A threaded connection is the main method of connecting parts. When making any metal device with your own hands, the need arises to cut threads yourself. Tapping allows you to create threads in various holes with your own hands.
In practice, we have to deal with various materials that differ in their properties. Cutting should take into account the characteristics of the material. There are certain rules, developed over the years, that allow for high-quality thread cutting. different sizes and types.
Features of the structure of taps
The tap, which belongs to the group of metalworking and turning cutting tools, has the shape of a rod on which the cutting element is made. It is intended for cutting internal thread, that is, inside the hole in various materials, as well as for restoring damaged internal threads.
Kit metal cutting tools: a - drills, b - countersinks, c - reamers, d - taps, d - dies.
The tools consist of a working and a tail part. In turn, the working part is divided into an intake (cutting) and calibrating section. The cutting section is responsible for the main function of the tap - cutting threads, and, most often, has a conical shape. It has teeth in the form of incisors placed around a circle. The calibrating section performs the task of final formation. It is made in the form of a cylinder with teeth that are a continuation of the teeth of the cutting section. This section is much longer than the fence. Working part in longitudinal direction cut with grooves that are designed to form cutters and remove chips. Taps with a diameter of up to 22 mm have three grooves. Devices special purpose can be manufactured without grooves. The grooves can be straight or helical.
The tail part has the shape of a cylinder. At the end of the section there is a square for installation in the fastening tool. In this part, the diameter marking is stamped out. Using a shank, the tool is fixed in a hand holder or machine chuck.
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Main types of taps
According to the method of use, taps are divided into two types - manual and machine. The first ones are installed in manual holders (knobs) and are designed for cutting internal threads manually. Machine ones are mounted in special holders for lathe chucks.
Based on the type of thread cut with a tap, they are divided into several types. Metric is designed for cutting the most common metric threads. Pipe forms internal threads on pipes, as well as reinforced threads in holes metal parts. Inch is a device for special inch threads, as well as cone-shaped ones. Specialized nut taps are made of very strong steel (P6M5) and have a special shank shape.
In addition, taps are divided into single and complete. Complete ones are used to cut in several passes. The set may contain two taps - finishing and rough; or three taps - roughing, medium finishing and finishing. Completeness is indicated on the tail of the instrument. The taps included in the set differ in the shape of the tooth: the roughing one has a trapezoidal tooth; the middle one has a triangle with a rounded top; the finishing one has a triangle with a sharp apex.
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Main settings
In general, cutting a thread means making a protrusion on inner surface holes so that it forms a helix. Such a protrusion, like all threads, is characterized by the following basic parameters: helix angle, pitch, type of protrusion profile and profile elevation angle, outer and inner diameter. In addition, it is customary to distinguish another depth, determined by the outer and inner diameters.
In direction, the thread can be right-handed, when the helical protrusion rises counterclockwise, and left-handed, when the direction of rise of the protrusion coincides with the clockwise movement. Based on the shape of the protrusion profile, there are two main types: threads with a rectangular profile and with a triangular profile. There are also special profile forms, but they are practically not used in everyday life.
The main thread is metric. This profile is a triangle with a profile angle of 60º. According to the pitch, metric is divided into threads with a large pitch and with a fine pitch. An example of the full designation of a metric thread is M10x1-6N. The designation should be understood as follows:
- M - metric thread;
- 10 - nominal diameter;
- 1 - thread pitch;
- 6H - tolerance limits for dimensional deviations.
With normal (large pitch) the designation is abbreviated (for example, M10). In the case of a left-hand thread, the designation LH is entered.
The second most common type in everyday life is the cylindrical pipe type. The profile is a triangle with an apex angle of 55º. This type is used when connecting pipes and cylinders, where increased tightness of the connection is required. Straight pipe threads are designated by the letter G, indicating the diameter in inches.
The thrust thread is based on a trapezoidal profile with inclination angles of 3º on one side and 30º on the other. The designation includes the letter S, diameter and pitch.
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Choosing the right tap
First, the type of tap is selected based on the type of thread and its purpose (profile shape, thread pitch, tolerances). According to the accuracy requirements (class), it is determined whether a single tap should be used or a set is required. In addition, taps are produced with different finishes of their cutting element, which affects the accuracy of cutting the thread profile.
The material in which the thread must be cut influences the choice of tap. Thus, the rake angle of the teeth must be taken into account. It is for steel - 5-10º, for copper alloys - 0-5º, for aluminum and alloys - 25-30º. Devices can be made from ordinary steels, high-strength steels or high-strength brazed steels, which must be taken into account when considering what strength of material is being processed.
The main choice is made based on the diameter of the hole in which the internal thread is cut. The diameter of the tap should be slightly smaller than the diameter of the hole. So, for a metric M20 thread (tap diameter 20 mm), the hole diameter is 19 mm. At metric thread, if there are no special requirements, then the standard step is performed. For example, M4 thread - pitch 0.7 mm; M5 - 0.8 mm; M10 - 1.5 mm; M12 - 1.75 mm, etc.
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Fastening tool
In order to ensure thread cutting, the tap must be given a rotational movement with the application of force. This function is performed hand holder- collar It provides vertical mount tool and the ability to apply significant loads using levers. The standard design of the driver contains a tap fastening unit and elongated handles, with which you can rotate the device manually with force.
The device is mounted in two ways. One of the knob designs consists of two parts. When these parts are joined, a hole is formed inside for installing the tap. Both parts come together at an adjustable distance, which is set with screws. The second option provides a single knob design with a hole in the center. The tap is inserted into this hole and clamped with 3-4 locking screws. The handles of the knob are made on both sides. Handle lengths can be 15-25 cm.
