The machining operation with chip removal, as a result of which external or internal helical grooves with a given profile and dimensions are formed on cylindrical or conical surfaces, is called thread cutting.
Thread cutting on screws, bolts, nuts and other parts is carried out mainly on machines. During installation and repair work In some cases, a mechanic has to cut threads manually or using pneumatic or electric machines - thread cutters.
The main elements of any carving, as noted in Chapter. 3, are profile, pitch, depth, outer, middle and inner diameters.
According to the shape of the thread profile, they are divided into triangular, rectangular, trapezoidal, thrust and round (Fig. 4.14).
The thread type or profile is selected according to GOST depending on the purpose.
Rice. 4.14. Profiles and thread elements:
a - triangular;
b - rectangular;
c - trapezoidal;
g - persistent;
d - round;
d is the outer diameter of the thread;
dcp - average thread diameter;
d1 - internal thread diameter.
In mechanical engineering, three thread systems are accepted: metric, in which the pitch and diameter are measured in millimeters; inch, having a different profile shape and characterized by the number of threads per inch of its length and diameter in inches;
pipe thread, which has a profile like an inch thread, but with a smaller pitch.
In plumbing practice, it often becomes necessary to determine the dimensions of thread elements on finished part. The outer diameter is measured using a caliper or micrometer, and the thread pitch is measured using a millimeter or inch thread gauge (a set of templates with threads of various sizes).
Taps are used to cut threads in holes, and dies are used to cut external threads.
It's called a tap cutting tool, which is a hardened screw on which several longitudinal straight or helical grooves are cut, forming cutting edges (Fig. 4.15). The tap has a working part and a shank ending in a square.
Rice. 4.15. Tap and its elements:
A - general form:
1 - cutting pen;
2 - cutting edge;
3 - square;
4 - shank;
5 - groove;
b - cross section:
1 - front surface;
2 - cutting edge;
3 - rear (back) surface;
4 - groove;
5 - cutting pen.
The tap shank is used to secure the tool in the chuck or driver during operation. Hand taps have a square end.
The working part is the threaded part of the tap that produces threads; it is divided into intake and calibrating parts.
The intake (cutting) part of the tap is the front conical part, which first enters the hole being cut and performs the main cutting work.
The calibration part protects and calibrates the hole being cut.
Longitudinal grooves are used to form the cutting edges of the tap and release chips. The threaded parts of the tap, delimited by grooves, are called cutting feathers.
According to the method of application, taps are divided into manual and machine. Hand taps are used for cutting threads by hand. They are usually produced in sets of two or three. A set of three taps includes rough, medium and finishing (or 1, 2, 3), and a set of two taps includes rough and finishing. They are used in the same order when cutting threads.
Taps are conventionally designated by marks (grooves): a rough tap has one circular mark on the shank, a medium tap has two, and a fine tap tap has three. The type of thread and its size are also indicated there.
Of great importance right choice diameters of holes for threading. Selection of drill diameters for this type and the thread size is made according to special tables. However, with sufficient accuracy for practice, the drill diameter can be determined using the formula
Dsv=dр - 2h
where Dsv - drill diameter, mm; dр - outer diameter of thread, mm; h - thread profile height, mm.
Threading with hand taps is done using cranks that fit onto the square ends of the shanks. There are collars various designs with fixed and adjustable tap holes.
The tool used for cutting external threads is called a die. The die is a hardened steel nut with chip grooves forming cutting edges (Fig. 4.16).
Rice. 4.16. Die and its elements:
a - general view;
b - geometric parameters dies.
1 - calibrating part;
2 - fence part;
3 - chip groove.
The dies are round (sometimes called dies), sliding dies (clamp dies) and special for cutting pipes.
To work with round dies, cranks (lever holders) are used, which are a frame with two handles, into the hole of which a die is placed and kept from turning by means of three locking screws, the conical ends of which fit into recesses on the side surface of the dies.
The clamps for sliding dies are an oblique frame with two handles. Half dies are inserted into the frame hole. The half-dies are installed to the required size using a special pressure screw.
To cut threads with a tap, perform the following techniques. The part is secured in a vice, the roughing tap is lubricated and, in a vertical position (without distortion), is inserted into the hole to be cut. Putting a knob on the tap and lightly pressing it against the part with your left hand, carefully turn the knob clockwise with your right hand (when cutting a Left thread - counterclockwise) until the tap cuts into the metal and its position in the hole becomes stable. Then the knob is taken with both hands and smoothly rotated (Fig. 4.17, a). After one or two full revolutions, the return movement of the tap by about a quarter of a turn breaks the chips, this greatly facilitates the cutting process. Having finished cutting, unscrew the tap from the hole (by rotating the knob in reverse side) or pass it through.
