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Theme number 11 “Cutting fastening threads by hand.
CONCLUSION
Thread Safety Guidelines
· When manually cutting threads in workpieces with strongly protruding sharp parts, it is extremely important to ensure that when turning the tap with the knob, do not injure your hand;
· In order to avoid breakage of the tap, do not work with a blunt tap, and when threading
blind holes should often remove chips from the hole;
·  special care should be taken when cutting small diameter threads (5mm or less) in order to avoid breakage of the tap;
· Wearing protective clothing, carefully tuck the hair under the beret;
· It is extremely important to firmly secure the workpiece in a vise;
· When filing workpieces with sharp edges, do not squeeze the fingers of the left hand under the file with the reverse stroke;
· In order to avoid injuries, the workbench, vise, working and measuring tools must be kept in order and stored in appropriate places.
So, if the sheet metal or pipes that you want to use in the work do not have visible damage: the sheets are even; pipes - not bent; metal is clean, without traces of rust, scale, then you are lucky. But more often than not, a locksmith strives to make something out of nothing, in connection with this material he uses all kinds of waste or used metal sheets or pipes. In this case, before proceeding with the bench work, they should be properly prepared: straighten, shade, rinse, clean the scale, possibly remove the varnish, paint or putty, and then only cut the internal or external threads.
The student must know: purpose and methods of performing operations when cutting external and internal threads by hand; types of thread; tools and fixtures; technical equipment; possible types and causes of marriage; organization and rules of the workplace; the basics of industrial sanitation.
The student must be able to: in the correct sequence, perform all operations when threading round and sliding dies in through and blind holes; determine the diameters of the rods and holes for the thread from the tables; check thread quality; use measuring and calibration tools; choose a tool when machining threaded surfaces; properly organize the workplace; comply with safety regulations; eliminate defects that occur when machining threaded surfaces.
Test questions:
1. What are the types of threads and their purpose?
2. What tool is used to locally increase the size of holes, processing sites?
3. What determines the cutting speed during hole processing?
4. In what sequence is the internal thread 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 breakage during threading?
8. What defects can occur and how to eliminate them when machining threaded surfaces?
9. What are the distinguishing features of inch threads?
10. What types of defects are possible when working with blunt tools?
11. What safety regulations are extremely important to observe when machining threaded
Surfaces?
Manual pipe threading
Purpose: to acquaint students with the technical requirements for the upcoming work in the locksmith workshop; learn to use tools and fixtures; the sequence of techniques when cutting fastening and pipe threads manually; with safety instructions for threading; with labor protection and fire safety
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Study guide to prepare
production workers Workshop on plumbing
Labor Safety Requirements for Threading
Handles of knobs, holders, traps and wrenches should have a clean, smooth surface. Do not use keys and knobs with bent handles or handles that have notches and burrs. Do not blow off chips or remove them with your fingers. To remove chips from a vice or threaded threads, use a brush or rag. In the process of work, one should be careful not to injure the hands on the burrs and protruding sharp edges of the workpieces.
Examine labor safety requirements when working with hand-held electric tools. After working with taps, dies, knobs and screw holes, it is necessary to thoroughly wash off the boiled oil with kerosene, wipe the tool with a clean, dry cloth and lubricate with a thin layer of engine oil.
Thread-cutting tools must be stored in sets in wooden cases, and measuring - in soft cases. Separate incomplete tools (hooks, rolls) should be stored in special pyramids, and taps - in specially drilled holes in wooden bars. |
Karaganda Railway College
METHODICAL DEVELOPMENT
EXPERIMENTAL LESSON
PRODUCTION TRAINING
TOPIC: Preparing holes for
tapping
Master p \\ o: Nenakhova N.V.
Karaganda 2014
Workshop lesson plan
"______" 2014
Sabaқ / Lesson No. ____
Toby / Group:
Section:
Locksmith work.
Lesson topic
: Preparing a tapping hole.
Sabaқtyң masқsaty / Lesson Objectives
:
Bіlіmdіk /
Training:
Teach students pick up drills and drill a hole for threading, cut the thread with a tap.
Damytushylyқ / Developing:
To develop independent work skills, attention, coordination of movements, speed and technique when working with the tool.
T
әrbielіk /
Educational:
To instill in students a love of work and a caring attitude to the instrument.