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Preparing for slicing
Cutting internal threads begins with drilling the desired hole - through or blind. The main condition: the hole must be smaller than the thread diameter. When drilling a hole, it is recommended to select a drill from the following condition:
- for M3 thread - drill diameter 2.5 mm;
- at M4 - 3.4 mm;
- at M5 - 4.2 mm;
- at M6 - 5 mm;
- at M8 - 6.7 mm;
- at M10 - 8.4 mm.
If it is necessary to cut a large thread, the hole diameter is determined by approximately multiplying the thread diameter by 0.8.
The hole for cutting internal threads is made on a drilling machine or electric drill. In the latter case, the workpiece is clamped in a vice. It is necessary to ensure that the drill is directed strictly vertically. The top edge of the hole is chamfered to facilitate entry of the tap. It can be done with a larger diameter drill or file. After drilling, the hole is thoroughly cleaned of chips, which is especially important for blind holes.
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Tapping threads
The part in which the hole for the internal thread is drilled is secured in a vice so that the chamfer on the hole is at the top. The axis of the hole should be strictly perpendicular to the table. The tap is securely fixed in the driver socket and inserted vertically into the chamfer of the workpiece hole. Holding the handles of the driver with both hands, the tap is pressed against the part and rotated clockwise. Rotation is smooth and even with light pressure. This is done two times forward. Then turn it half a turn back (counterclockwise). The entire hole is drilled in this sequence.
When cutting threads, the bolt must be secured.
When cutting threads, it is necessary to periodically cool the tool. It is recommended to use the following substances: when working with aluminum and its alloys - kerosene, with copper - turpentine, with steel parts - emulsion. For metals such as bronze or cast iron, cooling lubricants may not be used.
It is best to use complete taps for cutting internal threads with a tap. First, the rough thread is cut. Then the middle tap is passed in the same way, and only then the thread is finally formed using a finishing tap. Excluding any tap from the process will not significantly speed up the process, but will significantly degrade the quality of work.
Topic No. 11 “Cutting fastener threads manually.
CONCLUSION
Safety rules for thread cutting
· when cutting threads by hand in workpieces with strongly protruding sharp parts, it is extremely important to ensure that when turning the tap with the handle you do not injure your hand;
· to avoid breakage of the tap, do not work with a dull tap, and when cutting threads in
in blind holes, chips should be removed from the hole more often;
· 
Particular care should be taken when cutting small diameter threads (5mm or less) to avoid breakage of the tap;
· Having put on overalls, carefully tuck your hair under your beret;
· It is extremely important to firmly secure the workpiece in a vice;
· when filing workpieces with sharp edges, do not tuck the fingers of your left hand under the file when reverse stroke;
· to avoid injury, the workbench, vice, worker and measuring tool must be kept in order and stored in appropriate places.
So if sheet metal or the pipes you want to use in your work have no visible damage: the sheets are even; pipes – not bent; the metal is clean, without traces of rust or scale, then you are in luck. But more often than not, a mechanic strives to make something out of nothing; in connection with this material, he uses all kinds of waste or used sheets of metal or pipes. In this case, before you begin metalworking, you should properly prepare them: straighten, shade, wash, clean off scale, possibly remove varnish, paint or putty, and then only cut internal or external threads.
The student must know: purpose and methods of performing operations when cutting external and internal threads manually; types of thread; tools and devices; technical equipment; possible types and the reasons for the appearance of marriage; organization and rules for maintaining the workplace; basics of industrial sanitation.
The student must be able to: perform all operations in the correct sequence when cutting threads with round and sliding dies in through and blind holes; determine the diameters of rods and threaded holes from tables; check the quality of the thread; use measuring and testing tools; choose a tool when processing threaded surfaces; organize correctly workplace; comply with safety regulations; eliminate defects that arise when processing threaded surfaces.
1. What types of threads exist and their purpose?
2. What tool is used to locally increase the size of the hole and process sites?
3. What does cutting speed depend on when machining a hole?
4. In what sequence are internal threads cut by hand?
5. What are the main elements and types of round dies?
6. In what cases are sets of two and three taps used?
7. What causes thread stripping when cutting threads?
8. What defects can occur and how to eliminate them when processing threaded surfaces?
9. Which ones exist? distinctive features inch threads?
10. What types of defects are possible when working with dull tools?
11. What safety rules are extremely important to follow when processing threaded
Surfaces?
Manual pipe threading"
Target: introduce students to the technical requirements for upcoming work in a metalworking shop; learn to use tools and devices; sequences of techniques for cutting fastening and pipe threads manually; with safety rules when cutting threads; with labor protection and fire safety
Tapping internal threads begins with choosing the right tool. Then the first step is to drill the hole. In fact, this stage is the most important, since if you make a mistake with the selection of the diameter, then either the bolt will hang loose, or the tap will break due to overload when cutting a thread. It is best to determine the hole diameter using tables, but you can also make a rough estimate: by subtracting its pitch from the thread diameter, you can get an approximate value of the required hole diameter.
For example, if the outer diameter of the thread is 18 mm and the pitch is 1 mm, then you need to drill a hole of 17 mm. It is necessary to drill strictly perpendicular to the surface of the part (due to deviations, defects in cutting are possible). It is advisable to make a small chamfer at the drilled hole. For blind holes, the depth must be greater than the length of the part being cut so that the tool, when cutting, goes beyond the required thread length. If this margin is not provided, the thread will be incomplete.
