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机械类相关英语文章精选

学习啦【英语散文】 编辑:韦彦 发布时间:2016-09-14

  在发展传统机械工程技术的同时,在机械工程技术中还必须融入环境技术,走可持续发展的战略。下面是学习啦小编带来的机械类相关英语文章,欢迎阅读!

  机械类相关英语文章精选

  Dimension and Tolerance

  尺寸和公差

  In dimensioning a drawing, the numbers placed in the dimension lines represent dimensionthat are only approximate and do not represent any degree of accuracy unless so stated bythe designer.

  在图纸标注尺寸时,除非设计者有意标明,注在尺寸线上的数字代表的尺寸仅仅是近似的,并不代表任何精度等级。

  To specify a degree of accuracy, it is necessary to add tolerance figures to the dimension.Tolerance is the amount of variation permitted in the part or the total variation allowed in agiven dimension.

  为了详细标明精度等级,有必要在尺寸上增加公差数字。公差是零件允许的变动量或给定尺寸允许的总变动。

  A shaft might have a nominal size of 2.5in.(63.5mm), but for practical reasons this figurecould not be maintained in manufacturing without great cost. Hence, a certain tolerance wouldbe added and, if a variation of±0.003in.(±0.08mm) could be permitted, the dimension wouldbe stated 2.500±0.003(63.5±0.08mm).

  一根轴可能的名义尺寸为2.5in.(63.5mm),但由于实际原因不用大成本是不能在制造中保持这个数字的,因此要增加确定的公差。如果允许有±0.003in.(±0.08mm)的变化,则此尺寸可表达为2.500±0.003(63.5±0.08mm)。

  Dimensions given close tolerances mean that the part must fit properly with some other part.Both must be given tolerances in keeping with the allowance desired, the manufacturingprocesses available, and the minimum cost of production and assembly that will maximizeprofit.

  具有紧密公差的尺寸表示该零件必须恰当地与某些其它零件配合。所采用的制造工艺和使利润最大化的最小生产及装配成本都要求给定公差以保持所需允差。

  Generally speaking, the cost of a part goes up as the tolerance is decreased. If a part hasseveral or more surfaces to be machined, the cost can be excessive when little deviation isallowed from the nominal size.

  一般而言,零件的成本随着公差的减小而上升。如果一个零件有若干或较多表面要机加工且几乎不允许偏离名义尺寸,则成本会超过正常合理的界限。

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  允差

  Allowance, which is sometimes confused with tolerance, has an altogether different meaning.It is the minimum clearance space intended between mating parts and represents the conditionof tightest permissible fit.

  允差.有时会跟公差混淆,但其具有完全不同的含义。它是配合零件之间最小的预期间隙空间,代表着允许的最紧配合条件。

  If a shaft, size 1.498-0.003, is to fit a hole of size 1.500+0.003, the minimum size hole is1.500 and the maximum size shaft is 1.498. Thus the allowance is 0.002 and the maximumclearance is 0.008 as based on the minimum shaft size and maximum hole dimension.

  如果一根尺寸为1.498-0.003的轴与尺寸为1.500+0.003的孔配合,孔的最小尺寸为1.500而轴的最大尺寸为1.498。这样允差就是0.002,而由最小轴尺寸和最大孔尺寸形成的最大间隙为0.008。

  Tolerances may be either unilateral or bilateral. Unilateral tolerance means that any variation ismade in only one direction from the nominal or basic dimension. Referring to the previousexample, the hole is dimensioned 1.500+0.003, which represents a unilateral tolerance.

  公差可以是单向的也可以是双向的。单向公差意味着任何变动都是只从名义或基本尺寸出发向一个方向变动的。引用前例,孔的尺寸标注为1.500+0.003,它表示了一个单向公差。

  If the dimensions were given as 1.500±0.003, the tolerance would be bilateral; that is, it wouldvary both over and under the nominal dimension. The unilateral system permits changing thetolerance while still retaining the same allowance or type of fit.

  如果尺寸标为1.500±0.003,就是双向公差即它可以在名义尺寸之上或之下变化。单向体系允许在依然保留相同允差或配合类型的情况下改变公差。

  With the bilateral system, this is not possible without also changing the nominal sizedimension of one or both of the two mating parts. In mass production, where mating partsmust be interchangeable, unilateral tolerances are customary. To have an interference orforce fit between mating parts, the tolerances must be such as to create a zero or negativeallowance.

  而双向体系在不同时改变一个或两个配合零件名义尺寸的情况下,这是不可能做到的。大规模生产中配合零件必须能互换,单向公差是经常遇到的。为了使配合零件之间具有过盈或强制配合,公差必须产生零或负允差。

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  Tolerances, Limits and Fits

  公差、极限和配合

  The drawing must be a true and complete statement of the designer's requirementsexpressed in such a way that the part is convenient to manufacture.

  图纸必须按方便制造零件的方式将设计者的要求真实和完整地表达出来。

  Every dimension necessary to define the product must be stated once only and not repeatedin different views. Dimensions relating to one particular feature, such as the position and sizeof a hole, should, where possible, appear on the same view.

  对每一描述产品所需的尺寸都只须标注一次而不必在不同的视图中重复。有关同一特性的尺寸 诸如孔的位置和大小 如果可能应出现在同一视图上

  There should be no more dimensions than are absolutely necessary, and no feature should belocated by more than one dimension in any direction.

  除绝对需要的尺寸外 不应该有更多的尺寸而在任意方向上 只能在一个尺寸上标注特性要求。

  It may be necessary occasionally to give an auxiliary dimension for reference, possibly forinspection. When this is so, the dimension should be enclosed in a bracket and marked forreference. Such dimensions are not governed by general tolerances.

  偶尔也可能为了检查而必须给出供参考的辅助尺寸。在这种情况下 尺寸应该用括号括起来以便参考。这样的尺寸不受通用公差控制。

  Dimensions that affect the function of the part should always be specified and not left as thesum or difference of other dimensions.

  影响零件功能的尺寸总是应该标注的而不要留作其它尺寸的和或差。

  If this is not done, the total permissible variation on that dimension will form the sum ordifference of the other dimensions and their tolerances, and this will result in these toleranceshaving to be made unnecessarily tight. The overall dimension should always appear.

  如果不是这样 那尺寸允许的总的变化将形成其它尺寸及它们的公差的和或差 这会导致这些公差不得不定得过紧。总尺寸一般应该标注。

  All dimensions must be governed by the general tolerance on the drawing unless otherwisestated. Usually, such a tolerance will be governed by the magnitude of the dimension.Specific tolerances must always be stated on dimensions affecting function orinterchangeability.

  除非另行说明 所有尺寸都必须受图上的通用公差控制。一般这样的公差受到尺寸量值的控制。在影响功能或互换性的尺寸上必须标注专门的公差。

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