How to cut pipe threads on a lathe

Thread cutting on a lathe: classification, diagrams

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://VseOChpu.ru/nareznye-rezby-na-tokarnom-stanke/

Cutting threads with a cutter on a lathe: how to do it with a tap, die, video

In order to cut threads on a lathe, different tools can be used. Experienced craftsmen most often do this using a cutter.

But you can also use special-purpose working heads, taps, and dies. This operation is also carried out using knurling technology.

In this article we will figure out what types of threads there are, how to obtain them using different methods, and how to check their quality.

Receipt methods

There are two main methods for obtaining threads. They are divided into cutting and rolling. Also different methods are used for internal and external threads.

For example, for external work, you need to use different dies, cutters, thread cutters and combs, or rollers on thread rolling machines.

When choosing one method or another, you need to take into account the desired thread profile, the nature of the material, the required volume and accuracy.

How to cut on a lathe?

For example, cutting on a lathe using a cutter will look like this: the cutter moves along the axis of the rotating part, which moves back and forth in relation to the cutter, and with its pointed tip draws a screw-type line.

The helical line differs in the angle of its rise or increase. The magnitude of this angle is perpendicular to the axis of rotation, it is measured between the tangent and is determined by: the amount of feed of the cutting tool, which moves along the axis, with the rotational speed of the part.

Cutting internal and external

To cut internal or external threads, you need to use a rod cutter. Their production differs only in the shape of the cutter. For external applications, straight or bent incisors are used.

And for the internal ones, curved or straight incisors. The location of the cutter edge must coincide with the profile of the thread being processed.

Cutting with taps and dies

External threads are cut using dies. The part area is pre-processed. The diameter of the surface to be machined should be slightly smaller than the outer diameter of the thread.

First, a chamfer corresponding to the height of the thread profile is removed. Then the die is installed in the chuck (die holder).

And the speed is selected in accordance with the desired thread (it is indicated on the back of the machine).

Taps are often used for internal metric threads. As a rule, machine taps are used on the machine, this allows the part to be completed in one pass.

For threads made of hard, viscous materials, sets of 2–3 taps are used. In a set of two, the right one does 75% of the work, and the second one only brings it to the desired size.

In a set of three taps, the right or roughing one does 60% of the work, the middle (semi-finish) 30% of the work, and the third 10%.

Using Die Heads

Threading heads are used for pipes and bolts. They are installed in the machine, then the desired diameter is adjusted and moved along the pipe. They are able to carry out work with high precision.

Universal heads allow you to install dies from different companies. It is also possible to lubricate the combs and adjust the sizes; manual clamping is often found.

Features of the left

First, you need to switch the operating mode of the lead screw so that it starts turning to the left. This is done by switching the lever that determines the direction of unwinding. And then everything happens exactly the opposite compared to the right-hand thread.

You just need to take into account that when switching to reverse, the cutter will not move to the side of the tailstock, but, on the contrary, will move towards the chuck. To avoid their collision, you must carefully monitor your movements.

Quality control

To ensure that the workpiece has been processed correctly, it is necessary to use thread templates. With their help, the thread pitch is checked.

But for a comprehensive assessment, a thread gauge is used. For convenience, it is installed in a rack and adjusted according to a standard or template, then the movement of the part itself is checked.

You can also use the simplest and most commonly used method. Take a nut or bolt and scroll it over the completed part.

If scuffing is noticeable on the thread as you move, or more effort needs to be applied, then you have made an error in your work. Now you already know how to use a lathe to make various nuts, bolts or threaded connections.

It is important to remember that such parts require great care and tenderness with each pass, and even quality control. It’s better to spend more time on work than to ruin several pieces later.

Interesting video

Source: https://vseostankah.com/tokarnyj-stanok-po-metallu/narezanie-rezby-reztsom.html

Thread cutting on lathes

Threading is a broad topic in metalworking using lathes. This technology is used in more than 40% of works. The strength of the connection between detachable structural elements or mechanisms depends on the quality of the threads. Read more about this in the article.  

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.

thread cutting on a screw-cutting lathe 1K62

A thread is a helical line formed on the surface of a body of revolution by the top of a protrusion of a certain shape. The distance between adjacent protrusions is equal to the thread pitch. The shape of the protrusion depends on its type. Between two adjacent protrusions there is a depression.

