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

1. Design
2. Thread type
3. Direction of thread being cut

Every craftsman knows what a die or tool is, but it will be very useful for beginners in plumbing to study our article. In it we will give answers to the following questions.

1. What are dies and what are they used for?
2. What design features does the tool have?
3. How is a die different from a lerka?
4. What types of dies are used in plumbing?
5. What are they made of?
6. How to use dies?

Threading [ edit | edit code]

The tap is attached with the tail part to the driver, the working part is inserted into the hole in which, when turning the driver, a thread is cut in a reciprocating motion. The working part of the tap has cutting and calibrating parts. To avoid friction on the workpiece, the rear surface is backed (non-round). The thread profile of the tap must match the profile of the thread being cut.

When cutting threads, sets of two or three taps (rough, medium and finishing), differing in size and profile accuracy, are often used; on viscous materials (for example titanium alloys), sets of five taps are used. To perform most household plumbing work, two taps are enough; these are the sets that are sold in retail trade.

There are taps for blind and through holes.

Taps are made of carbide or high-speed steel.

Taps can be used on lathes, drills and machining centers (machine taps), as well as for manual threading. A machine tap differs from a manual tap in the shape of the lead. The tap is secured on the machine in a special chuck (chuck with axial compensation) or a regular collet chuck with a collet for taps. Also recently, as an alternative to axial compensated chucks, compensated collets have begun to appear, which can be used on a conventional collet chuck.

To obtain internal threads by plastic deformation (rolling), chipless taps (rollers) are used. Their main difference from cutting taps is the absence of chip flutes.

There are also nut taps used to make nuts. This type of tap has a longer shank and lead-in (calibrating) cutting part.

When cutting threads, the tap is pre-lubricated with grease, for example, grease. Periodically turn the tap in the opposite direction to break off the resulting chips. If you use a tap out of order (for example, finishing instead of rough), it can easily break.

A tap is a type of metal-cutting tool that is used to apply internal threads and calibrate existing ones. The application method - manual or automated, depends on the size of the workpiece. In appearance, the tap is similar to a screw or cylindrical roller. The maximum thread diameter is up to 50 mm for both blind and through holes. For the production of taps, steel grades are used: P9, P18, P6M5.

THREADING WITH TAPS AND DIES

Formation and classification of threads

A thread is a helical groove of a certain profile, cut on a cylindrical or conical surface. On lathes it is performed through two uniform movements - rotation of the workpiece and translational movement of the cutting tool along its axis. The threads used can be divided into a number of groups: 1) by location - external and internal; 2) by purpose - for fastening and running gear; 3) according to the shape of the original surface - cylindrical and conical; 4) in direction - to the right and left; 5) according to the profile shape - triangular, rectangular, trapezoidal, round; 6) by the number of passes - single and multi-pass. Fastening threads most often have a triangular profile. They are used to connect various parts. - Leading threads are used to convert rotational motion into linear motion. These include threads with a trapezoidal and, less commonly, rectangular profile. Tapered threads provide high tightness of the connection and are therefore used in places under high pressure of liquids and gases. For right-hand threads, the screw groove has a clockwise direction (when viewed from the end of the part), for left-handed threads it is the opposite. Single-start threads are threads that have one helical groove. Multi-start threads have several parallel helical grooves evenly spaced around the circumference. The number of thread starts can be determined by the number of starts of helical grooves at the end of the part.

Cutting threads with round dies

Scope and tools.

Round dies are used for cutting external threads of a triangular profile on parts that do not have high requirements for thread alignment with other surfaces. The limits of the threads performed are limited by the mechanical properties of the metal being processed. For example, on lathes, round dies are used to cut threads on steel parts in increments of up to approximately 2 mm. For softer non-ferrous metals this limit may be increased. Threads with large pitches are pre-cut with a cutter and then calibrated with dies. Round dies (Fig. 118, a) in appearance resemble a nut, in which chip holes (from 3 to 8 depending on the size) are drilled to create cutting edges. The working part of the die for cylindrical threads consists of three sections: two outer sections - cutting and the middle one - calibrating. The cutting parts of the die are conical with a cone angle of 2f = 50-60°. The calibrating part is cylindrical. It gives the thread its final dimensions and provides direction to the die during the cutting process. The geometric shape of the die tooth is created by the rake angle, which is performed by sharpening within 15-20° (for centrally manufactured dies). When cutting hard metals, it is recommended to reduce it to 10-12°, and for soft metals - increase4 to 20-25°. The rear angle a is performed by backing only on the cutting parts within 6-8°. For mounting in a die holder or thread-cutting chuck, conical recesses and an angular groove are provided on the outer surface of the die. The corner groove of the die allows, if necessary,

cut the die with a grinding wheel along the jumper (Fig. 118, b) and adjust its diameter within 0.1-0.3 mm. General purpose round dies are manufactured for the following threads: metric with large pitch Ml - M68; metric with small steps M1X0.2 - M135X6; inch 1/4—2′; pipe 1/8—1l/2′. The dies must ensure cutting threads of the 2nd accuracy class. Dies for tapered threads are wider and have only one cutting part on the larger diameter side. The peculiarity of the operation of the dies is that in the process of cutting a helical groove, not only the cutting part, but also the calibrating part is involved.

These dies are made for threads from 1/16′ to 2′. Dies are made of alloy steel 9ХС or high-speed steels Р9 and Р18. The dies are marked with the thread designation, accuracy class (3rd only), steel grade (9ХС is not indicated), and the letter L for left-hand threads.

