What is the basic format of thread callout?

The threads are drawn in the same way, but they must also be marked on the drawing to make it easier to distinguish them.

Annotation of common threads.

The annotation reads:

Feature code. Nominal diameter pitch.

Rotation direction. Middle diameter and top diameter tolerance code.

Screw-length designation.

Where: feature code.

m Single-wire coarse thread is only marked with nominal diameter, and single-wire fine thread is marked with nominal diameter pitch.

Rotation direction: divided into right-handed, left-handed, right-handed is not marked, left-handed is represented by LH.

Thread mid-diameter, top-diameter tolerance zone.

Code: Tolerance class is indicated by the designation.

and letters indicating the position of the tolerance zone, e.g., 6h, 6g (uppercase for internal threads and lowercase for external threads). If the middle diameter and top diameter tolerance zone codes are the same, only one code is noted, such as:

7h；If the middle diameter tolerance zone of the thread is different from the top diameter tolerance zone, it is marked separately, such as: 5g6g.

Thread length is specified as short (S), medium (N) and long (L), and the length of the thread is not marked, and the value of the length of the thread can be indicated when it is needed, such as M10-6G-40.

Example of a common thread callout.

Annotation of pipe threads.

The annotation reads:

Feature code. Nominal diameter.

Tolerance class code.

Where: feature code. grc

Example of pipe thread callouts.

Callouts of trapezoidal threads.

The annotation reads:

Feature code. Nominal diameter lead.

p-pitch) rotation direction.

Where: feature code.

TR single wire thread is marked with nominal diameter only, and multi-wire thread is marked with nominal diameter lead (p pitch), such as.

tr40x14(p7)。

The rotation direction is the same as that of ordinary threads.

Example of a trapezoidal thread callout.

Example of a zigzag thread callout.

Annotation of zigzag threads.

The annotation reads:

Feature code. Nominal diameter lead (p-pitch).

Rotation direction. Where: feature code.

b Single-wire threads are only marked with nominal diameter, and multi-wire threads are marked with nominal diameter leads (p pitch), such as.

tr40x14(p7)。

The rotation direction is the same as that of ordinary threads.

Annotations for non-standard threads.

In addition to marking the content of the standard thread, the limit dimensions of the middle diameter and top diameter of the non-standard thread also need to be marked, as shown in Figure 7-9. For special threads, the word "special" should be added before the thread code.

There are many kinds of threads, thick teeth and fine teeth are also different, you must first know which standard thread it is, and then mark the diameter, and then mark the tooth distance (some coarse thread type default, can not be marked), straight thread to mark the length, can also be marked the length alone.

The marking method and type of thread.

The basic format of thread annotation is: thread code + thread tolerance zone code (middle diameter, top diameter) + screw length. The format is:

Thread code Thread tolerance zone code (middle diameter, top diameter) + screwing length. The tooth type code of the ordinary thread is M, which is divided into coarse teeth and fine teeth, and the pitch of the coarse thread can be omitted; When the tolerance zone code of the middle diameter and the top diameter are the same, they are only marked once; The right-handed thread can not be injected with the screw code, and the left-handed thread screw code is lh; If the length of the screw is medium (N), it is not noted, the long type is represented by L, and the short type is represented by S.

Thread Measurement Method:

1.Measurement of thread angles. The thread angle is also called the tooth angle.

The measurement of the thread angle can be achieved by measuring the side angle, which is the angle between the side of the thread and the perpendicular face of the thread axis. The approximate contour of the thread teeth is sampled in the straight line segments on both sides of the thread, and the linear least squares fitting is performed on the sampling points.

2.Measurement of pitch. Pitch is the distance between a point on a thread and the corresponding point on an adjacent thread. The measurement must be parallel to the thread axis.

3.The measurement of the middle diameter of the thread, which is the distance along the middle diameter line perpendicular to the axis, and the middle diameter line is an imaginary line.

The above content refers to: Encyclopedia - Thread Annotation.

1. M 16 5g6g represents the common thread of the coarse tooth, the nominal diameter.

16. Right hand, the thread tolerance zone is 5g in the middle diameter, 6g in the large diameter, and the screwing length is considered as the medium length.

