wen)、鍛件表(biao)(biao)(biao)(biao)面的氧化(hua)皮，切削加(jia)工后的內應力層和表(biao)(biao)(biao)(biao)面粗糙度等(deng)，從而(er)提(ti)高鑄鐵平臺的精度。