The part with the drilled hole is secured in a vice. The tap is fixed in the driver (if not available, use an adjustable wrench) or in the machine chuck. The quality of the thread, cutting speed and tool life are significantly influenced by the correct selection of cutting fluid (coolant). In order not to damage the tool, and to obtain a clean thread with the correct profile, it is necessary to use the following coolant:
diluted emulsion (one part emulsion mixed with 160 parts water);
for parts made of brass and steel, you can use linseed oil;
For aluminum products– kerosene;
for parts made of red copper - you can use turpentine;
In products made of cast iron and bronze, cutting should be carried out dry.
Mineral and machine oils should not be used - they contribute to a significant increase in the resistance that the tool overcomes during operation, have a negative effect on the roughness of the thread and lead to rapid wear of the tap.
1.2. Rules for cutting internal threads with a tap
When manually cutting threads, the tool is inserted into the hole vertically (without distortion). The driver is not rotated in the desired direction (for right-hand threads clockwise) not all the time, but is periodically made 1–2 turns per reverse side.
With such a rotational-return movement of the tap, the cut chips break, become short (crushed) and are easier to remove from working area, and the process of thread formation is greatly facilitated. After cutting is completed, the tool is turned out by turning the knob in the opposite direction, then it is driven along the finished thread through or until it stops for blind holes. You must also adhere to the following rules:
When forming threads in tough and soft metals (aluminum, copper, babbitts and others), as well as in deep holes, the tool should be periodically unscrewed from the hole to clean the grooves from chips.
When using a tap kit, all tools in the kit must be used. Cutting immediately with a finishing tap or a medium one, and then finishing without a roughing pass does not speed up, but only slows down and complicates the cutting process. In addition, the thread turns out to be of poor quality, and the tool may break. The finishing and middle taps are screwed into the hole by hand (without a driver) until the tool follows the thread correctly, and only after that the driver is installed and work continues.
During the cutting process, it is necessary to carefully monitor the correct insertion of the tool so that it does not become distorted. To do this, it is necessary to check the position of the tap relative to the upper plane of the part using a square after every newly cut 2-3 threads of chips. Particular care should be taken when working with blind and small holes.
Tap design
Tap(Fig. 1) is a hardened screw on which several straight or helical grooves are cut, forming cutting edges tool. The grooves also provide accommodation for the chips generated during cutting; the chips can be removed from the cutting zone.
The tap consists of two parts- a working shaft and a shank, at the end of which there is a square (for hand taps). The working part of the tap includes: a cutting (taking) part, which ensures the removal of the main part of the processing allowance; a calibrating part that performs final processing of the thread; chip flutes; feathers (thread turns separated by chip grooves) and a core, which provides the tap with sufficient strength and rigidity for processing. The tail part of the tap serves to secure it in the driver, which is used to carry out working and idle movements of the tap.
The working part of the tap is made from tool carbon steels grades U11, U11A, high-speed steel or hard alloy. The choice of material for the working part depends on the physical and mechanical properties of the workpiece being processed. For solid taps, the material of the tail part is the same, but for taps consisting of two parts connected by welding, the tail part is made of structural steel grades 45 and 40X: The number of chip grooves made on the tap depends on its diameter (three grooves for taps with a diameter up to 20 mm and four - for taps with a diameter over 20 mm).
The main work when cutting threads is performed by the cutting edges formed by the intersection of the front surfaces of the groove with the rear (backed, made in an Archimedean spiral) surfaces of the working part. Relief of the back surface cutting teeth allows you to keep their profile constant after sharpening, which is carried out centrally in sharpening shops.
As a rule, taps are made with straight flutes, but to improve cutting conditions and obtain accurate and clean threads, taps with helical grooves are used. The angle of inclination of such a groove to the axis of the tap is 8... 15°. To obtain precise and clean threaded surfaces in through holes when machining soft and tough materials, fluteless taps are used.
Rice. 1 Tap:
a – design: 1 – thread (turn); 2 – square; 3 – tail; 4 – groove; 5 – cutting feather; b – geometric parameters: 1 – front surface; 2 – cutting edge; 3 – backed surface; 4 – back surface; 5 – cutting feather; α – clearance angle; β – cutting angle;δ – sharpening angle;γ – front angle; c – with a helical flute: 1 – groove; g - cutting blind threads; ω – angle of inclination of the helical groove.
Ministry of Education Nizhny Novgorod region
State budgetary professional educational institution
"Arzamas Commercial and Technical College"
on educational practice
on the topic "Thread cutting"
for the profession 01/23/03 Auto mechanic
Executor:
L.Yu.Makarova
master p/o
2015
Introduction
1. The system of activity of the industrial training master.
2. Organization educational activities students.
3. Methodology for conducting the main stages of the lesson on MDK.01.01 Plumbing and technical measurements on the topic “Thread cutting”.
4. Lesson project.
5. Structure and course of the lesson.
6. List of used literature.
Conclusion
Application
1. Test tasks for the lesson
2. Instructional and technological maps
3. Parts drawings
4. Evaluation criteria
Introduction
Road transport occupies one of the leading places in the unified transport system Russian Federation. The increasing range of bus and freight transportation, combined with improving vehicle performance, improving the condition of existing roads and building new ones, makes distant regions of the country, remote rural and mountainous areas accessible. settlements. In many regions, road transport is the main means of transportation and cargo transportation.
Knowledge of the structure of cars and plumbing allows you to organize high-quality maintenance and repair, as well as the operation of motor vehicles. Mastering thread cutting skills will allow students to quickly and efficiently repair components, mechanisms and assemblies of automobiles.
The most common connections for machine parts are threaded. Wide Application threaded connections in machines and mechanisms is explained by the simplicity and reliability of this type of fasteners, the convenience of adjusting the tightening, as well as the possibility of development and reassembly without replacing parts.
