How to cut a thread with a die on a lathe

Tool for cutting threads. We reveal the features of the work - Tool Master

Thread shaping in industrial and home environments is a common problem. Without such operations, it is impossible to lay plumbing communications, carry out repairs and lay pipelines, or manufacture fasteners. Dies (dies), as a tool for making carvings on pipes and solid metal rods, are an indispensable attribute of the home craftsman.

Classification of leroks

Thread cutting tools are distinguished according to the following characteristics:

According to the method of producing threads - machine or manual.

According to the materials from which this equipment is made.

According to the profile of the threaded part on the final product.

According to the characteristics of the thread being cut: its diameter and pitch.

Tools for obtaining internal threads are often called taps, but this is incorrect - such equipment is called taps.

A thread cutting tool is always used in conjunction with a die holder - equipment where the thread-forming tool is secured. The appearance of such devices is determined by the design of the lectern.

In particular, for manual thread cutting, die holders are equipped with a handle and three to four gougons that secure the blade, which are evenly distributed along the arc of the seating surface.

When machine-forming threaded profiles, the die holders have the form of a flat prism.

To universalize the designs of die holders, tool companies that produce die holders make their outer surface the same for the adjacent group of threads (for example, M10 and M12). The taps, designed to produce threads with the same diameter but different thread pitches, are also unified in their seats.

The standard marking of the lerka includes in its designation a letter that determines the type of thread - inch (D) or metric (M). Rarely, lugs with left-handed threads are also used (for example, in the seats of devices for tying cargo cables and ropes, in heating radiators, etc.). Then the Latin letters LH are added to the designation of lerki.

For trenches that form threads on pipes, the letter G is added to the designation. Such trenches can have a conical profile of the thread-forming part, and are used to produce threaded parts on pipes, in particular, on bends, adapters, etc.

The parameters and characteristics of domestically produced lechers are regulated by the requirements of GOST 9740.

Tools for manual thread cutting

When cutting threads manually, the workpiece (rod, pipe) is stationary, and the tool itself rotates. In this case, there is no peripheral sliding speed, so the thread cutting tools practically do not heat up to high temperatures.

To reduce mechanical wear of the thread-forming profile and reduce the effort, the area of ​​the workpiece required for cutting is lubricated.

If there are large differences between the diameter of the original workpiece and the diameter of the thread, it is also necessary to lubricate the inner surface of the hole.

It is believed that in order to form a full-fledged threaded profile, the diameter of the initial workpiece (for the most popular diameters) must correspond to the following values:

Diameter of cut thread M6 M8 M10 M12 M16

        M20

Diameter of the original rod (or tubular blank), mm 5.805.95 7.757.90 9.709.95 11.8011.95 15.8015.95

19,8019,95

Note. The data given in the table can also be used to determine the diameter of the initial workpiece for subsequent thread shaping on machines with flat dies.

An important element for choosing the right lecher is the material from which it is made.

The peculiarity of the thread cutting process - a gradual increase in force, with a sharp decrease towards the end of the process - determines the increased viscosity of the threading material, otherwise the thread profile will intensively chip.

Therefore, the optimal choice would be levers made of alloy tool steel X12F1 or 9ХС, with a hardness of 5961HRC. For cutting threads on heat-resistant and alloy steels, a tool made of high-speed steel grades R6M5 or R9K6, with a hardness of 6063 HRC, is suitable.

The price of such blades will be high, so their use is justified only for large volumes of production of threaded parts. For domestic purposes, it is quite acceptable to use lerks made from carbon tool steels U10 or U12.

Among the enterprises that produce such tooling, the highest ratings are those of Izhevsk, Chelyabinsk, Vladivostok, Samara, Bryansk, Nizhny Novgorod (Russia), Orsha, Minsk (Belarus), and Lvov (Ukraine). Foreign-made lechers from UFC (Italy) and CM Tools (Finland) have proven themselves to be excellent in operation.

Tools for machine thread forming

Unlike hand tools, when producing threads on specialized machines, dies perform a reciprocating movement, while the workpiece moves in a screw manner. Such lechers are divided into movable, which is fixed in the slide of the machine, and stationary, installed on its table.

The working area of ​​the fixed ladders consists of three main parts:

• The intake, with the help of which the rod workpiece is captured;
• Profiling, where the thread rolling itself is carried out;
• Calibrating, in the area of ​​which the basic parameters of the thread are calibrated and the product smoothly exits the thread formation zone.

This design eliminates sharp fluctuations in force, which are inevitable due to the operating characteristics of the equipment: high productivity (up to 400 rpm) and the presence of an idle stage, when the slide with the die holder returns to its original position after the next workpiece.

The movable die has a simpler design. Its receiving part in length is approximately 30-35% of the diameter of the original workpiece, while the rise of the profile to the main profiling level occurs at an angle of 470. Moreover, the length of the movable lever is always greater: this eliminates accidental capture of the knurled workpiece during the reverse stroke of the slide.

Machine tools can be used to cut not only ordinary types of threads, but also special profiles, for example, for grease nipple heads, as well as threads for self-tapping screws. For this purpose, a special comb is made on the form-forming part of the lerk, in the grooves of which the necessary sharpening of the end of the fastener is formed.

In order to avoid cracks during long-term use of tools for machine thread shaping, their hardness should be slightly lower than manual ones - within 5658 HRC.