The second and third taps are lubricated and inserted into the hole without a driver. After the tap is correctly installed on the thread, put on the driver and continue threading.
When cutting deep holes, it is necessary to completely unscrew the tap 2-3 times during the cutting process and clear it of chips, since excess chips in the grooves can cause breakage of the tap or thread failure.
Before cutting external threads with dies, ground to required diameter the rod is secured in a vice. At the very end of the rod, a small chamfer is removed at an angle of 45° (Fig. 4.17.6). The rod must have a clean surface, since cutting threads through scale or rust will greatly wear out the dies.
Rice. 4.17. Working techniques when cutting threads with hand taps (a) and dies (b, c).
To obtain the correct thread, the diameter of the rod is usually made 0.2-0.4 mm less than the required thread diameter.
At the end of the rod, fixed in a vice so that its end protrudes from the jaws 15-20 mm more than the length of the section being cut, place a die fixed in the driver and, with slight pressure, begin to cut the thread, turning the driver with short movements clockwise (Fig. 4.17, c). The first 1.0-1.5 threads are usually cut without lubrication, since the die grips dry metal more easily; then the rod is lubricated natural drying oil and continue to rotate the knob or clamp one or two turns to the right and half a turn to the left to break the chips.
At the beginning of cutting threads with dies, it is necessary to apply some pressure on the die (during the working stroke), avoiding its distortion. During the cutting process, the pressure on both hands should be even.
During the cutting process, the sliding dies in the die should be pressed only at the beginning of the passage; after passing along the entire length of the thread, the dies are screwed together (or, as they say, “driven”), then the dies are tightened with a screw again and the threads are threaded a second time.
If it is necessary to obtain an accurate and clean thread, cutting is done with two dies - roughing and finishing.
Mechanized thread cutting is carried out hand drill or threading electric machine, as well as on a drilling or threading machine. This work requires special attention and caution, especially when using a drill and an electric or pneumatic machine.
Hand drills cut threads with a diameter of up to 6 mm, and productivity is tripled compared to working with a wrench. The use of electric or pneumatic machines increases labor productivity by almost 5 times.
When cutting threads with a drill or machines, the tap is clamped in the chuck and Special attention ensures that there is no misalignment of the tap relative to the axis of the hole.
For thread cutting the most various instruments, among which we highlight the tap. It is used to create a threaded surface designed to accommodate a screw, stud, bolt, or other fastener. Relatively low cost and ease of use have determined the wide distribution of the product in question. hand tools. Let's take a closer look at how to properly cut a thread with a tap at home.
Classification of taps and their scope of application
Sufficient for cutting threads long period used turning or drilling machines. They are designed to rotate workpiece or tool. In almost all cases, the working tool is a tap.
The classification of such a tool is carried out according to a number of different characteristics:
As a rule, high-quality tool steel is used in the manufacture of tools. It can withstand long-term use and does not heat up during operation. Tap High Quality has strict geometric shape, looks neat. A similar tool is often used for cutting metric threads, but there are versions for producing inch threads. The shape of the base can be cylindrical or conical.
Preparatory stage
To ensure that the work of obtaining threads does not cause many difficulties, careful preparation should be made for such a technological operation. All applied methods related with internal threading, provide that a hole of the required diameter has already been obtained in advance. Get standard size thread is possible when creating a hole according to the correspondence table. For example, for an M10 thread, a hole with a diameter of 8.5 mm is created.
There is often a situation where you should get a thread custom size. In this case, the required hole diameter is calculated using a universal formula. Calculations are carried out as follows:
- The marking of the tool used is studied. You need to pay attention to the type of thread being cut, pitch and diameter.
- You can determine the required hole diameter when using an M5X0.75 tap as follows: 5−0.75=5.25 mm.
The easiest way to carry out the work is when you need to get a standard thread, since all necessary information can be taken from various tables regulatory documentation.
To get a quality hole, you need to choose the right drill. When drilling, it is recommended to use equipment that prevents runout during operation. When choosing a drill, it is worth remembering that it must have high-quality sharpening. Experts recommend selecting the sharpening angle depending on the hardness of the material being processed. With increasing hardness The recommended sharpening angle also increases, but it should not exceed 140 degrees.
