Draw an image and designation of the thread on the drawing. How pipe threads are shown and designated in the drawing

carved is a surface formed by the screw movement of a certain flat figure along a cylindrical or conical surface so that the plane of the figure always passes through the axis.

In mechanical engineering, parts with various threads are widely used, each of which most fully meets the purpose and operating conditions of the threaded connection.

Threads used for fixed connections are called fastening . Threads used in movable joints to transmit a given movement of one part relative to another are called kinematic (running ).

A thread formed on a cylindrical surface is called cylindrical threaded, on a conical surface - conical carving

When two parts are threaded together, one of them has external thread made on the outer surface, and the other - internal made in the hole (Figure 86).

The thread size refers to the value of its outer (largest) diameter, which is called the nominal thread diameter, for example, dimensions d and D in Figures 86 and 87.

Figure 86

Figure 87

The thread designation usually includes a letter designation that identifies the type of thread as well as the size of the thread. The main element of the thread is its profile established by the relevant standard.

Drawing a helical surface is a very labor-intensive process. Therefore, in the drawings, threads are depicted conditionally.

By GOST 2.311-68 All types of standard threads are depicted in the drawings in the same way - conditionally, regardless of their actual appearance.

The thread on the rod (external) is depicted with solid main lines along the outer diameter and solid thin lines along the inner diameter (Figure 87).

The internal thread in the hole in the longitudinal section is depicted by solid main lines along the internal diameter of the thread and solid thin lines along the outer diameter (Figure 87).

When depicting a thread, a solid thin line is applied at a distance of at least 0.8 mm from the main line and no more than the thread pitch.

Threads shown as invisible are shown with dashed lines along the outer and inner diameters (Figure 88).

Figure 88

The thread boundary is drawn to the line of the outer diameter of the thread and is depicted as a solid main line (Figures 87, 88) or a dashed line if the thread is shown as invisible.

Hatching in sections and sections is carried out to the line of the outer diameter of the thread on the rods and to the line of the internal diameter in the hole, i.e. in both cases to the solid main line (Figure 89).

Figure 89

Chamfers on a threaded rod and in a threaded hole that do not have a special structural purpose are not shown in projection onto a plane perpendicular to the axis of the rod or hole (Figure 87).

On sections of a threaded connection in the image on a plane parallel to its axis, only the part of the thread that is not covered by the thread of the rod is shown in the hole (Figure 90).

Figure 90

A solid thin line depicting the thread on the rod should intersect the chamfer boundary line (Figure 91)

Figure 91

Image of conical threads (Figure 92).

Figure 92

Thread designations indicate according to the relevant standards the dimensions and maximum deviations of threads and relate them for all threads, except conical and cylindrical pipe threads, to the outer diameter, as shown in Figures 93 and 94.

Designations for tapered threads and cylindrical pipe threads are applied as shown in Figure 95.

Figure 93

Figure 94

Figure 95

Threads are made with a cutting tool, removing a layer of material, rolling (by extruding screw protrusions), casting, pressing, stamping from various materials (metal, plastic, glass).

Due to the design of thread-cutting tools and equipment, technological features of the manufacturing process and operation of threaded products, some features appear in the design of threaded parts: chamfers, grooves, thread run-out (incomplete thread profile) and thread undercut.

Figure 96 shows the following technological features when cutting threads with taps, dies, cutters and cutters: x - thread run, a - thread undercut, z - chamfer, f - groove.

Figure 96

Grooves for metric threads (Figure 97 a - external; b - internal)

Figure 97

Metric thread most often used in fasteners (bolts, screws, nuts, studs).

The nominal profile and dimensions of metric thread elements are established by GOST 9150-81. The figure shows the profile of a metric thread: d - outer diameter of the external thread (bolt); d 1 - internal diameter of the bolt; d 2 - average bolt diameter; P - thread pitch; D - outer diameter of the internal thread (nut); D 1 - internal diameter of the nut; D 2 - average diameter of the nut. In this case, d = D, d 1 = D 1, d 2 = D 2.

GOST 8724-81 establishes the diameters and pitches of metric threads (Table 8).

