拉削是機械加工作(zuo)業(ye)的(de)一種類型，是使用(yong)拉床（拉刀）加工各(ge)種內外成形(xing)表面的切削工藝。
一.簡介
拉削刀具(ju)是非常復雜的組件，由一個(ge)單件制造而(er)成(cheng)。材料(liao)主要是高速鋼，硬質 合金(jin)作為刀具(ju)材料(liao)僅用于(yu)灰鑄(zhu)鐵的機械(xie)加工(gong)。
與許多其他切削作業不同，主(zhu)要考慮的(de)問題是刀(dao)具(ju)的(de)磨損或刀(dao)具(ju)使用壽命(ming)。
在拉(la)削情況下，數個(ge)齒同(tong)時(shi)嚙合，而(er)且切屑寬度經常(chang)很大(da)。移除切屑可能(neng)是非常(chang)成問題的，因而(er)通(tong)常(chang)也需要低黏度油。
從切削(xue)液的供送來看，內(nei)拉削(xue)比外拉削(xue)更成(cheng)問(wen)題，臥式拉削(xue)比立式拉削(xue)更困難。
二.分類
用拉(la)刀(dao)(dao)作為刀(dao)(dao)具(ju)的切削(xue)加工(gong)(gong)。當拉(la)刀(dao)(dao)相對工(gong)(gong)件(jian)作直線移(yi)動時，工(gong)(gong)件(jian)的加工(gong)(gong)余量由拉(la)刀(dao)(dao)上逐齒遞(di)增尺(chi)寸的刀(dao)(dao)齒依次切除（圖1）。通(tong)常，一次工(gong)(gong)作行程即能加工(gong)(gong)成形，是一種高(gao)效率(lv)的精加工(gong)(gong)方(fang)法(fa)。但因拉(la)刀(dao)(dao)結構復雜(za)，制造成本(ben)高(gao)，且有一定的專(zhuan)用性，因此拉(la)削(xue)主要用于成批大量生產。按(an)加工(gong)(gong)表面特(te)征不同，拉(la)削(xue)分為內拉(la)削(xue)和外拉(la)削(xue)。
①內(nei)拉(la)削：用來加(jia)(jia)工(gong)各種截(jie)面形狀的通孔(kong)(kong)(kong)(kong)(kong)和孔(kong)(kong)(kong)(kong)(kong)內(nei)通槽（圖2），如(ru)圓孔(kong)(kong)(kong)(kong)(kong)、方孔(kong)(kong)(kong)(kong)(kong)、多邊形孔(kong)(kong)(kong)(kong)(kong)、花鍵(jian)孔(kong)(kong)(kong)(kong)(kong)、鍵(jian)槽孔(kong)(kong)(kong)(kong)(kong)、內(nei)齒輪等。拉(la)削前要有已加(jia)(jia)工(gong)孔(kong)(kong)(kong)(kong)(kong)，讓拉(la)刀能(neng)從中(zhong)插(cha)入。拉(la)削的孔(kong)(kong)(kong)(kong)(kong)徑(jing)范圍為8～125毫(hao)米(mi)，孔(kong)(kong)(kong)(kong)(kong)深不超過孔(kong)(kong)(kong)(kong)(kong)徑(jing)的5倍(bei)。特殊(shu)情況下，孔(kong)(kong)(kong)(kong)(kong)徑(jing)范圍可(ke)小到(dao)3毫(hao)米(mi)，大(da)到(dao)400毫(hao)米(mi)，孔(kong)(kong)(kong)(kong)(kong)深可(ke)達10米(mi)。
②外(wai)拉(la)(la)(la)削:用來加工非封閉(bi)形(xing)表面（圖(tu)3），如(ru)平面、成形(xing)面、溝槽(cao)、榫槽(cao)、葉片榫頭(tou)和(he)外(wai)齒(chi)輪等,特別適合于在(zai)大(da)量生產中(zhong)加工比較大(da)的平面和(he)復(fu)合型面，如(ru)汽車和(he)拖拉(la)(la)(la)機的氣缸(gang)體、軸承座和(he)連桿等。拉(la)(la)(la)削型面的尺寸精(jing)度(du)可達IT8～5，表面粗(cu)糙(cao)度(du)為 Ra2.5～0.04微(wei)米，拉(la)(la)(la)削齒(chi)輪精(jing)度(du)可達6～8級（JB179-83）。
拉(la)(la)削(xue)時，從(cong)工(gong)(gong)(gong)件上切(qie)(qie)除加(jia)(jia)工(gong)(gong)(gong)余量的(de)(de)(de)順序和方(fang)式(shi)(shi)有成(cheng)形式(shi)(shi)、漸(jian)成(cheng)式(shi)(shi)、輪(lun)切(qie)(qie)式(shi)(shi)和綜合(he)輪(lun)切(qie)(qie)式(shi)(shi)等(deng)。①成(cheng)形式(shi)(shi)。加(jia)(jia)工(gong)(gong)(gong)精度(du)(du)(du)高，表(biao)面(mian)粗(cu)糙度(du)(du)(du)較(jiao)(jiao)(jiao)小，但效率(lv)較(jiao)(jiao)(jiao)低(di)；拉(la)(la)刀長度(du)(du)(du)較(jiao)(jiao)(jiao)長，主要(yao)用(yong)于(yu)加(jia)(jia)工(gong)(gong)(gong)中小尺寸(cun)的(de)(de)(de)圓(yuan)孔和精度(du)(du)(du)要(yao)求高的(de)(de)(de)成(cheng)形面(mian)。②漸(jian)成(cheng)式(shi)(shi)適用(yong)于(yu)粗(cu)拉(la)(la)削(xue)復雜的(de)(de)(de)加(jia)(jia)工(gong)(gong)(gong)表(biao)面(mian)，如方(fang)孔、多邊(bian)形孔和花鍵孔等(deng),這(zhe)種方(fang)式(shi)(shi)采(cai)用(yong)的(de)(de)(de)拉(la)(la)刀制造較(jiao)(jiao)(jiao)易,但加(jia)(jia)工(gong)(gong)(gong)表(biao)面(mian)質量較(jiao)(jiao)(jiao)差。③輪(lun)切(qie)(qie)式(shi)(shi)切(qie)(qie)削(xue)效率(lv)高，可減小拉(la)(la)刀長度(du)(du)(du)，但加(jia)(jia)工(gong)(gong)(gong)表(biao)面(mian)質量差，主要(yao)用(yong)于(yu)加(jia)(jia)工(gong)(gong)(gong)尺寸(cun)較(jiao)(jiao)(jiao)大、加(jia)(jia)工(gong)(gong)(gong)余量較(jiao)(jiao)(jiao)多、精度(du)(du)(du)要(yao)求較(jiao)(jiao)(jiao)低(di)的(de)(de)(de)圓(yuan)孔。④綜合(he)輪(lun)切(qie)(qie)式(shi)(shi)是用(yong)輪(lun)切(qie)(qie)法進行(xing)粗(cu)拉(la)(la)削(xue),用(yong)成(cheng)形法進行(xing)精拉(la)(la)削(xue),兼有兩者的(de)(de)(de)優點，廣泛用(yong)于(yu)圓(yuan)孔拉(la)(la)削(xue)。