Reading Special English
Engineering Collage,
Heilongjiang August First Land Reclamation University
Hu jun
E-mail:hjgj7275@126.com
Reading skills of scientific and technical English
? Reading for Main Idea (获取主题思想 )
? 我们可以把获取主题思想的阅读技巧分四步
? 1.辨认主题名词 identify subject word
? 2.找出主题词 find subject word
? 3.获取主题思想 gain main idea
? 4.避免不相关的内容 avoid disrelated content
（一）常见的前缀
1.表示否定意义的前缀
1)纯否定前缀
? a-,an- asymmetry（不对称） anhydrous（无水的）
? dis- dishonest,dislike
? in-,ig-,il-,im-,ir- incapable,inability,ignoble,
impossible,immoral,illegal,irregular
? ne-,n-,none,neither,never
? non-,nonsense（胡说、废话）
? neg-,neglect（忽视，疏忽）
? un- unable,unemployment
? 2)表示错误的意义
? male-,mal-,malfunction,maladjustment(失调 )
? mis-,mistake,mislead（误导）
? pseudo-,pseudonym(假名 ),pseudoscience(伪科学 )
3)表示反动作的意思
de-,defend,demodulation(解调 )
dis-,disarm,disconnect
un-,unload,uncover
? 4)表示相反，相互对立意思
? anti-,ant- antiknock( 防震 ),antiforeign,(排外的 )
? contra-,contre-,contro-,contradiction,controflow(逆流 )
? counter-,counterreaction（逆反应）,counterbalance（平
衡力）
? ob-,oc-,of-,op-,object（反对，拒绝）,oppose,occupy
? with-,withdraw（收回，撤回）,withstand(抵挡 )
2,表示空间位置，方向关系的前缀
? 1)a- 表示“在 …… 之上”，“向 ……”
aboard,aside,
? 2)by- 表示“附近，邻近，边侧”
bypath（小路）,bypass(弯路 )
? 3)circum-,circu-,表示“周围，环绕，回转”
circumstance（环境详细，环绕） circuit（电路，巡回）
? 4)de-,表示“在下，向下”
descend（下降）,degrade（降级）
? 5)en-,表示“在内，进入”
encage（关在笼中，禁闭）,enbed(上床 )
2,表示空间位置，方向关系的前缀
? 6)ex-,ec-,es-,表示“外部，外”
exit,eclipse,expand,export
? 7)extra-,表示“额外”
extraction （提取）
? 8)fore- 表示“在前面”
forehead,foreground
? 9)in-,il-,im-,ir-,表示“向内，在内，背于”
inland,invade,inside,import
? 10)inter-,intel-,表示“在 …… 间，相互”
international,interaction,internet
?11)intro-,表示“向内，在内，内侧”
introduce,introduce
?12)medi-,med-,mid-,表示“中，中间”
mediterranean,midposition
?13)out-,表示“在上面，在外部，在外”
outline,outside,outward
?14)over-,表示“在上面，在外部，向上”
overlook,overhead,overboard
?15)post-,表示 "向后，在后边，次”
postscript(附言，后记 )，
?16)pre-,表示 "在前”在前面”
prefix,preface,preposition
? 17)pro-,表示“在前，向前”
progress,proceed,
? 18)sub-,suc-,suf-,sug-,sum-,sup-,sur-,sus-,表示“在
下面，下”
subway,submarine,suffix,suppress,supplement
? 19)super-,sur-,表示“在 ….,之上”
superficial,surface,superstructure
? 20)trans-,表示“移上，转上，在那一边”
translate,transform,transoceanic
? 21)under-,表示“在 ….,下面，下的”
underline,underground,underwater
? 22)up-,表示“向上，向上面，在上”
upward,uphold,uphill(上坡 )
Unit 3
Engineering Drawings and Dimensions
? Engineering Drawings is your language.
? Why？
? You will be an Engineer！
What is Engineering Drawings？
Engineering drawing,A graphical language
used by engineers and other technical persons
associated with the engineering profession,The
purpose of engineering drawing is to convey
graphically the ideas and information necessary
for he construction or analysis of machines,
structures,or systems.
工程图：工程师及工程行业的技术人员所用的图形语
言。工程图的目的是用图形来转 达机器、结构或系统
的建造及分析所必需的概念和信息。
? Dimensions,Length,time,mass or combinations of
these quantities serving as an indication of a physical
quantity.