Machine lerks are usually manufactured by the same companies that produce the thread rolling equipment itself.

Tools listed are Italian (from the Sima and Sacma brands), Japanese (Sakamura) and Belgian-made (Malmedie).

It is better to avoid commercially available tools made in China and Taiwan: although its price is much lower, the stability of its performance characteristics and mechanical properties are highly questionable.

Source: https://cs-important.ru/sovety/lerka-dlya-narezki-rezby-raskryvaem-osobennosti-raboty.html

How to cut trapezoidal threads on a lathe

Thread cutting on a lathe is one of the most common operations performed on thousands of lathes every day. Cutters, thread-cutting heads, dies and taps are used as working tools. Carving using a cutter requires special skill and knowledge.

Types of incisors

types of incisors: a - straight; b - round; c - curved

The design of the lathe allows you to cut internal and external threads. For this purpose, many varieties of incisors have been created, belonging to three large groups:

• prismatic;
• round;
• rod-shaped

Rods are the simplest type of cutting tool. This is a rod (of any cross-sectional shape) with a working head. The profile is determined by the shape of the head. One of the varieties of rod cutters is with soldered carbide working edges. They are more resistant to abrasion and do not require frequent sharpening. Round and prismatic belong to the shaped category.

Prismatic cut only the outer side. Compared to rod ones, they are able to work with large surfaces. The cutter is held in a dovetail holder. Capable of more regrinding than rod ones.

Round ones make external and internal threads. They are more convenient to cut and have a wider range of applications than prismatic ones. They can be sharpened more times. They are installed in the holder relative to the end and the hole.

Threading technique

The cutter moves evenly along the workpiece and with its tip cuts a line in the shape of a screw. The inclination of the line to the axis perpendicular to the movement of the cutter is called the helix angle. This indicator depends on:

• speed of rotation of the part in the machine;
• features of the cutter feed.

As the cutter is inserted into the blank, it becomes covered with a helical groove. The thread provides reliable fastening, sealing or movement of elements in the planned direction.

Depending on the configuration of the blank, the name of the fastening is given: cylindrical or conical. The profile, which is also the diameter of the projection onto the thread plane, is selected taking into account the purpose. The following profiles are most applicable:

• rectangular;
• trapezoidal;
• acute-angled.

They are cut single-pass or multi-pass. The latter are created by several grooves located at equal intervals from each other, the former by a single groove.

The properties of a thread are determined by such concepts as pitch and stroke - the distance between identical elements of the thread. It is equal to the product of the number of entries per step.

Slicing rules

a thread template is used to check that threads are cut correctly

1. The cleanliness of the thread is determined by the position and direction of movement of the tool. There is a template to use the tool correctly. It is placed parallel to the center of the machine on the workpiece. The projections of the instrument and the template are superimposed and the lumen is examined. The cutter is placed exclusively along the center line of the machine.
2. Internal threads are cut with curved tools (with a small hole diameter).

   You can use a flat tool by inserting it into the mandrel. External - often bent, in rare cases even. The choice of cutter depends on the type of metal and thread parameters.

3. The rules for placing the working edge of the tool depend on the planned profile. Triangular is performed at an apex of 60 or 55 degrees. (for metric or inch). Since errors are sometimes possible during the movement of the caliper, use a tool with a tip of 59 degrees 30 minutes.
4. The rake angle of the tool is selected in accordance with the material of the part within the range of 0 - 25 degrees. The harder and more brittle the material, the smaller the angle. So, for steel blanks, use a tool with an angle of 0 degrees; high-alloy steels can be cut with an angle of up to 10 degrees.
5. The depression is made smooth, rounded or with a notch; the top of the cutter is selected to match the shape.
6. The lateral angles of the tool at the rear must be such that during cutting the lateral edges do not come into contact with the thread surface. Usually they are equal on the right and left: when the thread lift angle is above 4 degrees - from 6 to 8 degrees and from 3 to 5 degrees, if the angle is up to 4 degrees.
7. Internal threads are cut directly after boring or drilling. Due to the fact that the metal is deformed during operation, the diameter of the hole is taken to be slightly larger than the internal diameter.

   Therefore, up to 0.02 is added to the calculated indicator for brittle metals and up to 0.4 for viscous ones.

8. Sometimes the thread should end with a groove. The internal diameter of the groove should be made 0.3 mm smaller than the same characteristic of the thread.
9. In order to make a high-quality thread at the end, it is necessary to make a shoulder of up to 3 mm without changing the diameter. This protrusion marks the final pass of the cutter. At the end of cutting, the ledge is removed.
10. Roughing passes are performed at speeds of up to 30 meters per minute, finishing at speeds of up to 55 meters per minute. When processing cast iron, the speed is no more than 25 meters per minute. Carbide tools cut steel at speeds of up to 150 m/minute. When the thread pitch is less than 2 mm, increased speeds are used, when the pitch is from 6 mm, reduced speeds are used (exact indicators can be found in special tables).
11. The thread is cut in several passes; at the end of each pass, the tool is set to the initial position.
12. When it is necessary to apply an external thread to a long workpiece, the caliper is manually set to the initial position by disconnecting the connector nut. To make the next cutting pass, you must get exactly into the groove.