Classification of threads

Types of threaded features:

1. Helix direction:
   • right (it rises from left to right, and the bolt is screwed in a clockwise direction);
   • left (screwing occurs counterclockwise).
2. Protrusion shapes in the form:
   • triangle,
   • trapezoids,
   • unequal trapezoid,
   • rectangle,
   • semicircle.
3. The outer surface of the part (cylindrical or conical).
4. Location on the part (internal or external).
5. Number of visits (one, two, three);
6. Purpose (fastening and chassis).

Threads are divided into types:

• with profile angle:
  • 60⁰ (metric, conical inch);
  • 55⁰ (cylindrical pipe, conical pipe);
• persistent;
• round;
• trapezoidal shape (angle 30⁰).

Trapezoidal threads have greater strength than rectangular threads, while being less labor-intensive to manufacture. The purpose of a trapezoidal thread is to convert rotational motion into translational motion.

In addition, they use a thread called modular. It is used where rotation is transmitted from a worm to a worm wheel, the axes of which are at an angle of 90⁰.

The thread is designated: M12x1.25–7N. This means: metric internal (7H), diameter 12 mm, pitch - 1.25 mm, tolerance range 7H. For external threads, the tolerance field is written: 6h. The coarse pitch value is not given in the designation (M16–8g). The letters LH (M16–8g–LH) are added to the left-hand thread in the designation. GOST 8724–81 provides a table indicating the diameter and pitch of the required size.

Threading tool

Die. On the outer surface the thread is cut into dies. They are made in the form of a nut. To obtain cutting elements and remove chips, holes are drilled in them. On each side the die has cutting elements that form a fence cone (angle 20⁰–30⁰). In the middle part there is a calibrating zone.

The die is fixed in the collar using screws. After each revolution of the die, you need to turn it back a third of the circle. This is necessary to clean the holes from chips and obtain a high-quality threaded surface.

Tap. The tap is used for cutting internal threads. It has cutting edges obtained by making longitudinal or helical grooves. Grooves form the front surfaces on the teeth. The working area of ​​the tap forms the sampling and calibrating sections. The fence section is also called the cutting section. It is conical in shape and penetration occurs gradually.

There are hand, machine and nut taps. Hand taps are made single and in sets: for roughing and finishing passes when cutting threads. The set also consists of 3 taps. Its number is indicated by the number of circular marks on the shank (1 - rough, 2 - semi-finish, 3 - finishing).

The roughing tap has the largest intake part. The shank of the taps is made in the form of a square in order to transmit the working force to the driver. Taps are subdivided for cutting threads in through and blind holes. Nut taps are made with a straight or curved shank.

Cutter. The thread is cut by the tip of the cutter, fixed in the support, as it moves relative to the rotating workpiece. In this case, the thread pitch formed by the cutter is equal to the distance between the tops of adjacent protrusions along the axis of the part.

Cutters for cutting threads are structurally designed to:

• solid (made of high-speed steel or hard alloy);
• with soldered hard alloy plates (GOST 18885–73);
• prefabricated with mechanical fastening SMP (replaceable polyhedral plates).

A thread cutter with a brazed or replaceable multifaceted insert (SMP) must have sharpening angles that ensure the corresponding profile on the thread. Such cutters are used for cutting metric and trapezoidal threads.

Cutters with SMP are used on CNC turning and milling machines, which can provide the necessary cutting conditions and obtain the finished part in one processing cycle (machining centers).

To ensure the quality of the thread when cutting it, a cutting fluid (emulsion, sulfofresol and others) must be used.

High-speed steel grades for cutters: R6M5K5, R6M5, R9M4K8, R9K5, R12F3, R9M4K8.

Equipment used

Threads are cut by hand or on screw-cutting lathes. When cutting manually, a vice and tools are used: dies and taps. You can cut threads using a 16K20 screw-cutting lathe with a cutter, tap, die and other types of tools. They cut both external and internal threads.

On the feed box of the 16K20 machine there is a table that indicates the positions of the handles in order to adjust the desired thread pitch. Setting processing modes allows you to obtain a high-quality part. The technology for using the cutter provides:

• sharpening it correctly;
• setting machine operating modes;
• correct installation of the cutter in the center of the part using a device - a template;
• measuring the resulting dimensions using threaded templates or gauges.

