What is called tolerance in mechanical design?

This is for the interchangeability of the parts, the parts do not need to be matched, as long as the tolerance conditions are met, they can be used.

Dimensional tolerance: the nominal size of the design is a positive number, but also the ideal value, because the error always exists, so a certain deviation range is required, the difference between the maximum value of the part size and the nominal value is called the upper deviation, the difference between the minimum allowable value of the part size and the nominal value is called the lower deviation, and the lower deviation and the upper deviation are collectively referred to as the dimensional tolerance.

Geometric tolerance: After the parts are processed, there will inevitably be differences between the shape and the design, then there are shape tolerances and positioning tolerances and orientation tolerances, and the shape tolerance refers to such as: straightness, roundness, etc.

Positioning tolerances include: position, coaxiality, etc. Orientation tolerances include perpendicularity, parallelism, etc.

Tolerance = 1 upper deviation - lower deviation 1 (i.e. the absolute value of upper deviation - lower deviation), which is also equal to the absolute value of the maximum limit size minus the minimum limit size.

For example, if I give you a simple example, you will understand. Here's an example.

For example, the diameter of 50 is an example.

Then the upper deviation is +, and the lower deviation is, then its maximum limit size is, and the minimum limit size is.

Tolerances are. 50 is its basic size, and some are also called design sizes.

For example, if the design size is 50, then if you take it to the factory to produce tens of thousands of parts, will the size of each of them be 50? Impossible, at most only a few are exactly 50, so the rest of the parts are scrap? Neither is it.

As long as it is in between, it is a qualified product.

Tolerance definition: The amount of dimensional variation allowed for the part.

Like the example above, the allowable size variation is.

You should see it this time, right? Of course, some of the above mentioned cooperation, but it is even more complicated, and it is not clear in a word.

In mechanical drawing, the tolerance of the size without the tolerance was called the free tolerance in the past, and now this name has been abolished, and it should be called "the tolerance of the size without the tolerance", see the national standard "GB-T1804-2000 General Tolerance, Tolerance of Linear and Angular Dimensions without Tolerance".

The dimensions that are not marked are free tolerances, and the state has regulations GBT 1840--2000, which stipulates the general tolerance grades and limit deviation values of line types and angular dimensions that are not marked with tolerances. It is suitable for metal cutting and general stamping.

The dimensions of non-metallic materials and other processing methods can be used as a reference.

<> example: What is the free tolerance for size 32!

Linear Dimensions" 30 120

Limit deviation. f (precision grade).

m (intermediate grade).

c (rough grade).

v (coarseest grade).

In mechanical drawing, the tolerance of the size without the tolerance was called the free tolerance in the past, and now this name has been abolished, and it should be called "the tolerance of the size without the tolerance", see the national standard "GB-T1804-2000 General Tolerance, Tolerance of Linear and Angular Dimensions without Tolerance".

The dimensions that are not marked are free tolerances, and the state has regulations GBT 1840--2000, which stipulates the general tolerance grades and limit deviation values of line types and angular dimensions that are not marked with tolerances. It is suitable for metal cutting and standard machining, as well as for general stamping. The dimensions of non-metallic materials and other process processing methods can be used as a reference.

Dimensional tolerance, referred to as tolerance, refers to the absolute value of the maximum limit size minus the minimum limit size difference, or the allowable upper deviation minus the difference between the lower 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.