2. M16 1 lh 6g represents the fine tooth ordinary thread, the nominal diameter is 16, and the pitch is 16.

1. Left-handed, the middle diameter and large diameter of the thread tolerance zone are 6g, and the screwing length is considered as medium length.

3. G1 represents the inch unsealed pipe thread, the size code is 1 in, and it is right-handed.

4. RC 1 2 indicates the inch thread.

Sealing cone pipe thread, size 1 2 in, right-handed.

5. TR20 8 (P4) represents trapezoidal thread, nominal diameter 20, double wire, lead.

8, pitch 4, right-handed.

6. B20 2LH represents zigzag thread, nominal diameter 20, single wire, pitch 2, left-handed.

Commonly used tolerance zones for internal and external threads are specified as follows:

i, the internal thread is specified as g, h two positions; The external thread is specified in four positions: E, F, G, and H.

ii. Five tolerance classes are specified for the diameter and diameter of the internal thread.

The large diameter of the external thread is specified in three tolerance classes; The middle diameter of the external thread is defined as seven tolerance classes.

When the internal and external threads are screwed, the tolerance zone code is separated by a diagonal line, such as 6h 6g, 6h 5g6g, etc.

The above content refers to: Encyclopedia - Thread Annotation.

Thread calloutsIt refers to the method of marking with specific symbols in the place where the screw needs to be used, and the thread can be divided into two categories according to the use: connection thread and transmission thread, and the common annotation includes ordinary thread andPipe threads

The thread on the drawing needs to be marked with the specified thread code, except for the pipe thread, the annotation format of the thread code is: feature code Nominal diameter.

Pitch. Single-line) swivel lead.

p pitch) (multi-line) The annotation format of the pipe thread is: feature code + size code + rotation direction, wherein, the right-hand thread is omitted and the left-hand thread is represented by "lh".

Thread Callout Measurements:

Using machine vision technology, an automatic detection system for thread parameter measurement is designed, and parameters such as thread angle, pitch and middle diameter of standard thread specimens are measured. The measurement results show that the thread parameters are within the specified error range. Due to the high efficiency and reliability of visual inspection, it was considered that it could be used in production practice after further investigation.

The above content refers to: Encyclopedia - Thread Annotation.

The threaded hole is marked as M plus thread diameter or M plus thread diameter multiplied by the effective thread depth. Female and external threaded connection.

Representation: internal and external threaded connections, generally represented by cross-sectional views. At this time, their screwed parts should be drawn according to the drawing method of the external thread, and the rest of the parts should still be represented according to their respective drawing methods.

When drawing, it must be noted that the thick solid line representing the projection of the external thread and the thin solid line representing the projection of the base circle of the tooth base must be aligned with the thin solid line representing the projection of the inner thread and the thick solid line representing the projection of the crown circle, respectively. This is related to chamfering.

Size-independent, it indicates that the internal and external threads have the same large diameter and the same small diameter. According to the regulations, when the solid screw is cut through the axis, it is not cut.

Thread code marking features

The thread on the drawing needs to be marked with the specified thread code, except for the pipe thread.

In addition, the annotation format of the thread code is: the nominal diameter of the feature code.

When multiplying the pitch of a single line, the rotation guide path p pitch, and when multi-line, the annotation format of the pipe thread is: the feature code plus the size code plus the rotation to it, the right-hand thread is omitted and not not, and the left-hand is represented by lh.

The size of the ordinary thread, the tooth type code of the ordinary thread is M, there are coarse teeth and fine teeth, and the pitch of the coarse thread can be omitted; When the tolerance zone code of the middle diameter and the top diameter are the same, they are only marked once; The right-handed thread can not be injected with the screw code, and the left-handed thread screw code is lh; If the length of the screw is medium (N), it is not noted, the long type is represented by L, and the short type is represented by S.

1. The annotation method of thread length is as follows: on the drawing, the thread needs to be marked with the specified thread code, and there are differences in the annotation method for ordinary threads and pipe threads, and they are specifically elaborated for different thread forms. The size of the ordinary thread is composed of the thread length, the thread process structure size and the thread mark, of which the thread mark must be noted on the large diameter.