When forming threads, the following are not allowed: scuffing, crushing, torn threads, risks.

A special fixture or vortex heads with a separate drive expand the functionality of lathes.

Turret lathes increase machining productivity by reducing the time required to change tools.

Source: https://stankiexpert.ru/stanki/tokarnye/narezanie-rezby-na-tokarnykh-stankakh.html

How to cut threads on a lathe?

In the mass production of hardware, thread rolling is used on automatic machines. The production of individual parts is carried out by cutting threads on lathes. The pitch is maintained by a specially installed lead screw. Settings are performed using tables.

Threads with diameters up to 40 mm are made with taps and dies, regardless of the type of protrusion relief.

On large parts, weighing over 500 kg, with a diameter exceeding the length of the part, cutting can be done on rotary lathes that have a guitar in their design.

Thread cutting on a lathe

Classification of threads

Division of threads by surface type:

• conical;
• cylindrical.

In the direction of the turn:

Without indicating the direction, the thread is cut in the left direction. It is considered standard. The same tool is used. It changes to reverse rotation, and the cutting edge turns over 180⁰ - the caliper is brought in from the opposite side.

The tooth profile in section has different shapes. Types of threads used, made on lathes:

• metric;
• metric-conical;
• cylindrical pipe;
• pipe conical;
• inch;
• trapezoidal;
• persistent;
• round.

To use taps and dies, the part is mounted in a chuck. The threaded cutting tool is pressed by the center of the tailstock. When cutting with a cutter, the long part is pressed by the tailstock, the short part by the mushroom. The tool is mounted on a support and aligned in the axis of the part.

Dies and taps for cutting

Threading technique

There are different ways to cut threads on a lathe. The part undergoes preliminary processing and preparation. For knurling, the outer diameter is made smaller. The metal is not cut, but pressed with a roller. Excess material rises to form ridges. The groove size is indicated in special technological tables.

Cutting with taps and dies requires a slight undersizing, by 2–5% of the thread height. The diameter for the cutter is made with a plus allowance. During the work process, all excess is cut off.

The part is mounted in a chuck. The long one is pressed up by the tailstock. The cutter is brought to contact. Then the cutting depth is set. At the end of the cut, the cutter is sharply pulled back.

When using a tap, it is pressed by the tailstock. The die and threading head can be mounted in a chuck. The hardware is brought to them with a second cartridge or caliper.

The method of cutting a screw thread on a lathe is determined by the number and size of the part, and the availability of the appropriate tool.
How to cut threads on a lathe 1k62

Source: https://metalloy.ru/obrabotka/rezba/narezka-na-tokarnom-stanke

Thread cutting on a lathe - cutters, taps, dies, heads and dies

Thread cutting on a lathe is one of those operations for which various tools can be used. This problem is most often solved using a cutter. In addition to it, taps, dies, and special-purpose working heads are also used. In addition, on lathes this operation can be performed using knurling technology.

The process of cutting threads on a lathe with a cutter

Application of cutters

Thread cutting tools are required to cut threads using a lathe. They are made from high-speed steel, and the requirements for their characteristics are specified by the relevant GOST (18876-73). By design, such cutters are divided into the following types:

• prismatic;
• rod;
• round (disc).

A helical threaded groove on the surface of the workpiece is cut with a bent or straight cutter, and to form internal threads, straight and curved tools are required, which are fixed in a special mandrel. The top of the turning cutter, which is used to cut the turns, must have a configuration that fully corresponds to the profile of the thread being formed.

Cutters for cutting threads: a - rod; b - prismatic multi-profile; c - prismatic single-profile; g - disk multi-profile; d - single-profile disk; e - disk for internal thread; α—rear angle; γ — front angle; φ is the angle of the intake cone; h - installation height of the cutter axis

When forming a thread with a cutter, a number of features of this technology should be taken into account.