This indicates the relevance of the topic being studied, and in this regard, in lessons it is necessary to require students to perform particularly careful thread cutting operations, because The quality of the entire part largely depends on the quality of the thread.
Before starting work, students must have general information about threads, their designation and classification, about tools for cutting, measuring and monitoring threads, use reference tables. In addition, students must have certain physical characteristics, such as reaction speed and attentiveness.
1. The system of activity of the industrial training master.
When conducting induction training it is necessary to check the attendance of students and inspect their appearance; communicate the topic and purpose of the lesson; explain the nature and purpose of the lesson, update the knowledge and experience of students by questioning them on the topics of the theoretical lessons completed, because the topic contains material they have studied in class special technology.
It is necessary to familiarize students with the organization of the workplace and work safety rules. To repeat the material covered, we use oral survey students and use test control cards. Then the teaching master introduces students to learning objectives and the content of the topic with a list of exercises that students must complete.
Shows rational placement of the tool, demonstrates the student’s working position when performing the exercise. The explanation of the new material is carried out in the form of a story and demonstration of practical techniques for performing individual exercises when cutting threads.
When explaining the material, visual aids and posters on the topic “Thread cutting” are used. If the students understand the technique of performing practical work, the training master invites them to begin performing it, having previously drawn attention to the need for strict adherence to safety rules. To control the assimilation of the studied material during the lesson, the achievement of intermediate goals is assessed:
Teach how to prepare a workplace;
Learn to use the tool;
Teach compliance with safety regulations;
Teach careful and economical use of equipment and materials.
During practical work, the master monitors the correctness of execution and, if necessary, points out errors and methods for correcting them.
After completing the entire amount of work, an analysis of the lesson conducted is made, notes best works students, grades are announced. At the end of the lesson, it is necessary to announce homework: repeat the material covered in theoretical classes for the next practical lesson.
Organization of educational activities of students
The organization of educational activities of students when studying the topic “Thread cutting” is aimed at overcoming difficulties and individual problems, because in achieving a certain mastery, when performing exercises, students constantly advance in their perfection (“from simple to complex”).
The main methods used by training masters to organize educational activities can be:
For example, playing the role of a p/o master during a demonstration of techniques for performing this exercise. After demonstrating the techniques of the exercise by the master p/o, students are invited to play the role of the master and re-demonstrate the learned technique. This method can be used in two cases: when one of the students did not understand how to perform the technique (in this case, the role of the master is assigned to a student who has successfully mastered the exercise), or when it is necessary to activate the so-called “weak” student (in this case, the role of the master assigned to this student).
One of the ways to develop skills of self-control and mutual control, develop adequate self-esteem, and foster mutual assistance is for students to perform the role of a training master during the final briefing; at the end of the work, students check the quality of the completed task, comparing it with the standard; in case of uncertainty about the correct execution, they turn to the student - the “master”. The role of the master during the final instruction can be performed by several so-called “strong” students.
Organization of work in pairs (mentoring) during ongoing instruction. One of the reasons for using this method of organizing students is that a “person” learns best not when he is learning, but when he is teaching.
Therefore, in order to successfully master various thread cutting techniques during training, it is advisable to assign “weaker” students to stronger ones.
This method increases the student’s responsibility for the quality of the work performed, promotes the development of self-awareness, and helps overcome uncertainty and fear of mistakes.
Methodology for conducting the main stages of the lessonMDK.01.01 Plumbing and technical measurementson the topic "Thread cutting".
Organizational part.
Hello guys. The master listens to the report of the duty officer about those absent from the lesson, checks the appearance and readiness of the students for the lesson, and asks if there are any sick people.
Induction training.
The master informs the topic and purpose of the lesson.
For verification purposes background knowledge On the topic, the master updates knowledge:
a) frontal survey from the seat (see lesson progress);
b) issues test tasks(execution time - 5 minutes).
Before moving on to showing thread cutting techniques, the master considers the formation and classification of threads.
A thread is a helical groove of a certain profile, cut on a cylindrical or conical surface. On lathes it is performed through two uniform movements - rotation of the workpiece and translational movement of the cutting tool along its axis.
The threads used can be divided into a number of groups:
1) by location - external and internal;
2) by purpose - for fastening and running gear;
3) according to the shape of the original surface - cylindrical and conical;
4) in direction - to the right and left;
5) according to the profile shape - triangular, rectangular, trapezoidal, round;
6) by the number of passes - single and multi-pass.
Fastening threads most often have a triangular profile.
They are used to connect various parts.
Running threads serve to convert rotational motion into translational motion. These include threads with a trapezoidal and, less commonly, rectangular profile.
Tapered threads provide high tightness of the connection and are therefore used in places under high blood pressure liquids and gases.
For right-hand threads, the screw groove has a clockwise direction (when viewed from the end of the part), for left-handed threads it is the opposite.
Single-start threads are threads that have one helical groove. Multi-start threads have several parallel helical grooves evenly spaced around the circumference. The number of thread starts can be determined by the number of starts of helical grooves at the end of the part.
M12x1.5 – 6H
where the letter M is a metric thread,
12 – nominal thread diameter,
6 – accuracy class,
g – tolerance range and external thread,
N - tolerance range and internal thread,
1.5 – thread pitch,
L – left-hand thread.
Then the master explains to the students how to correctly select the diameter of the rod for external thread using reference tables or remembering the rule: the diameter of the rod should be 0.1-0.2 mm less than the nominal thread diameter. For example, for a M12-6g thread, the diameter of the rod should be 11.8 mm.