Techniques for cutting threads with a die.

Before cutting, the workpiece is cleanly ground to a size 0.1-0.4 mm smaller than the outer diameter of the thread. A large reduction in the diameter of the workpiece should be carried out for threads with large pitches and more ductile metals being processed. This is done in order to prevent the thread tips from breaking due to partial extrusion of the metal during cutting. For better centering of the dies, a small chamfer is machined at the end of the workpiece at an angle of 30-40° to the axis. The process of cutting cylindrical threads with dies has some features. After the die cuts into the workpiece approximately half its width, the thread is cut by self-tightening. This means that for further advancement the die does not need forced feeding and is screwed onto the workpiece, like a nut onto a screw. However, at the moment of cutting, the die must be applied to the workpiece with uniform force. In this case, the feed amount should be approximately equal to the thread pitch. Otherwise, the first turns may fail. In addition, during cutting, it is important to align the die with the axis of the workpiece. This is helped to some extent by the centering chamfer on the workpiece. If the die crashes with transfer, the profile of the thread being cut will be distorted or the threads will break.

Threading with dies on lathes is performed using thread-cutting chucks, one of the designs of which is shown in Fig. 119. The die holder 1 and a cylindrical mandrel with a tapered shank 4 are connected movably in the axial direction by a parallel key 8, secured by a screw 7 in the groove of the holder. The cylindrical part of the mandrel has a longitudinal groove ending in an annular groove 9, in which a single-acting spring-loaded stop 10 is installed. The die is inserted into the workpiece by moving the holder 1 forward by turning the handle 3 with the eccentric 5. Then, when the tool is self-tightening, the holder slides along the mandrel. At the end of thread cutting, the key 8 slides into the annular groove 9 and the holder, carried by the die, rotates freely

When the spindle turns on in reverse rotation, the key stops with stop 10 against the mandrel groove, enters it and allows the holder to move back while screwing the die. The chuck is adjusted to the length of the thread to be cut by setting pointer 2 to the required position on the scale marked along the groove of the holder. The through cutout 11 in the holder is intended for cleaning the chuck from chips. To mount smaller dies in the chuck, special adapter rings are installed in the mounting hole of the holder 1. Thread cutting with a die is usually carried out in one installation immediately after preparing the workpiece for threading. To do this, you should: 1) make sure that the tailstock quill and the machine spindle are aligned; 2) install the tailstock as close as possible to the workpiece and secure it to the bed; 3) secure the die in the thread-cutting chuck and install it in the tailstock quill; 4) adjust the thread-cutting chuck to the required cutting length for the first workpiece from the batch. After completing the preparatory steps, the die is brought to the rotating workpiece by hand, and uniform pressure is applied until 2-3 full turns of thread are cut. After this, the feed is stopped, since further cutting is carried out by self-tightening. Tapered threads are cut with forced feed over almost the entire processing length. At the end of cutting

the machine is switched to reverse rotation of the spindle and the die is screwed together. Sometimes you have to cut long threads that are not possible with a thread cutting chuck. In this case, the die can be secured in a mechanic’s die holder (Fig. 120, a) and cutting can be done as shown in Fig. 120, b. The die holder is held with the left hand by the handle, which is supported on the upper slide of the support or a rod fixed longitudinally in the tool holder. Having turned on the spindle rotation, rotate the tailstock handwheel with your right hand and move the die forward with a quill. After making sure that the cone of the cutting part of the die is aligned with the centering chamfer of the workpiece, plunge in 2-3 full turns with forced feed. After which the pressing of the die is stopped, since cutting continues by self-tightening. At the end of cutting, the spindle is turned back to screw together the die. If the thread is cut to a shoulder, the spindle rotation should be turned off when a few turns remain before the end of cutting, which are then cut manually. For cutting threads with dies, the following speeds for steel are recommended: 2-4 m/min; for non-ferrous metals - 8-12 m/min. Cutting should be performed using lubricating and cooling liquids: for steels - emulsion or sulforesol; for aluminum alloys - kerosene.

Tapping threads

1. Scope and tools. Taps, produced centrally according to current standards, are designed for cutting internal fastening threads. According to their shape, they are divided into cylindrical and conical; by purpose - manual, machine-hand and wrench; according to the number of tools - single and complete (of 2-3 pieces). Complete taps are used for sequential cutting of all required threads manually and machine-threads with a coarse pitch over 3 mm and in difficult-to-cut metals. A tap for cylindrical threads (Fig. 121) consists of a working part and a shank. The working threaded part with longitudinal or, less commonly, helical chip grooves is in turn divided into cutting (conical) and calibrating (cylindrical) parts. To reduce friction, the calibrating part is equipped with a small reverse cone of 0.05-0.1 mm per 100 mm of length, which runs along the entire threaded profile. The cylindrical shank ends in a square or flats to transmit the cutting force. In order to create normal cutting conditions, the teeth of the tap are given a certain geometric shape by sharpening. The clearance angle a on the cutting part is created by backing along the outer diameter within 6-10°. The rake angle has the same value along the entire length of the working part. It is performed depending on the properties of the material being processed: for steels 5-15°; for cast iron • and bronze 0—5°; for light alloys 25-30°. Larger values ​​within the specified limits are taken for softer materials. Taps for cylindrical threads are produced in four degrees of accuracy: C, D, E and N. Taps of the first two degrees of accuracy have a ground profile and allow cutting threads according to