• The rake angle of a turning thread cutting tool depends on the characteristics of the material being processed. You can choose this angle within a fairly wide range: 0–250. So, if a thread is cut using a machine on workpieces made of ordinary steels, the rake angle should be 0 degrees; for high-alloy steels that withstand temperature loads well, the rake angle can be 5–100. It can be greater, the higher the viscosity of the material, and the smaller, the higher the hardness and fragility of the metal from which the workpiece processed on the machine is made.
• The tip of the turning tool, which forms a helix on the workpiece, must have a shape identical to the thread profile.
• The rear side corners of the tool are chosen such that the surfaces of the cutter with which they are formed do not rub against the newly formed helical groove. Typically these angles are made equal on both sides of the turning tool. If the helix angle that characterizes the thread is less than 4 degrees, then such angles are chosen in the range of 3–50; if more than 40, then 6–8 degrees.
• Internal threads are cut in already prepared holes, which are obtained by boring or drilling.

Workpieces made of steel are processed on a lathe using tools with plates made of hard alloys T15K6, T14K8, T15K6, T30K4. If the part is made of cast iron, then to cut threads on it, use a tool with plates made of the following grades of hard alloys: VK4, V2K, VK6M, VK3M.

Technology for using taps and dies

Using taps, which are a screw with several longitudinal grooves that form cutting edges and facilitate chip removal, predominantly metric threads are cut on a lathe in small-diameter holes. If machine taps are used for thread cutting, the operation is performed in one pass.

Machine taps differ from ordinary ones in that they consist of two parts - a tapping and a calibrating one. If ordinary taps are used to cut threads using a lathe, then the technology for performing this process involves the use of a set of tools.

The set for cutting internal threads includes three types of taps: roughing, which does 60% of the work, semi-finishing (30%), finishing (10%). Sometimes in such a set there may be two tools: roughing, which does 75% of the work, and finishing, which accounts for 25% of the work.

To distinguish a rough tap from a finishing one, just look at its cutting part: it is much longer than that of a finishing one.

Design of a tap for thread cutting

The speed of thread cutting on a lathe using taps can be quite high:

• 6–22 m per minute – for parts made of cast iron, bronze and aluminum;
• 5–12 m per minute – for steel workpieces.

Using dies, which are a ring with an internal thread and several chip grooves, external threads are made on screws, bolts and studs. The surface of the part must be pre-ground to the required diameter, which must take into account the tolerance:

• 0.14–0.28 mm – for threads with a diameter of 20–30 mm;
• 0.12–0.24 mm – for threads with a diameter of 11–18 mm;
• 0.1–0.2 mm – for threads with a diameter of 6–10 mm.

The dies with which external threads are cut are secured in a special chuck (die holder) located in the tailstock quill of the lathe.

Threading dies

 Using dies, threads are cut at the following speeds (their setting also takes into account minimal tool wear during operation):

• 10–15 m per minute – on products made of brass;
• 2–3 m per minute – on cast iron parts;
• 3–4 m per minute – on steel workpieces.

In order for the die to fit smoothly onto the part, a chamfer is removed at the end of the part, the height coinciding with the height of the thread profile.

Application of Die Heads

When cutting threads using lathes, special heads are used much less often than the tools described above. Such heads can be used for cutting threads of any type.

Their working elements are combs: prismatic ones are used when it is necessary to cut internal threads; for cutting external threads, radial, round and tangential ones are needed.

The peculiarity of such heads is that their working bodies automatically diverge during the reverse stroke, so they do not come into contact with the newly cut thread.

Threading combs

Combs for cutting internal threads (their number in a set may vary) are made with a lead-in cone. When cutting external threads, round type dies are mainly used, which are distinguished by the simplicity of their design. In addition, combs of this type are characterized by high durability; they can be sharpened repeatedly, bringing their geometric parameters to their original values.  

In the event that on a lathe it is necessary to cut a screw surface on worms or screws of great length, then the threading heads are fixed on the machine support, which helps to increase the productivity of the technological process. Such heads can be equipped with both conventional cutters and cup-type tools.

You can understand the technology of thread cutting using a lathe from a video that clearly shows how this process is carried out. Below are several videos that show the process of making carvings in different ways.

Source: http://met-all.org/obrabotka/tokarnaya/narezanie-rezby-na-tokarnom-stanke-rezcom.html

All about cutting threads on pipes: 4 secrets of a turner

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.

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.

