GB/T 20333-2023 Taps for parallel and taper pipe threads general dimensions and marking
1 Scope
This document specifies the general dimensions and marking of hand taps for pipe threads.
It is applicable to the two following types of tap:
- taps for parallel threads (see Figure 1 and Table 1),
- taps for taper threads (see Figure 2 and Table 2),
having threads in accordance with ISO 7-1 and ISO 228-1.
Furthermore, it gives in Annex A the bases used for calculation of the dimensions, and in Annex B the relationship between designations in this document and the ISO 13399 series.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 237 Rotating tools with parallel shanks - Diameters of shanks and sizes of driving squares
Note: GB/T 4267-2004 Rotating tools with parallel shanks - Diameters of shanks and sizes of driving squares (ISO 237:1975,IDT)
ISO 5969 Ground thread taps for pipe threads G series and Rp series - Tolerances on the threaded portion
Note: GB/T 20334-2006 Ground thread taps for pipe threads G series and Rp series - Tolerances on the threaded portion (ISO 5969 : 1979, IDT)
3 Terms and definitions
No terms and definitions are listed in this document.
4 General dimensions
The general dimensions are given in Table 1and Table 2. Shank diameters and driving squares shall conform to the specifications given in ISO 237, the tolerances being as follows:
- on diameter, d₁:
h9 for precision shanks;
h11 for other shanks;
- on width across flats, a:
h11;
h12 (including errors of form of the square and of its position in relation to the shank).
5 Marking
Taps in accordance with this document and with the requirements of ISO 5969 shall be marked, on the shank, with the following indications:
a) the letter designating the thread series;
b) the designation of the thread.
Examples:
AG series parallel thread tap with designation 3/4 shall be marked as follows:
G 3/4
An Rp series parallel thread tap with designation 1/4 shall be marked as follows:
Rp1/4
An Rc series taper thread tap with designation 1 shall be marked as follows:
Rc 1
Where tools comply in all respects with the relevant International Standards, the symbol ISO may be appended to the mark at the discretion of the manufacturer.