Depending on the purpose of the part, metric threads are made with large (the only one for a given thread diameter) and small pitches, of which there may be several for a given thread diameter. Right-hand threads are predominantly used; LH is added to the designation of left-hand threads.

The thread designation includes a letter designation that identifies the type of thread as well as the size of the thread.

The pitch size is not included in the designation of a thread with a coarse pitch, since each outer diameter of the thread according to GOST 8724-81 corresponds to only one coarse pitch value.

The designation of a metric thread with a fine pitch must indicate the pitch size, since the fine pitch can be different for the same outer thread diameter (Table 8).

Metric threads with a large pitch are designated by the letter M and the size of the outer diameter, for example, M16, M24.

Metric threads with fine pitches are designated by the letter M, the size of the outer diameter and the thread pitch, for example, M16 x 0.5; M24 x 0.75.

A multi-start metric thread should be designated by the letter M, a nominal diameter, a numerical value of the stroke and in brackets by the letter P with a numerical value of the pitch, for example, a three-start thread with a nominal diameter of 24 mm, with a pitch of 1 mm and a stroke of 3 mm is designated - M24 x 3 (P1).

Table 8 - Diameters and pitches of metric threads

To designate a left-hand thread, the letters LH are placed after the symbol, for example, M16LH, M42 x 2LH.

Examples of metric thread designations in the drawings are shown in Figure 98.

The threads on the rods are depicted along the outer diameter with solid main lines, and along the inner diameter with solid thin lines.

You studied the basic elements of metric threads (outer and inner diameters, thread pitch, thread length and angle) in fifth grade. Some of these elements are indicated in the figure, but such inscriptions are not made on the drawings.

Threads in holes are depicted with solid main lines along the internal diameter of the thread and solid thin lines along the outer diameter.

The thread symbol is shown in the figure. It should be read like this: metric thread (M) with an outer diameter of 20 mm, third class of accuracy, right-handed, with a large pitch - “Thread M20 class. 3".

In the figure, the thread designation is “M25X1.5 class.” 3 left” should be read as follows: metric thread, outer thread diameter 25 mm, pitch 1.5 mm, fine, third class of accuracy, left.

Questions

1. What lines represent the threads on the rod?
2. What lines show threads in a hole?
3. How are threads indicated on drawings?
4. Read the entries “M10X1 class. 3" and "M14X1.5 cl. 3 left."

Working drawing

Each product - a machine or mechanism - consists of separate, interconnected parts.

Parts are usually made by casting, forging, and stamping. In most cases, such parts are subjected to machining on metal cutting machines- turning, drilling, milling and others.

Drawings of parts, provided with all instructions for manufacturing and control, are called working drawings.

The working drawings indicate the shape and dimensions of the part, the material from which it must be made. The drawings indicate the cleanliness of surface treatment and the requirements for manufacturing accuracy - tolerances. Manufacturing methods and technical requirements the finished part is indicated by an inscription on the drawing.

Cleanliness of surface treatment. On treated surfaces there are always traces of processing and unevenness. These irregularities, or, as they say, surface roughness, depend on the tool used to process.

For example, a surface processed with a garnish will be rougher (uneven) than after processing with a personal file. The nature of roughness also depends on the properties of the material of the product, on the cutting speed and feed rate when processing on metal-cutting machines.

To assess the quality of processing, 14 classes of surface cleanliness have been established. Classes are designated in the drawings by one equilateral triangle (∆), next to which the class number is indicated (for example, ∆ 5).

Methods for obtaining surfaces of different cleanliness and their designation in the drawings. The cleanliness of processing one part is not the same everywhere; therefore, the drawing indicates where and what kind of processing is required.

The sign at the top of the drawing indicates that for rough surfaces there are no requirements for cleanliness of processing. The sign ∆ 3 in the upper right corner of the drawing, taken in brackets, is placed if the same requirements are imposed on the surface treatment of the part. This is a surface with traces of processing with bastard files, roughing cutters, and an abrasive wheel.

