键是一种标准件，通常用于联接轴与轴上旋转零件与摆动零件，起周向固定零件的作用以传递旋转运动和扭矩，楔键还可以起单向轴向固定零件。而导键、滑键、花键还可用作轴上移动的导向装置。根据键的结构形式，键联接可分为平键联接、半圆键联接、楔键联接和切向键联接等几类。Thekeyisastandardpart,whichisusuallyusedtoconnecttherotatingpartsandswingpartsoftheshaftandtheaxletomovethefixedpartstotran***itrotarymotionandtorque,andthewedgekeycanalsoplayaone-wayaxialfixationpart.Theguide,slipperykeyandthesplinecanalsobeusedasaguidingdeviceformovingontheaxis.Accordingtothestructureofthekey,keyjoinscanbedividedintoaflatbond,asemicirclebond,awedgebondandatangentbond.花键联接由内花键和外花键组成。内、外花键均为多齿零件，在内圆柱表面上的花键为内花键，在外圆柱表面上的花键为外花键。显然，花键联接是平键联接在数目上的发展。Theconnectionofthesplineismadeupoftheinnerandouterspline.Theinnerandoutersplinearemultitoothparts,andthesplineonthesurfaceoftheinnercylinderistheinnerspline,andthesplineontheoutercylindricalsurfaceistheouterspline.Itisthatthesplineconnectionisthedevelopmentofthenumberofflatbondconnecti.矩形花键联接是应用为广泛的花键联接。应用广泛。如航空发动机、汽车、燃气轮机、机床、工程机械、拖拉机、农业机械及一般机械传动装置等等。渐开线花键的齿廓为渐开线，分度圆压力角α有30°及45°两种。齿顶高分别为0.5m和0.4m(m为模数)。Therectangularsplineconnectionisthemostwidelyusedsplineconnection.Itiswidelyused.Suchasaeroengine,automobile,gasturbine,machinetool,engineeringmachinery,tractor,agriculturalmachineryandgeneralmechanicaltran***issionequipmentandsoon.Thetoothprofileoftheinvolutesplineisinvolute,andthepressureangleofthedividingcircleis30and45degrees.Thetopofthetoothis0.5mand0.4mrespectively(Misthemodulus).机用虎钳的结构及原理。机用虎钳是机械加工中常用的装夹机构，其结构如图1所示。其主要工作原理：转动方头带动丝杠，在螺母（通过紧固螺钉固定在虎钳体上）的作用下，做螺旋运动的丝杠带动与之联接的活动座沿丝杠轴线方向来回移动。Thestructureandprincipleofmachinevise.Machineviseisacommonclampingmechani***inmechanicalprocessing.ItsstructureisshowninFigure1.Themainprinciple:rotationoftheleadscrewnutinthesquare,(fixedinthevisebodythroughafasteningscrew)undertheactionofmovingspirallydrivenscrewconnectedwiththemovableseattomovebackandforthalongthescrewaxis.)