Responsibly 1st and 2nd accuracy classes. Threads of the 3rd accuracy class are cut with taps with degrees of accuracy E and N. In Fig. 122 shows the main types of taps. Hand taps (Fig. 122, a) are used for cutting threads manually in through and blind holes. Sometimes they are used for similar work on lathes. These taps are produced in sets of 2-3 pieces. To distribute the load in the set, the outer and middle diameters of the roughing and middle taps are reduced and the cutting part is lengthened to 6 and 4 threads, respectively. The finishing tap has a full thread profile and a short cutting part - 2 threads. The serial number of the tap in the set (except for the finishing tap) is indicated by marks on the shank (see Fig. 122, a). Hand taps are designed for cutting the following threads: metric - up to M52; inch - up to 2′; pipe - up to 1 1/2′. They are made from steels U10A - U12A with degrees of accuracy E and N. Machine-hand taps (Fig. 122, b) are designed for cutting threads in through and blind holes by machine of all specified sizes and by hand - in increments of up to 3 mm inclusive; They are made in two types: single for through holes with a cutting part length of 6 threads and for blind holes - 3 threads; complete of 2 pieces with the number of threads on the cutting part 6 and 2; On the shank, such taps have a radius groove for mounting in a thread-cutting chuck. Machine-hand taps are made of P18 steel according to degrees of accuracy C and D and are intended for threads: metric - up to M52; inch and pipe - up to 2′. Nut taps (Fig. 122, c) are used for cutting threads in one pass in nuts and through holes with a depth of no more than the diameter. They are distinguished by an elongated cutting part (12 threads) and a long shank for threading nuts in order to save time on unscrewing the tap from the hole. They are made of P18 steel according to degrees of accuracy C and D for threads: metric - up to a diameter of 52 mm, inch - up to 1 1/4. Conical threads up to 2′ are cut with conical taps (Fig. 122, d) in one pass. Their calibrating part is involved in cutting, so it is backed up along the profile to create a clearance angle. Material of conical taps: high-speed steel P18. On the shank: taps are marked with the thread designation, the number of the tap in the set (except for the finishing tap) by means of marks, the degree of accuracy and the grade of steel. 2. Techniques for cutting threads with taps. Before cutting, a hole is drilled in the workpiece slightly larger than the internal diameter of the thread. This overestimation of the hole diameter is necessary to prevent the thread tips from breaking off as a result of partial metal extrusion during the cutting process. With sufficient accuracy for practice, the diameter of drills for metric threads can be determined by the formula where a is the outer diameter of the thread, mm, S is the thread pitch, mm: For other fastening threads, the required drill diameters are selected according to the corresponding reference tables. The drilling depth of a blind hole for a thread is determined from the FORMULA where lo is the length of the thread, mm; l1 - length of the cutting part of the tap, mm;. c is the guaranteed gap in mm, taken to be no less than the thread pitch. Cutting threads with taps is carried out similarly to making threads with dies. The tap is fixed in the thread-cutting chuck (see Fig. 119) by means of an adapter sleeve.2 (Fig. 123), in the hole of which there are cylindrical and square sections. In the sleeve, the tap is held by a pin 4, which slides into the annular groove of the shank under the action of a spring ring 3. To fasten taps without annular grooves, screw 1 is provided. Together with the chuck, the tap is installed in the tailstock quill, the axis of which must be aligned with the axis of the spindle. The tailstock is fixed to the bed as close as possible to the workpiece. Then, by manually feeding the quill, the tap is brought to the rotating workpiece, and an incision is made to a length of 2-3 full turns by turning the chuck handle. Further cutting is carried out by self-tightening, during which the tap is screwed into the workpiece, like a screw into a nut. At the end of thread cutting, the tap is unscrewed from the hole by turning the spindle back on. The thread-cutting chuck is adjusted to the thread length at the beginning of work on the first workpiece from the batch. If the thread is cut with a set of taps, it is necessary to follow the sequence of their work and promptly clean the hole from chips with a nylon brush or a stream of emulsion before each subsequent tap. When making individual parts, cutting small threads is sometimes done with hand taps using a bench wrench 1, as shown in Fig. 124. In this case, the tap with the driver put on it is supported with the center hole on the rear center, and the handle of the driver is supported on the upper slide of the caliper. Holding the tap with your left hand, feed it forward with the tailstock quill. The tap is inserted into the hole of the workpiece by 2-3 full turns with forced feed. Further cutting is carried out by self-tightening, during which the tap should be continuously supported by the center, since otherwise misalignment and breakage of the tap may occur. When cutting a thread in a blind hole, the spindle rotation is turned off a little before the end of the cutting. The remaining part is cut by hand. The cutting speed for cutting threads with taps is taken within the following limits: for machine-hand and nut taps - 8-12 m/min; for manual ones - 3-4 m/min. Cooling: for steel - emulsion, sulfofresol; for cast iron - kerosene. Author — nastia19071991

Application

Threading tools are divided into types according to design features and application:

1. • manual, where the teeth are arranged in a circle. Used in metalwork and manual cutting;
2. • nut, for through holes on nuts. With an extended or curved shank;
3. • machine, for creating blind holes by machine. Processing takes place on lathes;
4. • combined, it is possible to use both manual and machine methods of applying threads to the part.