? 尺寸（量纲）：长度、时间、质量或三个量的结合，
用来表示一个物理量。
What is Dimensions？
Dimensions:尺寸标注
Engineering Drawings
? The result of a designer's efforts must be translated
into a set of instructions to the shop in order that the
part or parts can be fabricated and assembled．
fabricate
vt,制作, 构成；捏造, 伪造；装配
assemble vt.装配，组合
为了加工零件和组装零部件, 设计者设计的零
件必须被表达成可以让车间看懂的形式 。
? Thus,a set of engineering drawings' are
prepared showing the sizes,shapes,and
dimensions to which parts are to be made．
于是, 一套表明零件尺寸, 形状的加工图就产生了 。
? Unfortunately,many designers consider this phase
of engineering design to be trivial．
? Realistically speaking,however,it may be of
greater importance than the design solution itself．,
trivial:无足轻重的,价值不高的
Realistically:实际上
? 不幸的是，一些设计者认为工程设计的表达形
式是无足轻重的。
? 事实上，它可能比设计本身更重要。
? Consider,for the moment,what an engineering drawing
represents．
? It is a detailed set of instructions（ that is,orders） that
tells the machinist,molder,die caster,and so on，
to“make this part in accordance with the information
indicated and to the dimensions specified——any
unauthorized deviations or errors made in fabrication are
your responsibility．,
此时，想一想一张工程图表达了什么？它（工程图）是
一组详细的加工说明，根据它所表达的信息和详细的尺
寸标注，机械工、制模工、压铸工等可以加工这个的零
件，制造中出现的任何无根据的的偏差与错误，都是你
们的责任。
? This statement is,of course,exaggerated．
? Nevertheless,it is meant to convey the importance of
the complete and proper dimensioning of engineering
drawings-the responsibility for which rests with the
designer．
? Careless dimensioning can lead to increase production
costs and/or outright waste as a result of errors．
当然, 这也许有些夸张 。
但是, 它说明了工程图完美尺寸标注的重要性, 这
有待于设计师去完成 。
粗糙的尺寸标注可能会导致成本的增加, （ 或者 ）
由于错误导致材料的全部报废 。
夸张的
Due to the fact that no part can be manufactured to an
“exact” dimension,shop drawings are prepared in
accordance with a system of tolerances and
allowances．
Many companies,by reason of their shop facilities and
experience,rely on their own standards for
dimensioning drawings．
由于没有零件能被加工成设计时的理想尺寸，所以
设计好的加工图样应注明尺寸公差和加工余量。
有些厂家根据自己的生产设施和生产经验制定自己
的标注标准。
Allowance,An intentional difference in sizes of two mating parts。
余量：两个配件之间的预留的尺寸差。
tolerances,公差
We all base our discussion on the widely use
ANSI(American National Standards Institute)“Preferred
limits and fits for cylindrical parts,’（ Standard B4.1—
1967） published by the American Society of Mechanical
Engineers．
(而 ） 我们是基于广泛应用的 ANSI（ 美国国家标准局 ）
,圆柱形零件的公差与配合, 标准 （ 标准 B4.1-
1967）, 该标准是由美国机械工程协会出版的 。
When closer fits than those indicated by the tables are
required,the designer may reduce the tolerance of the
mating parts．
However,taking such action could result in increased
fabrication costs,In order to avoid any increased cost，
the designer would of necessity have to resort to
selective assembly．
当实际需要的配合比计划的更紧时，设计者可以减
少配合零件的尺寸公差，然而这样做会造成加工成
本的增加。为了避免增加成本，设计者有必要采取
选择配合公差。
The idea behind selective assembly is to specify large
tolerances for the mating parts,and then grade them by
gaging in small,medium,and large fits．
Thus,a small shaft mating with a small hole,a medium
shaft mating with a medium hole,and a large shaft
mating with a large hole will all possess the same fit
allowance．
制定好加工零件的公差，然后按标准分成小、中、大三种尺
寸段的配合，这样，不同尺寸段的轴上加工不同的孔，将采
用一种配合公差。
然后，将用量规然后按标准分成小、中、大三种尺寸段的配合，这样，
小尺的轴与小尺寸的孔配合、中级尺寸的轴与中级尺寸的孔配合，大尺
寸的轴与大尺寸的孔要配合，这将使（各种配合）都能获得相同的配合
间隙，将采用一种配合公差，
Gage n.象徵挑战的物品 (如手套 ),挑战,抵押品,担
保品
vt.以,..为担保,以,..为赌注
n.(=gauge) 标准度量,计量器
vt.(=gauge) 精确计量,估计
? One should,nevertheless,keep in mind that the
additional cost of purchasing the gages as well as,the
labor required for gaging may offset any saving
achieved by selective assembly．
但是设计者应清楚, 购买工作人员需要的标准件的开支可
以通过选择配合公差得到补偿 。
Dimensions
? Definitions of Dimensioning Terms
? （ 1）尺寸标注术语定义
? For a thorough understanding of fits and
tolerances,the following term must be clearly
understood.
? Allowance,The allowance is the tightest fit
between mating parts．
? For interference fits,the allowance is negative.
