Homemade threading tool. Attachments for lathes

The question of how to cut threads with a tap arises when a pre-made hole needs to be prepared to accommodate a bolt, screw, stud, and any other type of threaded fastener. It is the tap in such situations that is the main tool that allows you to quickly and accurately cut the internal thread with the required geometric parameters.

Varieties and scopes of taps

Internal threading can be done manually or using machines of various types (drilling, turning, etc.). The working tools that perform the main work of cutting internal threads are machine-hand or machine taps.

Taps are divided into different types depending on a number of parameters. The following principles for classifying taps are generally accepted.

1. According to the method of bringing into rotation, machine-manual and machine taps are distinguished, with the help of which the internal thread is cut. Machine-hand taps equipped with a square shank are used in a set with a special device with two handles (this is the so-called wrench, tap holder). With the help of such a device, the tap is rotated and cuts the thread. Threading with a machine-type tap is carried out on various types of metal-cutting machines, in the chuck of which such a tool is fixed.
2. According to the method by which the internal thread is cut, universal (through) and complete taps are distinguished. The working part of the former is divided into several sections, each of which differs from the others in its geometric parameters. The section of the working part, which first begins to interact with the machined surface, performs roughing, the second - intermediate, and the third, located closer to the shank, - finishing. Threading with complete taps requires the use of several tools. So, if a set consists of three taps, then the first of them is intended for roughing, the second for intermediate, and the third for finishing. As a rule, a set of taps for cutting threads of a certain diameter includes three tools, but in some cases, when products made from especially hard material are processed, sets consisting of five tools can be used.
3. According to the type of hole on the inner surface of which it is necessary to cut the thread, there are taps for through and blind holes. The tool for processing through holes is characterized by an elongated conical tip (entry), which smoothly passes into the working part. Such a design is most often used for taps of a universal type. The process of cutting internal threads in blind holes is carried out by taps, the conical tip of which is cut off and performs the function of a simple milling cutter. This design of the tap allows you to cut threads with it to the entire depth of a blind hole. For threading this type, as a rule, a set of taps is used, which are driven manually using a wrench.
4. According to the design of the working part, the taps can be with straight, helical or shortened chip removal grooves. It should be borne in mind that taps with grooves of various types can be used for cutting threads in products made of relatively soft materials - carbon, low alloy steel alloys, etc. If the thread needs to be cut in parts made of very hard or viscous materials (stainless, steels, etc.), then for these purposes taps are used, the cutting elements of which are arranged in a checkerboard pattern.

Taps are usually used for cutting metric threads, but there are tools that cut pipe and inch female threads. In addition, taps also differ in the shape of their working surface, which can be cylindrical or conical.

Preparing for internal threading

In order for the process of cutting an internal thread with a tap not to cause any particular difficulties and to end with a quality result, it is necessary to properly prepare for this technological operation. All methods of threading with a tap assume that a hole with the appropriate diameter has already been made in the workpiece. If the internal thread to be cut has a standard size, then a special table with GOST data can be used to determine the diameter of the preparatory hole.

Table 1. Hole diameters for standard metric threads

In the event that the thread to be cut does not belong to the standard category, the diameter of the hole for its execution can be calculated using the universal formula. First of all, it is necessary to study the marking of the tap, which necessarily indicates the type of thread being cut, its diameter and pitch, measured in millimeters (for metric). Then, to determine the size of the cross-section of the hole to be drilled for the thread, it is enough to subtract the pitch from its diameter. For example, if a tool marked M6x0.75 is used to cut a non-standard internal thread, then the diameter of the preparatory hole is calculated as follows: 6 - 0.75 \u003d 5.25 mm.

For standard threads belonging to the inch category, there is also a table that allows you to choose the right drill with which to perform the preparatory work.

Table 2. Hole diameters for inch threads

Important for obtaining a high-quality result is the question not only of what the thread is cut with, but also of which drill to make the preparatory hole. When choosing a drill, it is necessary to pay attention to the parameters and quality of its sharpening, as well as to ensure that it rotates in the chuck of the equipment used without beating.

