What needs to be used to determine whether the tolerance requirements are achieved or not

According to the definition of the equal difference series, the general formula of the equal difference series is obtained, and the general term formula can be proved by using the definition of the equal difference series. Solution: is a series of equal differences.

Proof: Difference series, tolerance. , is a constant, and is a series of equal differences.

This problem mainly examines the proof and application of the equal difference series, and the key to solving this problem is to find the general term formula by using the definition.

There are two kinds of dimensions in the part drawing: one is a small but important size, and the size whose tolerance needs to be marked, which is called the size with note tolerance, such as the fit size, etc.; Another kind of large quantity is not important, or ordinary operators use ordinary equipment to process, the size will be qualified size (the size has no effect on the quality of the part and the size of the fit nature), in order to highlight the size of the note and look more concise, so the national standard stipulates that the size does not need to be marked, called the unmarked tolerance size, such as the total length of the part, etc.

It is worth noting that the unmarked tolerance size is not without tolerance requirements, on the contrary, there are tolerance requirements, but the requirements for it are relatively low (the tolerance value is larger).

Tolerance: The allowable variation of the actual parameter value. Parameters include not only geometric parameters in machining, but also parameters in physics, chemistry, electricity and other disciplines.

Therefore, tolerance is a concept that can be used in a wide range of applications. For machinery manufacturing, the purpose of formulating tolerances is to determine the geometric parameters of the product, so that its variation is within a certain range, so as to meet the requirements of interchange or fit.

Tolerance is the permissible machining error. No error is unlikely.

Dimensional tolerances. Referred to as tolerance, it refers to the absolute value of the difference between the maximum limit size and the minimum limit size that is allowed.

or the allowable deviation minus the difference between the deviation and the deviation.

A dimensional tolerance is an absolute value with no sign. Limit Deviation = Limit Dimension - Basic Dimension, Upper Deviation = Maximum Limit Dimension - Basic Dimension, Lower Deviation = Minimum Limit Dimension - Basic Dimension. Dimensional tolerance refers to the amount of variation allowed in the size of a part during a cutting operation.

With the same basic dimensions, the smaller the dimensional tolerance, the higher the dimensional accuracy.

Concept:

Dimensional tolerance refers to the fact that in the manufacturing process of parts, due to the influence of factors such as processing or measurement, there is always a certain error in the actual size after completion. In order to ensure the interchangeability of the parts, the actual size of the parts must be controlled within the allowable variation, and this allowable dimensional variation is called the dimensional tolerance.

Interchangeability and fit.

The smaller the error, the higher the accuracy, the better the quality and the higher the cost.

Therefore, on the premise of meeting the requirements of use, it is necessary to specify tolerances to select reasonable machining accuracy. Tolerance is the permissible machining error.

In a tolerance zone, an area defined by two straight lines representing the upper and lower deviations or the maximum and minimum limit dimensions. The tolerance zone includes two elements: the size of the tolerance zone and the position of the tolerance zone, the former is determined by the standard tolerance, and the latter is determined by the basic deviation. The fitting system of the tolerance zone is divided into base hole system and base shaft system.

The state stipulates that there are two ways to match, namely the base hole system and the base shaft system. Different datum systems will affect where the tolerance zone is located. And the position of the relative tolerance zone of the hole and shaft combined with each other is different, and both reference systems can form a gap fit, an overfit and an interference fit.

It restricts the mutual position relationship between two or more points, lines and planes of the part, including parallelism, perpendicularity, inclination, concentricity, symmetry, position, circular runout and total runout 8 items. Tolerances indicate the manufacturing accuracy requirements of the part and reflect how easy it is to be processed.

Tolerance classes are divided into IT01, IT0, IT1 、..., IT18 a total of 20 grades, the grade is reduced in turn, and the tolerance value is increased in turn. IT stands for International Tolerance.

The tolerance zone is determined according to the assembly requirements, there are clearance fit, transition fit, interference fit, according to different fitting requirements to choose different tolerance bands, gap fit to choose different tolerance zones according to the size of the gap, interference fit according to the size of the interference to choose different tolerance bands, transition fit with the distance to interference or clearance to choose different tolerance bands.

In actual production, the choice of base hole system or base shaft system is mainly considered from the factors of machine structure, process requirements and economy. In general, the base hole system is often used, because it is more difficult to machine the hole and shaft of the same grade than the shaft.

