渐开线花键的定心方式为齿形定心。受载时齿上有径向力，能起自动定心作用，有利于各齿受力均匀，强度高，寿命长。用于载荷较大，定心精度要求较高以及尺寸较大的联接，如航空发动机、燃气轮机、汽车等。压力角45°的花键多用于轻载、小直径和薄型零件的联接。Theinvolutesplineiscenteringintheshapeofthetooth.Thetoothhasradialforceonthetooth,anditcanplaytheroleofautomaticcentering,whichisbeneficialtotheuniformforceofeachtooth,highstrengthandlonglife.Itisusedforlargeload,highprecisionandlargesizeconnection,suchasaeroengine,gasturbine,automobileandsoon.Thesplinewithapressureangleof45degreesisusedfortheconnectionoflight,***alldiameterandthinparts.销联接一般用来传递不大的载荷或作安全装置；另一作用是起***作用。常与带孔螺栓和六角开槽螺母配对使用，把销插入螺栓的孔与螺母的槽中，以防螺母松脱。销按形状分为圆柱销、圆锥销和异形销三类。Pinconnecti***aregenerallyusedtotransfer***allloadsorsafetydevices;theotheristoplaytheroleof.Itisoftenpairedwithholeboltsandsixangleslottingnutstoinsertthepinintotheholeoftheboltandtheslotinthenutsoastopreventthelooseningofthenut.Thepinisdividedintothreetypes:cylindricalpin,conicalpinandspecialpin.螺旋副的间隙大，旋转时费力，使用中稳定性差。机用虎钳开合行程大，螺旋副的运行长度较长，为保证能够快速装夹，（金属加工真不错）机用虎钳螺旋副的螺距较大。较大的螺距意味着较大的螺旋升角，转动单圈进给量较大，使用时较费力；较大的螺距需要更大的配合间隙来确保螺旋副的正常使用。Theclearanceofthehelixpairislarge,therotationishardandthestabilityoftheuseispoor.Themachinehaslargeopeningandclosingstroke,andtheoperationlengthofthescrewpairislonger.Inordertoensurequickclamping,metalmachiningisgood.Largerpitchmeanslargerspiralangle,largersingleturnfeedandmorelaborioususe.Largerpitchneedsmorefitclearancetoensurethenormaluseofscrewpair.)