Required equipment
Tapping threads by hand only possible with the following tools:
After finding everything you need, you can begin the actual work.
Features of the technology used
Carry out the work in question you can do it yourself living conditions. To do this, you need to consider the recommendations below:
It is not recommended to apply a large load to the handle by using a lever or a gas wrench. Do not forget that the tap may burst due to high load, then remove the remaining the inside part will be quite difficult. IN While working, the master must feel how the tool moves: easily or with great effort. Form cutting edge does not allow removal of chips from the working part at the moment of rotation along the thread.
Threaded connections are simple, reliable, and make it possible to adjust the tightening, as well as disassemble and assemble parts and mechanisms. They are widely used in various mechanisms, devices, and devices.
Threads can be external (screw) or internal (nut). There are cylindrical triangular (sawtooth), conical triangular, rectangular, trapezoidal, thrust, and round threads. The most widely used is the cylindrical triangular or, as it is also called, fastening thread, figure No. 1.
Figure No. 1 – Thread elements on a bolt 1 - depth;
2 - top; 3 - step;
4 - depression;
5 - outer diameter;
6 - internal diameter.
Internal thread cutting:
First of all, you need to choose the right drill bit for drilling the hole. You should know that if you drill a hole for a thread with a diameter that exactly matches internal diameter thread, then the metal squeezed out during cutting will put pressure on the teeth of the tap, which can cause the thread to end up with torn threads, and the tap may break. When drilling a hole too large diameter The thread depth will be incomplete and the connection will be weak.
When drilling a blind hole for a thread, its depth must be made slightly larger than the part being cut, otherwise the thread will be incomplete in length.
Thread cutting is carried out in the following sequence: mark the drilling location with a center punch; secure the part in a vice; drill a hole; insert the tap into the hole (Figure 2) strictly vertically (along the square); put a crank on the tap, press it against the tap with your left hand, and turn it to the right with your right hand until the tap cuts into the metal on several threads and takes a stable position; take the knob by the handles with both hands and rotate it with the hands intercepted every 1-2 turns. Thread cutting is greatly facilitated if you use a tap to make 1-2 working turns to the right and 1-2 turns to the left; Having finished cutting, the tap is unscrewed from the hole, then once again driven along the resulting thread.
Figure No. 2 - Cutting internal threads with a tap: a - installation of the tap in the hole;
b - thread cutting.
Rules for working with taps:
When cutting threads in deep holes, in soft and tough metals (copper, aluminum, bronze, etc.), the tap must be periodically unscrewed from the hole and the grooves must be cleared of chips; You need to cut a thread with a full set of taps - rough, medium and finishing. The middle and finishing taps are inserted into the hole without a driver and only after the tap follows the thread correctly, a driver is put on the head and threading continues;
during the cutting process, you need to use a square to carefully ensure that there is no skew of the tap; The thread cutting area should be lubricated with oil.
External thread cutting:
At home, it is done with dies by hand.
The diameter of the rod for external threads should be 0.3-0.4 mm less than the outer diameter of the thread being cut. Deviations from this rule are not permitted.
Cutting external threads with a round die is done in the following order:
at the upper end of the rod, a chamfer is removed, which ensures that the die cuts into the metal;
The rod is clamped vertically in a vice so that its protruding end is 20-25 mm longer than the length of the part being cut (Figure No. 3); Place a die fixed in a knob on the rod and rotate it with slight pressure so that the die cuts into about 1-2 threads without distortion. After this, lubricate the rod with oil and smoothly rotate the knob 1-2 turns to the right and 1/2 turn to the left.
Thread cutting with sliding prismatic dies (Figure No. 3) is performed as follows: a chamfer is filed at the end of the rod; install dies into the die; clamp the rod in a vice; put the clamp on the rod and move the nuts tightly with a clamping screw; lubricate the dies and the rod with oil; The die is turned 1 - 1.5 turns clockwise, then 1-4, 1-2 turns back, and so on until the end of the thread; Having cut the thread, screw the die to the end of the rod, tighten the dies with a screw and pass the thread a second time; check the thread with a nut of the appropriate diameter; at the end of the work, the dies are removed from the die, cleaned of chips, wiped and lubricated with oil; wipe the clutch.
To slice internal thread On some part, you need to pre-drill a hole. Its size is not equal to the thread diameter, but should be slightly smaller. You can find the diameter of the drill for the thread in a special table, but to do this you also need to know the type of thread.
Main settings
- diameter (D);
- pitch (P) - the distance from one turn to another.