Parameters and corresponding GOSTs

Instructions for cutting threads in the video:

Source: http://ooo-asteko.ru/kak-narezat-trapetseidalnuyu-rezbu-na-tokarnom-stanke/

3.1 Thread cutting on lathes

Allows you to obtain the first and second degrees of accuracy. It is used in individual and mass production. Thread cutting is carried out using a measuring tool - a cutter. During processing, the part rotates, and the cutter moves per thread pitch per revolution of the workpiece. Thread formation is carried out in several passes.

The cutting method distinguishes between direct and oblique feed of the cutter.

The movement of the tool must be strictly connected with the rotation of the workpiece. Thread cutting is carried out at reduced cutting conditions - V cut = 15-20 m/min.

The cutting method with one cutter is unproductive. To improve productivity, a measuring tool in the form of a comb is sometimes used.

When cutting threads on large workpieces, in order to increase productivity, the vortex method is used.

With this method, the workpiece is installed in a centering device and rotated slowly. The threaded head, which has an individual drive, is placed on the machine support and has counter-rotational movement and slow longitudinal movement along the workpiece. These movements are coordinated through the kinematics of the machine. The workpiece rotates at a speed of 210m/min. Head speed up to 100 m/min. The head provides 2 and 3 degrees of accuracy and increases productivity by 2-8 times.

On lathes, dies can be used to cut threads , The performance of the dies is low, the accuracy is within the 3rd degree of accuracy.

Surface treatment methods

Lecture No. 10

Topic: METHODS FOR PROCESSING SHAPED SURFACES

3.2 THREAD MILLING

Milling is used in mass and large-scale production. single-thread and multi-thread cutters are used as tools. During the ( n = 12 rpm), and the cutter rotates (nФ = 100200 rpm) and moves in the longitudinal direction.

The disadvantage of this method is the need to have its own tool for each type of thread.

3.3 THREAD ROLLING

The thread rolling process occurs without removing chips, i.e. due to plastic deformation of the surface. Two rolling methods are used: flat dies and rollers.

When rolling with dies, the thread profile is formed in one working stroke of the movable die.

When rolling with rollers , the workpiece is installed on the support knife 1, the pressure working roller 2 ensures the feed of the workpiece in the transverse direction and forms the thread profile. The movement of the roller 2 is carried out using a hydraulic cylinder. The thread profile is formed in one revolution of the workpiece. Rolling speed - V NAC = 5060 m/min.

Disadvantages: limitations on the hardness of the HRC3540 material; one tool for one type of thread, low tool life, high complexity of setting up the machine.

It is used in serial and large-scale production.

4 Gear processing methods

Gear wheels are subject to high demands on manufacturing flow and the quality of processed surfaces.

In accordance with GOST, 12 degrees of accuracy of gears are provided, depending on the requirements for the size of the teeth and their location relative to the base surfaces. The most accurate first degree.

For each degree of accuracy, there are also standards for kinematic accuracy, smoothness, and tooth contact. In aircraft engine construction, gears with 5 to 8 degrees of accuracy are used. In this case, a 100% check of gears is provided.

The following methods are used for the manufacture of gears: milling, chiselling, grinding, shearing, honing, lapping, running-in, running-in, etc.

Source: https://studfile.net/preview/6337941/page:17/

How to cut a thread with a die on a lathe?

Thread cutting on a universal lathe is a common operation, especially in repair departments.

The presence of a lead screw and a large feed range make it possible to cover basic needs without readjustments and special tools - a few threaded cutters are enough.

The possibility of mechanized cutting with manual, machine taps, and lechers simplifies setup and speeds up the process while maintaining acceptable quality of fasteners.

Classification

In practice, cutters for external and internal threads with a rectangular section holder are used. Less common are disc, prismatic, sharpened along the front surface. The working profile of all corresponds to the dimensions of the screw groove. In the direction of the cut spiral, left and right ones are released.

There are solid and prefabricated instruments. The first ones are mainly made of high-speed steel, small section or disk. The bulk is equipped with cutting plates secured by soldering with refractory solder or mechanically, allowing replacement when worn.

Threaded cutters: external (Fig. 1), internal (Fig. 2)

Materials

For the manufacture of the cutting part are used:

• high-speed steels;
• hard alloys;
• mineral ceramics;
• superhard tool materials (STM).

The former are used for thread cutting of steels, non-ferrous metal alloys, and plastics. They are distinguished by high strength, thermal conductivity, but lower, compared to others, hardness, red-hardness, wear resistance, which limit the cutting speed.

The largest proportion of thread cutters used are those equipped with carbide inserts. This is due to high durability, hardness, sufficient strength and rigidity, and reasonable cost. Processing productivity is 2-3 times higher than with rapid.

A wide range allows you to select the optimal grade for processing in most cases.

Ceramics are relatively cheap, quite fragile, and are used for processing fine pitch threads of steel and cast iron parts, with a rigid AIDS system, with limited allowance removal per pass.

STMs based on polycrystalline diamond (PCD) or cubic boron nitride (CBN) are extremely hard, heat-resistant, but expensive. Indispensable for precision work on difficult-to-cut materials. PCD is used for cutting copper, aluminum, and tungsten carbide. CBN work on hardened steels and hardened cast irons. Successful application requires high rigidity and smooth running of the equipment.