为了透彻了解公差与配合。必须准确理解下
列术语。
间隙：是指两配合件之间紧配合的尺寸差，
对过盈配合来讲，间隙是负的。
? Nominal Size The nominal size is the designation used for
the purpose of general identification,For example,a
21/2-in,diameter nominal pipe is actually 2.875 in,in
diameter．
? Tolerance A tolerance is the total permissible variation in
the size of a part．
? Basic Size The basic size is that size from which limits of
size are derived by the application of allowances and
tolerances．
公称尺寸,设计给定的尺寸。如公称直径为 2 1/2英寸的管子，
实际直径为 2.857英寸。
公差,允许的零件尺寸变动量。
基本尺寸,基本尺寸与极限偏差构成的极限尺寸。
permissible variation
容许偏差
total v riation
全变差,总变差
? Unilateral Tolerancing
? Unilateral tolerancing is a system of dimensioning where
the tolerance(that is,variation) is shown in only tine
direction from the nominal size,Unilateral tolerancing
allows the changing of tolerance on a hole or shaft
without seriously affecting the fit．
? Bilateral Tolerancing
? Bilateral tolerancing is a system of dimensioning where
the tolerance(that is,variation)is split and is shown on
either side of the nominal size．
单向公差,单向公差是一个尺寸体系，仅沿公称尺寸一个方向有
公差。在不影响配合时，单向公差允许孔或轴的公差有变化。
双向公差,双向公差是沿公称尺寸的两个方向都有尺寸变动的尺
寸体系。
Limit Dimensioning
Limit dimensioning is a system of dimensioning
where only the maximum and minimum
dimensions are shown,
Thus,the tolerance is the difference between
these two dimensions,
极限尺寸：极限尺寸是只给出最大尺寸和最
小尺寸的尺寸体系。
公差是这两个极限尺寸差值（绝对值）。
? Two methods of designating limit dimensions are
considered as standard．
? One method is the maximum material method in which
the large dimensions is placed above the smaller
dimension for male parts,and the reverse is true for
female parts6．
? This method is well suited for small lot quantities because
it is likely that the machinist himself may check the
dimensions of the parts．
? In so doing,he will be verifying initially the larger
dimension of the male part and the smaller dimension of
the female part．
两种设计极限尺寸的方法已被作为标准。一种方法是最大实体
原则，对轴来讲是指最大极限尺寸，对孔则指最小极限尺寸。
这种方法适用小批量生产，便于机械师亲自检查零件的尺寸。
这样做，可以改变轴和孔的实体尺寸。
? The other method is the maximum number
method and is preferred by production and
quality control departments．
?In this method of designating a dimension，
the larger number is always placed above the
smaller number,regardless of whether the
part is male or female．
另一种方法是最大尺寸原则，常被生产和质量控制部门所采用。
这种方法设计尺寸，不管是孔还是轴，其实际尺寸不允许超过
最小实体尺寸。
? Clearance Fit, A clearance fit is one having limits of
size so prescribed that a clearance always results when
mating parts are assembled．
? Interference Fit, An interference fit is one having
limits of size so prescribed that a clearance doesn't
always results when mating parts are assembled．
间隙配合：间隙配合是一种有规定的极限尺寸的配合，
当配合件装配时间隙总是存在的。
过盈配合：过盈配合是一种有规定的极限尺寸的配合，
当配合件装配时，间隙总是不存在的。
空隙，间隙：
The Phases of Design
Transition Fit
A transition fit is one having limits of size so
prescribed that either a clearance or an interference
may result when mating parts are assembled．
过渡配合：过渡配合是既有间隙又有过盈的配合。
检索词
? Basic Hole System．
? A basic hole system is a system of fits in which the
design size of the hole is the basic size from which the
allowance is subtracted to obtain the diameter of the
shaft．
? The basic hole is the preferred system because standard
drills,reamers,and so on can be used and shafts can
then easily be machined to fit．
基孔制：基孔制是以设计孔的尺寸为基本尺寸，其
尺寸减去余量便得到轴的直径的一种配合制度。
基孔制是优先选用的配合制度，因为可以使用标准
的钻头、铰刀等 （来加工孔）,而轴可以很容易地
加工成与之配合的尺寸。
? Basic Shaft System．
? A basic shaft system is a system of fits in which the design
size of the shaft is the basic size from which the allowance
is added to obtain the diameter of the hole．
? （ Normally most design offices adhere to the basic hole
system because of standard tooling and the fact that
tolerance tables are based on the basic hole system．
? However the use of the basic shaft system has the great
advantage in that is possible to use a standard size shaft．）
基轴制：基轴制是以设计轴的尺寸为基本尺寸，孔的
尺寸加上余量得到孔的尺寸的一种配合制度。（一般
地，许多设计部门采用基孔制，因为可以使用标准工
具和基于基孔制的公差带这一事实。然而采用基轴制
也有很大优越性，它使采用标准尺寸轴成为可能。）
Classes of Fits
? As indicated,the ANSI Standard B4.1—1967，
,Preferred limits and fits for cylindrical parts，” is
widely used for establishing tolerances for various classes
of fits．
? The letter symbols appearing in this standard represent the
following classes,RC（ running or sliding fit),LC
（ locational clearance fit）,LT（ transition fit）,LN
（ locational interference fit）,and FN（ force or shrink
fit）
如第一部分所述,ANSI标准 B4.1-1967，即“圆柱形零件公差与
配合”被广泛应用于各种等级的公差配合。
在这个标准中划分了以下几种配合等级,RC（松动配合）,LC
（定位间隙配合）,LT（过渡配合）,LN（定位过盈配合）、
FN（压力紧配合）。
? 松动配合
? 在尺寸范围内，配合面间有润滑间隙。对于前两等级，这个
间隙主要用于滑动配合，在有相对运动的情况下，要为确定
定位基准，要求间隙随直径变化较小。有九种类型的 RC配
合描述如下：
? Running or Sliding Fits,Running or sliding fits
provide a similar running performance with suitable
lubrication allowance throughout the range of sizes．
? The clearance for the first two classes,used chiefly as