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://trubexpert.ru/repair/vsyo-o-narezke-rezby-na-trubax-sekrety-tokarya/

Cutting internal threads on a lathe

The joining of structural parts occurs through bolts, screws and studs, which in turn have special external and internal threads. This kind of connection is called detachable. Bolts, screws and studs are cylindrical rods with screw threads. The thread cutting process is carried out mechanically and manually, on machines with special tools.

Processing methods

Internal threads are applied with taps, external threads with dies. Taps are shaped like a screw, with a groove along the screw part that will allow the chips to slide off during the process. The geometric shape of the dies resembles a nut. Capable of cutting threads with a diameter of up to 52 mm. There are round, square, hexagonal and prismatic.

Features of internal thread cutting

A thread is a reliable way to connect two parts; this indicator increases significantly if the thread is internal. Tapping is the removal of metal material using cutting edges at different pitches. The operation is performed in one pass. Depending on the intended purpose, swords are divided into: metalworking (metric and inch threads), nut, master and die. By type of thread - left-handed for creating left-handed threads and, accordingly, right-handed.

• method of processing with a tap

The internal thread is applied with a tap, which is made of carbon or high-alloy steel. The tool consists of a shank attached to a cup chuck and a working area - a cutting part with longitudinal and helical grooves. The intake part - the upper part of the cone, carries out thread cutting work. Calibrating part – calibrates the direction of the process. General operating rules:

• • It is not recommended to immediately apply threads to products made by casting or stamping. It is necessary to pre-drill the hole, thereby removing carbon deposits and scale;
• • on drilling machines, the tap must be secured in reversible chucks to avoid the possibility of breakage;
• • mandatory chamfering in those places where work is planned.

Regardless of the cutting method: manual or automatic (on machines), the use of coolant is an important component for obtaining a quality result.

• cutting method on a lathe

The main problem with using taps is chip removal in holes 6 mm and over 16 mm. Due to the limited space, chip removal is difficult, which can cause tool failure. On lathe-type machines, threads are applied using a boring cutter and carbide inserts with a full or partial profile.

Features of external thread cutting

Threads are grooves of various geometric shapes, cut with special tools - dies, thread cutters, taps and grinding wheels. The thread is applied either manually or using a lathe and cutter.

• method of cutting with a die and tap

A tap is a screw with straight and helical grooves, designed for cutting internal threads. The manual cutting method requires 3 taps: rough, for applying the initial thread, medium and finishing. The machine cutting method is carried out on lathes and milling machines.

The dies are similar in shape and appearance to a nut; on the inside of the tool there are conical cutting teeth for cutting external threads. They are divided into round, square and hexagonal shapes. According to the design - solid, split and sliding.

To ensure smooth passage of the die through the part, it is necessary to remove the chamfer.

• turning method

In production, threads are cut using a lathe and a special tool - a thread cutter. For each product, an individual indicator of the helical pitch is established; it is determined by measuring the distance between adjacent turns.

The part is placed in a lathe, and as the workpiece rotates, the cutter moves along all axes, creating a helical surface. Based on their design features, thread cutters are divided into: prismatic, rod and round/disc.

The thread profiles used are triangular, rectangular, trapezoidal, thrust and round geometric shapes.

Read also: How to drill stainless steel at home

Features of pipe threading

In pipe threading, 3 types are used: on a lathe, using a die or a pipe die. In practice, the most common thread is the triangular type:

• • inch, with measurement calculations in inches. The thread has high strength due to the large pitch and large profile. Used for water pipes;
• • metric, measured in millimeters, used for pipe fasteners.

The clamp is a tool of limited functionality, used only for cutting threads on pipes.
On lathes, the process is structured as follows: the pipe is fixed in the spindle, then all excess is removed with a cutting cutter, the appropriate pitch is selected and the thread is applied.

Thread cutting is one of the most common operations in metalworking. To perform it in non-serial production, universal screw-cutting lathes are used. These machines work with workpieces in the form of bodies of rotation and small parts of asymmetrical shape that can be mounted on the faceplate of the machine. In other cases, threads are obtained by milling, rolling and other methods.

Thread cutting on a lathe

To form threads on a lathe, cutting tools are used, the top of which moves at a constant speed along the axis of the rotating workpiece. In this case, a helix line is formed on the surface of the workpiece.