The tool allows you to apply all types of threads - metric, inch, trapezoidal.

Tool selection

Let us note in advance that threads can be cut in different ways. You can work either manually or by machine. In the first case, as we noted above, you need to have a set of tools with you for creating threads, in the second, the work is carried out on a lathe.

Manual threading is recommended if your task is to machine only a few parts. For example, when assembling plumbing equipment, creating household pipelines, etc.

Processing parts on a lathe involves performing large-scale tasks. A person with experience with this type of equipment is able to cut threads on an industrial scale, up to a hundred parts per hour, and sometimes more. However, you are unlikely to need such performance.

Most often, a set of hand tools covers all the household needs of home craftsmen. With their help, you will also be able to cut threads correctly and efficiently, but it will only take more time and effort.

The set of equipment mentioned above is mainly represented by taps and dies, as well as various additional parts.

Features of taps

Taps are cone-shaped or cylindrical parts that are designed for cutting internal threads. In particular, they are used to make threads on pipes, nuts, small washers, various kinds of clamps and even flanges.

The taps are quite convenient to use. They consist of a working and a rear part. The working part has a unique shape and diameter. On its edges there are special incisors or teeth with a certain pitch. The teeth, when rotated, cut the metal in parallel with the removal of chips.

The back side is made in a certain shape, which makes it easier to fix the tap on the working tool.

A variety of taps for household use

Taps with the ability to cut threads without forming chips are also used, but much less often, because they are more expensive.

There are taps:

• Rough;
• Semi-draft;
• Finishing.

Roughers make the first pass, remove most of the chips and form rough grooves for the threads. This is not a full carving yet, but the preparation has already been completed.

Semi-draft models are extremely rare. They are intended for finishing rough grooves, cleaning them and forming a workpiece for a clean thread. Semi-rough taps are used primarily in the manufacture of complex parts.

The last sample, a finishing tap, forms a ready-to-use thread of precise dimensions and shape.

According to the type of actions performed, taps are divided into:

• Metric;
• Nuts;
• Pipe;
• Machine.

Note that taps, as well as dies, can cut threads of different sizes, directions and shapes. It all depends on the chosen equipment model.

Features of dies

A die is a cutting tool that is used when making external threads. The simplest example of an external thread is a bolt. While an example of an internal thread is a nut.

The dies are flat, from the outside they strongly resemble large washers or clamps for machine chucks. Only inside the die there is a cutting attachment with several rows of twisted cutters.

Tap and die, close up

Dies can have different shapes, types of assembly and dimensions. There are both round and square models. Some options are completely solid, others can be disassembled and the cutting attachment can be replaced.

The cutting part consists of three working zones. The two zones located at the edges consist of teeth, while the inner zone is responsible for removing chips and adjusting the direction of rotation.

It is thanks to the inner zone that the dies have a self-tightening property. That is, after several rotations on the pipe, the die is fixed.

You can then rotate it without pressure, since it will tighten in the direction of the thread formation. While the taps must be rotated with force throughout the entire process.

The types of dies are essentially the same as the types of taps. If you bought a large set of tools, you will probably receive several of these parts at once.

Design features

Any type of tap consists of a working area, a neck and a shank. All mechanical work falls on the working area, which in turn has a intake part and two types of teeth - cutting and calibrating. The role of fastener is performed by the shank, which is fixed on machines in a special thread-cutting chuck, and during manual work in a driver or tap holder. A characteristic feature of hand taps is that they come complete with at least 3 pieces. Each with its own working function: roughing, middle and finishing.

How to cut internal threads with a tap

To create internal threads in finished holes, you need to select the appropriate tap according to size and characteristics. Almost all indicators regarding the choice and quality of threads are regulated by the regulatory document GOST 19257-73. Recommendations for work:

1. • for products obtained by casting or stamping, additional preparation is required before applying the thread. The hole is countersinked or drilled to increase the diameter;
2. • for accurate and high-quality threads, it is recommended to mount the tap shank in chucks with reversible, self-centering and floating properties;
3. • all processed workpieces are first chamfered;
4. • during the cutting process, cooling and lubricating solutions must be used.

Thread types: metric, inch and pipe.

1. Metric - thread parameters are measured in mm, with the corresponding marking “M”.
2. Inch - used for conical taps, measured in inches.
3. Pipe – for cylindrical taps, threads are applied to pipe connections.

How to cut a thread using a die

To cut threads using a die, you will need a die holder or die. These are similar tools. You will understand the principle of their operation without any problems.

Photo #5: Die holder

The process of cutting threads using a die is divided into 3 stages.

1. Preparation.
2. Bevel the workpiece at an angle of 45°. This will make the cutting process easier.
3. Secure the workpiece in a vice in a strictly vertical position.
4. Install the die into the die holder.

1. Carefully bring the die to the workpiece.
2. Make at least two turns in the direction of the thread.
3. At the same time, press the die holder so that the die cuts into the metal.

1. Continue cutting the thread according to this principle: 2-3 turns forward and half a turn back.
2. By controlling the perpendicular position of the die, get the required number of turns.
3. Remove the tool by unscrewing the die holder in the opposite direction.
4. Check the quality of the cut thread using a matching piece with the appropriate thread.

Image #2: Cutting threads using dies

Note! The entire thread cutting process must be carried out using a cutting fluid. You can use motor oil, grease or special lubricants.