Decoding the writing of threads

Regulatory documents: GOST, OST, MN for a specific type contain samples of conditional recording.

Graphic materials are designed in accordance with the instructions of GOST 2.311-68 “Image of threads”.

A typical designation structure contains:

• the literal part defining the type;
• numbers corresponding to the nominal size in millimeters or inches;
• pitch (mm) is indicated only as fine, after the “×” sign;
• for multi-start ones, instead of the previous paragraph, the stroke (mm) is given, then the step in parentheses;
• direction: right is the default, left is LH;
• tolerance range or accuracy class;
• make-up length other than normal.

Example 1: М16×1.5LH–6H. Explanation:

• M – metric cylindrical;
• 16 – nominal diameter, mm;
• 1.5 – fine pitch, mm;
• LH – left;
• 6Н – tolerance range, where 6 – degree of accuracy; H – main deviation. Capital letters are used for internal (nuts), hence the threads in the hole.

The screw-in length is not indicated, which means it is normal.

Example 2: G1/2–A

• G – cylindrical pipe;
• 1/2 – thread size, inches; corresponds to the internal diameter of the pipe;
• A – accuracy class.

The designation options are illustrated below.

Thread cutting using lathe equipment

Shaping on the machine is carried out by copying the working profile of the tool onto the part along a helical line. Translational movement is transmitted to the cutter, tap, die, comb. In combination with the rotation of the workpiece, a screw movement is obtained, the tool surface coincides with the cut surface.

As a rule, cutting small batches of fasteners and fittings up to M36 is carried out using taps and lechers. It is more profitable to produce large orders using specialized machines. Large-diameter threads, running threads, power threads, and precision threads are processed with cutters on universal lathes when CNC models are not available or the production program is insufficient.

Cutting internal and external threads with a cutter

Threads with high coaxiality to other surfaces, transmitting movement and force are performed with a cutter. The rotation of the spindle is connected kinematically to the lead screw, which moves the support with the tool holder.

The general procedure includes:

• Grooving the surface along the length of the cut, forming a groove for the tool to exit.
• Selection, if necessary: ​​sharpening, finishing of the cutter with checking using corner templates.
• Setting modes on the machine, tuning the guitar to a pitch not provided by the box.

The movement of the cutter per revolution of the workpiece is equal to the step P or the move H for multi-start ones.

• Installation of the cutter according to the template.

•  Cutting for the number of passes selected from the directory.

Thread cutting of a batch of parts is divided into rough and finishing. For the latter, the tool is carefully sharpened. Threads with pitches greater than 2 mm are produced by lateral cutting. The left helical groove is obtained by switching the bit so that the lead screw rotates in the direction opposite to the spindle. The support with the cutter moves from left to right.

Average speeds when threading steel are 20–35 m/min with high-speed cutting tools, 100–150 m/min with carbide tools. Finishing strokes are performed at a speed increased by 50–100%. Internal threads are processed at 30% reduced conditions.

Using taps

The widespread grade R6M5 allows cutting workpieces with a hardness of up to 240 HB; taps made from tool alloy steels are used for “raw” parts. Carbide ones are rarely used, since the edges are chipped due to distortions and misalignment, which increase bending loads.

The range of typical sizes is limited to M36 – 42, G2. Large diameters with large pitches are processed with a set of 2, preferably 3, taps. The hole is bored slightly larger than the inner diameter of nut D1 (see Fig. 2), taking into account the bulging of the metal from the groove. When drilling, take into account the breakdown. Recommended values ​​are given in reference books.

There are several processing methods:

• Often, nuts smaller than M12 are cut by holding the knob with your hands. Strictly speaking, taking it is a violation of TB and can lead to injury. At the beginning of screwing, press the tap with the center of the tailstock for direction, then self-tightening occurs. Stop, unscrew in reverse.
• The tap is installed in the driver, rests against a bar fixed in the tool holder, and is supported by a center holder or rear center. Turn on low speed, cut on self-tightening. To eliminate runout of the turns, it is recommended to press the tap to half the working length until screwing, smoothly extending the quill.

• A swinging self-retracting tap holder is used.

• Large diameters are obtained by feeding the caliper along the lead screw, and the box is adjusted to the appropriate pitch. The tap is inserted into a mandrel clamped in the tool holder. A safety cartridge installed in the quill prevents the tap from breaking when reaching the bottom of a blind hole. Speeds up serial operations. Taps with staggered teeth are optimal for tough stainless and heat-resistant alloys. Recommended cutting speeds for steel are 3 – 15 m/min, for bronze, cast iron 4 – 22 m/min, work with cooling. For left-handed nuts, use tools with a left-hand thread, the rotation is opposite, the rest is the same.

Source: https://varimtutru.com/kak-narezat-rezbu-plashkoy-na-tokarnom-stanke/

How to cut a tapered thread on a lathe – Machine tools, welding, metalworking

Thread cutting on a lathe is one of the most common operations performed on thousands of lathes every day. Cutters, thread-cutting heads, dies and taps are used as working tools. Carving using a cutter requires special skill and knowledge.

How to cut tapered threads on a lathe? — Metals, equipment, instructions

Author Dmitry 779 Date Aug 31, 2016

Detachable connections of metal pipelines in a home water supply and sewerage system are made using threads. Inch pipe threads are used on pipe ends and fittings.

