精密異型鋼孔(kong)型形(xing)(xing)(xing)狀既要(yao)(yao)照顧穩(wen)定性(xing)，又要(yao)(yao)滿足(zu)寬(kuan)展的(de)要(yao)(yao)求，二(er)者相(xiang)(xiang)互聯(lian)系。在設計輕軌的(de)帽(mao)(mao)形(xing)(xing)(xing)前孔(kong)時，曾有這樣的(de)反復：最初帽(mao)(mao)形(xing)(xing)(xing)前孔(kong)采用兩墻帶斜度的(de)箱形(xing)(xing)(xing)孔(kong)，雖(sui)然(ran)軋(ya)制(zhi)穩(wen)定，但進入帽(mao)(mao)形(xing)(xing)(xing)孔(kong)后(hou)，因底部(bu)金屬不(bu)(bu)足(zu)而使帽(mao)(mao)形(xing)(xing)(xing)孔(kong)的(de)帽(mao)(mao)緣寬(kuan)度不(bu)(bu)夠。以后(hou)，為滿足(zu)帽(mao)(mao)形(xing)(xing)(xing)孔(kong)帽(mao)(mao)緣的(de)寬(kuan)度及與帽(mao)(mao)形(xing)(xing)(xing)孔(kong)側壁斜度相(xiang)(xiang)吻合(he)的(de)要(yao)(yao)求，帽(mao)(mao)形(xing)(xing)(xing)前孔(kong)采用了(le)楔形(xing)(xing)(xing)孔(kong)這樣，雖(sui)然(ran)帽(mao)(mao)形(xing)(xing)(xing)孔(kong)內軋(ya)制(zhi)十分穩(wen)定，帽(mao)(mao)形(xing)(xing)(xing)底寬(kuan)足(zu)夠，但帽(mao)(mao)形(xing)(xing)(xing)前孔(kong)不(bu)(bu)均勻(yun)變(bian)形(xing)(xing)(xing)十分劇(ju)烈，軋(ya)件(jian)產生嚴重的(de)水平(ping)彎曲，導板和翻鋼機構均無法矯正。

向上(shang)(shang)彎(wan)曲的(de)(de)(de)(de)軋(ya)件(jian)，使頭(tou)部進入(ru)帽(mao)形孔(kong)(kong)很(hen)困難，異型鋼軋(ya)件(jian)在輥道上(shang)(shang)很(hen)難立穩(wen)，工人(ren)操作(zuo)十分費力，軋(ya)件(jian)溫降(jiang)大，頭(tou)部彎(wan)曲造成單輥接觸(chu)，不易咬入(ru)，被冷卻水(shui)澆成黑(hei)頭(tou)鋼而頻繁發生纏輥事(shi)故。后又將(jiang)帽(mao)形前孔(kong)(kong)改(gai)(gai)為兩(liang)(liang)(liang)端帶斜度的(de)(de)(de)(de)箱形孔(kong)(kong)，并相應(ying)修改(gai)(gai)了兩(liang)(liang)(liang)個帽(mao)形孔(kong)(kong)的(de)(de)(de)(de)高度和切辣楔子的(de)(de)(de)(de)形狀，使上(shang)(shang)下兩(liang)(liang)(liang)道狡的(de)(de)(de)(de)軋(ya)制既(ji)穩(wen)定又保證了帽(mao)緣的(de)(de)(de)(de)寬度尺寸，懈決了穩(wen)定性與寬展的(de)(de)(de)(de)矛盾。