Machine and machine-hand taps

To calibrate and create threads in blind and through holes of various shapes, a tool is used - a tap, machine or machine-hand type.

— Machine metal-cutting tools are used to work on lathes, drilling, aggregate and turret machines to cut threads of all types. They process products much faster and can be used for conveyor production and large orders. With this type of equipment you can cut threads in one go if you need threads with pitches of up to three millimeters. Coarse pitch threads are made using several passes using a tap on the metal product.

— Machine-manual equipment can be used to cut threads both manually and using drilling devices (machines). The tool is available in quantities of one or two pieces. In a set of two taps, one metal-cutting tool is used for roughing work, and the other for finishing work. Often a set of machine-manual equipment is used to work with different types of materials: mild steel and cast iron are processed with one tool, and hard steel is processed with two taps. Machine-manual types differ from simply manual thread cutters in the type of shank - there is a square and an annular recess, thanks to which the equipment does not fall out of the chuck during processing of products. A machine-made product for working with metal can make threads in automotive parts, cut fastening threads and small-metric, cylindrical and conical threads. In through armholes and blind ones.

Tapping threads

Among the existing detachable connections, threaded ones are considered especially reliable. At one time (before the first use of a screw-cutting lathe in the 17th century), each nut-bolt pair was made individually and they could not be interchangeable. In the 19th century, humanity began to apply special standards for the application of internal threads. It can be done either using a machine or using taps.

Design Features

A modern tap must have the following design elements:

• The intake (aka head) part is in the form of a hollow cone, necessary to begin the formation of the cutting profile;
• Several side grooves (usually from two to six), which will provide lubricant supply and chip ejection;
• A calibrating element, in the form of an elongated cylinder, which will complete the formation of the profile;
• The shank responsible for securing the tap in the clamp of the chuck or turn signal.

When making a cross cut, the formation of the groove will depend on two of its surfaces: the front edge of the cutting tooth of the tap and the back of this tooth.

Chip flutes can vary and be of the following types:

• Single-radius - they are used on calibration tools and are a cross-section in the shape of a circular arc;
• Straight-line - used for applying nut threads and their cross-section has the shape of the letter “U”;
• Mixed - the rear groove has the shape of an arc, and the front groove has the shape of a straight line (most universal tools are made according to this pattern).

Unique characteristics of taps

The main types of taps have only their own exclusive characteristics. Knowing these characteristics, you can always choose the right tap model:

• Threaded pitch;
• Profile and with its height;
• Maximum profile height;
• Threaded diameter outside;
• Length of the fence part;
• Back length;
• Corner of a fence cone.

IMPORTANT! It is worth remembering that any taps are divided into devices with left-hand and right-hand threads.

Types by Application

According to their area of ​​use, taps are divided into:

• Bench tools - they have a square-shaped shank and are used manually. They come complete with a collar, through which rotation and threading occur. The set contains two taps, slightly different from each other in diameter, and where each removes only its share of the allowance from the surface of the hole being machined. Tools in such a set differ in the number of lines that are engraved on the shank or stamped there (particularly precise is indicated by three lines, intermediate by two, and coarse by a single line).
• Machine (machine) or machine-manual - they can produce cutting both manually and on industrial equipment (for these purposes, drilling/lathes and even large industrial processing centers are required). Unlike the above mentioned ones, these taps have a shortened tapping element, since the alignment of the axes is ensured by the machine. They are made from high-quality tool steel, are heat-resistant, and are little susceptible to mechanical pressure.
• Nuts - they are used in automatic machines for applying threads inside nuts. In terms of their design, they are distinguishable by their more elongated shank, which has a smooth cylindrical shape. Upon completion of the thread rotation, the nuts move one after another to the shank, waiting there for the end of work throughout the series. After serial production is completed, the shank comes out of the chuck, and all the resulting nuts fall into the receiving tray.

Differences in types based on design features

Taps according to their design can vary greatly from each other:

• Grooveless - they are used when interacting with soft/viscous materials and therefore have very small grooves (ductile materials include light metal alloys and several types of low-carbon and high-alloy steels);
• Screw - they contain grooves in an upward spiral, through which threads are made inside blind holes on production machines/automatic equipment;
• Stepped - the working element is divided into two sectors, the first cuts and the second smoothes;
• Combined - a drill is installed directly in front of the entry element, during one approach a hole is drilled and a thread is applied there;
• Broaches - they are needed for applying threads in passing holes using a lathe;
• “Bell” type - they are needed for applying threads of increased diameters (up to 0.5 meters) and include several cutting systems that are fixed in a common frame.

There are also exclusive designs that are determined by special production tasks.

Types of applied threads

Each thread size and type requires its own taps. They are not interchangeable, just like threaded ones. The main types may differ:

• Metric - denoted by the letter "M" is a triangular isosceles profile, where the apex angle is 60 degrees, and its dimensions are determined in millimeters;
• Inch - denoted by the letter “W”, its profile is a pointed angle of 55 degrees, and the diameter is displayed in inches and fractions, and the number of turns per inch is used as a pitch mark;
• Pipe - its difference is the different inclination of the rear/front parts of the profile, which ensures a guaranteed connection and also prevents self-unwinding.

Manufacturing materials

All taps endure large mechanical/thermal impacts during operation, and the tool itself must cut a large number of holes at this time. Accordingly, high-quality tool steels are required for production materials:

• Manual models - U10A or U12A - high-carbon types of steel;
• Machine models – PM5 high-speed steel;
• For automatic machines with increased productivity - hard alloys with increased heat resistance.

