2极限与配合

2 Limits and Fits of smooth Cylindricality
光滑圆柱体结合的极限与配合
Tolerance Dimensioning尺寸公差
• Tolerance is the total amount that a specific dimension is
permitted to vary; • 公差为尺寸允许变动的范围。
IT7the tolerance value is IT7标准公差值为： 0.018mm IT12 the tolerance value is IT12标准公差值为：0.18mm
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0.025mm 0.25mm
0.035mm 0.35mm
Basic deviation
基本偏差
称公差带) 在公差带图中，由代表上、下偏差的两条直线所限定的一个区域 。
ES
EI
es
ei
Hole
孔公差带
0
+
―
Shaft
Basic size 基本尺寸
Zeor line 零 线
轴公差带
Standards specify that the size and location of the tolerance zone are determined separately, by the standard tolerance and basic deviation.
there is a high neutral requirement. 过渡配合 可能具有间隙或过盈的配
合。孔的公差带与轴的公差带相互重叠，一般用于对中性要求较高处。
(2) Reference system of fits 配合的基准制：
1) Hole-based system of fit 基孔制 ： A system formed by both the tolerance zone of the hole, with definite basic deviation, and that of the shaft, with different basic deviations. 基本偏差为一
c
cd d
f e ef
fg g
h
j js
n p r k m
s t
u v
z x y
za zb
zc
ei
Shaft 轴
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基本尺寸 a
(Basic size)
Fitting
配合
(1)General concept of fitting and its types 配合的基本概念及其种类 Fitting is the relationship between the matched hole and shaft with the same basic size. 基本尺寸相同的、相互结合的孔与轴公差带 之间的关系称为配合。
the manufactured part may be 1.627 or 1.623, or anywhere between these limit dimensions. • 例如给定尺寸1.625 ± 0.002 ，意思是允许工件的尺寸为 1.627 或 1.623，或介于极限尺寸之间。 • 注：区别公差、偏差、误差？
0.013
Φ50.005 Φ50
Φ49.992
ES 0.005 EI －0.008
0.013
Φ49.992 Φ50
Φ50.005
ei 0.008 es 0.005
(6) Size tolerance zone In the tolerance zone diagram, an area bounded by the two lines represents the upper and lower deviation. 尺寸公差带(简
Size tolerance=|Maximum limit size–Minimum limit size| |最大极限尺寸-最小极限尺寸| =| 50.005 -49.992|=0.013 =| Upper deviation –Lower deviation | =|0.005-(-0.008)|=0.013 |上偏差 -下偏差| 请点击相应部分显示其内容
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公差带的“大小”由“标准公差”确定, 公差带的“位置” 由“基本偏差”来 确定。
Standard tolerance
标准公差
Any tolerance specified in the limit standards and system of fits in GB/T 1800 series .Standard tolerance is represented with the ‘symbol IT’. The grade code of the tolerance is represented with numbers and there are 20 grade codes in total: IT01，IT0，IT1、IT2，…，IT18. In turn， total limit deviation falls from IT01 to IT18. 标准公差是在GB/T 1800系 列标准极限与配合制中规定的任一公差。标准公差用符号“IT” 表示,数字表示公差等级,共有20个等级,IT01,IT0,IT1,IT2,…IT18 。
尺寸公差大 017级用于精密量具；
IT01
IT0
IT1
IT2
……
IT18
312级用于配合尺寸；
1218级用于非配合尺寸 尺寸精度高 Example: The tolerance grade of the hole is IT7 and IT12 ,Φ16、Φ44、Φ104 the tolerance value is: 例如,公差级别为IT7和IT12时,Φ16、Φ44、Φ104的公差值分别为:
ES 0
EI=0
b a
cd d
j js
za zb zc
+ 0 基本尺寸
(Basic size)
f e ef
fg g
h
s t m n p r k
u v
z x y
H
c
ah 表示间隙配合； 配合性质： j、jsn 表示过渡配合； pzc 表示过盈配合。
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2) Shaft-based system of fit 基轴制 ： A system formed by both the tolerance zone of the shaft with definite basic deviation, and that of the hole with different basic deviations. 基本偏差为
一定的轴的公差带与不同基本偏差的孔的公差带形成各种配合的一种制度。
The shaft of the shaft-based system is a basic shaft, represented with h, the upper deviation of which is zero. 基轴制的轴称为基准轴 , 用代号 h表示, 其上偏差 es = 0。
请 1) Clearance Fit Fit with clearance (including minimum clearance 点 zero). It is used where there is relative movement between the hole 击 and shaft. 间隙配合 具有间隙(包括最小间隙等于零)的配合。用于轴、 相 孔有相对运动处。 应 部 2) Interference Fit Fit with interference (Including minimum 分 interference zero). It is used where there is no relative movement 显 between the hole and shaft. 过盈配合 具有过盈(包括最小过盈等于零) 示 的配合。一般用于轴、孔无相对运动处。 其 Fit having clearance and interference. The 内 3) Transition Fit 容 tolerance zone of the hole overlaps that of the shaft. It is used where
• It is the difference between the maximum and the minimum
limits for the dimension. • 公差也可以为极限尺寸的差值。
• For Example a dimension given as 1.625 ± 0.002 means that
Basic concept of limits and fits 极限与配合的基本概念
(1) Basic size Nominal size specified in design. (如Φ50) 基本尺寸 设计时给定的尺寸； (2) Actual size The size obtained by measuring; (如Φ49.992 ) 实际尺寸 制造后的实际尺寸； (3) Limit size The limit values of an allowed range that is the size of a part varies. 极限尺寸 允许实际尺寸变化的极限值； Maximum limit size 最大极限尺寸 (如:Φ50.005 ) Minimum limit size 最小极限尺寸 (如:Φ49.992 ) (4) Size deviation Difference of a given size minus its basic size. 尺寸偏差 极限尺寸与基本尺寸之差值； Upper deviation 上偏差 ES孔/ es轴=最大极限尺寸-基本尺寸 Lower deviation 下偏差 EI孔/ ei轴=最小极限尺寸-基本尺寸 ES孔/ es轴 =50.005-50=0.005 EI 孔/ ei轴 = 49.992-50 = 0.008 (5) Size tolerance The allowable range for size variation. 尺寸公差 允许实际尺寸的变动量。