非標機械加工的(de)(de)定(ding)義是(shi)按步驟、按工(gong)序完成各工(gong)件(jian)外(wai)形尺寸或功(gong)能的(de)(de)最終(zhong)加工(gong)，包括工(gong)件(jian)平行(xing)度，外(wai)表(biao)光(guang)亮(liang)度，外(wai)表(biao)垂(chui)直度，外(wai)表(biao)硬(ying)度等等，使零件(jian)的(de)(de)加工(gong)精度和加工(gong)外(wai)表(biao)質(zhi)量到達(da)圖紙要(yao)(yao)(yao)求(qiu)(qiu)的(de)(de)進程。 平行(xing)度要(yao)(yao)(yao)求(qiu)(qiu) 所謂平行(xing)度要(yao)(yao)(yao)求(qiu)(qiu)，就是(shi)要(yao)(yao)(yao)求(qiu)(qiu)非標精細(xi)機加工(gong)工(gong)件(jian)的(de)(de)四周的(de)(de)公(gong)(gong)差(cha)(cha)要(yao)(yao)(yao)求(qiu)(qiu)，比(bi)如是(shi)矩形工(gong)件(jian)，則要(yao)(yao)(yao)求(qiu)(qiu)工(gong)件(jian)四個角(jiao)的(de)(de)厚(hou)度到達(da)一定(ding)的(de)(de)公(gong)(gong)差(cha)(cha)范圍(wei)。假如測量四邊的(de)(de)厚(hou)度達(da)不(bu)到公(gong)(gong)差(cha)(cha)要(yao)(yao)(yao)求(qiu)(qiu)，則達(da)不(bu)到平行(xing)度要(yao)(yao)(yao)求(qiu)(qiu)。

一(yi)個(ge)零件通常(chang)由多(duo)個(ge)表面組成，各表面的加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)一(yi)般都(dou)需(xu)要(yao)分(fen)(fen)階(jie)段(duan)進行。在安(an)(an)(an)排非標機械加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)順序時，應(ying)先集中(zhong)安(an)(an)(an)排各表面的粗加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)，中(zhong)間根據需(xu)要(yao)依(yi)次安(an)(an)(an)排半精(jing)加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)，最后安(an)(an)(an)排精(jing)加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)和光整加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)。對于精(jing)度要(yao)求較高的工(gong)(gong)(gong)(gong)(gong)(gong)件，為了減小(xiao)因粗加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)引起的變(bian)形對精(jing)加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)的影響，通常(chang)粗、精(jing)加(jia)工(gong)(gong)(gong)(gong)(gong)(gong)不應(ying)連續進行，而應(ying)分(fen)(fen)階(jie)段(duan)、間隔適當時間進行。