The inclination of the helix to the plane perpendicular to the central axis of the workpiece depends on the ratio of the spindle rotation speed and the tool movement speed and is indicated by the helix angle.

The distance between two adjacent identical thread elements, measured along the axis, is called the thread pitch.

When the tool is deepened into the workpiece along a helical line, a surface is formed with the same shape as that at the top of the tool. The thread profile is the contour of the thread section on a plane passing through its axis of rotation.

Depending on the profile, threads are divided into triangular, trapezoidal, rectangular and round, which are used extremely rarely.

Threads with a rectangular profile are persistent; they are used for threaded pairs operating under significant load.

Depending on the shape of the base surface, threads are divided into cylindrical and conical. Tapered threads are used in oil, water, fuel and air systems, in short, where a tight connection is required. Based on the type of base surface, threads can be divided into external and internal.

By direction, left and right threads are distinguished; the right thread is twisted when rotating clockwise, and the left thread is twisted counterclockwise. Based on the number of threads, threads are divided into single-start and multi-start. Multi-start threads allow you to travel a greater distance in one revolution. The number of passes can be determined by looking at the end of the part. Depending on the units of measurement, meter and inch threads are distinguished.

Thread cutting with cutters

Cutting turning threads with cutters is the most common method. It is used to create external and internal threads. To create threads, prismatic, rod and prismatic cutters are used. Their sizes and shapes are close to those of shaped incisors.

For external threads, straight and bent cutters are used; for internal threads, with a small hole diameter, curved cutters are used, and for large diameters, straight cutters mounted on a mandrel are used. It is impossible to make small holes with a cutter.

In blind holes, when making a thread with a cutter, a recess is provided for its exit and chamfers on the edges of the hole.

A large selection of cutters and other cutting tools for lathes can be found in the “Cutting tools for lathes” section.

Cutters for thread cutting have plates made of high-speed steels and hard alloys as a cutting edge. For preliminary operations, plates made of alloys T15K6, T14K8 and their analogues are used, and for finishing operations - T30K4 and T15K6. In processing cast iron workpieces, elements made from alloys V2K, VK3M, VK4, VK6M show high efficiency.

Internal thread cutting

For internal threads, in addition to cutters, taps and dies are used . The tap is a tool in the form of a threaded rod made of hardened steel. On the surface of the rod along its axis there are milled grooves, thanks to which the thread has cutting edges. The tail part of the tap has a square cross-section, which allows it to be secured in a chuck or driver.

Read also: What are your individual qualities?

During thread cutting, the metal is not only cut into chips, but also plastically deformed due to the cutting of the tool, and the internal diameter of the hole increases. Taking this feature into account, the diameter of the thread hole is calculated by subtracting the thread pitch from the outer diameter of the tap.

There are many different taps, of which nut, hand and machine taps are widely used. To cut a thread using a tap, the part is fixed on the machine, a hole is drilled in it and the spindle is adjusted to the required number of revolutions. The tap installed in the tailstock is inserted into the hole due to the movement of the quill, and the part rotates.

Taper thread cutting

Of the conical threads, the most widely used is the standard one, which has a profile symmetrical with respect to the normal to the cone axis. To cut such threads, the same methods are used as for conventional cylindrical threads.

For external tapered threads, turning is carried out along the outer diameter to a cone. This can be easily done using thread cutters on a screw-cutting lathe using a copy ruler, but this method is characterized by low productivity.

On turret lathes, tapered threads are cut using dies. If it is necessary to obtain high-precision threads, then threading heads with dies of various shapes are used. During the operation, the dies automatically move apart.

Also, for tapered threads, rolling rollers are used, which allow thread rolling. For internal tapered threads, specially designed taps are used.

Setting up a lathe for thread cutting

To perform turning threads with the specified parameters, it is necessary to fine-tune the machine. First of all, you need to connect the rotation of the spindle with the movement of the caliper. The longitudinal feed per spindle revolution must be equal to the thread pitch.

Screw-cutting lathes allow you to adjust the feed of the cutter by interlocking the gears of their feed guitar and feed box. There are a large number of combinations of the clutch of these wheels, which allows you to configure the machine for any thread being cut.

