Tolerance General Js13
Trinh Livingston
Viktor
RE: Metric Tolerances brakemeister (Automotive)(OP)4 Dec 02 16:41I have seen such a chart. It is part of the documentation kept by journeymen machinists in europe. I was just hoping I could find a copy on the web.
The application I have is not a "fit" application but rather tolerances which reflect the capability of a manufacturing process. RE: Metric Tolerances jimengr (Mechanical)4 Dec 02 20:15I think you are asking for DIN7168 "General tolerances for linear and angular dimensions and geometrical tolerances". This standard has 4 different degrees of accuracy for general tolerances. For example, the engineering drawing may specify DIN7168 m (for medium). For a linear dimension, the tolerance is then based on the length. For example, a linear dimension over 120mm up to 400mm the tolerance is +/- 0.5mm deviation. This doesn't cover dimensions that have tolerances for fits (H7 etc) or otherwise specified. It only applies for "parts produced by machining with cutting tools or metal-forming tools, provided there are no other standards for general tolerances for special manufacturing methods". This simply means that this standard doesn't apply to welded parts, burned or thermal cut parts (gas, plasma, or laser) and others as they have their own DIN standards for tolerances. Welding is DIN8570 and thermal cutting DIN2310 for example.
Finally, DIN7168 is obsolete and replaced by ISO2768 which is available on the ISO website. I would guess the others I mentioned are also replaced by ISO standards.
Hope this helps,
Jim RE: Metric Tolerances GDTGUY (Aerospace)5 Dec 02 08:59The U.S. standard for indicating metric tolerances is ASME B4.3-1978, "General Tolerances for Metric Dimensioned Products". Like DIN7168, it also specifies metric tolerances based on dimension length. (However, I have not compared the values to see if they are the same as used in the DIN standard) It also offers several other methods for indicating general (or "block") tolerances on an engineering drawing including: decimal place indication, formulas based on International Tolerance Grades and direct reference to the ASME B4.3 standard itself.
GDT GUY RE: Metric Tolerances pvdvyve (Mechanical)9 Dec 02 04:21Hay, in a lot of factories they use their own tolerances. I give you an example of a note of ours that is on each drawing.
ISO TOLERANCES, IF NOT INDICATED: MACHINE WORKED SURFACES
DIAMETRICAL DIMENSIONS JS13 -js13, LONGITUDINAL DIMENSIONS
JS14 - js14, OTHER SURFACES JS16 - js16.
Sometimes it's just noted:
overall tolerances:+/- 0,1mm
I'm workin' in a former American factory in Europe and I thought that workin' with those zero's after the comma was an English or American habit? I was never taught that in school over here!
Greetings
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We have customer who sometimes tell us to make parts with general tolerance Js13. Is there a way to define the parts tolerance with Js13 ? For the moment we define every dimension, but if we could do it on a general basis it would make us save time.
This book includes tables and calculations for easy option of fits of machine parts and determination of their dimensional tolerances and deviations. Using this tool the following tasks can be solved:
It is necessary that the dimensions, shape and mutual position of surfaces of individual parts of mechanical engineering products are kept within a certain accuracy to achieve their correct and reliable functioning. Routine production processes do not allow maintenance (or measurement) of the given geometrical properties with absolute accuracy. Actual surfaces of the produced parts therefore differ from ideal surfaces prescribed in drawings. Deviations of actual surfaces are divided into four groups to enable assessment, prescription and checking of the permitted inaccuracy during production:
As mentioned above, it is principally impossible to produce machine parts with absolute dimensional accuracy. In fact, it is not necessary or useful. It is quite sufficient that the actual dimension of the part is found between two limit dimensions and a permissible deviation is kept with production to ensure correct functioning of engineering products. The required level of accuracy of production of the given part is then given by the dimensional tolerance which is prescribed in the drawing. The production accuracy is prescribed with regards to the functionality of the product and to the economy of production as well.
d=D ... basic size
Dmax , Dmin ... limits of size for the hole
dmax , dmin ... limits of size for the shaft
ES ... hole upper deviation
EI ... hole lower deviation
es ... shaft upper deviation
ei ... shaft lower deviation
This paragraph can be used to choose a fit and determine tolerances and deviations of machine parts according to the standard ISO 286:1988. This standard is identical with the European standard EN 20286:1993 and defines an internationallyrecognized system of tolerances, deviations and fits. The standard ISO 286 is used as an international standard for linear dimension tolerances and has been accepted in most industrially developed countries in identical or modified wording as a national standard (JIS B 0401, DIN ISO 286, BS EN 20286,CSN EN 20286, etc.).
