以下摘自網(wǎng)絡(luò):
(ANSI花鍵標(biāo)準(zhǔn)中對(duì)form circle的說明)Form Circle is the circle which defines the deepest points of involute form control of the tooth profile. This circle along with the tooth tip circle (or start of chamfer circle) determines the limits of tooth profile requiring control. It is located near the major circle on the internal spline and near the minor circle on the external spline.
漸開線終止圓：漸開線終止圓是用于控制齒廓上漸開線的極限距離的圓。漸開線終止圓與齒頂圓（或者修緣線的起點(diǎn)所在的圓）共同限制了所要求控制的漸開線齒廓的范圍,。漸開線終止圓的位置靠近內(nèi)花鍵的大圓（齒根圓）或者外花鍵的小圓（齒根圓）,。
譯者注：這段話的意思是：只有在漸開線終止圓與齒頂圓（或者修緣線的起點(diǎn)所在的圓）之間的花鍵的齒形為漸開線齒形，其余部分不一定按照漸開線成形,。
譯者注2：在《GB/T 3478.1-1995 圓柱直齒漸開線花鍵》中,，將Form Cycle定義為兩個(gè)圓：內(nèi)花鍵的漸開線終止圓和外花鍵的漸開線起始圓。而在本標(biāo)準(zhǔn)中,，將這兩個(gè)圓統(tǒng)稱為Form Cycle,，譯者將Form Cycle翻譯為漸開線終止圓。