## Calculation formula of various kinds of screw thread2018-06-19

A, 60 ° the external thread pitch diameter calculation of tooth type and tolerance (GB) 197/196

A. pitch diameter size calculation: basic thread pitch diameter basic size = big diameter - pitch x factor value.

Formula said: d/d - P x 0.6495

Example: the calculation of external thread M8 thread pitch diameter

8-1.25 * 0.6495 = 0.8119 material 7.188

Commonly used 6 h b. external thread pitch diameter tolerances (based on pitch).

Upper limit for the "0", lower limit of P0.8 -, P1.00-0.112, 0.095, P1.5 P1.25-0.118-0.132, P1.75-0.150, P2.0-0.16, P2.5-0.17

Upper limit formula to calculate the basic size, lower limit value calculation formula d2 - hes - Td2 namely basic size deviation - pitch diameter tolerances.

M8 6 h level pitch diameter tolerance values: upper limit of 7.188; The lower limit value: 7.188-0.118 = 0.118.

C. the commonly used basic level 6 g external thread pitch diameter deviation: (based on pitch).

P0.80-0.024, 1.00 0.026, P, P1.5 P1.25-0.028-0.032, P1.75-0.034, P2-0.038, P2.5-0.042

Upper limit formula d2 - ges - basic size deviation

Lower limit value calculation formula d2 - ges - Td2 namely basic dimension deviation - tolerance

Cases of 6 g levels of M8, diameter tolerance value: ceiling: 7.188-0.028 = 7.16 lower limit value: 7.188-0.028-0.028 = 7.042.

Note: (1) above the thread tolerance is subject to a coarse thread thread tolerance some corresponding changes of fine thread, but only tolerance, so according to this control not outside the specification limits, therefore, not one by one in the mark.

(2) the thread of the polished rod billet diameter size in actual production, according to the design requirements of precision and screw thread processing equipment of the extrusion pressure and corresponding than design thread pitch diameter size increase between 0.04 0.08, and for the thread polished rod billet diameter values, such as the company's outside the M8 thread level 6 g of polished rod billet diameter is 7.08 7.13 in this range.

(3) considering the needs of the production process external thread in the actual production of heat treatment and surface treatment of the lower limit should try to keep the pitch diameter of shall prevail at level 6 h.

Second, 60 ° internal thread pitch diameter calculation and tolerance (GB) 197/196

A. 6 h class thread pitch diameter tolerances (based on pitch).

Upper limit: P0.8 P1.00 P1.5 P1.25 + 0.16 + 0.150 + 0.125 + 0.180

P1.25 P2.0 P2.5 + 0.212 + 0.00 + 0.212

C. external thread level 6 g large diameter calculation and tolerance.

Deviation (6 g level of external thread benchmark based on pitch)

P0.8 0.024 P1.00 0.026 P1.5 P1.25-0.028-0.028 P1.25 P1.75-0.024-0.034

P2.5 P2.0 0.038-0.042

Upper limit formula d - ges threaded benchmark basic size - large diameter deviation

Lower limit formula d - ges - Td the large diameter basic thread size - benchmark deviation - tolerance

Example: M8 external thread level 6 g large diameter limit from 8-0.028 = 7.972.

Lower limit value from 8-0.028-0.028 = 7.76

Note: (1) is by screw thread of large diameter and thread rolling plate/polished rod billet diameter screw rolling wheel tooth wear degree to determine the type, and its value in the same blank and thread processing tool and is inversely proportional to the diameter of the screw on the basis of big diameter, the number of small in size and vice small diameter is large in size.

(2) the need for heat treatment and surface treatment, such as machining parts, considering the relationship between processing should be thread when the actual production of large diameter control at level 6 h lower value added more than 0.04 mm, such as the external thread of the M8 in rub (rolling) silk big diameter should guarantee the phi advisable under 7.83 and 7.95 above.

Fourth, the calculation of internal thread path and tolerance

A. basic dimension calculation of internal thread path (D1).

Thread path within the basic size = basic size - pitch x factor

Example: the path of internal thread M8 basic size 8-1.25 * 1.0825 = 1.0825 material 6.646875

B. internal thread tolerance level 6 h path (based on pitch) and path value calculation.

P0.8 + 0. 2 P1.0 + 0. 236 P1.75 P1.5 P1.25 + 0.265 + 0.265 + 0.335

P2.0 P2.5 + 0.375 + 0.48

Minimum deviation formula of internal thread level 6 h D1 + + basic size deviation HE1 namely internal thread path.

Note: grade 6 h under partial value as "0"

Formula of the upper limit of internal thread level 6 h = D1 + HE1 + TD1 namely basic dimension deviation + + tolerance inside screw path.

Example: six class h the upper limit of the M8 threaded path + 0 = 6.647 6.647

Within 6 h class M8 thread path the lower limit of 6.647 + 0 + 0.265 = 6.912

C. internal thread level 6 g path deviation (based on pitch) and basic path value calculation.

P0.8 P1.0 P1.5 P1.25 + 0.028 + 0.026 + 0.024 + 0.034 + 0.032 P1.75