slide fits,increases more slowly with diameter than the
other classes,in order that accurate location is
maintained even at the expense of free relative motion．
? There are nine types of RC fits which are defined as
follows：
? RC1,Close sliding fits are intended to locate
accurately parts that must assemble without perceptible
play．
? RC2,Sliding fits are intended for accurate location，
but with greater maximum clearance than class
RCl, Parts made to this fit move and turn easily but are
not intended to run freely and,in the larger sizes,may
seize with small temperature changes．
RC1（紧滑动配合）：适用精密定位配合，这些零
件必须无明显间隙装配。
RC2（滑动配合）：适用精密定位配合，但最大间
隙较 RC1级大。这种配合的零件可以容易转动，但
不能随意转动，适应较小的温度变化范围。
? RC3,Precision running fits are the closest fits that can
be expected to run freely and are intended for precision
work at slow speeds and light journal pressures．
? However,they are not suitable where appreciable
temperature changes are likely to be encountered．
? RC4,Close running fits are intended chiefly for running
fits on accurate machinery with moderate surface speeds
and journal pressures where accurate location and
minimum play is desired．
RC3（精密动配合）：是最紧的配合在低速和轻载条件
下，可以自由运动，适合精密工作。然而，这种配合不
适于温度变化的场合。
RC4（紧动配合）：主要适用表面有匀速运动和有轴向
载荷的精密配合件，配合处要求定位基准和最小间隙。
? RC5和 RC6（中等动配合）：主要用于具有较大的
速度或较大的轴向载荷或者两者都有的零件表面。
? RC7（一般动配合）：适用表面精度不高或温度变
化较大，或两者都有的工作情况。
? RC5 and RC6, Medium running fits are intended for
higher running speeds or heavy journal pressures or both．
? RC7,Free running fits are intended for use where accuracy
is not essential or where large temperature variations are
likely to be encountered,or under both of these conditions
．
? RC8 and RC9, Loose running fits are intended
for use where materials such as cold-rolled
shafting and tubing made to commercial tolerances
are involved．
? RC8和 RC9（松动配合）：适合材料如冷轧的轴
和管子要求普通公差配合。
? Location Clearance Fits．
? Location clearance fits are intended to determine
only the location of the mating parts,they may
provide rigid or accurate location,as with
interference fits,or some freedom of location，
as with clearance fits,Accordingly,they are
divided into three groups,clearance fits，
transition fits,and interference fits．
定位动配合
主要用于零件定位，并提供准确严格的位置公差，象
静配合公差，或普通的位置公差如间隙配合公差。
定位动配合可分成三组：间隙、过盈、过渡。
These fits are more fully described as follows：
? LC,Locational clearance fits are intended for
parts that are normally stationary but can be
freely assembled or disassembled．
? They run from snug fits for parts requiring
accuracy of location,through the medium
clearance fits for parts such as spigots,to the
looser fastener fits where freedom of assembly is
of prime importance．
LC（定位间隙配合）：一般适用于无相对运动的场
合，但可轻松安装或拆卸零件。螺栓连接需用一般
定位间隙配合。定位间隙配合从连接件要求精确定
位到松紧配合都允许的装配起到很重要的作用。
snug a,温暖的，舒适的；整齐的；隐
藏的；小巧的；坚固的；合身的
vt,使舒适；使坚固
vi,偎依；舒适地蜷伏
? LT,Transition fits are a compromise
between clearance and interference fits for
application where accuracy of location is
important,but either a small amount of
clearance or interference is permissible．
? LT（过渡配合）：即有间隙又有过盈的
配合，适用精密定位，但允许有较小的
间隙或过盈。
? LN．
? Locational interference fits are used where
accuracy of location is of prime importance and
for parts requiring an alignment with special
requirements for bore pressure．
? Such fits are not intended for parts designed to
transmit frictional loads from one part to another
by virtue of the tightness of fit,as these
conditions are covered by force fits．
? LN（定位静配合）：
? 用于定位精度特别重要，能以最好的定位精度
达到部件的对中的性能要求，不依靠配合的紧
固性传递磨擦负荷，这些情况通过压配合实现
? Force Fits,压力配合
? Force fits or shrink fits constitute a special type of
interference fit,normally characterized by maintenance
of constant bore pressures through the range of sizes．
? The interference,therefore,varies almost directly with
diameter,and the difference between its minimum and
maximum values is small to maintain the resulting
pressures within reasonable limits．
? 压力配合或热压配合是一种特殊的过盈配合。一般
通过恒压进行配合。
? 过盈量随直径的改变而改变，在允许条件下，公差
值足够小。
? FN1, Light drive fits are those requiring
light assembly pressures and produce more
or less permanent assemblies,They are
suitable for thin sections or long fits or in
cast iron external members．
? FN1（轻压力配合）：需要较小的装配压
力，当需要时易于拆卸，适合于薄件或
长配合件或铸铁件。
? FN2, Medium drive fits are suitable for
ordinary steel parts or for shrink fits on light
sections,They are about the tightest that
can be used with high grade,cast iron
external members,
? FN2（中压力配合）：适用普通钢零件或
轻度热压配合。这种配合是最紧的，外
部零件可以是高等级铸铁件。
? FN3, Heavy drive fits are suitable for
heavier steel parts or for shrink fits in
medium sections．
? FN3（重压力配合）：适用于大型钢零件，
或者中等热压配合件。
? FN4 And FN5,Force fits are suitable for
parts that can be highly stressed or for
shrink fits where the heavy pressing forces
are impractical．
? FN4和 FN5（压力配合）：适合于能承受
较大的压力的零件或不适于用重压力的
热压紧配合处。
Thanks!