To determine the diameter of a drill for internal threads, use reference tables or the formula:
D St. = D r. - R,
where D St. - drill diameter;
D r. – nominal thread diameter;
P – thread pitch.
For example:
M12x1.5 – 6H
D St. = 12 – 1.5 = 8.5mm,
those. in this case, a drill with a diameter of 8.5 mm is required.
When cutting threads in blind holes, it is necessary to take into account that the tap has a chamfer and if you drill a hole to the length of the thread according to the drawing, the cut thread will be shorter in length. Therefore, the hole must be drilled longer to the length of the intake part of the tap.
Now, guys, we can move on to threading techniques.
1. Cutting external thread M12 -6g:
We take a rod with a diameter of 11.8 mm and fasten it vertically in a vice to the length of the thread being cut;
We select a die M12 - 6g, attach it to the collar;
Using a file, remove the chamfer on the rod;
Lubricate the rod machine oil;
A die fixed in the collar is placed on the rod and with slight pressure the die is rotated so that it cuts into 1-2 threads, and the die must be in a strictly horizontal plane;
Thus, we cut the thread to the full length;
2. Cutting internal thread M12 -6N:
Drill a hole on a drilling machine;
Use a countersink to remove the chamfer;
Then continue moving 1-2 turns to the right and half a turn to the left;
We cut the thread to the full length,
We check the quality of the thread visually and with a thread gauge.
3. Cutting an internal thread M12 -6H in a blind hole:
We select a drill with a diameter of 8.25 mm (coarse thread - thread pitch 1.75 mm);
We make markings according to the drawing;
We drill a hole on a drilling machine to a length greater than the intake part of the tap;
Use a countersink to remove the chamfer;
We fasten the part with the drilled hole in a vice;
We select a set of taps M12 – 6H (No. 1 and No. 2);
Lubricate the hole with machine oil;
We insert tap No. 1 into the hole and install a knob on it;
We rotate the tap to the right 2-3 turns, while the tap should be strictly in vertical plane(use a square);
Then continue moving 1-2 turns to the right and half a turn to the left;
We cut the thread to the full length, while periodically removing chips from the hole
(turning the tap completely out);
We check the quality of the thread visually and with a thread gauge.
Next the wizard shows possible reasons occurrence of defects when cutting threads: torn threads (dull tool, tool misalignment); blunt thread (incorrect tool diameter); inaccurate thread profile (insufficient length of the intake cone, incorrect sharpening of the tool); breakage of the tap. The wizard shows how to remove broken taps.
Then the master disassembles technological process manufacturing parts according to the drawings (stud M5 -6g; nut M12 - 6N; part with a blind hole).
The master informs the children of the assessment criteria (see Appendix No. 4).
Before you start independent work the master explains the safety rules:
Do not remove chips by hand;
Blow chips off the part;
Operate with a faulty tool;
Follow safety rules when working at drilling machines.
The group is divided into 3 subgroups and each student is given the appropriate workpiece, tool, instructional and technological map and part drawing.
Current briefing.
In the process of performing independent work, the master makes targeted walkthroughs of workplaces in order to check:
Correct performance of work techniques;
Compliance with safety regulations;
Correct self-control;
Correctness of observance technical specifications.
As the work is completed, the subgroups change jobs.
Upon completion of the work, the master accepts and evaluates the work performed.
Final briefing.
Conducting the final briefing, the master reports on the completion of the lesson goal, analyzes the success of each student’s work, analyzes typical mistakes and disadvantages, ways to prevent and eliminate them. Analyzes students' compliance with safety rules, work organization, use of working time, reports grades to each student according to evaluation criteria.
Gives out homework (N.I.Makienko Plumbing with the basics of materials science; pp. 353 – 378.)
Project of a practical training lesson (industrial training)
Profession: 01/23/03 Auto mechanic
Master p/o: L.Yu.Makarova
Program topic: Thread cutting.
Lesson topic: External thread cutting, internal thread cutting in through and blind holes.
The purpose of the lesson:
– teach how to correctly select the diameter of a rod for cutting external threads and cut threads on the selected rod; teach how to select drills for internal threads and drilled hole cut threads, contribute to the improvement of thread cutting methods;
To promote the development of students’ cognitive activity, self-control, and skills to justify their choice of working methods;
Contribute to the formation and development of students’ personalities, improve teamwork skills, and cultivate a caring attitude towards equipment, tools, and raw materials.
Lesson type: combined.
Teaching methods: reproductive
Interdisciplinary connections: “Plumbing”, “Materials Science”, “Drawing”, “Technical Measurements”.
Qualification requirements
Must know: types and purposes of threads. Tools and equipment for thread cutting. Safety regulations.
Should be able to: select the diameter of the rod for the thread to be cut, select drills for internal threads, possess the appropriate techniques and skills for thread cutting, identify defects and, if possible, eliminate them.
Location: training and production workshop.
Pedagogical technologies used: developmental education technologies, information and communication technologies, health-saving technologies.
Material and technical equipment of the lesson:
Threading tool poster, samples of threaded parts, technological maps, multimedia projector, tabletop and vertical drilling machines, workbenches, taps, dies, drills, sandpaper, files, center finder, center punches, hammers, compasses, scribers, rulers, measuring tools, test cards, machine oil, brush, rags.
5. Lesson structure and flow
I. Organizational part (5 minutes.)
1.Greeting
2. Checking the attendance of students;
3. Check appearance;
4. Readiness of students to work.
II. Induction training.(35 min.)
Target setting: communicate the topic and purpose of the lesson.
Repetition of covered material:
What does this inscription M20-6N mean? M20-6e; M20x1.5; M20x1.5LH
What is a tap?
What is a die?
What material are thread cutting tools made from?