The diameter of its cutting is determined by the size of inches, or their fractions, where the characterizing value is the number of turns made according to the number of turns on the length of a single inch.

The main advantage of a threaded pipe joint is the ability to disconnect and replace one worn part, instead of removing the entire structure and welding installation of another. Cutting inch threads is done using dies, taps, or special cutters.

Pipes with threaded inch thread

The thickness of the pipe walls is added to the diameter of the internal hole of the pipeline. If the inch size is 25.4 mm, then the pipe inch size is 3.3249 cm. The choice of the inch part determines the exact match of the cross-sectional dimensions.

What is an inch thread?

Threaded connections are characterized by the following factors: by type of fit: sliding, clearance, transitional, interference fit. According to the use of complementary parts: conventional direct connections and in combination with elements: ball, sleeve, spiral. Without or with a stopper.

1. cylindrical or conical shape
2. cutting method – external and internal cutting,
3. type of direction of the screw line - left and right,
4. approaches – multi-entry and single-entry,
5. profiling parameter: metric, cylindrical, trapezoidal, conical pipe, conical inch, round, rectangular, thrust,
6. Dimension – metric thread or inch pipe thread,
7. purpose - for fastening, running threads, regulating,
8. type of processing: cutting a part with a cutter, die, tap.

Bushing with inch connection

In modular slicing, the pitch is determined by modules. To convert to mm. "M" is multiplied by the number pi.

Pitch threads are measured in pitches (to determine the number of inches, pi is divided by pitch).

Options

GOST for inch threads 6257 - 81 determines the main precise parameters of the pass pitch and diameter. In this case, the measurement of the outer pipe diameter is equal to the distance between each upper point of the opposing ridges. The diameter of the internal lumen is measured from one point at the bottom of the groove cavity to the opposite point. The thread pitch is a constant value, it is measured by the distances between adjacent ridges or depressions.

Differences between metric and inch threads:

• metric dimensions - in mm, inch dimensions - in inches or their fractions,
• inch threads are characterized by sharper angles of inclination of crests and valleys,
• The threads have a rounded shape.

Upper angle size = 55 degrees, thread pitch is measured by the number of threads.

The following types of products are used in everyday life:

with a parameter of 1 inch - 14 threads, step length 1.814 mm, diameter ¾ or ½,

11 threads in 1 inch - with a pitch size of 2, 309, and a diameter of 1; 1 and ½; 1 and ¼.

Relation between inch and metric threads:

Table of ratio between inch and metric threads

Making pipe threads

Threading is done on a lathe with a cutter, as well as with the help of dies, combs and taps, manually or mechanically. To clarify the dimensions, you will need a thread gauge tool (comb, gauge) or a caliper.

Pipe thread pitch determination

When cutting metrically, you first need to determine the thread pitch: measure the distance separating the vertices, then divide by the number of threads.

It is important to check first the pitch and profile, then the dimensions of the internal and external diameters.

To find out the step using a ruler, or determine it with a caliper, you need to measure the length of two or three passing steps, then divide by the number of steps. When checking with a thread gauge, the teeth of the nail file should fit tightly and without gaps to the thread being measured.

The accuracy of measurements depends on the following conditions:

• degree of wear and cleanliness of the part;
• convenience of measurement operation,
• cleanliness and appearance of the instrument,
• correct use of the measuring instrument.

Using the inch method, calculate the number of threads per 1 inch of pipe. After processing, verification is required.

To determine the pitch of an inch thread using a fitting (coupling) with an internal thread of the required dimensions, you need to screw a bolt into the part. If it goes in smoothly, tightly, effortlessly, then the pitch and cutting diameter dimensions are selected correctly. To measure the external size of the ridges, screw-on parts of the nozzle are used. If the sizes do not match, use other calibers in turn until they match.

How to use a thread gauge? The plates that are included in the tool are applied to the external, then internal thread of the pipe. If the profile corresponds to the size of the file, it is clarified visually: the free clearance is examined. Exact match means the size parameters indicated on the files (plates) of the thread gauge.

Calipers and micrometers accurately measure only outer diameters, so a more acceptable option is to use a thread gauge.

To avoid mistakes, you need to measure each diameter of the part three times, calculate and select the average value.

To avoid mistakes, you need to measure each diameter of the part three times, calculate and select the average value.

Example of an adapter with applied internal and external threads

Pipe thread cutting

To accurately cut threads on a lathe (inch), it is important to choose the right tools: an inch thread gauge is used to determine the pitch and design of the cutter.

Then determine the direction of the thread and fine-tune the parameters for the machine.

Cutters for cutting threads are sharpened taking into account the size of the rake angle γ = 0, and are adjusted exactly at the linear height of the center of the machine. Profile angle = 55 degrees.

The thread cutter for external threads is supplemented with durable steel plates (or carbide). The part is processed under the condition that the size of its outer diameter is smaller than the cutting diameter, since during processing the metal is deformed, leading to an increase in the diameter of the workpiece.

To make the internal surface, the workpiece is first bored or drilled, then ridges should be cut to create a ledge of 2 - 2.5 mm. (to accurately determine the last cut of the cutter) then it is removed.

For accuracy, use a template, combine the thread cutting tool with the template, focusing on the clearance in strict accordance with the center line of the machine.