Sabaқtyң tүrі
/ Type of lesson
: combined
Sabaқtyң әdіsі
/ Method of conducting
: lecture with elements of conversation, practical work, use of an interactive whiteboard.
Forms of training
: group.
Oқu materialin zhabdyқtau / Educational-material equipment
: blackboard, chalk, posters, metalwork bench, taps, drill bits for thread, selected according to the tables of the corresponding reference books, countersinks of 90-120 degrees, caliper (0.1mm), screwdriver.
Mon Aralı Baylan
/ Interdisciplinary communications
: materials science, drawing.
Sabaқtyң barysy /
During the classes:
Ұйымдаширу кезені
Organization of the educational process:
09.00 – 09.05
Induction training
:
09.05. –
1
0.
3
0
Actualization of previous knowledge (repetition of material)
1)
External threading.
2) Determination of the die.
3) Types of dies
5) Countersink
6)
Workplace safety
of the issue
Question
the answer
Answers
1.
Threading-this
for cutting or rollingmale threador on machines
2.
Definition of a die -
dies designed for external threadingdiameter up to 52 mm in one pass.
3.
Types of dies:
Threaded dice are(lerki), sliding (kluppovye).
4.
Manual round dies
processing the top of the hole to get a bevel. Countersink using countersinks or a larger diameter drill.
5.
Countersinking is
The operation of obtaining on the surface of the part of the helical groove using special tools
Report the topic and purpose of the lesson
Explanation of the new material:
1.
.
2.
Preparing a hole for threading.
3. A gate for taps.
4.
Definition and types of taps
.
5.
Tapping
m
6.
7.
Thread Safety
.
1.
Selection of drill diameters for drilling a threaded hole
.
Of great importance is the correct choice of the diameter of the hole prepared for threading. If the diameter is larger than it should, then the internal thread will not have a full profile. With a smaller diameter of the hole, the tap entry into it is difficult, which leads either to the breakdown of the threads or to jamming and breakage of the tap. It should be borne in mind that when threading under the action of the feed force and the rotational movement of the tap, the workpiece metal is not only cut, but also “flows” in the direction of the axial force, that is, it is partially extruded, and to different degrees with different materials. Hard metals
and brittle give smaller changes in the size of the hole when threading than metals viscous and soft. fig. 1
If you prepare the hole exactly according to the size of the internal diameter of the thread, then the metal extruded during the cutting process will reduce the diameter of the hole, put excessive pressure on the teeth of the tap, contribute to their enhanced heating and adhesion of metal particles to the teeth. The thread in this case will turn out to be of poor quality, with torn threads, and in some cases it is possible to jam the tap in the hole and break the tool. This is especially noticeable when threading in soft and viscous materials.As a result, pwhen threading, the material is partially extruded, so the drills should be slightly lessthan the inner diameter of the thread.
The diameter of the drill is taken according to the table.
2. Tab.
Thread diameter mm
Hole diameter mm
1,0
0,75
1,2
0,95
1,4
1,1
1,7
1,35
2,0
1,6
2,3
1,9
2,6
2,15
3,0
2,5
3,5
2,9
3,3
2.
Preparing a hole for threading
To cut the internal thread with a tap, first prepare a hole for the thread by drilling. The resulting threaded hole is countersunk to a depth of 1 ... 1.5 mm with a conical countersink with an angle of 90 °. After preparation
the holes select a set of taps according to the size of the thread. The working part of the first (draft) tap is lubricated with oil and inserted with its intake part into the hole so that the axis of the tap coincides with the axis of the hole. In the holes prepared for threading them, from the side of the tap entrance, bevels must be taken off at an angle of 60 degrees and a height of at least one thread pitch.The diameter of the hole for metric threads can be approximately calculated by the formula
where a is the diameter of the cut thread, mm The dimensions of the screw for fixing the tap are selected depending on the diameter of the thread being cut. The approximate length of the collar can be determined by the formula
L \u003d 20D + 100 mm
where D is the diameter of the thread, mm
3
3. Gate for taps
Designed for fastening the shank of the taps when cutting internal threads.Taptail section attached tocrank, the working part is inserted into the hole in which, when turning the knob, the thread is cut by reciprocating movements. The back surface to eliminate friction against the workpiece is performed backed (non-circular). The thread profile of the tap should match the profile of the thread being cut.
rice4.
Tap fixed in crank
4.
Definition and types of taps.