What is thread pitch?
Conducting a test to consolidate the material covered.
Presentation of new material:
Demonstration of a video on repairing spark plug threads in the cylinder head;
To cut a thread on a rod (stud, bolt), you need to select required diameter rod, die and, using appropriate techniques, cut the thread (plate with parameters);
Show thread quality control, show the possible occurrence of defects and methods for eliminating it (show a video);
To cut internal threads in through holes, you need to: select the appropriate drill and tap, drill a hole on the machine (observing safety precautions) and, using the appropriate techniques, cut the thread. Thread quality control. Showing possible defects and methods for eliminating them. Methods for removing a broken tap from a hole;
Techniques for cutting internal threads in blind holes. Which tap should I use to cut the thread (with a smaller chamfer). How to measure thread length?
Disassemble the drawing of the part and the manufacturing process, and warn against defects.
Provide evaluation criteria.
Safety precautions when cutting threads.
Issuing assignments to subgroups.
III. Current briefing. Independent work.(5 o'clock)
Making a hairpin and cutting threads on it (I subgroup)
Making a nut and cutting a thread on it (II subgroup)
Threading in a blind hole (III subgroup).
As parts are manufactured, subgroups change tools and make other parts and, thus, each subgroup must make three parts.
Targeted workplace walkthroughs:
I – check the contents of jobs
II – check the correctness of work practices and compliance with safety regulations
III – check the correctness of self-control
IV – check the correctness of compliance with technical conditions. Accept and evaluate work.
IV. Final briefing.(20 minutes.)
Summing up the work;
Communication of the assessment to each student;
Analysis of the most characteristic shortcomings in the work;
Cleaning of workplaces;
Message homework(N.I. Makienko “Plumbing with the basics of materials science” pp. 353-372)
Bibliography.
Main sources:
1. Dolgikh A.I. etc. Locksmith work. – M.INFRA, 2007 – 528 p.
2.V.A. Skakun Organization and methodology of vocational training; -M. Forum-Infra, 2007 – 335s.
3. Chumachenko Yu.T. Car mechanic. – M.: Phoenix, 2008 – 534 p.
4. Shishmarev V.Yu. Measuring instruments. – M.: “Academy”, 2009 – 320 p.
1.Kosyachenko A.P., Molchan I.A. Plumbing. – M: Publishing House of Mechanical Engineering Literature, 1961 – 213 p.
2. N.I. Makienko Mechanical engineering with the basics of materials science; - M. Higher school, 1974 - 464 p.
3. N.I. Makienko Practical work in plumbing. - M. Higher School, 1987 - 192 p.
4. E.E. Feldshtein et al. Driller’s Handbook. - Mn.: Higher School, 1986 - 336 p.
Conclusion
The considered approaches to organizing training allow students to develop sustainable skills in performing thread cutting work, develop independence, professional Creative skills, form the necessary for successful activities personal qualities. This, in turn, ensures the inclusion of students in the profession of “Auto mechanic” in the production activities of the technical school.
Annex 1
Test
Thread. Thread cutting.
Largest diameter, measured along the tops of the thread turns is called
a) thread pitch;
b) outer diameter of the thread;
c) internal diameter of the thread.
If a nut screwed onto a bolt is turned one turn, how much will it move along the bolt?
by the value of the internal diameter;
c) by the thread pitch.
3. What are the names of the threads used to convert rotational motion into translational motion (vises, jacks, machines)?
a) fastening;
b) running gear.
4. What profile does fastening thread?
a) rectangular;
b) persistent;
c) round;
d) triangular;
e) trapezoidal.
5. How are carvings shown on the drawing?
6. What does the inscription mean?M24x1.5?
a) meter thread, outside diameter 24 mm, inner diameter 1.5 mm, right;
b) metric thread, outer diameter 24 mm, thread pitch 1.5 mm, right;
c) millimeter thread, internal diameter 24 mm, thread pitch 1.5 mm, left.
7. WITH What tool is used to cut internal threads?
a) dies and collar;
b) die and tap;
c) tap and driver;
d) die and die holder.
8. What is the purpose of the grooves on the tap and the windows in the die?
a) form cutting edges and serve to release chips;
b) to reduce the weight of the tool;
c) for beauty.
10. What does the inscription on the shank of the M 12 tap mean?
finishing tap, for cutting metric threads with an outer diameter of 12 mm;
roughing tap, for cutting metric threads with an outer diameter of 12 mm;
c) medium tap (semi-finish), for cutting metric threads with an outer diameter of 12 mm.
11. For what purpose is the die or tap turned back half a turn?
a) to break off chips to facilitate the thread cutting process;
b) speed up the thread cutting process.
12. How to choose the correct diameter of a rod or threaded hole?
a) must be equal to the internal diameter of the thread;
b) must be equal to the outer diameter of the thread;
c) slightly smaller than the outer diameter of the thread (determined from the table in the reference book).
Thread. Thread cutting.