The system of tolerances and fits ISO can be applied in tolerances and deviations of smooth parts and for fits created by their coupling. It is used particularly for cylindrical parts with round sections. Tolerances and deviations in this standard can also be applied in smooth parts of other sections. Similarly, the system can be used for coupling (fits) of cylindrical parts and for fits with parts having two parallel surfaces (e.g. fits of keys in grooves). The term "shaft", used in this standard has a wide meaning and serves for specification of all outer elements of the part, including those elements which do not have cylindrical shapes. Also, the term "hole" can be used for specification of all inner elements regardless of their shape.
The tolerance of a size is defined as the difference between the upper and lower limit dimensions of the part. In order to meet the requirements of various production branches for accuracy of the product, the system ISO implements 20 grades of accuracy. Each of the tolerances of this system is marked"IT" with attached grade of accuracy (IT01, IT0, IT1 ... IT18).
The tolerance zone is defined as a spherical zone limited by the upper and lower limit dimensions of the part. The tolerance zone is therefore determined by the amount of the tolerance and its position related to the basic size. The position of the tolerance zone, related to the basic size (zero line), is determined in the ISO system by a so-called basic deviation. The system ISO defines 28 classes of basic deviations for holes. These classes are marked by capital letters (A, B, C, ...ZC). The tolerance zone for the specified dimensions is prescribed in the drawing by a tolerance mark, which consists of a letter marking of the basic deviation and a numerical marking of the tolerance grade (e.g. H7, H8, D5, etc.). This paragraph includes graphic illustrations of all tolerance zones of a hole which are applicable for the specified basic size [1.1] and the tolerance grade IT chosen from the pop-up list.
Though the general sets of basic deviations (A ... ZC) and tolerance grades (IT1... IT18) can be used for prescriptions of hole tolerance zones by their mutual combinations, in practice only a limited range of tolerance zones is used. An overview of tolerance zones for general use can be found in the following table. The tolerance zones not included in this table are considered special zones and their use is recommended only in technically well-grounded cases.
The tolerance zone is defined as a spherical zone limited by the upper and lower limit dimensions of the part. The tolerance zone is therefore determined by the amount of the tolerance and its position related to the basic size. The position of the tolerance zone, related to the basic size (zero line), is determined in the ISO system by a so-called basic deviation. The system ISO defines 28 classes of basic deviations for shafts. These classes are marked by lower case letters (a, b, c,... zc). The tolerance zone for the specified dimensions is prescribed in the drawing by a tolerance mark, which consists of a letter marking of the basic deviation and a numerical marking of the tolerance grade (e.g.h7, h6, g5, etc.). This paragraph includes graphic illustrations of all tolerance zones of ashaft which are applicable for the specified basic size [1.1] and the tolerance grade IT chosen from the pop-up list.
Though the general sets of basic deviations (a ... zc) and tolerance grades (IT1... IT18) can be used for prescriptions of shaft tolerance zones by their mutual combinations, in practice only a limited range of tolerance zones is used. An overview of tolerance zones for general use can be found in the following table. The tolerance zones not included in this table are considered special zones and their use is recommended only in technically well-grounded cases.
This paragraph can be used to choose a recommended fit. If you wish to use another fit than the recommended one, define hole and shaft tolerance zones directly in the paragraphs [1.9, 1.10]. When designing the fit itself, it is recommended to follow several principles:
The list of recommended fits given here is for information only and cannot be taken as a fixed listing. The enumeration of actually used fits may differ depending on the type and field of production, local standards and national usage and last but not least, depending on the plant practices. Properties and field of use of some selected fits are described in the following overview. When selecting a fit it is often necessary to take into account not only constructional and technological views, but also economic aspects. Selection of a suitable fit is important particularly in view of those measuring instruments, gauges and tools which are implemented in the production. Therefore, follow proven plant practices when selecting a fit.
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