They are determined by GOST 1973257-73. A large step is considered normal, but it corresponds to several smaller ones. A small pitch is used when applying to thin-walled products (pipes with a thin wall). They also make a small turn if the applied thread is a way to adjust any parameters. Also, a small step between turns is made to increase the tightness of the connection and to overcome the phenomenon of self-unscrewing of the part. In other cases, a standard (large) step is cut.
There are many types of threads, since each has its own formation characteristics; the diameter of the hole for the thread is different in each case. All of them are prescribed in GOSTs, but most often they use triangular metric and conical metric thread. We will talk about them further.
We usually see triangular threads on bolts and other similar fasteners, conical threads on most plumbing products that involve plug connection.
Adaptations
To apply carvings with your own hands, use small devices:
All these devices are made of alloys characterized by increased strength and abrasion resistance. Grooves and grooves are applied to their surfaces, with the help of which their mirror image is obtained on the workpiece.
Any tap or die is marked - they have an inscription indicating the type of thread that this device cuts - diameter and pitch. They are inserted into holders - collars and die holders - and secured there with screws. Having clamped the thread cutting device in the holder, it is put on/inserted into the place where you want to make a detachable connection. By turning the device, turns are formed. How correctly the device is positioned at the beginning of work determines whether the turns will “lay down” evenly. Therefore, make the first revolutions, trying to keep the structure level, avoiding shifts and distortions. After a few turns, the process will become easier.
You can cut small or medium diameter threads by hand. Complex types (two- and three-way) or working with large diameters by hand are impossible - too much effort is required. For these purposes, special mechanized equipment is used - lathes with taps and dies attached to them.
How to cut correctly
Threads can be applied to almost any metals and their alloys - steel, copper, aluminum, cast iron, bronze, brass, etc. It is not recommended to do it on hot iron - it is too hard, it will crumble during operation and it will not be possible to achieve high-quality turns, which means the connection will be unreliable.
Tool for the job
Preparation
You need to work on clean metal - remove rust, sand and other contaminants. Then the place where the thread will be applied must be lubricated (except for cast iron and bronze - they must be worked “dry”). There is a special emulsion for lubrication, but if it is not there, you can use soaked soap. You can also use other lubricants:
You can often hear advice to use machine or mineral oil or even lard. They work well, but experts say that it is better not to do this - the chips will stick to the viscous substance, which will lead to rapid wear of the tap or die.
Slicing process
When cutting external threads, the die is placed strictly perpendicular to the surface of the pipe or rod. During operation, it should not wiggle, otherwise the turns will turn out uneven and the connection will be ugly and unreliable. The first turns are especially important. How they “lay down” determines whether the connection will then be skewed.
By applying the internal thread, the part is fixed motionless. If it is a small piece, you can clamp it in a vice. If the plate is large, ensure that it does not move. available methods, for example, fixed with bars. M
The tap is inserted into the hole so that its axis is parallel to the axis of the hole. With little effort, little by little, they begin to twist in the given direction. As soon as you feel that the resistance has increased, unscrew the tap back and clear it of chips. After cleaning, the process continues.
Photo cutting process
When cutting a thread in a blind hole, its depth should be slightly greater than required - this excess should include the tip of the tap. If this is structurally impossible, the tip of the tap is cut off. At the same time, it is not suitable for further use, but there is no other way out.
In order for the turns to be of high quality, two taps or dies are used - rough and finishing. The first pass is done as a rough pass, the second as a finishing pass. There are also combined devices for applying threads. They allow you to do everything in one pass.
Another practical advice: to prevent chips from falling into work area, when cutting, make one full turn clockwise, then half a turn counterclockwise. After this, return the tool to the place where you stopped and make one revolution again. Continue this way until the required length.
Tables for selecting the diameter of a drill for threading
When making an internal thread, a hole is pre-drilled for it. It is not equal to the diameter of the thread, since when cutting, part of the material is not removed in the form of chips, but is squeezed out, increasing the size of the protrusions. Therefore, before application, it is necessary to select the diameter of the drill bit for the thread. This can be done using tables. They are available for every type of thread, but here are the most popular ones - metric, inch, pipe.