Thread cutting with a cutter on a machine is done in stages.

• After each operation, the cutter is moved to its original position.
• New depth parameters are set and the working passage is repeated, while shifting the cutter to the right or left, and moving the caliper by 0.1 - 0.15 mm.
• Number of passes 3 – 6 roughing, only 3 finishing operations. For them, cutters are used, supplemented with soft-spring holders so that the surface is even and smooth.
• When performing a rough cutting, the turning cutter is mounted on a rigid holder.
• The head of the flat cutter, which performs internal cutting of the part, is adjusted perpendicular to the axis of the part in order to obtain a symmetrical element to avoid distortion.
• To perform finishing operational passes when machine-cutting coils, durable spring holders are used.
• Rough working thread cutting on a machine is done with a cutter mounted inside a rigid structure holder, and the finishing operation is done with a cutter placed inside a springy machine holder.

  Tape thread GOST

To simplify the manual cutting operation, use a KLUPP device, consisting of a body with handles, equipped with movable combs, or buy a special die, complete with profile replaceable combs.

A carefully executed inch pipe thread is a guarantee of safe, long-lasting operation of the water supply system at home, so if you do not have specific cutting skills, order the production from a master turner or milling machine.

Source: https://spb-metalloobrabotka.com/kak-narezat-konicheskuyu-rezbu-na-tokarnom-stanke/

How to cut threads on a lathe with a cutter?

Threads are the most common element of fasteners. It is divided according to a number of characteristics, has wide application and can be obtained on parts with hand tools or cutters on screw-cutting lathes. Despite the fact that prices for turning work can be quite high, the quality of the resulting thread is incomparably higher. The key to this, for example, is the experience of the specialists of the SibPromDetal company.

Thread parameters

Before we look in more detail at how to cut a thread on a lathe with a cutter, let’s take a closer look at the basic elements of a helical groove. It can be found both on steel rods or nuts, and on pipe fittings in gas, heat and water pipelines. To characterize the thread, the following main elements of its profile (longitudinal section) are distinguished:

1. Outside diameter;
2. Thread pitch;
3. Apex angle.

In diameter, standard metric threads up to 6 mm have a pitch of 1 mm, then 2 mm. If necessary, it is not difficult to cut seven-millimeter or nine-millimeter threads on the machine. It is impossible to perform such work with hand thread-cutting tools - taps and dies.

Based on the thread pitch, they are divided into standard (1 mm), small (less than 1 mm) and large (more than 1 mm). As a rule, all taps are designed for a standard distance between turns. You can get small or large threads only on a screw-cutting lathe.

Based on the angle at the top of the thread, they are divided into metric (angle is 60°) and inch (angle is 55°). For manual cutting, you need to have a set of tools for each diameter with different angles. For mechanical cutting, it is enough to purchase only two threaded cutters with the required sharpening angles.

Threading technology

Based on the specified parameters, the appropriate cutter and thread cutting modes are selected. Before proceeding to obtain a helical groove of a triangular, rectangular or trapezoidal cross-section on the surface of the part, it is necessary to grind the workpiece to the required diameter.

This type of work is carried out with a standard through cutter at appropriate speeds. Due to the partial expansion of the metal during cutting, the diameter of the workpiece must be made 0.1 mm less than the required diameter of the future thread.

The next stage is setting up the machine, and more specifically, the guitar mechanism that regulates the feed speed of the cutter. Using the appropriate tables, depending on the desired step, it is necessary to install the necessary gears. After this, you can cut the threads on a lathe.

To do this, install a threaded cutter with the required sharpening angle into the tool holder and use the handle for connecting the caliper to the lead screw to control it. Thanks to this device, the tip of the cutting tool carries out a spiral movement along the surface of the part, gradually, pass by pass, deepening to the required depth until a complete triangular profile is obtained.

To obtain maximum quality of the manufactured thread, do not forget to periodically lubricate the surface of the part with machine oil. This will reduce roughness and partially cool the rod being processed. You can see the technology for producing threads on a lathe in more detail in the video below:

Source: http://smogem-sami.ru/instrumenty-oborudovanie/kak-narezat-rezbu-na-tokarnom-stanke-rezakom.html

How to cut tapered threads on a lathe

Forming threads on metal workpieces in the form of bodies of rotation is one of the most popular and at the same time complex turning operations. The difficulty lies in both making basic equipment settings and preparing auxiliary tools. In order for thread cutting on a lathe to comply with the technical specifications, you must adhere to the technology for its implementation and do not forget about safety rules.

Preparing the machine

Regardless of the type of lathe and working tool, carving will be done by machining.

Through the machine settings, the operator determines the angle of the helical line of influence on the surface of the workpiece, which will have a perpendicular position relative to the axis of rotation.

Here it should be noted that the machines have different power and, accordingly, spindle speeds - in order for the cutting tool to efficiently cope with its task, it is important to initially correctly correlate the angle of influence and the speed of the engine.

An important parameter is the step between the cutting lines - it is also taken into account in the equipment settings and appropriate adjustments are made in terms of the position of the tool relative to the workpiece.

Since thread cutting on a screw-cutting lathe is usually carried out in several approaches, it is advisable to save the primary parameters until the operation is completed.