IMPORTANT! However, such metals have one major drawback - if damaged, the tap for threading cannot be drilled/removed freely.

Technological process of threading

In total, it includes four main stages:

• The preparatory stage is the selection of a drill of the required diameter and the implementation of drilling, while it is impossible to prevent the drill from leaving. Before this, it must be sufficiently sharpened, otherwise the material will overheat and the reliability of the thread will decrease. The hole is countersinked, and in the case of a blind hole, a small allowance must be given in relation to the depth;
• Direct cutting - at this stage, all movements performed are carried out measuredly, clearly and accurately, you must not allow lines to be missed, but use all three in sequence from rough to precise;
• Cleaning stage - here the passage holes are cleaned with a wire brush, and the blind holes are cleaned with pressurized air or a construction vacuum cleaner;
• Checking stage - here you need to screw the screw into the existing hole, and the entry should be smooth along the thread, without unnecessary effort and any distortions.

Taps - broaches

To obtain large-profile threads in metal products, use a broach tap. It is used to process complex through or trapezoidal holes. Broaches can only be used in a lathe. The thread is cut in one pass along the hole. This tap differs from other types in its more precise design and rigidity. It works in tension rather than compression like conventional threading tools. Due to the broaching function, the thickness of the cut is reduced, and the length of the cutting part is increased.

Nut taps

Nut-type tools are designed for thread cutting in nuts of different diameters. The design of the nut tap is such that the tool does not need to be turned out at the end of the nut hole machining process. Nut accessories can be with different shanks: curved and elongated. With curved ones - used in working with automatic nut-tapping machines. The shank of a nut tap is, in any case, longer than that of other types; this is necessary in order to string nuts onto it as threads are cut into them. This increases speed and productivity.

Damage to the tap - possible causes and their elimination

The instrument in question, naturally, is not entirely durable and is prone to simple obsolescence and natural wear and tear. The most common cases of damage:

• Warping;
• The working opening is too narrow;
• Excessive force applied by the operator to the gate;
• Failure to follow the reverse half-turn rules at the end of each full turn.

If any of the above cases occur, then there is no need to rush and try to run the thread faster or try to skip the tap from the set. All this can result in temporary losses, and therefore all extraction actions should be carried out slowly.

Bench taps

To work with holes of different types and shapes, craftsmen take a set of metalworking taps. Thread-cutting equipment is manufactured in sets that include roughing cone-shaped tools, semi-finishing and finishing cylindrical equipment. Using metalworker's taps you can process the part manually. Using a set of metal-cutting equipment, a master can cut large and metric threads. Taps for metalwork are left and right depending on the direction of their rotation.

Classification of threads

A helical groove cut inside or outside parts in the form of a cone or cylinder is called a thread.

It can be cut manually or on lathes using special tools: taps and dies.

The method of cutting using these methods differs: the machine version involves rotating the workpiece, while in the manual version it is rigidly fixed and the tool itself rotates.

All existing types of thread are divided into several groups:

• Depending on the direction of wrapping, they are either right or left. If you look clockwise, then for the first the groove goes along its course, and for the second - against it.
• Depending on location, there are internal and external threads.
• According to their purpose, there are trapezoidal and rectangular threads that serve to transform rotation into movement. They are called running gear. For normal connection of parts there is a fastening thread.
• The cutting form can be cylindrical or conical. The latter are used to obtain the most airtight connection.
• Depending on the profile of the thread section, there are triangular, rectangular, trapezoidal, and round.
• Single-thread tools with one threaded groove are available. Multi-pass ones have several of them. The number of passes is determined by the number of starts at the end of the workpiece.

What materials are taps made from?

Metal-cutting tool dies are made from high-quality steel of different grades: tool, high-speed, alloy. Modern production technology allows taps to be made from carbide steel and powder steel; in the latter case, the tool is produced by sintering powders. Taps made of carbide alloys are of higher quality, as they are resistant to high temperatures, wear-resistant and can work for a long time at high speeds, which allows processing a large number of metal products. Tools made from steel powders also have their advantage - high strength due to the lower hardness of the tool.

GOST standards

Machine-manual with straight/helical/shortened grooves made of carbon steel are regulated by GOST3266-71-71/GOST17933-72/GOST 17931-72. Nut taps with straight/curved shank are made from low-alloy steel in accordance with GOST1604-71/GOST6951-71. Machine-manual, where the teeth are staggered, made of stainless steel - GOST 17927-71. Nuts with a staggered arrangement and a straight shank (taps made of heat-resistant steel) in accordance with GOST 17929-72. Machine tools with screw or shortened types of grooves (tools made of light alloys) - GOST 17932-72/17930-72.

Preparing for Threading

The hole is prepared in several ways before cutting a thread - by sharpening, grinding or drilling the surface of a metal workpiece. For external threads, the diameter must be reduced by 0.1 - 0.4 millimeters. At the beginning of the section where the thread will be, a chamfer is made by sharpening - this is necessary to dull the entry of the thread. And if the hole is bored before threading, its diameter increases to 0.4 mm. The hole for the thread should be slightly larger in diameter than the diameter of the thread itself - this helps prevent breakage of the thread-cutting equipment.