Engineering Collage,
Heilongjiang August First Land Reclamation University
Hu jun
E-mail:hjgj7275@126.com
Reading skills of scientific and technical English
? Reading for Main Idea (获取主题思想 )
? 我们可以把获取主题思想的阅读技巧分四步
? 1.辨认主题名词 identify subject word
? 2.找出主题词 find subject word
? 3.获取主题思想 gain main idea
? 4.避免不相关的内容 avoid disrelated content
（一）常见的前缀
1.表示否定意义的前缀
1)纯否定前缀
? a-,an- asymmetry（不对称） anhydrous（无水的）
? dis- dishonest,dislike
? in-,ig-,il-,im-,ir- incapable,inability,ignoble,
impossible,immoral,illegal,irregular
? ne-,n-,none,neither,never
? non-,nonsense（胡说、废话）
? neg-,neglect（忽视，疏忽）
? un- unable,unemployment
? 2)表示错误的意义
? male-,mal-,malfunction,maladjustment(失调 )
? mis-,mistake,mislead（误导）
? pseudo-,pseudonym(假名 ),pseudoscience(伪科学 )
3)表示反动作的意思
de-,defend,demodulation(解调 )
dis-,disarm,disconnect
un-,unload,uncover
? 4)表示相反，相互对立意思
? anti-,ant- antiknock( 防震 ),antiforeign,(排外的 )
? contra-,contre-,contro-,contradiction,controflow(逆流 )
? counter-,counterreaction（逆反应）,counterbalance（平
衡力）
? ob-,oc-,of-,op-,object（反对，拒绝）,oppose,occupy
? with-,withdraw（收回，撤回）,withstand(抵挡 )
2,表示空间位置，方向关系的前缀
? 1)a- 表示“在 …… 之上”，“向 ……”
aboard,aside,
? 2)by- 表示“附近，邻近，边侧”
bypath（小路）,bypass(弯路 )
? 3)circum-,circu-,表示“周围，环绕，回转”
circumstance（环境详细，环绕） circuit（电路，巡回）
? 4)de-,表示“在下，向下”
descend（下降）,degrade（降级）
? 5)en-,表示“在内，进入”
encage（关在笼中，禁闭）,enbed(上床 )
2,表示空间位置，方向关系的前缀
? 6)ex-,ec-,es-,表示“外部，外”
exit,eclipse,expand,export
? 7)extra-,表示“额外”
extraction （提取）
? 8)fore- 表示“在前面”
forehead,foreground
? 9)in-,il-,im-,ir-,表示“向内，在内，背于”
inland,invade,inside,import
? 10)inter-,intel-,表示“在 …… 间，相互”
international,interaction,internet
?11)intro-,表示“向内，在内，内侧”
introduce,introduce
?12)medi-,med-,mid-,表示“中，中间”
mediterranean,midposition
?13)out-,表示“在上面，在外部，在外”
outline,outside,outward
?14)over-,表示“在上面，在外部，向上”
overlook,overhead,overboard
?15)post-,表示 "向后，在后边，次”
postscript(附言，后记 )，
?16)pre-,表示 "在前”在前面”
prefix,preface,preposition
? 17)pro-,表示“在前，向前”
progress,proceed,
? 18)sub-,suc-,suf-,sug-,sum-,sup-,sur-,sus-,表示“在
下面，下”
subway,submarine,suffix,suppress,supplement
? 19)super-,sur-,表示“在 ….,之上”
superficial,surface,superstructure
? 20)trans-,表示“移上，转上，在那一边”
translate,transform,transoceanic
? 21)under-,表示“在 ….,下面，下的”
underline,underground,underwater
? 22)up-,表示“向上，向上面，在上”
upward,uphold,uphill(上坡 )
Unit 3
Engineering Drawings and Dimensions
? Engineering Drawings is your language.
? Why？
? You will be an Engineer！
What is Engineering Drawings？
Engineering drawing,A graphical language
used by engineers and other technical persons
associated with the engineering profession,The
purpose of engineering drawing is to convey
graphically the ideas and information necessary
for he construction or analysis of machines,
structures,or systems.
工程图：工程师及工程行业的技术人员所用的图形语
言。工程图的目的是用图形来转 达机器、结构或系统
的建造及分析所必需的概念和信息。
? Dimensions,Length,time,mass or combinations of
these quantities serving as an indication of a physical
quantity.
