Calculation and tolerance of the pitch diameter of the external thread of 60° tooth profile (GB 197/196)
a. Calculation of the basic size of the pitch diameter: the basic size of the pitch diameter of the thread = the major diameter of the thread-the pitch × the coefficient value.
Formula: d/D-P×0.6495
Example: Calculation of the pitch diameter of external thread M8
8-1.25×0.6495=8-0.8119≈7.188
b. Commonly used 6h external thread pitch tolerance (based on the pitch).
The upper limit value is "0"
The lower limit is P0.8-0.095 P1.00-0.112 P1.25-0.118
P1.5-0.132 P1.75-0.150 P2.0-0.16
P2.5-0.17
The upper limit calculation formula is the basic size, and the lower limit calculation formula d2-hes-Td2 is the basic size-deviation-tolerance of the pitch diameter.
M8's 6h-level pitch diameter tolerance value: upper limit 7.188 lower limit: 7.188-0.118=7.07.
c. The basic deviation of the commonly used 6g level external thread pitch diameter: (based on the pitch).
P 0.80-0.024 P 1.00-0.026 P1.25-0.028 P1.5-0.032
P1.75-0.034 P2-0.038 P2.5-0.042
The upper limit calculation formula d2-ges is the basic size-deviation
The lower limit calculation formula d2-ges-Td2 is the basic size-deviation-tolerance
Example M8's 6g-level pitch diameter tolerance value: upper limit 7.188-0.028=7.16 lower limit: 7.188-0.028-0.118=7.042.
Note: (1) The thread tolerances above are based on coarse threads, and there are some changes to fine threads, but the tolerances are only larger. Therefore, the control will not exceed the specification limit according to this control, so it is not mentioned in the above. One marked out. Add WeChat: Yuki7557 to send a copy of macro program tutorial
(2) In the actual production, according to the accuracy required by the design and the extrusion force of the thread processing equipment, the diameter of the threaded rod blank is increased by 0.04-0.08 compared with the design thread diameter. It is the threaded polished rod blank diameter. For example, our company’s M8 external thread 6g-level threaded polished rod blank diameter is actually in the range of 7.08-7.13.
(3) Taking into account the need for external threads in the production process, the lower limit of the pitch diameter control in the actual production without heat treatment and surface treatment should be kept as far as possible at 6h level.
02
Calculation and tolerance of 60° internal thread pitch diameter (GB 197/196)
a. 6H thread pitch tolerance (based on the pitch).
Upper limit:
P0.8+0.125 P1.00+0.150 P1.25+0.16 P1.5+0.180
P1.25+0.00 P2.0+0.212 P2.5+0.224
The lower limit is "0",
The upper limit calculation formula 2+TD2 is the basic size + tolerance.
Example M8-6H internal thread pitch diameter is: 7.188+0.160=7.348 Upper limit: 7.188 is the lower limit.
b. The calculation formula for the basic size of the inner thread's pitch diameter is the same as that of the outer thread, that is, D2=D-P×0.6495, that is, the major diameter of the inner thread's pitch diameter × the coefficient value.
c. The basic deviation of 6G thread pitch diameter is E1 (based on the pitch).
P0.8+0.024 P1.00+0.026 P1.25+0.028 P1.5+0.032
P1.75+0.034 P1.00+0.026 P2.5+0.042
Example: M8 6G internal thread pitch diameter upper limit: 7.188+0.026+0.16=7.374
Lower limit: 7.188+0.026=7.214
The upper limit formula 2+GE1+TD2 is the basic size of the pitch diameter + deviation + tolerance
The lower limit formula 2+GE1 is the pitch diameter size + deviation