| Metric thread | Inch thread | Pipe thread | |||||
|---|---|---|---|---|---|---|---|
| Thread diameter, inches | Thread pitch, mm | Drill diameter, mm | Thread diameter, inches | Thread pitch, mm | Drill diameter, mm | Thread diameter, inches | Threaded hole diameter, mm |
| M1 | 0.25 | 0,75 | 3/16 | 1.058 | 3.6 | 1/8 | 8,8 |
| M1.4 | 0,3 | 1,1 | 1/4 | 1.270 | 5.0 | 1/4 | 11,7 |
| M1.7 | 0,35 | 1,3 | 5/16 | 1.411 | 6.4 | 3/8 | 15,2 |
| M2 | 0,4 | 1,6 | 3/8 | 1.588 | 7.8 | 1/2 | 18,6 |
| M2.6 | 0,4 | 2,2 | 7/16 | 1.814 | 9.2 | 3/4 | 24,3 |
| M3 | 0,5 | 2,5 | 1/2 | 2,117 | 10,4 | 1 | 30,5 |
| M3.5 | 0,6 | 2,8 | 9/16 | 2,117 | 11,8 | - | - |
| M4 | 0,7 | 3,3 | 5/8 | 2,309 | 13,3 | 11/4 | 39,2 |
| M5 | 0,8 | 4,2 | 3/4 | 2,540 | 16,3 | 13/8 | 41,6 |
| M6 | 1,0 | 5,0 | 7/8 | 2,822 | 19,1 | 11/2 | 45,1 |
| M8 | 1,25 | 6,75 | 1 | 3,175 | 21,3 | - | - |
| M10 | 1,5 | 8,5 | 11/8 | 3,629 | 24,6 | - | - |
| M12 | 1,75 | 10,25 | 11/4 | 3,629 | 27,6 | - | - |
| M14 | 2,0 | 11,5 | 13/8 | 4,233 | 30,1 | - | - |
| M16 | 2,0 | 13,5 | - | - | - | - | - |
| M18 | 2,5 | 15,25 | 11/2 | 4,33 | 33,2 | - | - |
| M20 | 2,5 | 17,25 | 15/8 | 6,080 | 35,2 | - | - |
| M22 | 2,6 | 19 | 13/4 | 5,080 | 34,0 | - | - |
| M24 | 3,0 | 20,5 | 17/8 | 5,644 | 41,1 | - | - |
Once again, please note that the diameter of the drill bit for the thread is given for large (standard thread).
Table of rod diameters for external threads
When working in external thread the situation is very similar - part of the metal is squeezed out, not cut off. Therefore, the diameter of the rod or pipe on which the thread is applied should be slightly smaller. How accurate - see the table below.
| Thread diameter, mm | 5,0 | 6 | 8 | 10 | 12 | 16 | 20 | 24 |
|---|---|---|---|---|---|---|---|---|
| Rod diameter, mm | 4,92 | 5,92 | 7,9 | 9,9 | 11,88 | 15,88 | 19,86 | 23,86 |
Any technical product consists of individual parts fastened together using fasteners. Although threaded connections were known back in Ancient Rome, China, as well as the Mayan civilization, the tap began to be used as a thread-forming tool only at the end of the Middle Ages (XV-XVI centuries). Before this, the inner spiral of the nut was made by other methods, including using a lathe.
Device Features
At first, a three- or four-sided rod was used, on which the teeth were cut. The end was sharpened into a shallow cone. When screwing such an artifact into the hole of a nut or body, toothed bridges cut an internal thread. It is clear that such a tool was far from perfect, since the cutting teeth did not have a back angle, and the front angle was negative. However, its design was gradually improved until it became more rational. Today, any tap for threading has similar structural elements:
- Grooves for the release of chips and the supply of cooling and lubricating fluid (coolant). Their number is usually from 2 to 6.
- The profile of the depressions can be different: single-radius, straight front and rear surfaces, straight front and radius rear.
- Groove direction: straight, spiral right and left. The former are used in conventional universal taps. Flutes with a left-handed helical line are used to cut threads for passage. In this case, the chips go in front of the tap so as not to spoil the cutting. Right-hand recesses are used for blind holes so that the chips are brought back, otherwise they, being compressed, will break the tool.
- The intake part is made conical in order to facilitate cutting of the cutting teeth into the material of the part. The tilt angle is from 3 to 20 degrees, depending on the purpose of the tap (roughing, intermediate, finishing).
- The calibrating part is cylindrical, has a reverse lowering of up to 0.1 mm, which serves to reduce the friction force. For the same purpose, the calibrating teeth are backed at a distance of 1/3 of the width of the feather from the top of the tooth. The reduction is about one tenth of a millimeter for threads with a diameter of 12 to 30 mm.