? 尺寸（量纲）：长度、时间、质量或三个量的结合，
用来表示一个物理量。
What is Dimensions？
Dimensions:尺寸标注
Engineering Drawings
? The result of a designer's efforts must be translated
into a set of instructions to the shop in order that the
part or parts can be fabricated and assembled．
fabricate
vt,制作, 构成；捏造, 伪造；装配
assemble vt.装配，组合
为了加工零件和组装零部件, 设计者设计的零
件必须被表达成可以让车间看懂的形式 。
? Thus,a set of engineering drawings' are
prepared showing the sizes,shapes,and
dimensions to which parts are to be made．
于是, 一套表明零件尺寸, 形状的加工图就产生了 。
? Unfortunately,many designers consider this phase
of engineering design to be trivial．
? Realistically speaking,however,it may be of
greater importance than the design solution itself．,
trivial:无足轻重的,价值不高的
Realistically:实际上
? 不幸的是，一些设计者认为工程设计的表达形
式是无足轻重的。
? 事实上，它可能比设计本身更重要。
? Consider,for the moment,what an engineering drawing
represents．
? It is a detailed set of instructions（ that is,orders） that
tells the machinist,molder,die caster,and so on，
to“make this part in accordance with the information
indicated and to the dimensions specified——any
unauthorized deviations or errors made in fabrication are
your responsibility．,
此时，想一想一张工程图表达了什么？它（工程图）是
一组详细的加工说明，根据它所表达的信息和详细的尺
寸标注，机械工、制模工、压铸工等可以加工这个的零
件，制造中出现的任何无根据的的偏差与错误，都是你
们的责任。
? This statement is,of course,exaggerated．
? Nevertheless,it is meant to convey the importance of
the complete and proper dimensioning of engineering
drawings-the responsibility for which rests with the
designer．
? Careless dimensioning can lead to increase production
costs and/or outright waste as a result of errors．
当然, 这也许有些夸张 。
但是, 它说明了工程图完美尺寸标注的重要性, 这
有待于设计师去完成 。
粗糙的尺寸标注可能会导致成本的增加, （ 或者 ）
由于错误导致材料的全部报废 。
夸张的
Due to the fact that no part can be manufactured to an
“exact” dimension,shop drawings are prepared in
accordance with a system of tolerances and
allowances．
Many companies,by reason of their shop facilities and
experience,rely on their own standards for
dimensioning drawings．
由于没有零件能被加工成设计时的理想尺寸，所以
设计好的加工图样应注明尺寸公差和加工余量。
有些厂家根据自己的生产设施和生产经验制定自己
的标注标准。
Allowance,An intentional difference in sizes of two mating parts。
余量：两个配件之间的预留的尺寸差。
tolerances,公差
We all base our discussion on the widely use
ANSI(American National Standards Institute)“Preferred
limits and fits for cylindrical parts,’（ Standard B4.1—
1967） published by the American Society of Mechanical
Engineers．
(而 ） 我们是基于广泛应用的 ANSI（ 美国国家标准局 ）
,圆柱形零件的公差与配合, 标准 （ 标准 B4.1-
1967）, 该标准是由美国机械工程协会出版的 。
When closer fits than those indicated by the tables are
required,the designer may reduce the tolerance of the
mating parts．
However,taking such action could result in increased
fabrication costs,In order to avoid any increased cost，
the designer would of necessity have to resort to
selective assembly．
当实际需要的配合比计划的更紧时，设计者可以减
少配合零件的尺寸公差，然而这样做会造成加工成
本的增加。为了避免增加成本，设计者有必要采取
选择配合公差。
The idea behind selective assembly is to specify large
tolerances for the mating parts,and then grade them by
gaging in small,medium,and large fits．
Thus,a small shaft mating with a small hole,a medium
shaft mating with a medium hole,and a large shaft
mating with a large hole will all possess the same fit
allowance．
制定好加工零件的公差，然后按标准分成小、中、大三种尺
寸段的配合，这样，不同尺寸段的轴上加工不同的孔，将采
用一种配合公差。
然后，将用量规然后按标准分成小、中、大三种尺寸段的配合，这样，
小尺的轴与小尺寸的孔配合、中级尺寸的轴与中级尺寸的孔配合，大尺
寸的轴与大尺寸的孔要配合，这将使（各种配合）都能获得相同的配合
间隙，将采用一种配合公差，
Gage n.象徵挑战的物品 (如手套 ),挑战,抵押品,担
保品
vt.以,..为担保,以,..为赌注
n.(=gauge) 标准度量,计量器
vt.(=gauge) 精确计量,估计
? One should,nevertheless,keep in mind that the
additional cost of purchasing the gages as well as,the
labor required for gaging may offset any saving
achieved by selective assembly．
但是设计者应清楚, 购买工作人员需要的标准件的开支可
以通过选择配合公差得到补偿 。
Dimensions
? Definitions of Dimensioning Terms
? （ 1）尺寸标注术语定义
? For a thorough understanding of fits and
tolerances,the following term must be clearly
understood.
? Allowance,The allowance is the tightest fit
between mating parts．
? For interference fits,the allowance is negative.