The sharpening angle of the cutting part is selected depending on the hardness of the material to be drilled. The higher the hardness of the material, the greater the sharpening angle of the drill should be, but this value should not exceed 140 °.

How to cut a thread correctly? First you need to pick up tools and supplies:

1. an electric drill or drilling machine capable of operating at low speeds;
2. drill, the diameter of which is calculated or selected according to reference tables;
3. a drill or countersink, with which a chamfer will be removed from the edge of the prepared hole;
4. a set of taps of the appropriate size;
5. manual holder for taps (knob);
6. bench vise (if the product in which the thread is to be cut must be fixed);
7. core;
8. a hammer;
9. machine oil or other composition, which during the processing process needs to lubricate both the tap and the thread section cut by it;
10. rag.

Technology features

When cutting an internal thread with a tap, the following algorithm is used.

• In the place on the surface of the workpiece where the hole for threading will be drilled, it is necessary to form a recess for a more accurate entry of the drill using a core and a conventional hammer. The drill is fixed in the chuck of an electric drill or drilling machine, on which low rotational speeds of the tool are set. Before starting drilling, the cutting part of the drill must be treated with a lubricant: the lubricated tool enters the structure of the material being processed more easily and creates less friction in the processing area. You can lubricate the drill with a piece of ordinary lard or grease, and when processing viscous materials, machine oil is used for this purpose.
• If it is necessary to cut threads in small parts, they should be pre-fixed using a bench vise for this. Starting drilling, the tool fixed in the equipment chuck must be positioned strictly perpendicular to the surface of the workpiece. You should regularly lubricate the tap and make sure that it does not warp and moves strictly in the specified direction.
• At the entrance to the hole made, as mentioned above, it is necessary to chamfer, the depth of which should be 0.5–1 mm (depending on the diameter of the hole). For this purpose, you can use a larger diameter drill or countersink by installing them in the chuck of drilling equipment.
• The process of cutting internal threads begins with tap # 1, which is the first to be installed in the knob. We should not forget about the lubricant, which must be applied to the tap for threading. The position of the tap relative to the hole to be machined must be set at the very beginning of work, since later, when the tool is already inside the hole, this will not work. When cutting a thread with a tap, it is necessary to adhere to the following rule: 2 turns of the tap are made in the direction of threading, 1 - against the course. When the tap is made one turn back, chips are dropped from its cutting part and the load on it is reduced. Threading with a die is performed using a similar technique.
• Having cut the thread with tap No. 1, tool No. 2 is installed in the knob, and after it - No. 3. They are processed according to the method described above. When threading with taps and dies, you need to feel when the tool starts to rotate with force. As soon as such a moment comes, you should turn the knob in the opposite direction to throw chips from the cutting part of the tool.

When a pipeline is being repaired, it becomes necessary to tie it into an existing pipeline. If metal pipes are laid, you can use welding. To connect the shut-off valves, you must have a special tool for cutting threads on pipes. Moreover, its manufacture with such a device can be easily carried out at home with your own hands.

In most cases, a threaded connection remains the main type of joining of metal pipes. It has several parameters that are taken into account when installing reinforcement. Properly selected dimensions allow you to create a reliable and tight connection.

To work with a thread cutter, it is necessary to distinguish between the types of thread, its parameters and characteristics.

Inch and metric cutting

Several parameters are considered a characteristic difference:

In Russia, all measurements are made in the metric system. Thread cutting was no exception. . The characteristic differences are:

• Dimensions are in millimeters.
• The profile resembles an equilateral triangle.
• Small step.

The inch system is used to connect water pipes, the manufacture of fasteners is done in the metric system. If the fitting is wound in a clockwise direction, the connection is called right. Otherwise, the thread is considered to be left-handed.

Types of tools

For the manufacture of threaded connections, the industry produces special cutting devices. They are designed to perform certain technological operations. A tool for creating internal threads, similar to a screw, is called a tap. The device cuts chip grooves on the pipe body. For fastening in the collar, the tap has a long shank. The tool is produced in accordance with the current standard. There are special tables that indicate the size of the tap, its number and type.

The cutting kit includes two taps. Their main difference is the depth of groove penetration:

• Chernova - No. 1.
• Finishing - No. 2.