Even if the step along the threading line is maintained, there remains a risk of violating the positions of the beginning and end of the deformation sections, which may not coincide with each other. It is important to keep these nuances in mind before starting work.

Types of thread

Turners distinguish between even and odd threads. In the first case, we are talking about cuts, which ultimately form an even number of cutting lines in steps. Accordingly, odd cutting leaves odd threads. From the point of view of the operation, even cutting threads on a lathe will have its advantages.

For example, after each approach, the operator can launch a sliding nut in the support and quickly return it back with the cutter manually, without stopping the operation of the equipment.

Then, with each new pass of the sliding nut, the tool will automatically be directed to the original cavity, which ensures a certain accuracy of the operation.

In turn, odd cutting requires, after each pass, the support to return to its original position along with the cutter, which cannot be done without starting the reverse stroke.

Multi-pass and vortex cutting can be placed into separate categories. So, in the first case, cutting multi-start threads on a lathe will require precise angular separation of the workpiece during transitions from one groove to another.

The initial calculation of the pitch and cutting line parameters is important here. As for the whirlwind thread, it requires additional installation of a rotating cutting head on the support carriage.

Several individual cutters can be fixed on it, each of which will cover its own area of ​​work.

Inch and metric cutting

Inch cuts are used for metal pipes. Typically, such threads are obtained from fittings, which are subsequently used to assemble a metal or plastic pipeline. The standards for creating such cutting are determined by GOST 6357-81. Based on the technical document, we can conclude that the main parameters of inch cutting are pitch and diameter. Moreover, the second characteristic is estimated as the distance between the extreme points of the thread ridges.

Typical cutting of inch threads on a lathe is carried out by cutters and taps with modifications of the technology as applied to internal processing. Metric cutting is performed taking into account the same parameters, but the shape of the thread flange profile is added to them. In the case of inch cuts, it is most often sharp - in the shape of a triangle. In addition, as the name suggests, classic pipe cutting is calculated in inches, while metric pipe cutting is calculated in millimeters.

Forming threads with cutters

A cutter is a tool that directly performs cutting. It is made of carbide steel and before work receives a special sharpening in a shape that meets the requirements of the task. It can be used for threading bolts, nuts, studs and other workpieces. The cutter is installed in a machine chuck or multiple head. The work process is divided into several passes - upon completion of each of them, the tool is moved to the side.

Correction of thread formation parameters in this case is carried out by adjusting the caliper, which sets the required depth. At the same time, there are standardized settings. In particular, cutting threads on a lathe with a cutter in increments of up to 0.2 cm will imply that the feed in the transverse movement of the caliper screw will average 0.1 mm per pass.

Simultaneous work with two cutters is also allowed. But here it is necessary to take into account a nuance that can affect the quality of the thread line - the chips released by the leading cutter will cling to the waste of the second tool, which will have, although insignificant, still an impact on the parameters of the edge being formed.

Application of dies

Dies are purposefully used to work with the same hardware in the form of bolts and studs, but only when creating external threads. The area that is planned for slicing is pre-processed and cleaned.

Also, the diameter of the threaded surface is calculated so that it is smaller than the outer diameter of the applied thread. In the case of metric technology, this difference can be 0.2 mm for small threads.

To form a thread entry, a chamfer corresponding to the height of the thread profile is first removed at the end of the workpiece.

Although the process itself can be carried out manually, most often machine threading with a die is performed on a lathe using a special die chuck. The cartridge itself is fixed in the rear quill or in a head socket with several mounting niches. The average speed of such cutting will be 5-6 m/min.

Application of taps

Taps are used specifically for working with metric threads applied from the inside. In this case, the diameter should be no more than 50 mm. Lathes usually use machine taps, which allow the operation to be completed in one pass.

This opportunity largely arises due to the one-time use of several tools that are installed in multi-purpose universal chucks.

If in the case of a conventional cutter the process is divided into several stages by passes, then thread cutting with a tap on a lathe can be segmented according to the quality of processing with different types of tools.

Again, they work simultaneously, following one after the other, which compensates for the load that falls on one cutter. There are taps for roughing and finishing threads. Moreover, the first tool removes about 75% of excess metal from the target ditch.

Cutting with Die Heads

To use several cutters at the same time, special heads with chucks are also used. This is a revolving tool, into which you can integrate the same screw-cutting attachments - tangential, radial and round.

After cutting is completed, their combs diverge on the reverse stroke and no longer contact the completed thread.

The most common are round cutters of this type, since they are capable of several sharpenings, have increased durability and are easier to maintain.

However, internal threading on a turret-type lathe is performed only with prismatic combs that have a special lead-in cone. To work with worms and long screws, cutting heads are used that are integrated directly into the machine support. They allow you to form both external and internal threads.

Features of internal thread cutting

Different types of screw-cutting equipment can work on such threads. Unlike surface external machining, such operations require the initial creation of a hole by drilling. In some cases, a corresponding boring is required, which will allow the thread to be used in the future to mate with parts of a specific diameter.

But if the diameter is calculated incorrectly, cutting an internal thread on a lathe can ruin the workpiece. This occurs in cases where the initial diameter itself matches the dimensions of the target part that is to be integrated into the target cavity. This can be avoided by allowing technological thickening of the internal walls before drilling. This tolerance must correspond to the height of the thread flange.