2. The complete thread marks are as follows: nominal diameter, pitch rotation-middle diameter tolerance code;

3. Top diameter tolerance code: the thread type code of the ordinary thread of the screwing length code is M, which is divided into coarse teeth and fine teeth, and the pitch of the coarse thread can be omitted; When the tolerance zone code of the middle diameter and the top diameter are the same, they are only marked once; The right-handed thread can not be injected with the screw code, and the left-handed thread screw code is lh; If the length of the screw is medium (N), it is not noted, the long type is represented by L, and the short type is represented by S.

4. The length of the rotation is specified as short (represented by S), medium (represented by N) and long (represented by L). In general, the thread length is not marked, and the thread tolerance zone is determined by the medium length of the thread (n). If necessary, the screw-length code S or L can be added, e.g. "M20-5G6G L".

If it is specially required, the value of the screwing length can be indicated, such as "M20-5G6G 30".

1. Standard drawing method of thread: In mechanical drawing, the view drawing of threads and threaded fasteners is more cumbersome. In order to improve the efficiency of cartography, the prescribed drawing method is usually adopted.

The international standard ISO and the Chinese mechanical drawing standard both stipulate that the thread top is represented by a thick solid line, and the bottom of the thread is represented by a thin solid line, and in the view of the projection surface perpendicular to the axis of the thread, the thin solid line representing the bottom of the thread is only drawn 3 4 turns, and the termination limit of the thread is represented by a thick solid line. The thread profile, diameter, pitch ......etc. are marked with the thread code in the dimension.

In the cross-sectional view of the assembly drawing, it is specified that the threaded fasteners are drawn as uncut, and a simplified drawing method is prescribed for common threaded fasteners, such as a hexagon head bolt, a hexagon nut and a set of fasteners of a washer can be drawn according to the drawing method in the drawing.

2. Thread labeling description: In the standard thread labeling method specified in the national standard, the first letter represents the thread code, for example: M represents the ordinary thread, G represents the pipe thread of non-thread sealing, R represents the pipe thread sealed with thread, and TR represents the trapezoidal thread, etc.

The second number indicates the nominal diameter of the thread, which is the greater diameter of the thread. It represents the maximum diameter of the thread in millimeters. The symbols after that are pitch, lead, rotation, mid-diameter tolerance code, top diameter tolerance code, and screwing length code.

Code callout

In addition to the pipe thread, the annotation format of the thread code is: feature code, nominal diameter pitch (single line) Rotation direction Lead (p pitch) (multi-line) The marking format of the pipe thread is: feature code + size code + rotation direction Among them, the right-handed thread is omitted and the left-handed thread is represented by "lh".

Dimensioning of common threads.

The tooth type code of the ordinary thread is M, which is divided into coarse teeth and fine teeth, and the pitch of the coarse thread can be omitted; When the tolerance zone code of the middle diameter and the top diameter are the same, they are only marked once; The right-handed thread can not be injected with the screw code, and the left-handed thread screw code is lh; If the length of the screw is medium (N), it is not noted, the long type is represented by L, and the short type is represented by S.

The above content refers to: Encyclopedia - Thread Standard.

1. When marking the diameter, the symbol "r" should be added before the size number "When the radius is marked, the symbol "r" should be added before the ruler and the inch number; When marking the diameter or radius of a sphere, it should be marked with a slippery mark".

or "r" before the symbol "s".

For the head of screws and rivets, the ends of shafts (including screws), and the ends of handles, the symbol "s" may be omitted so as not to cause misunderstanding.

2. When marking the arc length, the symbol should be added above the size number".

3. When marking the reference size, the size number should be added with parentheses.

4. When marking the size of the cross-section as a square structure, the symbol can be added before the number of the length of the square side

or with b b".

5. When marking the thickness of the plate-shaped parts, the symbol "t" can be added before the size number

6. When it is necessary to indicate that the radius size is determined by other dimensions, the dimension line and the symbol "r" should be marked, but do not indicate the size number.

7. When marking the slope or taper, the line width of the symbol is h

10。The direction of the symbol should be consistent with the direction of the slope and taper.

If necessary, the taper can be marked at the same time, and the angle value of the wheel can be assigned in parentheses.