Marks ∆ 4 - ∆ 6 - semi-clean surface, with barely noticeable traces of processing with a finishing cutter, personal file, grinding wheel, fine sandpaper.

Marks ∆ 7 - ∆ 9 - clean surface, without visible traces of processing. This treatment is achieved by grinding, filing with a velvet file, or scraping.

Mark ∆ 10 - a very clean surface, achieved by fine grinding, finishing on whetstones, filing with a velvet file with oil and chalk.

Signs ∆ 11 - ∆ 14 - surface cleanliness classes, achieved by special treatments.

Manufacturing methods and technical requirements for the finished part are indicated in the drawings with an inscription (for example, blunt sharp edges, harden, burnish, drill a hole together with another part, and other requirements for the product).

Questions

1. What symbols indicate the cleanliness of the surface treatment?
2. After what type of treatment can a surface finish of ∆ 6 be obtained?

Exercise

Read the drawing in the figure and answer the questions in writing using the form provided.

Questions for reading a drawing	Answers
1. What is the name of the part?	–
2. Where is it used?	–
3. List the technical requirements for the part	–
4. What is the name of the drawing type?	–
5. What conventions are there in the drawing?	–
6. What is the general shape and size of the part?	–
7. What thread is cut on the rod?	–
8. Specify the elements and dimensions of the part	–

“Plumbing”, I.G. Spiridonov,
G.P. Bufetov, V.G. Kopelevich

A part is a part of a machine made from a single piece of material (for example, a bolt, nut, gear, lead screw lathe). A node is a connection of two or more parts. The product is assembled according to assembly drawings. A drawing of such a product, which includes several units, is called an assembly drawing; it consists of drawings of each part or unit and depicts assembly unit(drawing of a single...

1. Types of threads

Threads and threaded connections are widely used in technology. Their advantages include ease of assembly and disassembly and ease of manufacture.

Threads are classified according to the following characteristics. Depending on the shape of the surface on which the thread is cut, they are divided into cylindrical and conical.

Based on their location on the surface of the rod or hole, they are divided into external and internal.

Depending on the shape of the profile, threads of triangular, rectangular, trapezoidal, round and other profiles are distinguished.

According to their operational purpose, threads are divided into fastening threads (metric, inch), fastening and sealing threads (pipe, conical) and running threads (trapezoidal, thrust, rectangular).

In accordance with GOST 11708-66, the main elements and thread parameters have the following definitions.

The right-hand thread is formed by a contour rotating clockwise and moving along an axis in the direction away from the observer.

The left-hand thread is formed by a contour that rotates counterclockwise and moves along an axis in the direction away from the observer.

Thread profile - the contour of the thread section in a plane passing through its axis.

Profile angle - the angle between the sides of the profile.
Thread pitch P - the distance between adjacent sides of the same name

sides in a direction parallel to the thread axis.

Thread stroke Ph is the distance between the nearest identical sides of the profile belonging to the same screw surface in a direction parallel to the thread axis. Thread stroke is the amount of relative axial movement of the screw (nut) per revolution.

There is a relationship between the thread lead Ph and pitch P: Ph = P n,

where n is the number of visits.
Since in a single-start thread n = 1, then Ph = P.

The outer diameter of the thread (d - for a bolt, D - for a nut) is the diameter of an imaginary cylinder described around the tops of an external thread or the valleys of an internal thread.

2. Conventional image of the thread

The rules for depicting threads in drawings are established by GOST 13536-68. All carvings are depicted the same way.

On the rod, the thread (external) is depicted by solid main ones, thick lines along the outer diameter and thin lines along the inner diameter (Fig. 1, a). In a view where a threaded rod is projected into a circle, its contour is drawn with a solid thick main line, and the inner contour is depicted as a circular arc drawn with a thin line approximately 3/4 of the circle, in which the gap can be located anywhere, but the ends of the arc are not resolved placed on the axes. When depicting a thread, a thin solid line is drawn at a distance of at least 0.8 mm from the solid thick main line and no more than the value of the thread pitch.

