This standard specifies the special tolerances for the cutting diameter of the reamer. This standard applies to reamer tolerances other than m6, GB/T1131.1 "Hand reamer Part 1: Types and dimensions", GB/T1132 GB/T 4246-2004 Special tolerances for reamer GB/T4246-2004 Standard download decompression password: www.bzxz.net

ICS 25. 100. 30
National Standard of the People's Republic of China
GB/T 4246—2004/ISO 522:1975 replaces GB/T4246-1984
Special tolerances
Special tolerances for reamers (ISO522:1975.IDT)
Issued on 2004-02-10
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Administration of Standardization of the People's Republic of China
Implemented on 2004-08-01
This standard is equivalent to ISO522:1975 "Special tolerances for reamers" (English version). For ease of use, the following editorial changes have been made to this standard: - The decimal point "" is used instead of the comma "," as a decimal point; "this standard" is used instead of "this international standard"; the foreword of the international standard has been deleted.
In the "Scope" of GB/T 4246-2004/ISO 522:1975, ISO236-1 "Hand Reamers" is replaced by GB/T1131.1 "Hand Reamers Part 1: Types and Dimensions", ISO236-2 "Morse Taper Shank Long Edge Machine Reamers" is replaced by GB/T4243 "Morse Taper Shank Long Edge Machine Reamers", and ISO521 "Straight Shank and Morse Taper Shank Machine Reamers" is replaced by GB/T1132 "Straight Shank and Morse Taper Shank Machine Reamers". This standard replaces GB/T4246-1984 "Special Tolerances for Reamers" from the date of implementation. Compared with GB/T4246-1984, this standard has the following changes: the standard name has been modified;
the scope of application has been modified;
instructions and examples have been added;
inch sizes have been added.
This standard is proposed by China Machinery Industry Federation. This standard is under the jurisdiction of the National Technical Committee for Tool Standardization. The drafting unit of this standard is Chengdu Tool Research Institute. The main drafters of this standard are Fan Jin and Xu Gang. The previous versions of the standards replaced by this standard are:—GB/T4246--1984.
1 Scope
GB/T4246—2004/ISO522:1975
Special tolerances for reamer
This standard specifies the special tolerances for the cutting part diameter of the reamer. This standard is applicable to the reamers specified in GB/T1131.1 "Hand reamers Part 1: Types and dimensions", GB/T1132 "Machine reamers with straight shanks and Morse taper shanks", and GB/T4243 "Machine reamers with Morse taper shanks and long edges" when the reamer tolerance is not m6. 2 Determination of tolerances
Unless otherwise specified, reamers are manufactured to tolerance m6. It is impossible to infer in advance the tolerance of a hole machined with a reamer with tolerance m6. In practice, the actual size of the hole reamed by the reamer depends on many factors, including: a) the type of material being machined and the machining allowance; the cutting angle of the reamer;
the conditions under which the reamer is used;
d) the clamping and operating methods;
the lubrication conditions.
If the tolerance of the hole is given, the above factors should be considered when determining the special tolerance of the reamer for machining the hole. It is impossible to formulate a standard "special" tolerance that can guarantee the result under various conditions. However, for the sake of uniformity, the following recommended method of determining the upper and lower limits of the reamer tolerance based on the machined hole should be used as much as possible when designing special reamers.
2.1 Rules for determining reamer tolerance limits (see Figure 1) When the hole tolerance is IT:
The upper limit of the reamer diameter is equal to the maximum diameter of the hole minus 0.15IT. The value of 0.15IT should be rounded to an integer multiple of 0.001mm (or 0.0001in).
The lower limit of the reamer diameter is equal to the maximum diameter of the reamer minus 0.35IT. The value of 0.35IT should be rounded to an integer multiple of 0.001mm (or 0.0001in).
Note: The IT value of the imperial size is directly converted from the IT value of the metric size. Tolerance zone of hole
Tolerance zone of reamerbzxZ.net
GB/T4246-2004/ISO522:1975
2.2 General description
It is possible to manufacture reamer with higher accuracy than that specified in this standard while complying with the limit dimensions specified in this standard. 2.3 Example
2.3.1 When the diameter of the hole is 12mm and the accuracy is H7: IT7=0.018mm; the maximum size of the hole is: 12.018mm, the minimum size is: 12.000mm, the upper limit size of the reamer diameter is 0.151T below the maximum diameter of the hole: 0.15×0.018mm=0.0027mm, this value is rounded to 0.003mm;
The upper limit size of the reamer diameter = 12.018mm-0.003mm=12.015mm; the lower limit size of the reamer diameter is 0.35IT below the maximum diameter of the reamer: 0.35×0.018mm=0.0063mm, this value is rounded to 0.007mm;
The lower limit size of the reamer diameter = 12.015mm-0.007mm=12.008mm. 2.3.2 When the hole diameter is 0.5in and the accuracy is H7: IT7=0.0007in (0.018 minimum value is directly converted); the maximum size of the hole is: 0.5007in, the minimum size is: 0.5000in; the upper limit of the reamer diameter is 0.15IT below the maximum diameter of the hole: 0.15×0.0007in=0.00010in, the value is rounded to 0.0001in; | |tt||The upper limit of the reamer diameter = 0.5007in0.0001in=0.5006in; the lower limit of the reamer diameter is 0.35IT below the maximum diameter of the reamer: 0.35×0.0007in=0.00024in, which is rounded to 0.0003in;
The lower limit of the reamer diameter = 0.5006in—0.0003in=0.5003in.
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