Die fixture

This device is sometimes called a lerka. The tool is equipped with a kind of nut with several holes. It is she who creates the cutting edges.

The industry produces lerks of various shapes:

• Klupp.
• Round.
• Split.
• Sliding.
• Whole.

Klupp description

It differs from other devices in a special guide, which centers the die relative to the pipe. The device can be electrically driven or manual. For use at home, when cutting will take place no more than two or three times, it will be more rational to work with a manual screw clamp. Its cost is much less than an electric tool.

This tool is very easy to work with. The thread is very clean and reliable. The light weight of the fixture, the simplicity of the design allows you to quickly replace the cutters.

The most important characteristic of the klupp is the material from which it is made. To create a die, expensive tool steel is used. But the carving is created only by incisors. They must be highly durable.

Klupp has no expensive non-functional elements. Therefore, a set of klupps costs much less. The cost of threading a stainless steel pipe is drastically reduced. Home craftsmen, not wanting to incur large financial losses, prefer to work with such a tool.

Self cutting

You can use several tools to work:

• Tap.
• Die.
• Klupp.

Which tool kit to choose depends on several factors. This is especially true for the type of thread. After all, it can be internal or external. After selecting a plate, there are several steps to follow.

If everything is in order, the number of turns corresponds to the mating part, you can seal the connection and start installing the pipeline system.

When cutting pipe threads 1/2 "(1/2 inch) on water pipes manually, you first have to cut a lead-in chamfer at the end of the pipe. Then, by rotating the wrench with the die and applying a fairly significant longitudinal (axial) force to the wrench, we achieve cutting the die into the end pipes If there is not enough force or the die is skewed, it is not possible to start threading, so you have to chamfer the pipe again.

Thread cutter

The simplest device that eliminates these difficulties and allows threading without any effort at all along the pipe and even without a chamfer on the pipe is shown in the figure. The die itself is fixed in a die holder with two handles. The body of the die holder is provided with screws that fix the die in it (not shown in the figure). A steel coupling with a 3/4" internal thread is welded to the body. From a piece of pipe with a diameter of 3/4" and a length of 40 mm, a sleeve is made with three nuts welded to it around the circumference, into which stoppers are screwed (M8 bolts 25 mm long). A 3/4" external thread is cut at one end of the sleeve (at a length of 18 mm), and the internal hole of the sleeve is enlarged to a diameter of 22 mm (by hand, with a file), so that a 1/2" pipe can easily pass through the sleeve.

1/2" thread cutter for pipes:
1 - die; 2 - die holder handle; 3 - die holder body; 4 - coupling with internal thread 3/4"; 5 - bushing with external thread 3/4"; 6 - locking bolt; 7 - nut;
8 - 1/2" pipe.

To cut threads on a 1/2" pipe, a die holder with a sleeve is screwed onto the sleeve, and from the end of the sleeve to the end of the thread on the sleeve, a distance L is set equal to the length of the thread being cut on a pipe with a diameter of 1/2". Next, insert the 1/2 "pipe, on which it is supposed to cut the thread, into the sleeve so that the end of the pipe rests against the die, after which the pipe is locked in the sleeve with all three stoppers. Now, rotating the die holder with the help of handles, screw the coupling (together with the die) on the sleeve, ensuring the movement of the die with a step of t = 1.814 mm (14 threads per inch) without applying longitudinal force and regardless of whether there is a chamfer on the pipe or not. This situation develops because the 1/2 "thread on the pipe and the thread The 3/4" on the coupler and bushing are the same pitch.

Practice has shown that threading a pipe with this device is a pleasure. Of course, when threading a pipe, the latter must be securely clamped in a vise.

Technological tips, failure to comply with which will lead to the inoperability of the device

1. To ensure the alignment of the die and the coupling, it is necessary to assemble the entire fixture on a pipe with a diameter of 1/2 "with a pre-cut pipe, screw the pipe into the die and only then weld the coupling to the body of the die holder.

2. To ensure the alignment of the threads for the stoppers present in the nuts and cut into the wall of the sleeve, you must first weld three nuts, evenly distributing them around the circumference of the sleeve, then drill the wall of the sleeve, using the nut as a jig (through the nut), and then cut the thread into bushing wall.