The thread in a hole in a longitudinal section is depicted by solid thin lines along the outer diameter and solid thick lines along the internal diameter. The thread boundary is shown with a solid thick main line (Fig. 1, b).

In the view where the threaded hole is projected into a circle, draw a thin line along the outer diameter of the thread, approximately equal to 3/4 of the circle, open anywhere (the ends of the arcs are not recommended to be placed on the axes). The inner circle, the diameter of which is equal to the inner diameter of the thread, is drawn with a solid thick main line. If the threaded hole is blind, then it is shown as in Fig. 1, b. The length of the part of a blind hole without thread in the drawings is taken equal to half the outer diameter of the thread. The end of the hole from under the drill has the shape of a cone with an apex angle of 1200. The value of this angle is not indicated on the drawings.

In drawings in which threads are not made, the end of a blind threaded hole may be depicted as in Fig. 2.

Chamfers on a threaded rod and in a threaded hole that do not have a special structural purpose on a plane perpendicular to the axis are not shown.

A drawing of a threaded connection is made up of images of its constituent parts. Figure 3 shows two parts: a threaded rod and a part with a blind threaded hole. In the same figure, the parts are shown in connection (in section). The threaded rod is considered to cover the threads in the hole, so the threads in the hole are shown only where they are not covered by the end of the rod. Solid thick main lines corresponding to the outer diameter of the threads on the rod transition into solid thin lines corresponding to the outer diameter of the threads in the hole. Conversely, solid thin lines corresponding to the internal diameter of the threads on the rod transition into solid thick main lines corresponding to the internal diameter of the threads in the hole. Particular attention should be paid to the hatching: the hatching lines extend to solid thick main lines on both the shaft and the hole.

It should be remembered that although the connection drawing (Fig. 3) contains a section, the threaded rod is not shaded, since the secant plane runs along a solid (non-hollow) part, which is cut but not shaded.

3. Thread designation

Since all threads in the drawing are depicted the same way, the type of thread and its main dimensions are indicated on the drawings with a special inscription called the thread designation. Examples of symbols for general purpose threads are given in table. 1.

Single-start metric threads with the same outer diameter can have several pitch values. The step with the maximum value is called large, and the rest are called small. The choice of the coarse pitch value is made from the condition that the angle of elevation of the screw thread is no more than 2030/. The large step is not indicated in the symbol.

Left-hand threads are designated by the Latin letters LH. For example, M20¥1.5LH - metric thread, diameter 20 mm, fine pitch - 1.5 mm, left.

The designation of threads is applied on the drawings: metric, trapezoidal, thrust (Fig. 4), pipe (Fig. 5). Since rectangular threads are non-standard, they do not have a designation. In the drawing, this thread is depicted as shown in Fig. 6.

Standard threads are shown identically in the drawings. It is impossible to determine from the conventional image what type of thread should be cut into the part.

The type of thread and its main dimensions are indicated in the drawings by a special inscription called thread designation(see Fig. 7.3, 7.7, etc.).

Before applying the thread designation, extension and dimension lines should be drawn.

Designations of threads, except for pipe and conical threads, are written above the dimension line.

Extension lines for drawing the dimension line are drawn from the outer diameter of the thread. In order not to make a mistake when drawing extension lines, you should remember that the outer diameter is always the larger thread diameter, from which extension lines should be drawn. Designations for pipe and tapered threads are placed on shelves with a leader line ending in an arrow. The leader line is brought to the thread contour.

For all standard threads, symbols are constructed according to the following general scheme (Fig. 7.14). The sequence of arrangement of designation elements indicated in this diagram is established by standards and should not be violated.

Examples symbols general purpose threads and some special ones are given in table. 7.1.

Rice. 7.14.

For metric threads with a large pitch, the pitch is not indicated in the designation. This is explained by the fact that, with the same diameter, it is the only one for a thread with a large pitch. For threads with fine pitches, the standard provides several different pitch sizes and therefore you need to indicate which one to choose.