为了透彻了解公差与配合。必须准确理解下
列术语。
间隙：是指两配合件之间紧配合的尺寸差，
对过盈配合来讲，间隙是负的。
? Nominal Size The nominal size is the designation used for
the purpose of general identification,For example,a
21/2-in,diameter nominal pipe is actually 2.875 in,in
diameter．
? Tolerance A tolerance is the total permissible variation in
the size of a part．
? Basic Size The basic size is that size from which limits of
size are derived by the application of allowances and
tolerances．
公称尺寸,设计给定的尺寸。如公称直径为 2 1/2英寸的管子，
实际直径为 2.857英寸。
公差,允许的零件尺寸变动量。
基本尺寸,基本尺寸与极限偏差构成的极限尺寸。
permissible variation
容许偏差
total v riation
全变差,总变差
? Unilateral Tolerancing
? Unilateral tolerancing is a system of dimensioning where
the tolerance(that is,variation) is shown in only tine
direction from the nominal size,Unilateral tolerancing
allows the changing of tolerance on a hole or shaft
without seriously affecting the fit．
? Bilateral Tolerancing
? Bilateral tolerancing is a system of dimensioning where
the tolerance(that is,variation)is split and is shown on
either side of the nominal size．
单向公差,单向公差是一个尺寸体系，仅沿公称尺寸一个方向有
公差。在不影响配合时，单向公差允许孔或轴的公差有变化。
双向公差,双向公差是沿公称尺寸的两个方向都有尺寸变动的尺
寸体系。
Limit Dimensioning
Limit dimensioning is a system of dimensioning
where only the maximum and minimum
dimensions are shown,
Thus,the tolerance is the difference between
these two dimensions,
极限尺寸：极限尺寸是只给出最大尺寸和最
小尺寸的尺寸体系。
公差是这两个极限尺寸差值（绝对值）。
? Two methods of designating limit dimensions are
considered as standard．
? One method is the maximum material method in which
the large dimensions is placed above the smaller
dimension for male parts,and the reverse is true for
female parts6．
? This method is well suited for small lot quantities because
it is likely that the machinist himself may check the
dimensions of the parts．
? In so doing,he will be verifying initially the larger
dimension of the male part and the smaller dimension of
the female part．
两种设计极限尺寸的方法已被作为标准。一种方法是最大实体
原则，对轴来讲是指最大极限尺寸，对孔则指最小极限尺寸。
这种方法适用小批量生产，便于机械师亲自检查零件的尺寸。
这样做，可以改变轴和孔的实体尺寸。
? The other method is the maximum number
method and is preferred by production and
quality control departments．
?In this method of designating a dimension，
the larger number is always placed above the
smaller number,regardless of whether the
part is male or female．
另一种方法是最大尺寸原则，常被生产和质量控制部门所采用。
这种方法设计尺寸，不管是孔还是轴，其实际尺寸不允许超过
最小实体尺寸。
? Clearance Fit, A clearance fit is one having limits of
size so prescribed that a clearance always results when
mating parts are assembled．
? Interference Fit, An interference fit is one having
limits of size so prescribed that a clearance doesn't
always results when mating parts are assembled．
间隙配合：间隙配合是一种有规定的极限尺寸的配合，
当配合件装配时间隙总是存在的。
过盈配合：过盈配合是一种有规定的极限尺寸的配合，
当配合件装配时，间隙总是不存在的。
空隙，间隙：
The Phases of Design
Transition Fit
A transition fit is one having limits of size so
prescribed that either a clearance or an interference
may result when mating parts are assembled．
过渡配合：过渡配合是既有间隙又有过盈的配合。
检索词
? Basic Hole System．
? A basic hole system is a system of fits in which the
design size of the hole is the basic size from which the
allowance is subtracted to obtain the diameter of the
shaft．
? The basic hole is the preferred system because standard
drills,reamers,and so on can be used and shafts can
then easily be machined to fit．
基孔制：基孔制是以设计孔的尺寸为基本尺寸，其
尺寸减去余量便得到轴的直径的一种配合制度。
基孔制是优先选用的配合制度，因为可以使用标准
的钻头、铰刀等 （来加工孔）,而轴可以很容易地
加工成与之配合的尺寸。
? Basic Shaft System．
? A basic shaft system is a system of fits in which the design
size of the shaft is the basic size from which the allowance
is added to obtain the diameter of the hole．
? （ Normally most design offices adhere to the basic hole
system because of standard tooling and the fact that
tolerance tables are based on the basic hole system．
? However the use of the basic shaft system has the great
advantage in that is possible to use a standard size shaft．）
基轴制：基轴制是以设计轴的尺寸为基本尺寸，孔的
尺寸加上余量得到孔的尺寸的一种配合制度。（一般
地，许多设计部门采用基孔制，因为可以使用标准工
具和基于基孔制的公差带这一事实。然而采用基轴制
也有很大优越性，它使采用标准尺寸轴成为可能。）
Classes of Fits
? As indicated,the ANSI Standard B4.1—1967，
,Preferred limits and fits for cylindrical parts，” is
widely used for establishing tolerances for various classes
of fits．
? The letter symbols appearing in this standard represent the
following classes,RC（ running or sliding fit),LC
（ locational clearance fit）,LT（ transition fit）,LN
（ locational interference fit）,and FN（ force or shrink
fit）
如第一部分所述,ANSI标准 B4.1-1967，即“圆柱形零件公差与
配合”被广泛应用于各种等级的公差配合。
在这个标准中划分了以下几种配合等级,RC（松动配合）,LC
（定位间隙配合）,LT（过渡配合）,LN（定位过盈配合）、
FN（压力紧配合）。
? 松动配合
? 在尺寸范围内，配合面间有润滑间隙。对于前两等级，这个
间隙主要用于滑动配合，在有相对运动的情况下，要为确定
定位基准，要求间隙随直径变化较小。有九种类型的 RC配
合描述如下：
? Running or Sliding Fits,Running or sliding fits
provide a similar running performance with suitable
lubrication allowance throughout the range of sizes．
? The clearance for the first two classes,used chiefly as