End of thread line

The quality of the created thread will be determined not only by the accuracy of the edges and the convergence of individual sections that were performed in different passes. It is also determined by how the thread lines are completed. The technology requires that the contour end with a special waste groove - it will ensure the free entry of the screw part.

In addition, cutting threads on a lathe in the final stage should reduce the height of the flange. That is, when the working tool retreats, it forms a groove run-out, as well as its reduction. Sometimes, for a better design of the final line, a special pass is provided, which allows you to correctly adjust or even trim the already created groove run.

  Main types of turning tools

Cutting quality control

After completing the operation, the operator checks the thread for compliance with the required parameters. For this, a template is used, on the surface of which the imprints of the thread ridges are applied. There are different templates for metric and imperial threads, and both groups also have bars for checking the pitch, depth and angle of the grooves.

A comprehensive assessment is already given by calibers - these are devices that allow you to evaluate the correctness of the profile. If, for example, cutting a thread on a lathe with a cutter was carried out with a critical slope, this will be recorded with a suitable gauge. Micrometers and inserts are also used for similar tasks. Accurate verification readings are given only if the thread surfaces are pre-cleaned.

Conclusion

Creating threads on a lathe requires the use of high-quality cutting tools and the attentiveness of the operator himself. First of all, a device is prepared for cutting threads on a lathe in the form of a cutter, tap, die or turret. It is the user's responsibility to set up the equipment correctly.

The least hassle for the operator is the preparation of CNC machines with program control. They physically adjust and position the equipment according to specific data that is entered through a special input panel. The risk of making mistakes when working with such models is much lower than with conventional lathes.

Source: https://respect-kovka.com/kak-narezat-konicheskuyu-rezbu-na-tokarnom-stanke/

how to cut threads on a lathe

Thread cutting on a lathe is one of the most common operations performed on thousands of lathes every day. Cutters, thread-cutting heads, dies and taps are used as working tools. Carving using a cutter requires special skill and knowledge.

1 Thread cutting on a lathe - important information

When moving with a (constant) feed along a part processed on a turning unit, the tip of the cutter draws a helix line on the workpiece. The inclination of the latter to a plane oriented perpendicular to the axis of movement of the specified part is among specialists called the angle of increase in the helix. The slope we describe depends on two factors:

• on how the cutting tool is fed;
• on the frequency at which the turning spindle rotates.

Source: https://crast.ru/instrumenty/video-kak-narezat-rezbu-na-tokarnom-stanke

How to cut a thread on a lathe with a cutter: video, number of revolutions, dimension

Thread cutting on a lathe is one of the most common operations performed on thousands of lathes every day. Cutters, thread-cutting heads, dies and taps are used as working tools. Carving using a cutter requires special skill and knowledge.

Thread cutting on a screw-cutting lathe

Allows you to obtain first and second degrees of accuracy. Used in individual and small-scale production. Thread cutting is carried out using a measuring tool - a cutter. During processing, the part rotates, and the cutter moves per thread pitch per revolution of the workpiece. Thread formation is carried out in several passes.

According to the cutting method, a distinction is made between straight and oblique feed of the cutter.

The movement of the tool must be strictly connected with the rotation of the workpiece. Thread cutting is carried out at reduced cutting conditions - V cut = 15-20 m/min.

The cutting method with one cutter is unproductive. To improve productivity, a measuring tool in the form of a comb is sometimes used.

When cutting threads on large workpieces, in order to increase productivity, the vortex method is used.

With this method, the workpiece is placed in a centering device and rotated slowly. The threaded head, which has an individual drive, is placed on the machine support and has a counter rotational movement and slow longitudinal movement along the workpiece. These movements are coordinated through the kinematics of the machine. The workpiece rotates at a speed of 2.10m/min. Head speed up to 100m/min. The head provides 2 and 3 degrees of accuracy and increases productivity by 2-8 times.

On thread cutting lathes, dies can be used, usually to finalize the thread profile after the cutter. The performance of the dies is low, the accuracy is within the 3rd degree of accuracy.

Methods for obtaining threads

Threaded connections are used in mechanical engineering and construction. The use of threaded hardware allows you to connect mechanical parts and structural elements during construction through the use of bolts, nuts, screws, and studs. Threaded products are also designed to transmit force or movement in mechanisms such as jacks, gearboxes, presses, and machine tools.

Scheme of cutting a thread with a tap on a lathe

Jacks and lead screws are made with trapezoidal threads.

There are the following methods for making threads:

• manually (with a tap or die);
• on machines:

• screw-cutting lathe (mod. 16K20);
• thread rolling using rollers and flat dies;
• milling (mod. RTS 161F4) for producing threads with large pitches;
• grinding using wheels with a given profile for the production of small and precise threads;
• screw-cutting (mod. 1622);
• for cutting threads on nuts (mod. 2064);
• providing whirlwind cutting of threads using multi-cutter heads.

Whirlwind cutting is provided by 4 cutters located in a rotating head, driven by its own motor. This device is mounted on the support of a lathe. Due to the alternate insertion of the cutters, a high processing speed is ensured, since the cutters heat up slightly. This also ensures lower roughness of the resulting threaded surface and increased profile accuracy.

Source: https://MyTooling.ru/instrumenty/narezanie-rezby-na-tokarno-vintoreznom-stanke