Threads cannot be cut on a CNC lathe - basic mistakes

1. does not cut at all (the start light is on - the axes do not move - most likely there is no response about the spindle rotation speed from the sensor or the spindle rotation has not started) 2. does not get into the turns (the presence of large mechanical play, slipping of the encoder sensor or its kinematics) 3.

cuts threads with a pitch different from the specified one (check the thread cutting cycle, the maximum feed speed during thread cutting, work in mm) General checks - check the thread cutting program, entry and exit according to the operating manual (text provided for analysis) - check the suitability of the material, cutter , spindle revolutions, feed, spindle range - (thread pitch, mm) * (number of spindle revolutions rpm) should not exceed the maximum working feed speed along the axis (P1430) => reduce the spindle rotation speed (the problem occurs when cutting large threads with a pitch of more than 8-10 mm) - check the fastening of the electrical cables (connectors) and the cables themselves from the encoder to the CNC - check the fastening of the encoder on the spindle head, the encoder coupling, the gear on the encoder shaft in the spindle head - Check the parameter and set value of the sensor pulses spindle per 1 revolution. P3720=4096 pulses

*parameters are specified for Fanuc 0i series CNC

Source: https://morflot.su/narezanie-vnutrennej-rezby-na-tokarnom-stanke/

Cutting threads on a lathe with various tools

Threaded connections are actively used in almost all sectors of human activity, from agriculture to the space industry. To cut threads in small volumes, a lathe is used in conjunction with a special tool: cutters, dies, taps and threading heads. The method is selected depending on the required strength, size, profile and location of the screw surface.

Features of thread cutting

When performing work on a turning wall with a cutter installed, the top of the tool draws a screw recess, moving along the axis of rotation of the workpiece. This groove is called a thread. It is characterized by the following parameters:

• Pitch is the distance between adjacent turns. Measured along the axis of the workpiece.
• The angle of increase in the helix is ​​an indicator of the inclination of the line relative to the plane perpendicular to the axis of rotation of the workpiece. It is determined by the rotation frequency of the part and the speed of movement of the cutting tool along its axis.
• Stroke (for multi-start thread) is the distance between the nearest turns formed by one thread.

There are 5 thread profiles that affect the characteristics of the threaded connection:

• round;
• persistent;
• rectangular;
• trapezoidal;
• triangular.

The surface of the part itself can have a conical or cylindrical shape. A helical line cut by a tool on a machine is formed in one or more passes. For threads with two or more threads, the latter are located equidistant relative to each other. To count their number, just look at the beginning of the thread surface.

Cutting threads on a lathe with a cutter

Thread cutting on pipes can be performed both on a universal lathe and on semi-automatic thread lathes using an automatic cycle.

Thread cutting machine TV 16

Cutting internal threads on pipes with a carbide cutter on a lathe is now considered one of the most effective methods.

Features of the lathe

For cutting internal threads on pipes, machines such as S-225 and VMS-N-14 are widely used. The thread cutting machine is equipped with a cutter to which the workpiece (pipe) is fed.

The lathe has a mechanism that pneumatically clamps the pipes placed on the carriage. The pipe is brought to the cutter with your own hands, and its subsequent movement is ensured by self-tightening.

During operation of the unit, burrs from metal shavings located in the pipes can be removed using a countersink, which is located in the spindle of the machine. The upper plane of the frame is equipped with a gearbox.

Thread cutting on a modern lathe

Its drive is provided by a V-belt drive coming from an electric motor located below. The gearbox is equipped with a spindle on which a flange is fixed. A cutter is attached to the flange, thanks to which threads are cut in the pipe.

The machine is equipped with a self-centering vice that moves along the bed using a hydraulic cylinder. Special compartments of the frame include cooling units and electrical equipment.

The machine control panel is located on the front wall of the bed. The machine for cutting internal threads on pipes is presented in the form of a semi-automatic machine, in which all processes are mechanized as much as possible - only the removal and fastening of the pipe is done manually.

About the design of cutters

When cutting internal threads in pipes using a machine, cutters made using high-speed steel can be used, they can be:

• core;
• equipped with a welded cutting blade;
• with a head and a cutting insert secured to the cutter by a clamping device.

thread cutting with M30 cutter

cutters equipped with a soldered plate can be equipped with a mechanical fastening, as well as a grindable and non-grindable plate.