The dimensions of pipe and tapered threads indicated in the designations are arbitrary, since in most cases they refer to the internal diameters of the pipes, and not to the external diameters of the threads. For example, if the designation of a cylindrical pipe thread contains the size 2" (2 inches), then the outer diameter of the thread according to the standard for pipe thread sizes will be equal to 59.616 mm, with the inner diameter of the pipe being 50 mm.

According to GOST 16093–2004, the accuracy of metric threads is indicated by a tolerance field, in the designation of which the number indicates the degree of accuracy, and the letter indicates the main deviation. For example, for a thread on a rod: 4 h; 6 g; 8g, and in the hole: 6H, 7H.

For threads on a rod, there are the following designations of tolerance fields (preferred) according to GOST 16093–81:

• exact – 4 To,
• average – 6h; 6 g, 6e; 6d;
• rough - 8h; 8g.

For threads in a hole, there are the following designations of tolerance fields (preferred):

• exact – 4H5H;
• average – 5H6H; 6H; 6 G;
• coarse – 7H; 7 G.

The screwed parts must, as a rule, have the same thread accuracy. Mating threads should be designated as follows: exact class - rod Ah, hole 4H5H; middle class 6g rod, 6H hole; rough grade - 8g shaft, 7H hole. Examples of designations of mating threads are shown in Fig. 7.15.

Rice. 7.15.

A– metric; b– trapezoidal; V– pipe

The designations of threads do not include the most common data: the right direction of the rise of the thread and single-start. For example, Tr80 × 10–6H should be understood when reading the drawings as follows: trapezoidal thread with a nominal diameter of 80 mm, pitch 10 mm, tolerance range 6H, single-start right.

Table 7.1

Thread symbols

	Thread type and standard number	Literal designation	Components of the designation	Example notation
	Metric GOST 8724–81 with large pitch		Outer diameter, mm	M1 2 – 6g (external) M12 – 6Ya (internal)
	with fine steps		Outer diameter and pitch, mm	Ml 2× 1 6 g Μ 12 × 1 – 6H
	multi-pass		R) and pitch, mm	M20 × 3(P1) – 6g
			Latin letters are added L.H.	M12LH – 6g M20 × 3 (P1)LH – 6g
	Metric conical GOST 25229-82		Nominal diameter and pitch	MK20× 1.5
	Internal cylindrical		The standard number is added	M20 × 1.5 GOST 25229-82
			Latin letters are added L.H.	MK20× 1.5 L.H. MK20× 1.51H GOST 25229–82
	Trapezoidal single-thread GOST 24738-81		Outer diameter and pitch, mm	Tr40×7– 8e(external) Tr40 × 7 – 8 H(internal)
	multi-pass GOST 24739-81		Outer diameter, stroke size, pitch designation ( R) and pitch, mm	Tr20 × 8(P4) – 8e (external) Tr20 × 8( P4) – 8H (internal)
			Latin letters are added L.H.	Tr40×7 LH – 8e Tr20× 8 (P4)L.H.– 8H
	Thrust GOST 10177-82 single-thread		Large diameter and pitch, mm	580 × 10 – 6g (external) 580 × 10 – 6H (internal)
	multi-pass		Outer diameter, stroke size, pitch designation ( R) and pitch, mm	580 × 20(P10) – 6H
			Latin letters are added Sh	580 × 10LH-6g 580 × 20(P10)LH – 6Ya
	Pipe cylindrical GOST 6357-81		Designation of thread size in inches (without the " sign) and accuracy class of average diameter	G1½ – A(accuracy class A)
			Latin letters are added L.H.	G1½ LH – B(accuracy class IN)
	Pipe conical GOST 6211–81 external (left)		Designation of thread size in inches (without the " sign)	D¾(R¾ L.H.)
	inner (left)			Rc¾ (Rc¾ L.H.)
	internal cylindrical (left)			Rp¾ ( Rp¾ L.H.)
	Conical inch with a profile angle of 60°, GOST 6111–52		Designation of thread size in inches, standard number	K1½ GOST 6111–52
	Conical valves and cylinders for gases GOST 9909-81		Nominal size, mm
			Outer diameter, mm
			Latin letters are added L.H.
	Ocular GOST 5359-77		Outer diameter and pitch, mm, and standard number	OK12× 1.5 GOST 5359-77
	Edison round GOST 6042–83 for metal elements		Outer diameter, mm, and standard number	E27 GOST 6042-83
	for non-metallic elements			E27/N GOST 6042-83

