This standard specifies the tooth structure type, diameter, pitch, thread number and basic dimensions of eyepiece threads for optical instruments. This standard applies to single-thread and multi-thread eyepiece threads with a diameter of 5mm to 8mm for optical instruments. JB/T 8240-1999 Eyepiece threads for optical instruments JB/T8240-1999 Standard download decompression password: www.bzxz.net

JB/T8240-1999
This standard is a revision of JB/T8240-95 (GB10158-88) "Eyepiece Thread for Optical Instruments". During the revision, editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces JB/T8240-95 from the date of implementation. This standard was proposed and managed by the National Technical Committee for Standardization of Optics and Optical Instruments. The responsible drafting unit of this standard is Shanghai Institute of Optical Instruments. This standard was first issued in March 1962 and revised for the first time in 1995. 704
1 Scope
Machinery Industry Standard of the People's Republic of China
Ocular screw thread for optical instruments
Ocular screw thread for optical instrumentsJB/T 8240---1999
Replaces JB/T8240---95
This standard specifies the tooth profile structure type, diameter, pitch and number of threads, and basic dimensions of eyepiece threads for optical instruments. This standard is applicable to single-thread and multi-thread eyepiece threads with a diameter of 5mm~8mm for optical instruments. 2 Structural type of thread profile
2.1 Structural type of thread profile (1) According to the provisions of Figure 1 and Table 1. Internal thread
External thread
Figure 1 Structural type (1)
Original triangle
I 0. 866 P
Original triangle
H/2-0.433P
Thread profile heightbZxz.net
H -h20.350P+Z
The structural type of the thread profile (2) shall be as specified in Figure 2 and Table 2. Approved by the State Bureau of Machinery Industry on August 6, 1999 Thread contact
Tooth bottom width
Implemented on January 1, 2000
Original triangle
H-0.866 P
JB/T 8240—1999
External thread
Figure 2 Structural type (2)
Original triangle
H/20. 433 P
Structural type (2) is suitable for eyepiece threads with high centering accuracy. 2 The ones in parentheses are not preferred.
3 Thread diameter, pitch and number of threads
3.1 The thread diameter, pitch and number of threads shall be selected in accordance with the provisions of Table 3. 3.2 The first series of thread diameters shall be preferred when selecting. 3.3 In Table 3, the pitch of 1.5 mm shall be preferred.
3.4 ​​To improve the centering requirements when connecting optical parts, it is recommended to use a pitch of 1mm. 3.5 The thread diameter, pitch and number of threads in brackets should be used as little as possible. 3.6 The calculation formula for multi-thread:
Where: S
Lead, mm
Number of thread threads:
P--—Pitch, mm.
3.7 Marking
Tooth profile height
H2-hz—0.350 P
+-+o+++
Tooth bottom width
3.7.1 The eyepiece thread for optical instruments using structural type (1) is represented by the code "MJA" and "nominal diameter×lead/number of threads"; "MJA\" can be abbreviated as "MJ\".
JB/T 8240—1999
3.7.2 The eyepiece thread for optical instruments adopting structural type (2) is indicated by the code \MJB\ and \nominal diameter × lead / number of threads". 3.7.3 The "number of threads" of single-thread threads can be omitted. 3.7.4 When the thread is left-handed, add the word "left" after the thread mark. Example 1: MJ40X6/4 or MJA40X6/4
indicates a left-handed eyepiece thread for optical instruments adopting structural type (1) with a nominal diameter of 40mm, a lead S of 6mm, a pitch P of 1.5mm, and a number of threads n of 4||tt ||Example 2: MJB40×6/4 left
indicates a left-handed optical instrument eyepiece thread with a nominal diameter of 40 mm, a lead S of 6 mm, a pitch P of 1.5 mm, and a thread number n of 4.
Example 3: MJ40x1.5 or MJA40X1.5
indicates a single-line right-handed optical instrument eyepiece thread with a nominal diameter of 40 mm, a lead S of 1.5 mm, and a pitch P of 1.5 mm.
Nominal diameter d
（15）
1.5 [1.5)]
(9)10（11)1216(18)）20(22)
（16）
Nominal diameter d
Series
(1.2)（1.2）
（1.2）
1.5↓1.5
JB/T 8240--1999
Table 3 (continued)
(9)
10(11)12
lead s
16(18)
(18)24
1824(27)
15(16.5)1824
(30)|| tt||(22)24(25)
Nominal diameter d
JB/T8240--1999
Table 3 (continued)
(9)|10[(11)
216(18)20(22)24 (25)
(20)
(16)
[1.5]1.53
(12)j(16)
(12)
18 24
(20)
(20)
((50)
Nominal diameter||tt ||Series「Series
(2)(2)
(6)(6)
JB/T 8240--1999
Table 3 (continued)
(9)10(11)12
(10)(12)(16)
(12)(13.5)
15(16.5)18
16(18)/20
[(22)24(25)|| tt||912(13.5)15(16.5)18
(12)
40（44）48
Nominal diameter d
（4.5）
Note: Those in parentheses are not preferred
JB/T8240—1999
Table 3 (End)
(9)1011
5（18)
24（25）
20(22)
(36)10
Basic dimensions of thread
JB/T 8240
—1999
Structural type (1) The nominal dimensions of the major diameter, pitch diameter and minor diameter of the thread shall comply with the provisions of Figure 1 and Table 4. Table 4
Thread diameter
External thread
Pitch diameter of external thread and
Internal thread
Tooth profile height
External thread
JB/T 8240—1999
Table 4 (continued)
Thread diameter
External thread and
Internal thread diameter
35-475
38-475
Internal thread
Tooth profile height
External thread
Note: Those in parentheses are not preferred, 714
JB/T 8240--1999
Table 4 (Complete)
Thread diameter
External and internal thread pitch diameter
59-475
Internal thread
Tooth profile height
JB/T 8240--1999
4.2 Structural type (2) The nominal dimensions of the major diameter, pitch diameter and minor diameter of the thread shall conform to the provisions of Figure 2 and Table 5 Table 5
Thread diameter
External and internal thread
Tooth profile height
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