Such parts are distinguished by their simplicity of design, but nowadays they are used extremely rarely due to some shortcomings of the fastening mechanism.

Nowadays, the most widespread are cutters that use mechanical fastening of plates made of hard alloys. this significantly increases the mechanical resistance of the cutters.

The use of so-called non-sharpenable multifaceted inserts in turning tools is relevant.

In addition to general durability and long service life, the inserts can be quickly replaced when the cutting edge wears out. To speed up replacement, interchangeable cutters are used.

In order for them to be adjusted, special threaded stops are used. The setting of such a cutter does not take place in the machine on a special device in which the standard cutter is installed.

work rules

The process of cutting internal threads on pipes using a machine is carried out according to the following algorithm:

1. The workpiece is installed with your own hands in the vice of the clamping device, the “clamp” handle is rotated to the limit, and the product is tightly secured.
2. In order to ensure a minimum stroke of the clamping tubes, the workpiece is placed on the end side of the clamp.
3. The handle marked “forward” is turned and the caliper with the installed pipe is directed towards the cutter.
4. Once the pipe is captured by the dies of the cutter, threading will be carried out by self-tightening as it is gradually screwed into the head.

When cutting threads, you should also pay attention to a number of technological points. So, for example, when the handle is turned to a position designated as “unclamping,” the clamping device of the vice is released, and the finished product can be removed.

Internal thread cutting

If necessary, you can open the cutter dies with your own hands using the handle.

To ensure thread rolling, the vice is lightly tightened using a wedge. Knurling will be successful if the pipe, which was clamped in a vice, has a slight backlash .

Some freedom of movement of the workpiece in the machine vice will ensure the necessary self-centering relative to the cutter.

Thus, as the spindle rotates clockwise, the cutter will plunge into the pipe and form an internal thread. It is important to remember that before starting rolling, the pipe must be thoroughly cleaned of traces of dirt and scale.

Some rolling machines may use a special thread rolling die. It is presented in the form of a cylinder with a diameter of 80-90 mm with a through hole in the center of the body.

After thread rolling is completed, the spindle will begin to rotate in the opposite direction and the cutter will come out of the pipe. Next, the vice is released, and the finished threaded pipe is removed.

It is worth noting that knurling is performed in semi-automatic mode; push-button switches are used for this.

Thread control

When creating internal threads in a pipe using a lathe, its pitch is measured using thread templates. This template is presented in the form of a plate on which there are special cutters.

The cutters are marked with a thread pitch, which is indicated on the face plane of the template. There are sets of templates that can be used to measure both metric and inch threads. Such templates can only measure the thread pitch parameter.

To evaluate the accuracy of the threads made inside the pipe, various thread gauges are used. These calibers can be pass through.

Continuous gauges combine a full thread profile and are considered a prototype of the future internal pipe connection.

Non-go gauges are capable of controlling the average thread diameter and are equipped with a shortened profile. Before making control measurements, all parts are thoroughly cleaned of metal shavings and dirt.

Mechanically fastened cutter inserts

The gauges must be applied extremely carefully to prevent scratches and abrasions from appearing on their surface. To measure the internal, external and average pitch diameters of the internal connection, a thread micrometer is used.

Its spindle is equipped with a number of mounting holes. Kits with replaceable inserts are inserted into them; they fully correspond to the thread elements that need to be measured.

In order to conveniently carry out such measurements, the micrometer is fixed on a stand, after which adjustment is made based on a template or standard.

Safety rules at work

In order to prevent accidents when working with a pipe cutting machine, the following requirements must be strictly observed:

• if threading is being done in a long pipe, then one end of it should rest on a stand specially designed for this purpose;
• power supply wires must be reliably insulated and located in a protective tube;
• the power supply switch is located in a special protective box;
• all parts of the machine that rotate during operation should be fenced off;
• Both the electric motor and the switch are grounded after installing the machine.

It is also worth noting that when cutting threads in pipes, protective glass is installed on the machine, which will protect the operator’s eyes from flying chips.

Source: https://trubypro.ru/soedinenie/rezbovoe/stanok-dlya-narezki-rezby.html