Metchi
to-
this is a threaded rod.The tap consists of two parts: the working and the shank. On the working part, a fence (below) and a gauge (above) are distinguished. Taps usually come in three varieties: for preliminary cutting (one risk is applied), for deepening the thread (2 risks are applied) and for calibration, fine cutting (3 risks or without them). In addition, there are three-in-one taps that allow you to cut full threads in one pass.Taps are made of carbon, high speed steel.
rice
5
. Types of Taps
To understand the difference between taps with different risks, let's look at a photograph with enlarged cutting edge profiles. As you can see, the tap on the left does not cut the thread completely, the tap in the middle cuts it deeper, and only the tap on the right cuts it to the end. Of course, you can cut the thread immediately with a fine tap, only in the first place you will need more effort, as a result of which the tap can be broken, and in the second it will not last long.
rice 6. The difference between taps
Damage to the tap requires a lot of time to remove it and, in addition, spoils the thread, and sometimes even leads to the defect of the part. To prevent breakage, you must work carefully, use a serviceable and sharp tap, and often remove the tap to remove chips.
Torn thread is usually obtained when working with a blunt tap, in the absence of lubrication and improper installation of the tap relative to the cut part.
An incomplete thread is obtained when the diameter of the hole for the thread is larger than is required for the given working conditions (part material and thread size), and also when the diameter of the stem for the thread is less than the specified.
The breakdown of the thread occurs in those cases when the diameter of the drilled hole for the thread is less than required, when a blunt tap is used, the chips are hammered into the grooves.
5.
Tapping
.
After preparing the hole for the thread and selecting the knob, the part is fixed in a vise, the draft tap is lubricated and inserted into the cut hole in a vertical position. Having put the knob on the tap and gently pressing it to the part with your left hand, carefully turn the knob to the right with the right hand until the tap cuts into the metal and its position in the hole becomes stable. Then the handle is taken with both hands and gently rotated.
Fig. 7
After one or two full revolutions, the chip is broken by about a quarter of a revolution by breaking the chip, this greatly facilitates the cutting process. 
rice eight
Hhaving finished cutting, turning the knob in the opposite direction, turn the tap out of the hole or pass it through.
The second in the third taps are lubricated with oil and introduced into the hole without a collar; only after the tap is correctly installed on the thread, do they put the knob on and continue threading.
6.
Safety when drilling holes.
Correctly without distortions and firmly fix the drill in the chuck of the rotor and drills.
It is forbidden to keep the rotor and drills with the drill turned toward you.
When drilling holes, do not press firmly on the chest rot with your chest or chin. The feed is easy and smooth.
Do not allow drills to fall on the floor; when sharpening, the drill should be firmly fixed in a vice.
Firmly fix the workpiece on a workbench or on a machine.
7.
Thread Safety:
The tap is securely fixed to the gate;
Be careful that the hand does not fall between the handle of the collar and the support;
Lubricate using a brush or oiler.
To remove chips, use a sweeping brush;
Keep oil away from clothing and hands.
Taқyrypty қorytyndylau
Pin a new topic:
oral survey test
Test questionnaire.
External thread cutting.
1. Tool for cutting external threads.
1) die
2) tap
3) knob
4) drill
2.What angle do you install the rod in a vise when cutting an external thread?
1) 25 degrees
2) 30 degrees
3) 45 degrees
4) 90 degrees
3. Why do the dies turn in the opposite direction when threading?
1) for lubrication
2) for chip breaking
3) for relaxing hands
4) for safety
4. What are holes in the die for?
1) for ventilation
2) for lubrication
3) for chip evacuation
4) to reduce weight
5. A metal rod on both sides of which the thread is called:
1) a nail
2) with a screw
3) screw
4) with a hairpin
Students' independent work:10.30 – 13.5
Current briefing:
Getting the job.
Preparation of the workplace and tool.
Completing of the work.
Performing control and mutual control.
Target Bypasses
jobs to:
checking the timely start of work
safety compliance check
verification of the correct implementation of techniques and operations
providing practical assistance to students
Final briefing:
14.00 – 14.50
Summarize the lesson
Mark the best work
Parse common mistakes
Remove workplace
Report grades
Thapsyrsmasy / Homework
:
Master p \\ o Nenakhova N.V.
In addition to the general rules for safe operation on lathes when cutting threads, additional precautions must be observed.