Appendix 2
for the production of M5-6 studsg
| Technical | Equipment and tool |
||
| Measure size 90 -0.2 mm, if necessary, bring the workpiece to the required level by filing | Size 90 -0.2 mm | Bench vice Calipers File |
|
| vertically for size more than 15mm (~18mm) above jaws | Bench vice |
||
| Remove a chamfer from the end of the workpiece 1x45 o | Flat file |
||
| Measure the diameter of the workpiece, if necessary, bring it to the required one (4.9 mm) | Calipers Sandpaper |
||
| Draw a line from the end of the workpiece at a distance of 15mm | Scriber Triangular file |
||
| Lubricate the workpiece rod protruding above the vice with machine oil. | Machine oil Brush |
||
| Cut thread | Thread length 15mm | Die M5-6g |
|
| Wipe the workpiece from oil, remove chips | |||
| Check the quality of the thread visually and screw on the nut M5-6N | Nut M5-6N |
||
| Take out the workpiece, turn it over and clamp it in a vice with the other end to a height of 28mm | Bench vice |
||
| Repeat steps 3-9 to cut a thread at a length of 25mm | Thread length 25mm | Flat file Scriber Triangular file Calipers Sandpaper Machine oil Brush Die M5-6g Nut M5-6N |
Instructional and technological map
for the production of nuts M12-6N
| Sequence and content | Technical | Equipment and tool |
|
| Mark the workpiece. Mark the resulting center and corners of the hexagon with a center punch. | Hexagon with the side size 27 -0.2 mm. | Center finder |
|
| Place the workpiece in a bench vise so that one side of the hexagon is flush with the jaws of the vice and parallel to them | Bench vice |
||
| File the protruding part of the workpiece to marking | Flat file |
||
| Repeat operations 2-3 to file the other 5 edges | size 27 -0.2 mm | Flat file Calipers |
|
| Remove burrs and sharp edges | Flat file |
||
| Install the drill into the chuck of the drilling machine No. 1 | Drill diameter 10.2mm Drilling machine |
||
| Machine vice |
|||
| Drill a hole. Remove the workpiece. | diameter 10.2mm | Drilling machine Drill diameter 10.2mm |
|
| Install the drill into the chuck of the drilling machine No. 2 | Drill diameter 13mm |
||
| Secure the workpiece in a machine vice | Machine vice |
||
| Chamfer both sides Remove the workpiece. | Drill diameter 13mm |
||
| Place the workpiece in a bench vise | Bench vice |
||
| Lubricate the hole with machine oil | Machine oil Brush |
||
| Cut the thread with tap No. 1 | Tap No. 1 Square |
||
| Cut the thread with tap No. 2 | Tap No. 2 Square |
||
| Remove the workpiece. | Bench vice |
||
| Inspection of threads visually and with a thread gauge | Thread gauge |
Instructional and technological map
tapping blind holes
| Sequence and content completing the task | Technical requirements | Equipment and tool |
|
| Secure a drill with a diameter of 10.2 mm in the drill chuck | Drilling machine Drill diameter |
||
| Secure the workpiece in a machine vice | Machine vice |
||
| Drill a hole Remove the workpiece | Diameter10.2mm Depth-15mm | Drilling machine Drill diameter Vernier caliper with depth gauge |
|
| Secure the workpiece in a bench vice | Bench vice |
||
| Lubricate the hole and tap M12-6N machine oil | Machine oil Brush Tap M12-6N |
||
| Cut thread | Length-10mm | Tap M12-6N Vernier caliper with depth gauge |
|
| Thread quality control (visual) | Thread gauge |
Appendix 3
Hairpin M5-6g
Nut M12-6N
Appendix 4
Consolidated statement
| P/ P | Last name, first name student | Work from place (1 answer, -1 point) | Manufacturing of parts | Violation (- 2 points) | Total |
||||
| Hairpin (max.-5 points) | screw (max.-6 points) | (max. - 4 points) |
|||||||
Criteria for evaluation:
15b – 5 (excellent);
13b – 4 (good);
11b – 3 (satisfactory).
Note:
non-compliance linear dimensions- minus 1 point;
non-compliance with thread length – minus 1 point;
discrepancy in thread quality – minus 1-2 points.
Goal of the work – acquisition of practical skills in metalworking operations: thread cutting. There are two types of thread: external and internal. Carvings are made on machines or by hand.
Thread cutting techniques, and especially the cutting tool used, largely depend on the type and profile of the thread.
Threads can be single-start, formed by one helical line (thread), or multi-start, formed by two or more threads.
According to the direction of the helical line, the threads are divided into right and left.
The profile of a thread is the cross section of its turn with a plane passing through the axis of the cylinder or cone on which the thread is made.
To cut a thread, it is important to know its basic elements: pitch, outer, middle and inner diameters and the shape of the thread profile (23).
The thread pitch S is the distance between two points of the same name on adjacent thread profiles, measured parallel to the thread axis.
Outer diameter d - greatest distance between the outermost points, measured in a direction perpendicular to the axis of the thread.
Internal diameter di is the smallest distance between the extreme internal points of the thread, measured in a direction perpendicular to the axis.
Average diameter di is the distance between two opposite parallel flanks of a thread profile, measured in a direction perpendicular to the axis.
Base of thread Top of thread
According to the shape of the thread profile, they are divided into triangular, rectangular, trapezoidal, thrust (profile in the form of an unequal trapezoid) and round.
Depending on the sizing system, threads are divided into metric, inch, pipe, etc.
In metric threads, the angle of the triangular profile φ is 60°, the outer, middle and inner diameters and thread pitch are expressed in millimeters. Example of designation: M20X X1.5 (the first number is the outer diameter, the second is the pitch).
Pipe thread differs from inch thread in that its initial size is not the outer diameter of the thread, but the diameter of the pipe hole, on outer surface which the thread is cut. Example of designation: pipes. 3/U" (numbers are the internal diameter of the pipe in inches).
Thread cutting is carried out on drilling and special thread-cutting machines, as well as manually.
At manual processing In metals, internal threads are cut with taps, and external threads are cut with dies.
Taps according to their purpose are divided into manual, machine-hand and machine, and depending on the profile of the thread being cut - into three types: for metric, inch and pipe threads.
