GB/T 34632-2017 in English

Maximum diameter of rough blank: $$ d_{0\mathrm{max}} = \left\{\frac{\tan(\alpha/2)}{3P}\big[3d_{2\mathrm{max}}'(d_{2\mathrm{min}}'^2 - d_{1\mathrm{min}}'^2) - 2(d_{2\mathrm{max}}'^3 - d_{1\mathrm{min}}'^3)] + \frac{1}{2}(d_{2\mathrm{min}}'^2 + d_{1\mathrm{min}}'^2)\right\}^{\frac{1}{2}} $$ Minimum diameter of rough blank: $$ d_{0\mathrm{min}} = \left\{\frac{\tan(\alpha/2)}{3P}\big[3d_{2\mathrm{min}}'(d_{2\mathrm{max}}'^2 - d_{1\mathrm{max}}'^2) - 2(d_{2\mathrm{max}}'^3 - d_{1\mathrm{max}}'^3)] + \frac{1}{2}(d_{2\mathrm{max}}'^2 + d_{1\mathrm{max}}'^2)\right\}^{\frac{1}{2}} $$ Where: $\alpha = 60^\circ$, $P$ is the pitch ($\mathrm{mm}$), and other parameters such as $d_{2\mathrm{max}}'$, $d_{2\mathrm{min}}'$ Nominal diameter-number of threads and thread series code Gross diameter $d$ (unit: mm) 3Aa 2A max min max min 0-80 UNF 1.312 1.301 1.297 1.278

Thread tool accuracy level and process recommendations

It is recommended to use wire drawing or grinding to process the blank diameter. When using the turning process, it is necessary to add twice the surface roughness value ($2R_a$) on the basis of the provisions in Table 1. For non-full-profile extrusion processes, the minimum diameter of the blank can be appropriately reduced. If the tolerance is too small, it can be optimized by improving the tool accuracy or adjusting the ring gauge shrinkage.

Implementation recommendations

1. Strictly select the blank diameter range according to the standard table to ensure a reasonable machining allowance.
2. According to the actual process and material characteristics, adjust the tolerance range appropriately.
3. Regularly check the thread ring gauge and tool parameters to ensure compliance with JB/T 8824.6—2012 and JB/T 8824.7—2012 requirements.