1. It is necessary to secure the cartridge on the spindle to avoid self-unscrewing when reversing.
2. It is impossible to work on the machine with faulty or not adjusted
friction clutch speed box and brake.
3. The handle for switching the direction of rotation of the spindle of the machine must operate reliably and be fixed in the appropriate positions.
4. You can not cling to the bed during operation, as the rapidly rotating spindle can capture the floor of the robe.
Sequence of work
1. Examine the machining methods for tapering surfaces on lathes, cutting tools and fixtures for securing the workpiece. Familiarize yourself with the processing schemes and elements of the technological system necessary for processing the cones, based on the materials of work 1.1 and demonstration stands.
2. Listen to the introductory wizard. Observe the actions of the training wizard for setting up the machine for tapering the surface with a wide cutter, turning the upper caliper, shifting the tailstock and demonstrating the processing of the cones with these methods.
3. Perform exercises for turning cones with a wide cutter and turning the upper support in accordance with the current instruction of the training master.
4. Receive and execute an individual task for the independent production of a stepped roller according to the drawing and flow chart given in Table. 4.5.
5. Check the dimensions of the manufactured part, hand over the finished products to the training master and listen to his final instruction.
6. Run a report on the individual task.
1. Name of work.
2. The number, wording and initial data of the individual task
(see table. 4.5).
Task: “Describe the sequence of manufacturing the part, provide data on the parameters of the cutting mode when setting up the machine for threading (turning a conical surface) and technological equipment, give the results of measuring the dimensions of the manufactured part”.
3. Drawing step roller.
4. The sequence of processing the workpiece.
Given in the form of a list of auxiliary and technological transitions
5. A sketch of the technological transition indicating the resulting size
surface roughness (given on the instructions of the teacher from
rivers 5 and 6).
6. Sequence description and calculations for setting up the machine at a given transition:
- determination of the spindle speed of the machine nrachby form-
le (1.1) and choice nstaccording to the table on the machine;
- purpose of filing So (according to the table on the machine);
- calculation of the number of working strokes irequired for processing specified
noah teacher surface blank.
7. The list used when performing technological
the course of devices, cutting and measuring tools.
8. Sketches of the arrangement of the arms of the gear boxes and feeds for
this technological transition.
9. The results of the dimensions control of the manufactured part,
hlenny in the form of tab. 4.6.
Brief theoretical information
External threading
The thread is a helical groove formed on the details of rotation.
Many parts of machines, building structures and household appliances are fastened together with threaded connections. Bolts, studs and screws are used in threaded connections.
Bolt - a cylindrical rod with a head at one end and threaded at the other (Fig. 75, a).
Hairpin - a cylindrical rod with a thread at both ends (Fig. 75, 6). One end of the stud is screwed into one of the parts to be joined, and on the other end they install the fastened part and screw the nut.
Screw- a cylindrical threaded rod for screwing into one of the parts to be joined and a head of various shapes (Fig. 75, c).
Thread - These are the protrusions on the surface of the screws and nuts located along a helix. The main elements of the thread are the helix angle α, the thread pitch p, the profile angle γ, the outer and inner diameters of the thread (Fig. 76).
The image of the thread in the drawing is shown in Fig. 60
For cutting outdoorfixing threading use a special tool - dice (Fig. 77, a). The plate has the form of a hardened steel nut. Thread dies cross through longitudinal holes. The cutting edges formed by these holes at the intersection with the thread profile are wedge-shaped and ensure the cutting of the workpiece. The chips come out into the holes.
In order to cut the thread with a die on the rod, it is necessary according to table 6 to determine the diameter of the rod for a given thread and pierce the workpiece to this diameter with the obligatory chamfer at the end of the rod. The chamfer is necessary so that the die in the initial stage of threading more easily captures the metal.