slide fits,increases more slowly with diameter than the
other classes,in order that accurate location is
maintained even at the expense of free relative motion．
? There are nine types of RC fits which are defined as
follows：
? RC1,Close sliding fits are intended to locate
accurately parts that must assemble without perceptible
play．
? RC2,Sliding fits are intended for accurate location，
but with greater maximum clearance than class
RCl, Parts made to this fit move and turn easily but are
not intended to run freely and,in the larger sizes,may
seize with small temperature changes．
RC1（紧滑动配合）：适用精密定位配合，这些零
件必须无明显间隙装配。
RC2（滑动配合）：适用精密定位配合，但最大间
隙较 RC1级大。这种配合的零件可以容易转动，但
不能随意转动，适应较小的温度变化范围。
? RC3,Precision running fits are the closest fits that can
be expected to run freely and are intended for precision
work at slow speeds and light journal pressures．
? However,they are not suitable where appreciable
temperature changes are likely to be encountered．
? RC4,Close running fits are intended chiefly for running
fits on accurate machinery with moderate surface speeds
and journal pressures where accurate location and
minimum play is desired．
RC3（精密动配合）：是最紧的配合在低速和轻载条件
下，可以自由运动，适合精密工作。然而，这种配合不
适于温度变化的场合。
RC4（紧动配合）：主要适用表面有匀速运动和有轴向
载荷的精密配合件，配合处要求定位基准和最小间隙。
? RC5和 RC6（中等动配合）：主要用于具有较大的
速度或较大的轴向载荷或者两者都有的零件表面。
? RC7（一般动配合）：适用表面精度不高或温度变
化较大，或两者都有的工作情况。
? RC5 and RC6, Medium running fits are intended for
higher running speeds or heavy journal pressures or both．
? RC7,Free running fits are intended for use where accuracy
is not essential or where large temperature variations are
likely to be encountered,or under both of these conditions
．
? RC8 and RC9, Loose running fits are intended
for use where materials such as cold-rolled
shafting and tubing made to commercial tolerances
are involved．
? RC8和 RC9（松动配合）：适合材料如冷轧的轴
和管子要求普通公差配合。
? Location Clearance Fits．
? Location clearance fits are intended to determine
only the location of the mating parts,they may
provide rigid or accurate location,as with
interference fits,or some freedom of location，
as with clearance fits,Accordingly,they are
divided into three groups,clearance fits，
transition fits,and interference fits．
定位动配合
主要用于零件定位，并提供准确严格的位置公差，象
静配合公差，或普通的位置公差如间隙配合公差。
定位动配合可分成三组：间隙、过盈、过渡。
These fits are more fully described as follows：
? LC,Locational clearance fits are intended for
parts that are normally stationary but can be
freely assembled or disassembled．
? They run from snug fits for parts requiring
accuracy of location,through the medium
clearance fits for parts such as spigots,to the
looser fastener fits where freedom of assembly is
of prime importance．
LC（定位间隙配合）：一般适用于无相对运动的场
合，但可轻松安装或拆卸零件。螺栓连接需用一般
定位间隙配合。定位间隙配合从连接件要求精确定
位到松紧配合都允许的装配起到很重要的作用。
snug a,温暖的，舒适的；整齐的；隐
藏的；小巧的；坚固的；合身的
vt,使舒适；使坚固
vi,偎依；舒适地蜷伏
? LT,Transition fits are a compromise
between clearance and interference fits for
application where accuracy of location is
important,but either a small amount of
clearance or interference is permissible．
? LT（过渡配合）：即有间隙又有过盈的
配合，适用精密定位，但允许有较小的
间隙或过盈。
? LN．
? Locational interference fits are used where
accuracy of location is of prime importance and
for parts requiring an alignment with special
requirements for bore pressure．
? Such fits are not intended for parts designed to
transmit frictional loads from one part to another
by virtue of the tightness of fit,as these
conditions are covered by force fits．
? LN（定位静配合）：
? 用于定位精度特别重要，能以最好的定位精度
达到部件的对中的性能要求，不依靠配合的紧
固性传递磨擦负荷，这些情况通过压配合实现
? Force Fits,压力配合
? Force fits or shrink fits constitute a special type of
interference fit,normally characterized by maintenance
of constant bore pressures through the range of sizes．
? The interference,therefore,varies almost directly with
diameter,and the difference between its minimum and
maximum values is small to maintain the resulting
pressures within reasonable limits．
? 压力配合或热压配合是一种特殊的过盈配合。一般
通过恒压进行配合。
? 过盈量随直径的改变而改变，在允许条件下，公差
值足够小。
? FN1, Light drive fits are those requiring
light assembly pressures and produce more
or less permanent assemblies,They are
suitable for thin sections or long fits or in
cast iron external members．
? FN1（轻压力配合）：需要较小的装配压
力，当需要时易于拆卸，适合于薄件或
长配合件或铸铁件。
? FN2, Medium drive fits are suitable for
ordinary steel parts or for shrink fits on light
sections,They are about the tightest that
can be used with high grade,cast iron
external members,
? FN2（中压力配合）：适用普通钢零件或
轻度热压配合。这种配合是最紧的，外
部零件可以是高等级铸铁件。
? FN3, Heavy drive fits are suitable for
heavier steel parts or for shrink fits in
medium sections．
? FN3（重压力配合）：适用于大型钢零件，
或者中等热压配合件。
? FN4 And FN5,Force fits are suitable for
parts that can be highly stressed or for
shrink fits where the heavy pressing forces
are impractical．
? FN4和 FN5（压力配合）：适合于能承受
较大的压力的零件或不适于用重压力的
热压紧配合处。
Thanks!
