GD&T中英文学习资料02
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半径和控制半径半径半径是从圆心到圆弧或圆的表面的一条直线。
半径的符号是R。
符号R使用时，就产生了由两条圆弧（最小半径和最大半径）定义的公差带。
零件表面必需位于公差带内。
控制半径控制半径是不准许平直和相反的半径。
控制半径的符号为CR。
当CR使用时，就产生了由两条圆弧（最小半径和最大半径）定义的公差带。
零件表面位于新月型的公差带内，并且不是平直和相反圆弧。
6Radius and Controlled RadiusRadiusA radius is a straight line extending from the center to the surface of an arc or a circle. The symbol for a radius is “R”. When the “R” symbol is used, it create a zone defined by two arcs(the minimum and maximum radii). Thepart surface must lie within this zone.Controlled RadiusA controlled radius is a radius with no flats of reversals allowed. The symbol for controlled radius is “CR”. When the “CR” symbol is used, it creates a tolerance zone defined by two arcs (the minimum and maximum radii). The part surface must be within the crescent-shaped tolerance zoneand be an arc without flats or reversals.6统计公差符号统计公差符号表示被应用的尺寸公差是由统计方法建立的.。
当这个符号用在图纸上时，零件形体用统计制程管制进行生产。
该符号用注记标在后面，如下图所示：形体定义为统计公差时，生产时用统计制程管制。
统计公差符号适用于尺寸公差或一个形位公差控制的公差值。
7Statistical Tolerancing SymbolThe statistical tolerancing symbol denotes that the dimension of tolerancing to which it is applied was established by statistical methods. When this symbol is used on a drawing, the part feature should be manufactured using statistical process controls. The symbol isaccompanied by a note as shown in the example below.FEATURES IDENTIFIED AS STATISTICALLY TOLERANCEDSHALL BE PRODUCED WITH STATISTICAL PROCESS CONTROLS.The statistical tolerance symbol may be applied to a dimensional tolerance or to the tolerance value of a geometric control.7形体控制框形体控制框包括：1.控制特性（几何特性）2.公差带尺寸3.公差带修正表示：⏹公差带形状().⏹直径() 符号表示圆柱公差带。
球径() 符号表示球形公差带⏹公差应用以下条件()4.选用参考基准和参考基准修正5.参考基准修正8Feature Control FrameThe feature control frame consists of:1.Type of control (geometric characteristic)2.Tolerance zone size.3.Tolerance zone modifiers denote:⏹The tolerance zone shape ().⏹The diameter() symbol denotes a cylindrical tolerance zone.The spherical diameter() symbol denotes a sphericaltolerance zone.⏹The conditions under which tolerance applies()4.Datum references if applicable and any datum reference modifiers.5.Datum references modifiers.8一般规则规则1：单独形体尺寸规则常常参考为包容原则和在MMC时的理想形状。
规则1 规定在仅指定尺寸公差的地方,尺寸界限也控制形体界限规则1 例子包容原则(单独形体尺寸原则)以上都是规则1的例子（或包容原则），详述见a，b，c三段a：形体上各表面，不得超出在最大实体下的边界。
该边界是图纸所要表达的实际几何形状。
如果形体已达到最大实体状态尺寸，那么形体形状就不准许有任何偏差。
9General RulesRule #1 Individual Feature of Size RuleOften referred to as the “envelope principle” or “perfect form at MMC”Rule #1 states where only a tolerance of size is specified, the limits of size also control the limits of form.Rule #1 ExampleThe Envelope PrincipleThe examples above are affected by Rule #1 (or the envelope principle) as described in paragraphs a, b,& c.a: The surface(s) of a feature shall not extend beyond a boundary (envelope) of perfect from at MMC. This boundary is the true geometric form represented by the drawing. No variation in form is permitted if the feature is produced at its MMC limit of size.9一般原则（续）包容原则（续）b：在特征实际尺寸偏离最大实体状态趋向最小实体状态的地方，准许特征在等于此偏离量的范围内变动。
(补偿公差??)C：对在最小实体状态时的理想边界没有要求。
因此，当达到尺寸的最小实体状态时，准许特征形状至最大实体状态下所准许的理想边界之间做变动。
规则1仅适应于尺寸，并不影响个特征间的位置，方向或相互关系。
因此，单个特征间的相互关系必须定义以避免图纸要求的不足；通常用几何公差来控制特征间的位置，方向和相互关系。
如何不考虑规则1通过控制形体轴（或面）的直线度，可以不考虑规则1。
见35页例子。
规则1的例外规则1有两个例外：1, 非刚性零件2，原料尺寸，比如薄片，管材等规则2 （所有适用的几何公差规则）独立原则应用时，对于公差状态，参考基准或两者都没有实体状态调整。
(独立原则不论特征尺寸在尺寸公差内如何变化，其几何公差要求不变（没有补偿）。
)10General Rules (Cont.)The Envelop Principle (Cont.)b. where the actual local size of a feature has departed from MMC toward LMC, a variation in form is allowed equal to the amount of such departure.C. there is no requirement for a boundary of perfect from at LMC. Thus, afeature produced at its LMC limit of size is permitted to vary from true form to the maximum variation allowed by the boundary of perfect form at MMCRule #1 only applies to the size. Rule #1 does not affect the location, orientation, or interrelationship between features of size. Therefore, the relationship between individual features must be defined to avoid incomplete drawing speciations; geometric tolerances are often used toControl the location, orientation, or interrelationship between features.How to Override Rule #1Rule #1 can be overridden by applying a straightness control to an axis (or plane) of a feature of size. An example is shown on page 35.Exception to Rule #1There are two exceptions to Rule #1:1.Non-rigid parts2.Stock sizes, such as sheets, tubing. etc.Rule #2 (All applicable geometric tolerances rule)RFS applies, to the tolerance condition, datum references, datum references, or both, where no material condition modifier is specified.10一般原则（续）螺纹螺纹上规定的方向，位置的公差及参考基准，都是应用在螺纹节圆轴线上的。