Using dies for outdoor work

As a rule, this threaded equipment is made from alloy tool steel grade 9ХС. On one side there is a marking containing the name of the material from which the hole is made, the accuracy class of the thread being cut and the size in inches or millimeters.

Types of leroks

There are many types of dies for cutting external threads. The use of each of them serves a specific purpose. To select equipment, you need to understand its types:

• For high-quality slicing, solid blades of increased rigidity are used.
• In special devices - clamps - a sliding type tool is used. The thread diameter can be adjusted using the adjusting screw.
• The least rigidity is characteristic of split taps, the use of which allows you to change the diameter of the cut thread by 0.1 - 0.3 millimeters.
• For working on machines there are round leashes with conical recesses for fixing in chucks. In manual gates they are secured with five screws.

The choice of specific equipment depends on its intended use. For different types of work there are the following types of dies:

• The most common external thread is metric. It has several pitch sizes: fine and coarse, suitable for connections under shock loads.
• To cut threads on pipes, a tool with a fine pitch and a sharpening angle of 55 degrees is used.
• For work with imported fasteners there is a die with an inch thread.

Die processing technology

There are several rules for cutting external threads. Failure to comply with them leads to deterioration in the quality of work and damage to the tool. These are the recommendations:

• The tool must be in good working order, sharp and clean.
• Movements are performed smoothly and evenly.
• The size of the die must match the workpiece.
• The surface of the part must be cleaned of dirt.
• A chamfer is removed along the edge using a grinder or file to make it easier to insert the tool.
• Application of cooling lubricant.
• Every 2-3 turns the die is turned back to remove chips.
• To improve quality, the entire length of the thread must be re-threaded.
• It is necessary to avoid distortions that lead to thread breakage.

For high-quality work on cutting any thread, internal or external, the serviceability and correct selection of tools is important. In this case, the quality of the manufactured parts will be high.

How to remove a broken tap from a hole

The tap may break if the thread is cut into a hole with a small diameter, and chips may become trapped when the tool is removed.

Extraction methods

1. 1. The double ends of the rigid wire must be inserted into the grooves of the tap and unscrewed;
2. 2. You can weld the handle to the broken instrument and use it to remove it;
3. 3. There are special mandrels and countersinks that will help cope with this problem;
4. 4. If part of the tap remains outside, you can weld a shank with a square tip to it;
5. 5. Drilling with screw drills;
6. 6. Burning with electrical erosive machines;
7. 7. Etching with dilute nitric acid.

A set of taps and dies will save us in situations where we need to create a thread. Of course, today this is more an attribute of mechanical engineering, and, in most cases, these operations are mechanized, but home craftsmen sometimes have tasks of this kind.

Devices and accessories

Thread cutting is carried out by rotation and translational movement of the corresponding tool. To perform work with dies and taps, you need to secure them, direct them in the desired direction, and also ensure their simultaneous rotation and slow translational movement. For these purposes, special devices or devices are used.

Cutting external threads with dies is done using a die holder (collar). This device is a sleeve with handles on both sides. 4-6 threaded holes are drilled in the bushing, into which screws (bolts) are screwed in to secure the die inside the die holder bushing. To cut a thread, the die is inserted into the sleeve and firmly secured with screws. When fastening, the die is centered relative to the holder axis. Handles allow you to create torque manually.

When cutting internal threads with taps, wrenches are used. Such a device has a square socket in the center into which the end of the tap shank is inserted, as well as two handles for turning it manually. The fixing screws allow you to securely secure the tap into the device.

Lanyards and taps - how to differentiate?

Threads have to be cut in several versions - external and internal. This requires different tools, but the principle of their operation is very similar. Perhaps many have heard somewhere such words as lerki, taps, dies. These are exactly the devices that help accomplish this task. The differences here are quite simple, if you do not delve into the design and classification of each device. We will try to indicate them in several terms so as not to confuse you.

Ledges, also known as dies, create external threads, that is, along the top of some product, for example, a pipe. Of course, they do this at the manufacturing plant, but if you suddenly decide to make repairs at home and cut pipes, then just such a tool will help you create a new thread. Today these two names are identified, but previously they were separated. A ladle was considered a non-separable device, and a die was considered a collapsible and adjustable device. It was believed that the lerka creates better quality carvings.

Taps are used to form a threaded connector inside a part or its workpiece . To describe a tool, many people ask to imagine an ordinary screw, on which grooves are cut in a special way, which alternate with cutting teeth. At one end, this device is attached to the machine (for mechanical cutting) or a crank (for manual cutting), this place is called the shank. The other end of the tap is inserted into the hole and rotated; as it advances, it forms a carving.

What is a die?

In general, a die (die) is a cutting tool for making external threads. It is made in the form of a very strong nut, in the hole of which cutting edges with teeth are made. The teeth are arranged so that they form a coil. The cutting part of the die is formed as an internal cone. The thickness of the die is usually 8-10 teeth (turns).

Drawing of a round die.

Dies are divided by type - solid, split and sliding; in shape - round, square, hexagonal, prismatic. For manual slicing, solid round ones are most often used. For fastening in the holder (collar), up to five recesses (grooves) are made on the surface of the round die.

The die hole forms a working part consisting of three zones. At the top and bottom of the working area there are conical sections - cutting zones. In the central part, the cylindrical section forms a calibration zone. The taper angle of the cutting zones is 50-60º. The shape of the cutting tooth is set by the rake sharpening angle within 15-20º (for carbon steels) and the rear angle within 6-8º.