Attachments for lathes make it possible to facilitate some work and expand the functionality of serial machines. Devices can be factory-made, which are produced by some companies, or they can be home-made. In this article, I will describe several interesting fixtures that will be very useful to any craftsman who has a lathe in his workshop, and most of the fixtures can be made by hand.

Homemade fixtures for lathes.

Milling attachment for lathe .

Let's start with the most necessary and useful device that will help turn an ordinary lathe into a milling machine and significantly expand the capabilities of any master. This homemade milling attachment is designed for the TV-4 lathe and similar schoolchildren. But such a device is easy to make for any lathe by adjusting the dimensions to the dimensions of a particular caliper.

This simple but reliable design of the milling attachment was developed back in the Soviet years and published in the magazine Modelist Constructor. And with the help of this attachment, you can perform milling of planes on a lathe, processing various parts along the contour, and sampling various grooves and grooves.

And in general, it is possible to process any surfaces of parts with end and end mills, due to the fact that the carriage and support of the machine moves along three coordinates, the carriage moves in a vertical plane, and the attachment bracket moves in a horizontal plane.

As can be seen from the drawings, the main part of the fixture is a bracket that is fixed on the lathe support, instead of the removed carriage (sled) of small longitudinal feed. And the small longitudinal feed carriage itself is removed from the machine support and fixed with two bolts on the front wall of the attachment bracket vertically and allows you to move the workpiece vertically.

The tool holder can be used to fix in it not a cutter, but some kind of flat part to be milled. Or you can remove the tool holder and use some homemade vise instead, if the workpiece is more voluminous.

Also, instead of a tool holder, it is possible to fix not a vise on a standard stud, but a chuck from a small lathe, if the milled part is cylindrical and not flat. Or instead of a chuck, use the faceplate from the lathe kit. And it is the variant with faceplate 3 (with tacks 4) that is shown in the drawing below.

The faceplate is mounted on a regular stud for the tool holder and clamped with a nut. Well, the workpiece is already clamped in the faceplate using clamps 4, as usual. In general, there may be several options for fixing the workpiece, depending on its configuration and size.

The attachment bracket is cut out by a grinder from ordinary sheet steel 8 mm thick and then its front wall 1, side walls 2 and base 3 are welded together by electric welding. When welding, of course, we always take into account that right angles are maintained.

When the bracket is welded, using drills and cutters, we make a central hole in it and holes for attaching the bracket to the machine support, using standard M8 studs and nuts. To center the bracket on the machine support, a guide washer 4 is used, which is welded to the bottom plate and is clearly visible in the top drawing.

Thanks to the semicircular grooves in the front wall 1 of the bracket, which are made 30º in each direction, it will be possible to scroll the fixed carriage and the part in the vertical plane by the same 30º in different directions, which expands the possibilities of processing the part with a milling cutter at different angles.

And thanks to the regular grooves in the caliper, the entire console can be deployed in a horizontal plane, using the standard scale in degrees on the caliper. In general, it will be possible to scroll and clamp the workpiece in both planes, and move it during processing both in the vertical and in the horizontal plane.

The milling cutter for processing the part is fixed in a regular lathe chuck, and if the cutter has a tapered shank that matches the Morse taper in the spindle of your machine, then you can remove the chuck and fix the cutter directly in the machine spindle.

And in order to make accurate tracking of the movement of the cutter, it does not hurt to make a tablet holder for drawings 7, along which the tracking pointer 8 will slide, fixed on the machine support and which is shown in the figure.

By making such a simple fixture, you will significantly expand the functionality of your lathe.

Milling attachment for processing round timber (cylindrical billets).

Well, if you need, for example, to make a square or a hexagon out of round timber, or to cut a keyway on some shaft, then for these operations you can make a simpler milling attachment, based on a lathe chuck and some piece of iron. How I made it from garage trash and how it works, those who wish can see it in the video below, or on my YouTube channel suvorov-custom. All pleasant viewing.

Device for smooth movement of the tailstock.