In the designation of multi-start threads, first the following is written: 1) the designation of the type of thread, 2) its outer diameter, 3) through the multiplication sign the stroke value in mm, then 4) the designation of the pitch in a capital Latin letter is indicated in parentheses R and step size in mm. This is followed by 5) indicating the direction of the thread (if the thread is left-handed) in capital Latin letters L.H. At the end of designation 6) the tolerance field is indicated through a dash.

Examples of notation

Tr20 × 4(Р2)-8е – trapezoidal thread, outer diameter 20 mm, stroke 4 mm (double-start), pitch 2 mm ( P2), right-hand thread (no indication of thread direction), tolerance range 8e, external thread, as indicated by the lowercase letter.

Tr20×4( P2)LH-8e – the same, left.

TR20× 4 (P2)-8H– internal thread, as indicated by a capital letter.

TR20× 4 (P2)LH-8H – the same, left.

S100× 60 (P20)-4H– means a thrust thread, the outer diameter of which is 100 mm, stroke 60 mm, pitch 20 mm, tolerance range AN(internal thread, as indicated by a capital letter), right-hand thread (no indication of thread direction).

OK40 × 6 (Р1.5) GOST 5359–77, where OK - designation of eyepiece thread, 40 – nominal diameter in mm, stroke 6 mm, R– designation of the step, which is equal to 1.5 mm. The standard designation is indicated at the end.

The designation of the surface roughness of the working sides of the thread can be applied according to general rules on the image of the profile of this thread, if the profile is shown in the drawing, or on the extension lines near the thread designations (Fig. 7.15). The designation of the roughness of conical and pipe threads is placed on leader lines (Fig. 7.15, c).

• Preferred application tolerance fields.

The carving in the drawings is depicted conditionally. This means that it is not shown as it is seen in nature (see Fig. 7.3, A and 7.7, A), where you can distinguish the profile, curved lines depicting thread turns, and are depicted according to the rules established by GOST 2.311–68.

Rice. 7.3.

A - natural; b– conditional

Rod thread

According to these rules, the thread on the rod (external thread), regardless of its profile, is depicted solid main lines along the outer diameter and solid thin lines along the internal diameter of the thread (see Fig. 7.3, b).

A continuous thin straight line along the inner diameter of the thread is drawn along the entire length of the thread, including the chamfer. In views where a threaded rod is projected as a circle, its contour is outlined with a solid main line, and the internal diameter of the thread is depicted as a circular arc drawn by a thin line approximately 3/4 of the circle, open anywhere (but not on the center lines) ( Fig. 7.3, b and etc.).

When depicting a thread, a solid thin line is drawn at a distance of at least 0.8 mm from the solid main line and no more than the thread pitch.

The border of the cut section is shown by a solid main line, which is drawn to the line of the outer diameter (Fig. 7.4, a). The boundary of the cut section (end of the thread) is considered to be the end of the full thread profile, i.e. before the run begins.

Thread run - this is the length of the section of an incomplete profile in the transition zone from the thread to the smooth part of the part (Fig. 7.4, b).

Rice. 7.4.

A - no escape; b, c – with an escape

Usually the carving is depicted without a run (Fig. 7.4, A). If you need to show a run, then it is depicted as a solid thin line inclined to the axis of the rod (Fig. 7.4, b, c). The run-out is shown when you need to apply its size (Fig. 7.4, c) or the size of the length of the thread with the run-out (Fig. 7.4, b).

When the thread on a rod is shown in section, the border of the cut section is drawn with a dashed line (Fig. 7.5).

Rice. 7.5.

Hole thread

The threads in the hole, shown as invisible, are depicted with dashed lines (Fig. 7.6).

Rice. 7.6.

The thread in a hole in a longitudinal section is depicted by solid thin lines along the outer diameter and solid main lines along the inner diameter.