Table 6
| Thread diameter, mm |
|
|
|
|
|
|
| Rod diameter, mm | 2,9
| 3,9
| 4,8
| 5,8
| 7,9
| 9,9
|
| The workpiece is fixed vertically in a vice, pre-marking on the rod the length of the thread being cut. The length of the part of the rod protruding above the jaws should be greater than the length of the thread being cut by 20 ... 25 mm. The die for cutting the required thread (the thread diameter and its pitch are marked on the die surface) is fixed in ram holder (Fig. 77, 6), impose on the upper end of the rod and with a little pressure, without distortions, rotate it (Fig. 78). The first threads can be cut without lubrication, since the die captures the dry metal more easily, then the rod is oiled. Rotate the die holder as follows: one or two turns clockwise and half a turn in the opposite direction to break the chip. The quality of the cut thread in the conditions of school workshops can be checked by screwing the appropriate nut on it. |
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Internal thread (thread in the hole) cut taps (Fig. 79). It consists of a shank and a working part. The working part of the tap is a screw with longitudinal grooves. The cutting edges are formed by the intersection of the surface of the groove with the thread profile of the tap. In the grooves when cutting threads coming off chips.
Hand taps for cutting metric threads are released one by one, or for difficult-to-work materials in a set of two (finishing and draft) or three (draft, medium and finishing) pieces. On the tail of all taps circular risks (one, two or three) are applied or numbers of taps are put down and the diameter and thread pitch are indicated.
Before threading a tap into a part, a hole of the appropriate diameter is made (Table 7).
Table 7.
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| The workpiece with a hole is fixed in a vice so that the axis of the hole is perpendicular to the plane of the jaws of the vice. Then they put a knob on the shank of the rough tap and lubricate the working part of the tap with oil. The tap is placed vertically without tilting into the cut hole and, pressing it to the part with the left hand, gently rotate the knob clockwise until the tap hits the metal and stands firmly. After that, the knob is taken with both hands and rotated with light pressure: one or two turns clockwise and half a turn against. So cut all the hole. Having finished cutting with a rough tap, they twist it, insert the middle one and repeat cutting. Finally bring the thread fine tap. The quality of the thread in the workshop can be checked by screwing the corresponding bolt into the hole. When cutting threads, the following defects sometimes occur, which should be avoided: 1) rough or torn cutting - it turns out if there is no lubricant, as well as due to the taper or die skewing; 2) thread incomplete profile - if the hole diameter is larger than normal or the diameter of the rod is less than the norm; H) misalignment of the thread or breakage of the tap and the die - if the hole diameter is less than the norm or the diameter of the rod is more than the norm. |
Tapping a die on a screw-cutting lathe
1. Set the machine to the minimum spindle speed.
2. Secure the workpiece to the three-jaw chuck.
H. Fix the required die in the die holder.
4. Move the tailstock to the right end of the workpiece and secure it so that the holder can be inserted between the quill and the end of the workpiece.
5. Place the die with the intake part on the work chamfer and press down the die holder with the tailstock quill. Hold the handle of the die holder on the bar fixed in the tool holder (Fig. 81).
6. Turn on the machine. Rotating the tailstock flywheel, press the pin holder to the rotating workpiece. As soon as the plate begins to screw onto the workpiece itself, the rotation of the flywheel should be stopped.
7. Without reaching 3 ... 4 mm to the end of the section to be cut, turn off the machine, take the quill and move the cross slide to itself. Rotate the die holder by hand to cut the threads to the end.
Note: threading can be done without turning on the machine by turning the spindle manually.
1. To determine the tools for threading from among the proposed, and their characteristics.
2. Using the reference book, select the drill of the required diameter for cutting the internal thread set by the teacher.
3. Perform internal threading.
4. Using the reference book, select the rod of the required diameter for cutting the external thread specified by the teacher.
5. Perform external threading.
6. Using a pedometer and a caliper to determine the diameter and pitch of the proposed thread.
Questions for self-control
1. What is the essence of threading?
2. Types of threads?
3. Tools for tapping internal threads.
4. Characteristics of the thread. Determination of the main characteristics of the thread.
5. Technique of tapping internal thread.
6. Tools for external threading.
7. Technique cutting external thread.
8. Safety when cutting threads.
1. Pokrovsky B.S. Evstegneev N.A. General course plumbing.- M: Publishing Center "Academy", 2016-80s.
2. N.I. Makienko Plumbing with the basics of materials science. - M: "High School", 1973. - 464s.
3. Muravyov EM, Molodtsov MP A workshop in training workshops: Textbook. student manual ped. Inst Part 1. Metal processing / Ed. EAT. Muravyov. - M: Enlightenment, 1987. - 272s.
4. Pokrovsky B.S. Basics plumbing: a textbook for early. prof. Education / B.S.Pokrovsky.-3rd ed., Pererab.-M .: 2010.-320s.