The tap (24) consists of two main parts: the working part and the shank. The working part is a screw with several longitudinal grooves and is used for direct thread cutting. The working part, in turn, consists of an intake (cutting) and a guide (calibrating) parts. The intake (cutting) part does the main work when cutting threads and is usually made in the form of a cone. The calibrating (guiding) part, as the name suggests, guides the tap and calibrates the hole.
Longitudinal grooves serve to form cutting feathers with cutting edges and accommodate chips during the thread cutting process.
The shank of the tap is used to secure it in the chuck or in the driver during operation.
To cut a thread of a certain size, hand (mechanism) taps are usually made in a set of three pieces. The first and second taps pre-cut the thread, and the third taps give it the final size and shape. The number of each tap in the set is marked by the number of marks on the tail. There are sets of two taps: preliminary (rough) and finishing.
Taps are made from carbon, alloy or high-speed steel.
When cutting threads with a tap, it is important to choose the correct drill diameter to obtain a hole for the thread. The diameter of the hole should be slightly larger than the internal diameter of the thread, since the material during cutting will be partially extruded towards the axis of the hole. The dimensions of the threaded hole are selected according to the tables.
Dies used for cutting external threads, depending on the design, are divided into round and prismatic (sliding).
The round die (25, a) is a solid or cut ring with a thread on the inner surface and grooves that serve to form cutting edges and release chips. The diameter of the split dies can be adjusted within small limits. This allows you to restore their size after wear and extend the service life of the dies.
When cutting a thread, round dies are secured in a special die holder (25, b).
Prismatic (sliding) dies (25, c), unlike round ones, consist of two halves, called half-dies. Each of them indicates the thread sizes and the number 1 or 2 for correct fastening in special device(kluppe). The angular grooves (grooves) on the outer sides of the half-dies are used for installing them into the corresponding protrusions of the die. Dies are made from the same materials as taps.
When cutting external threads, it is also important to determine the diameter of the rod for the thread, since in this case there is some extrusion of the metal and an increase in the outer diameter of the resulting thread compared to the diameter of the rod. The thread diameter is selected according to special tables.
The thread is divided as follows:
According to the profile - triangular, rectangular, trepezoidal, persistent and round.
According to the number of passes - single-pass and multi-pass
In the direction of the helix - right and left
The thread is cut manually using a tap tool.
Tap- a tool for cutting internal threads. A tap is a screw with straight or helical flutes cut into it to form cutting edges. The tap with its tail part is attached to the driver, the working part is inserted into the hole in which, when turned, the driver cuts a thread in a reciprocating motion.
There are taps for blind and through holes.
Taps are made of hard alloy or high-speed steel.
Taps can be used on lathes, drills and machining centers (machine taps), as well as for manual threading. A machine tap is different from manual form entry part. The tap is fixed on the machine in a special chuck (chuck with axial compensation), or a regular one collet chuck With collet for taps. Also in Lately As an alternative to axial-compensated chucks, compensated collets began to appear that can be used on a conventional collet chuck.
To obtain internal threads by plastic deformation - rolling- use chipless taps (rollers). Their main difference from cutting taps is the absence of chip flutes.
When drilling holes and tapping threads, you should follow the safety rules for drilling machines.
When manually cutting threads on parts with protruding and sharp parts, be careful not to injure your hands when turning the gate.
Studying safety features when cutting
threads
When drilling holes and cutting taps on a machine, you should follow the safety rules for working on drilling machines.
When cutting threads by hand on parts with protruding sharp parts, be careful not to injure your hands when turning the driver.
Inspection of threaded connections
Checking the cut internal threads is done with thread plug gauges, and external threads are checked with thread ring micrometers and thread templates.
Student's independent work
The student’s independent work consists of mastering the rules for cutting internal and external threads and performing work using the thread cutting operation.
The student must:
receive from the master a task and a blank for thread cutting;
learn the rules of thread cutting;
internal thread cutting. To do this, you need to pre-drill a hole. Since the material is partially “extruded” when cutting a thread, the diameter of the drill must be slightly larger than the internal diameter of the thread. The diameter of the drill for cutting metric and pipe threads is determined using reference tables. After preparing the hole for the thread and selecting the driver, the workpiece is secured in a vice and a tap lubricated with a cutting fluid is inserted vertically into its hole. Pressing the crank against the tap with your left hand, turn it to the right with your right until the tap cuts into the metal on several threads and takes a stable position. Then they take the handles of the knob with both hands and rotate them with their hands intercepted every half turn. The driver is rotated one or two turns to the right and half a turn to the left, etc. As a result of the reciprocating rotational movement of the tap, the chips are broken, and the cutting process is greatly facilitated. Having finished cutting, turn the knob in the opposite direction to unscrew the tap from the hole, then drive it through;
cutting external threads. It is necessary to select the diameter of the rod for the external thread - it should be slightly smaller than the external diameter of the thread. Then the rod is secured in a vice so that its end protruding above the level of the jaws is 10 - 20 mm longer than the length of the part being cut. Place a die on the rod perpendicularly and rotate it with slight pressure so that the die cuts into approximately 1 - 2 threads. The part of the rod to be cut is lubricated with oil and then the die is rotated with uniform pressure on both handles, similar to cutting with a tap;
cut external and internal metric threads;
after finishing the work, present the part to the foreman for inspection;
clean your workplace and hand it over to the foreman.
Basic rules when working as a tapper.
Basic rules when working with a die.
Rules for cutting external and internal threads.
Selecting the diameter of the hole for the thread.
Types of thread according to the number of starts, in the direction of the helix, etc.
Programmed control issues
Safety rules for thread cutting.
Parameters of metric, inch and pipe threads.
Inspection of threaded connections.
