GB/T 28254-2012Spiral pointed taps (English PDF)

Foreword Foreword

This standard is drafted according to the rules given in GB/T 1.1-2009. It was proposed by the China Machinery Industry Federation and is under the jurisdiction of the National Technical Committee on Cutting Tools of Standardization Administration of China (SAC/TC 91). The foreword also names the four drafting organizations and the four main drafters.

1 Scope

This standard fixes the type and dimensions, the designation, the technical requirements and the basic requirements for marking and packaging of general-shank spiral pointed taps, in the high-performance grade and in the ordinary grade.

This standard applies to general-shank spiral pointed taps used to cut general purpose metric screw threads according to GB/T 192, GB/T 193, GB/T 196 and GB/T 197.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only the edition cited applies to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 192 General purpose metric screw threads - Basic profile; GB/T 193 General purpose metric screw threads - Diameter and pitch series; GB/T 196 General purpose metric screw threads - Basic dimensions; GB/T 197 General purpose metric screw threads - Tolerances; GB/T 968 Tolerances for tap threads; GB/T 969 Taps - Technical specifications.

3 Type and dimensions of the taps

3.1 Spiral pointed taps with a plain thick shank follow Figure 1 and Tables 1 and 2. Figure 1 shows the tap with a square drive at the end of the shank and carries the dimension symbols: the thread diameter d, the shank diameter d1, the length of the threaded portion l, the length l1, the overall length L, the square length l2 and the square width a in the section A-A. Table 1, headed Coarse general purpose metric thread spiral pointed taps with a thick shank and expressed in millimetres, sets against each designation, from M1 to M2.5, the nominal diameter d, the pitch P, the shank diameter d1, the length l, the overall length L, the length l1 and, under the heading square, the width a and the length l2. Table 2, headed Fine general purpose metric thread spiral pointed taps with a thick shank and expressed in millimetres, has the same columns and covers the designations from M1 x 0.2 to M2.5 x 0.35.

3.2 Spiral pointed taps with a thick shank and a neck follow Figure 2 and Tables 3 and 4. Figure 2 shows the tap with a necked portion between the threaded portion and the shank, and adds to the symbols of Figure 1 the neck diameter d2. Table 3, headed Coarse general purpose metric thread spiral pointed taps with a thick shank and a neck and expressed in millimetres, sets against each designation, from M3 to M10, the nominal diameter d, the pitch P, the shank diameter d1, the length l, the overall length L, the minimum neck diameter d2, the length l1 and, under the heading square, the width a and the length l2. A footnote to the table states that the tap is allowed to have no relief groove, and that where there is no relief groove the length dimension of the threaded portion shall be l plus half of the difference between l1 and l. Table 4, headed Fine general purpose metric thread spiral pointed taps with a thick shank and a neck and expressed in millimetres, has the same columns and the same footnote, and covers the designations from M3 x 0.35 to M10 x 1.25.

3.3 Spiral pointed taps with a plain thin shank follow Figure 3 and Tables 5 and 6. Figure 3 shows the tap and carries the symbols d, d1, l, L, l2 and the square width a. Table 5, headed Coarse general purpose metric thread spiral pointed taps with a thin shank and expressed in millimetres, sets against each designation, from M3 to M68, the nominal diameter d, the pitch P, the shank diameter d1, the length l, the overall length L and, under the heading square, the width a and the length l2. Table 6, announced in the text of 3.3, is not on the sheets available.

Clause 4, the technical requirements, and Clause 5, marking and packaging, both announced in the scope, fall beyond the last page available.