The round die is designed for cutting metric, inch and pipe threads. The dies ensure cutting with an accuracy of at least second class. One of the main features of the use of dies is that all three zones of the working area are involved in the formation process.

Tap sizes or what to consider when working?

The work that these tools perform can be serial, so most of the devices are machine-manual taps, that is, they can be used both on machines and in the household. Moreover, it is easy to guess that only very strong material can cope with such a volume of work, so they are made of hard alloys so that wear is minimal, or high-speed steels so that the process is faster and easier.

To get high-quality cutting, it is advisable to select the size of the taps for the hole. If you have to create a large-diameter thread, then for the best effect you need to use several sizes in succession; most often, two or three are enough. If you are processing soft material, you will have to “stretch” the pleasure of working over five taps. When there is no hole at all, the drill is used first, the tap comes into play later. Moreover, for metal workpieces, the drill should also be quite strong.

It is worth carefully choosing the profile of the cutting tool, because what you get in the hole depends on it.

Do not confuse taps for through and blind holes, because if you choose the wrong one, the part will be rejected. Also, if you do not want to use a universal threading tool, when purchasing a machine or hand tap, pay attention to the shank to see if it is suitable for your fastening. Sometimes the chipping option for thread formation is not suitable, then rolling can be used, where grooves are formed due to plastic deformations. This also requires a special tap.

Internal thread

If such a procedure is necessary, a special tool is needed . In this case, the tap becomes such. This is one of the most commonly used locksmith tools.

Tap design

Such equipment is made of high-quality tool steel. Its main components are:

• The shank is used to secure the tap in the holder.
• The working part has helical grooves and longitudinal grooves. It is used to cut threads.
• The intake part that first enters the prepared hole.
• Calibration, which, in addition to indicating the size, performs the function of cleaning the channel.
• The teeth that directly cut metal are called cutting feathers. They are sharpened according to special technological rules.
• There are special grooves between the teeth that separate them from each other. These are called grooves that form the cutting edges. Through these channels the chips formed during the work exit.

Metric tool

These taps operate in the metric system, where all dimensions are measured in millimeters and are designated by the letter M. The M 6 marking indicates that the thread cut by this device corresponds to 6 millimeters. The range of taps ranges from 2 to 60 millimeters.

Hand taps are used for metalworking work . They are:

• Nut-type, with a special device and an extended shank that holds the nut on itself.
• Die-type, with a large intake cone for single-pass cutting.
• Masterbatch, for cleaning the threaded channel.
• Special.

The working set of hand tools used for cutting internal threads includes three taps:

• Rough, for the initial drilling of a hole, which has its own designation on the shank or one ring.
• The middle one, which determines the thread size, is marked with two rings.
• The finishing one, for final calibration, has three rings.

Special equipment

This type includes grooveless taps. They do not have a longitudinal groove and are made with a shortened intake area. Due to its increased strength, such a tool rarely breaks and produces fewer defects. The longer working part allows for repeated sharpening. Such devices cut both through and blind holes.

There are also universal taps, in which each part is separated by a special groove. After passing the rough groove, the head is removed and the next one is installed in its place. The use of such a tool reduces the time for the cutting operation and does not require the purchase of a whole set of taps.

Pipe fittings

The diameter of such taps, like pipes, is measured in inches. The G marking and the size indicated next to it indicate that it belongs to this type of instrument. The most common tap size is G 1/2, half-inch, which is used in the plumbing system of most apartment buildings.

This thread is cut in two passes. The first is made with a rough tap with a sharp lead. Then a pass is made with a finishing tool, in which this part is blunt. Just like metric equipment, such taps are available with left and right thread directions.

Boring process

First you need to select a cutting tool. For steel, the sharpening angle of the tap should be 5-10 degrees, copper and its alloys 0-5 degrees, aluminum - 25-30 degrees.

To perform the job efficiently, the part must be firmly fixed in a vice. First, a hole is drilled, which should be slightly larger in diameter than the tap (selected from a reference book). The entry is processed by a countersink to remove the chamfer, which will facilitate the entry of the tap inside. Rotation is carried out with a special crank using smooth movements. First, 2-3 turns are made, after which the tool returns half a turn back. This ensures complete cutting to size. This operating scheme is used throughout the entire excavation.

The operation is performed with a full set of taps using coolant. Skipping one of the stages will speed up the work, but will worsen the quality of the result. During cutting, constant monitoring of the vertical position of the tap is necessary.

A set of taps - the pros and cons of such a tool

In theory, everything seems simple when working with taps, but this is not entirely true. If we look at the process in more detail, this is a rather expensive undertaking in terms of physical strength, especially if you set to work manually. After all, cutting metal with metal is not easy, the friction forces are enormous, the chips are not as pliable as in wooden products when drilling, they are also very resistant when exiting through the grooves. Due to the presence of grooves in the body of the tap, the strength of the body is somewhat reduced, so these devices are prone to breakage, especially when using a thin size.

But not everything is so depressing, because it’s not for nothing that the tap was used before and has not disappeared from the toolkit to this day. The structure itself is simple, easy to make and use, you don’t have to think long about how to use it and where to attach it. The accuracy of the thread is quite high, and for very demanding parts it can be increased by improving the quality of the tap itself, which is easier than building complex devices to control the cutting process itself. Having made a more perfect tap, you can already count on the same perfect thread.