This simple device makes it possible to move the tailstock smoothly and at minimal cost. And you will need such a device, for example, for drilling very deep holes, because the movement of the quill on small machines is only 50 - 60 mm. And if the lathe is large enough, then the heavy tailstock can be moved effortlessly.

To begin with, we drill a couple of holes in the tailstock plate on the side and cut the M 10 or M12 thread into them with a tap. Further, using these holes to the tailstock plate, we bolt a self-made angle bracket 1 (see figure) in which the rollers 4 and 5 rotate. The drive gear 3 and the drive handle 2 are mounted on the roller 4.

And on the roller 5, the driven gear wheels 6 and the wheel 7 of a smaller diameter are mounted, which runs on the standard gear rack of the machine bed and thereby drives the tailstock of the machine. If desired, you can still make a small casing from tin or sheet plastic, which will cover the gears from dust, which it is desirable to lubricate.

Device for fixing drills on the machine support .

This lathe attachment will also be useful if you need to drill deep enough holes with long drills. In addition, it will allow you to quickly periodically remove the drill from the hole to remove chips and lubricate the drill.

After all, the speed of movement of the tailstock quill is very small, and the speed of the longitudinal movement (mechanical feed) of the caliper is much higher. And this device will increase the productivity of drilling parts, especially if there are a lot of them and if the depth of the holes is significant.

The basis of the fixture is the drill holder 1 (see figure), which is fixed in the tool holder of the machine. The holder has a tapered hole for fixing the tapered shank of a drill chuck or a drill with a tapered shank.

Of course, the axis of the tapered hole of the holder for the drill (or chuck) must coincide with the axis of the spindle of the headstock of the lathe. The same should be taken into account when fixing the drill holder in the tool holder of the machine. Since at the slightest misalignment, a decrease in the quality of drilling, breaking of the walls of the hole and even breakage of the drill is possible.

The feed when drilling holes in parts is carried out by the longitudinal movement of the caliper slide. And the advantage of this device, as mentioned above, is the higher speed of movement of the cutting tool, especially when you have to drill deep holes and you have to often remove the drill to remove chips.

In the manufacture of such a drill holder, it is not necessary to make its body cylindrical as in the figure, it is possible to make the body in the form of a bar and it is much easier to make it on a milling machine. But it is also possible to make a cylindrical body on a lathe, and then weld a plate 10–15 mm thick to it on the side, for which the fixture will be clamped in the tool holder of the lathe.

Improved die holder .

When threading with dies, which are installed in conventional die holders, the cut thread often turns out to be of poor quality due to the misalignment of the cutting tool. To avoid this, at the beginning of threading, you always have to support a conventional die holder with a tailstock quill.

However, it is much faster and more convenient to work when threading with the help of an improved die holder, which you can make yourself on the same lathe. The figure on the left shows one of the designs of such a die holder.

The mandrel 1 with its tapered shank is inserted into the tapered hole of the tailstock quill. On the mandrel, a glass 2 and a replaceable sleeve 4 are mounted freely (but with a minimum gap), in which the die is fixed with a screw. The tailstock with the tool is brought to the rotating workpiece. Further, the movement of the tool is carried out by moving the quill.

In contact with the part, glass 2 is kept from rotating by handle 3, on which, by the way, you can put a tube on and rest it against the machine frame. Cup 2 moves freely along the mandrel 1 during threading. At the end of threading, the rotation of the machine spindle is reversed and the tool moves away from the part.

For those who do not have small revolutions, it is best to cut the thread by rotating the spindle of the machine manually, by the chuck or using a special handle that is inserted from the back of the spindle.

Device for simultaneous drilling and tapping .

A fixture for a lathe that allows you to simultaneously drill a hole and cut an external thread in one installation of the tool is shown in the figure below.

Mandrel 4 of this device is also inserted into the quill of the tailstock of the lathe. In front of the mandrel there is a nest for fixing the drill. And the outer movable mandrel 2 is put on the mandrel 4 and moves along it in the axial direction. Key 3 keeps it from turning.