In particular, when machining small size precision holes, it is necessary to use expensive fixed-value tool measuring tools (such as reamers, broaches, etc.), and each specification of this tool is generally only used to process one size of holes, so the demand is large. If a base hole system is used, the number of tools and gauges can be reduced. However, the machining of the shaft is different, and the shaft of different sizes can be processed with the same tool, so the economic effect of using the base hole system is better.

The relationship between the tolerance value and the basic size is achieved through ().

Correct Answer: Standard Tolerance Liquid Mill Due to Front Bridge.

Legal Analysis: The value of the standard tolerance is determined by the basic dimensions and the tolerance class. where the tolerance class determines the level of dimensional accuracy.

The standard tolerance of fiber pants is divided into 20 grades, namely IT01, IT0, IT1, and ITI8. Its dimensional accuracy ranges from IT01 to ITI8

Decreasing in turn, it is a grade that reflects the accuracy of the ruler width. IT01 has the smallest tolerance value and the highest accuracy; IT18 has the largest tolerance and the lowest accuracy.

Legal basis: Tolerances for linear and angular dimensions without notation of tolerances in general (GB T 1804-2000) (ISO 2768-1:1989).

4 Technical Bundle.

The 8 of the main quasi-double hall has two equal slowness.

Class F is used for a precision oxygen piece; e-oxygen is used for suction parts with higher castability.

Standard tolerance values are related to nominal dimensions and tolerance classes.

Standard tolerances are any tolerance specified by national standards to determine the size of the tolerance zone. The tolerance grade specified in the national standard is the grade that determines the dimensional accuracy of the part, and the national standard divides the standard tolerance into 20 grades, which is represented by the symbol "IT" and the code composed of Arabic numerals, namely IT01, IT0, IT1 IT18.

The tolerance grade specified in the national standard is the grade that determines the dimensional accuracy of the part. The standard tolerance specified in the national standard is determined by the product value of the tolerance grade coefficient and the standard tolerance factor. In the case of a certain basic size, the tolerance class coefficient is the only parameter that determines the size of the standard tolerance.

From IT01 to IT18, the tolerance level decreases sequentially, while the corresponding standard tolerance value increases sequentially.

When the size is 500mm, the standard tolerance of all levels below IT5 is calculated according to the table below, and each tolerance grade has a definite tolerance grade coefficient, such as 7, 10, 16 ,... in the table, 2500 and other values, it can be seen from the table that from IT6 IT18 level, the grade coefficient of the male front regret is increased according to the R5 priority system, and the common ratio is , that is, the tolerance of every 5 grades increases by 10 times.

According to the standard tolerance calculation formula, there should be a tolerance value corresponding to the stove book for each basic size. However, in production practice, if there are too many basic dimensions, a huge tolerance value table will be formed, and the hidden macro will bring a lot of difficulties to production. In order to reduce the number of tolerances, harmonize the tolerance values, simplify the tolerances**, especially for ease of application, the national standard has divided the basic dimensions.

After dimension segmentation, the same standard tolerance is specified for all basic dimensions within the same dimension segment with the same tolerance class.

1. Shape tolerance

The shape tolerance refers to the allowable variation of a single actual measured element to its ideal measured element, including straightness, flatness, roundness, cylindricity, line profile without datum requirements and surface contour without datum requirements.

2. Direction tolerance

The direction error refers to the allowable change of the measured element in the direction of the datum, including parallelism, perpendicularity and inclination.

3. Position tolerance

The position tolerance is the allowable variation of the position of the reference of the actual measured elements, including the position, coaxial (centric) degree and symmetry.

4. Runout tolerance

The runout tolerance is the maximum amount of runout allowed for one or more weeks of rotation of the actual measured feature around the datum axis.

Scope of application, these limit deviations apply to:

1) Linear size: such as outer size, inner size, step size, diameter, radius, distance, rounding radius and chamfer height;

2) Angular dimensions: including angular dimensions that are not usually marked with angular values, such as right angles (90°); Linear and angular dimensions of machined assemblies.

These limit deviations do not apply in the following cases:

1) Linear and angular dimensions specified in other general tolerance standards;

2) Reference dimensions in parentheses.

The tolerance principle has the principle of independence and the principle of tolerance. The principle of independence, the tolerance requirements are relatively strict; The principle of tolerance, tolerances can be conditionally "relaxed", which is conducive to the economy of processing and assembly.