The thread boundary is shown with a solid main line (Fig. 7.7, b), bringing it to the outer diameter of the thread.

Rice. 7.7.

A - natural; b– conditional

In views where a threaded hole is projected as a circle, draw a thin line along the outer diameter of the thread, approximately equal to 3/4 of the circle, open anywhere (but not on the center lines), and the contour of the hole (inner diameter of the thread) outlined with a solid main line (Fig. 7.7, b).

The hatching in the section is adjusted to the internal diameter of the thread in the hole, i.e. before solid main line(Fig. 7.7, b). This rule also applies to the depiction of threads on a rod: no matter what thread is depicted, the hatching in the section is always brought to a solid main line (see Fig. 7.5 and 7.7, b).

If the threaded hole is blind, then it is shown as in Fig. 7.8, A. In drawings in which threads are not made, the end of a blind threaded hole may be depicted as in Fig. 7.8, b, c, even if there is a difference between the depth of the thread hole and the length of the thread. The length of the part of a blind hole without thread (Fig. 7.8, A) in the drawing is taken to be equal to half the outer diameter of the thread. The end of the hole from under the drill has the shape of a cone. It is depicted with an apex angle of 120° (approximately like a drill). The value of this angle is not indicated on the drawings (Fig. 7.9). It is usually not included in the hole length size (Fig. 7.9). It should be noted that the diameter of the base of the cone is equal to the internal diameter of the thread (Fig. 7.9). You should not make the mistake of depicting it as in Fig. 7.10, where this diameter is greater than the diameter of the hole and, therefore, the drill.

Rice. 7.8.

Rice. 7.9.

A - Right; b – wrong

Rice. 7.10.

Chamfers on a threaded rod and in a threaded hole that do not have a structural purpose are not conventionally depicted on a plane perpendicular to the axis of the rod or hole (see Fig. 7.3 and 7.7). This is done so that the solid main line of the circle, depicting one of the chamfer diameters, does not cover the image of the thread.

Conical threads are depicted according to the same rules as cylindrical threads (Fig. 7.11, a, b).

Rice. 7.11.

A – on the rod; b – in the hole

To determine the internal diameter of the thread (for drawing), you need to multiply its external diameter by 0.85, i.e. di ≈ 0,85d(if necessary, the exact size of the internal thread diameter is taken from the relevant standard).

A thread with a non-standard profile is shown with all the required dimensions and maximum deviations on a local section (Fig. 7.12) or an extension element. For multi-start threads, in addition to the dimensions and maximum deviations, data on the number of starts is indicated.

Rice. 7.12.

When the thread direction is left, it is added L.H. for all threads. In all cases, the designation of a non-standard thread begins with the word Thread.

Connecting parts using threads

A drawing of a threaded connection is made up of images of its constituent parts.

In Fig. 7.13, A two parts are presented: a rod with a thread cut at the end, and a part with a blind threaded hole. Pay attention to the lines that show the outer and inner diameters of the threads. In Fig. 7.13 , b these parts are shown in connection (section).

Rice. 7.13.

A– parts to be connected; b– a rod screwed into the hole; V – typical mistake when shading

Notice how the threaded rod is depicted screwed into the hole.

The threaded rod is considered to cover the threads in the hole. Therefore, the thread in the hole is shown only where it is not closed by the end of the rod (Fig. 7.13, b). The bottom of the blind hole is not filled with a threaded rod. Therefore, solid main lines corresponding to the outer diameter of the thread on the rod turn into solid thin lines corresponding to the outer diameter of the thread in the hole. Conversely, solid thin lines corresponding to the internal diameter of the thread on the rod turn into solid main lines corresponding to the internal diameter of the thread in the hole (Fig. 7.13, b). An incorrectly executed carving, where the shading is extended only to a continuous thin line, is shown in Fig. 7.13, V.

Please note that although the connection drawing shown in Fig. 7.13, b, and contains a cut, the threaded rod is not shaded. Let us recall that when, when making a cut to connect parts, the secant plane passes along a solid (non-hollow) part, it is not cut and, therefore, not shaded.