In the front part of the outer mandrel there is a hole for a replaceable sleeve with a die and there is a screw 1 that fixes them. After the inner mandrel is inserted into the tailstock quill, a ring 5 with a handle 6, an outer mandrel 2 are put on the mandrel and a drill and a die are inserted.

At the end of drilling, without removing the drill from the hole, we switch the spindle speed to a number that corresponds to threading. The outer mandrel is fed by hand from right to left. In this case, the thread is correct and concentric with respect to the drilled hole. At the end of threading and when changing the direction of rotation of the machine spindle, the outer mandrel moves vice versa from left to right.

Another simple, but useful home-made adapter device is described here in and it will help to fix a thicker cutter that does not fit into the regular lathe tool holder.

Well, in conclusion about homemade devices for lathes, I publish just below another video from my suvorov-custom channel, in which I show another simple, but very useful device with which you can very quickly center the workpiece and then finally clamp it exactly in the lathe chuck.

Factory fixtures for lathes.

There are a lot of factory devices, but I will describe the most common and useful ones.

Universal cone ruler .

It is used for processing conical surfaces on a lathe. The ruler is installed parallel to the generatrix of the conical surface, and the upper part of the lathe caliper is turned 90 degrees.

The reading of the angle of rotation of the cone ruler is made according to the divisions (millimeter or angular) marked on the scale. The angle of rotation of the ruler must be equal to the angle of the slope of the cone.

And if the scale of the ruler does not have degree divisions, but millimeter divisions, then the amount of rotation of the ruler is determined by one of the formulas published below:

Where h is the number of millimeter divisions on the scale of the cone ruler,

and H is the distance from the axis of rotation of the ruler to its end, at which the scale is not carried. The letter D is the largest diameter of the cone, the letter d is the smallest diameter of the cone, the letter L is the length of the cone, the letter α is the angle of the taper, and the letter R is the taper.

Stationary and movable steady rests .

Designed for processing non-rigid (thin) shafts. The steady rest, shown in the figure, consists of a cast-iron body 1, with which a hinged cover 6 is fastened with a bolt 4, which facilitates the installation of the part. The base of the body of the steady rest has a shape corresponding to the guides of the bed, on which it is fixed by means of a bar 2 and a bolt 3.

Two cams 8 move in the body with the help of adjusting bolts 9, and one cam 7 moves in the cover. Screws 5 serve to fix the cams in the required position. Such a device allows you to install shafts of various diameters in the steady rest.

But a modernized steady rest (see the figure below) is much more efficient, in which the lower rigid cams are replaced by ball bearings 8. They are adjusted according to the diameter of the surface to be machined using the control shaft located in the center, or by the part itself.

After that, the lid 2 of the lunette is lowered and, adjusting the position of the rod 5 with the nut 4, the lid is installed so that the gap between the lunette base and the lid is 3-5 mm. This position of the rod 5 is fixed with a lock nut 3.

Then, using the eccentric 1, the cover is pressed against the base of the steady rest, while under the action of the spring 6, the upper ball bearings 7 press the workpiece with force. The runout of the part is perceived not by ball bearings, but by spring 6, which serves as a shock absorber.

Movable lunettes. Unlike fixed steady rests, which are fixed on control machines, there are also movable steady rests (see the figure below), which are fixed on the caliper carriage.

Since the movable steady rest is fixed on the caliper carriage, it moves along with it along the workpiece, following the cutter. Thus, it supports the part directly at the point of application of force and protects it from deflections.

The movable rest is used for fine turning of long parts. It has two or three cams. They are extended and fixed in the same way as the cams of a fixed lunette.

The cams should be well lubricated so that the friction is not too great. To reduce friction, the cam tips are made of cast iron, bronze or brass. Better yet, instead of cams, use rollers from bearings.

And in conclusion, those who wish can watch in the video just below how I saved a machine of especially high accuracy 16B05A from scrap metal.

And a little lower, I posted a video about a homemade dividing device for my TV 4 lathe, which I made in just a couple of hours.

Well, even below it is shown and told about the restoration of my machine TV - 4.

That seems to be all. Of course, not all fixtures for lathes have been published here, but if at least the fixtures published in this article appear in your workshop, then the possibilities of your workshop will expand significantly, creative success to everyone.

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