Types of taps
By purpose
- Bench (hand) taps used for making threads using a crank. In order to reduce the effort, they are made in a set, which includes 2-3 tools, each of which removes only part of the processing allowance. The first tap is rough, the last is finishing. To distinguish them from each other, markings in the form of dashes (one, two, three dashes) are applied to the shank. Bench taps are mainly used for cutting threads in body parts.
- Machine (machine-manual). They are used for mechanized thread cutting on machines: drilling, turning, aggregate, such as a machining center. Structurally they do not differ from metalwork ones, except that they have a shortened fence part and higher durability. The main purpose is cutting threads in parts.
- Nuts. As the name suggests, they are used for cutting nuts. They always consist of one tap with an elongated intake cone. During operation, the tap is not unscrewed from the nut, but the finished nuts are threaded onto an elongated shank, which has 2 designs: straight and radius (curved). The first is used on drilling and turning machines. After filling the storage part of the shank, the tool is removed from keyless chuck and shake off the finished nuts. The curved tap is used on automatic threading machines. In this case, the nuts, under the pressure of each other, move to the end of the tool, where they fall into the container.
Design versions
- Taps with short flutes (fluteless). Used for cutting threads in aluminum alloys, tough low-carbon or high-strength alloy steels.
- With screw grooves. Used on machining centers for cutting blind threads.
- With staggered teeth. The latter on the calibrating part are cut off one at a time, thereby reducing the friction force, which is important for viscous materials.
- Stepped. Cutting part The tool is divided into two sections, each of which operates according to its own shaping scheme. For example, the 1st section cuts according to a generator circuit, the 2nd - according to a profile circuit. Or, the 1st one works as a cutting tool, the 2nd one as a smoothing tool.
- Combined. The 1st stage is a drill, the 2nd is a tap. As they say - two in one.
- Broach tap. With its help, threads of any diameter and pitch are cut in parts with through hole on lathe. The part is put on the tool shank, after which it is clamped into the machine chuck, and the shank is secured in the tool holder. Install automatic feeding, equal to the cutting step and turn on the corresponding spindle rotation. Once the broach leaves the workpiece, the thread is ready.
- With internal coolant supply. Used on specialized or multi-operational machines to increase productivity.
- Bell type. Used when cutting through threads of large diameter (50–400 mm). The tool is made as a composite tool, consisting of individual cutting sectors. Coolant is supplied inside, the number of feathers reaches 16, and spacious grooves accommodate a large volume of chips.
According to the type of thread being cut
- Metric, designated by the letter M. Dimensions, including thread pitch, are measured in millimeters. Below is a table of parameters for taps with a main (large) pitch. For each standard size, GOST 8724–2002 establishes several additional (small) steps. Three millimeters is the maximum that can be cut using a wrench.
Designation Dimensions, mm Main step Tap drilling
- Inch conical. Diameter is expressed in English units of length - inches (25.4 mm), and instead of the step, the inverse value is written - the number of turns per 1”, or in the technical lexicon - the number of threads. The more threads, the smaller the thread pitch. Middle surface The thread has a slope of 1° 47' 24", so the tap at the end of cutting reaches the stop, which should be borne in mind so as not to break it.
- Pipe cylindrical. A variety of inch threads, limited to a range of standard metal pipes. Pitch is also expressed in threads per inch.
- Pipe conical. The same as cylindrical ones, but with a slope. The diameter of the drilling for the thread is several tens smaller. The thread is cut all the way.
The summary table contains the parameters of taps with inch thread pitch
Conical
Designation Thread pitch (threads per inch) Hole diameter, mm
K 1/16” 27 6.0
K 1/4” 18 10.7
K 3/8” 18 14.3
K 1/2” 14 17.5
K 3/4” 14 23.0
K 1” 11.5 28.7
Pipe cylindrical
G 1/4” 19 11.5
G 3/8” 19 15.0
G 1/2” 14 18.7
G 5/8” 14 20.6
G 3/4” 13 24.2
G 7/8” 12 27.9
Pipe conical
Rc 1/8” 28 8.2
Rc 1/4” 19 11.0
Rc 3/8” 16 14.5
Rc 1/2” 14 18.1
Rc 3/4” 12 23.6
Instrumental material
Hand taps heat up slightly during operation, so they are made from high-carbon tool steels U10A, U12A. For machine taps operating at high speeds, use high speed steels R6M5, R6M5K5, R6M5K8. The best quick cutter is P18. Finally, high-performance machines are equipped with carbide tools. Small taps are made entirely of carbide, medium ones are brazed, and large ones usually have a prefabricated design.