GB/T1804 is a Chinese standard. The “-m” indicates the tolerance class.
This standard is equivalent to ISO 2768.
Detail Information of GB/T 1804-2000
Description : General tolerances Tolerances for linear and angular dimensions without individual tolerance indications
Sector / Industry: China National Standard
Classification of Chinese Standard: J04
Classification of International Standard: 17.040.10
Date of Issue: 2000-07-24
Date of Implementation: 2000-12-01
Older Standard (superseded by this standard): GB/T 1804-1992; GB/T 11335-1989
Quoted Standard: GB/T 1800.1-1997; GB/T 1184-1996; GB/T 4249-1996; GB/T 6403.4-1986
Adopted Standard: ISO 2768-1-1989, MOD
Drafting Organization: Mechanical Engineering Research Institute
Administrative Organization: National product size and geometry specifications Standardization Technical Committee
Proposing organization: National Machinery Industry Bureau
Issuing agency(ies): State Quality and Technical Supervision
This standard specifies the satellite broadcast system integration down converter technical requirements and methods of measurement.
For the same measurement uncertainty can ensure that any equivalent measurement methods may also be used. Dispute should be based on this standard shall prevail.
This standard applies to radio and television satellite broadcast system integrated down converter development, production, use, and operation and maintenance.
According to DIN ISO 2768-1
General tolerances for linear measures and level squares with four tolerance classes are useful for simplifying drawings.
By choosing the tolerance class precision levels common in workshops should be taken into account.
If smaller tolerances are needed or bigger ones are more economical,
then these tolerances are indicated next to the nominal size.
Table 1 Limits for linear measures
For nominal sizes below 0,5 mm the limit measures are to be indicated directly at the nominal measure.
Table 2 Limit measures for radius of curvature and chamfer height
Table 3 For nominal masses below 0.5 mm, the dimensions of the boundary shall be given directly at the nominal size.
ISO 2768 – m or general tolerance ISO 2768 – mFor nominal sizes below 0.5 mm the limit measures are to be indicated directly at the nominal measure. If general tolerances according to ISO 2768-1 are valid,
the following has to be inserted in the title box, i.e. for tolerance class medium
For new designs only the general tolerance according to DIN ISO 2768-1 should be valid. The limit measurements of the tolerance classes m and f of DIN ISO 2768-1 are identic with those of DIN 7168-1.
According to DIN ISO 2768-2
DIN ISO 2768-2 is for simplifying drawing and fixes general tolerances in three tolerance classes for form and position.
By choosing a special tolerance class exactly the precision level common in workshops should be taken into account.
If smaller tolerances are needed or bigger are more economical these tolerances should be mentioned directly according to ISO 1101.
General tolerances for form and position should be used while the tolerance principle according. to ISO 8015 is valid and while this is mentioned in the drawing.
This tolerance principles says that no opposite relation between measure, form and position tolerance exists (principle of superposition).
General tolerances for form and position are valid for form elements for which form and position tolerances are not indicated individually.
They are applicable for all characteristics of the form elements accept cylinders, profiles of any line or surfaces, inclines, coaxiality, position and total movement.