How to cut metric threads on a lathe

Cutting threads on a lathe with a cutter

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

Thread cutting machine TV 16

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

Features of the lathe

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

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

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

Thread cutting on a modern lathe

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

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

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

About the design of cutters

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

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

thread cutting with M30 cutter

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

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

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

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

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

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

work rules

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

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

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

Internal thread cutting

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

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

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

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

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

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

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

Thread control

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

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

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

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

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

Mechanically fastened cutter inserts

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

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

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

Safety rules at work

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

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

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

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

How to cut tapered threads on a lathe

Cutting a thread with a cutter on a lathe is not the most technologically complex process, but it requires increased attention, certain skills and theoretical knowledge. It is the latter that we will tell you about, which will allow you to get as close as possible to the desired quality of processing workpieces by cutting threads with cutters.

articles

• 1 Incisors
• 2 Slicing technique
  • 2.1 Rules for obtaining threads

Scheme of cutting threads on a lathe with a cutter

To obtain carvings, craftsmen use different cutters:

• Pipe cutting tools;
• Threading heads;
• Taps;
• Dies.

Due to the design of the lathe, cutting threads on a lathe allows you to obtain internal and external variations in its execution.

In this case, a device that allows you to process wood by cutting threads is divided into three large categories:

1. Prismatic group. This cutter can be used to process the outer sides of workpieces. At the same time, the device of the prismatic group allows you to work with large-sized workpieces. The tool is held in the machine holder by a special device called a dovetail. Thread-cutting elements of the prismatic group are subject to multiple regrinding, which makes them stand out compared to rod tools.
2. Core group. The simplest device for cutting. The rod can have any cross-sectional shape; it has a working head. Depending on the shape of the head, the profile is determined. A rod jig is a shaped category of woodworking tools. The most popular of them has soldered carbide edges to cut off excess wood. They have a long service life and require sharpening less often than others.
3. Round group. The heads of such devices allow you to cut internal and external threads. With such a cutter you can perform a wide range of operations, which is why they compare favorably with the prismatic group. An important feature is the ability to resharpen the tool multiple times without losing its original characteristics.

Slicing technique

Drawing of a thread cutting diagram on a lathe with a cutter

• The operator, controlling the cutter, moves it evenly along the workpiece;
• The working head itself makes a helical line with its top;
• Depending on the inclination of the line to the axis, which is perpendicular to the movement of the working tool, the angle of increase in the helical lines is determined;
• This angle depends on the characteristics of the tool feed and the rotation speed of the workpiece on the lathe;
• When the cutting device is deepened into the workpiece, it is covered inside with helical grooves;
• Using threads, you can provide high-quality fasteners, seal parts, or move elements in the required directions with a given pitch;
• Based on the configuration of the blank, the fastening receives the corresponding name - conical or cylindrical;
• The profile, which simultaneously projects across the diameter of the projection on the surface of the thread, is selected based on the purpose;
• The most commonly used profiles are acute-angled, trapezoidal and rectangular;
• Profiles are cut using a single-pass or multi-pass method;
• Multi-start ones are created from several grooves, which are located at the same distance relative to each other;
• Single-start ones are created by one groove;
• Thread characteristics are determined by pitch and stroke. This is the distance available between identical components of a threaded thread;
• To determine the distance, you need to step by the number of passes.

Rules for obtaining threads

Threading operations require that the master uses conical pipe cutting, cylindrical pipe cutting, inch, and thrust types of thread.

In order for the execution of a pipe cutting structure to proceed correctly and without errors, it is necessary to rely on certain rules when working with a die, head, tap, etc.

1. First, the machine itself is configured. Threading and pipe cutting operations cannot be performed efficiently in the absence of equipment that has the appropriate characteristics and capabilities. Setting up involves adapting the device to a specific type of thread, thread-cutting and pipe-cutting heads, taps, and dies used. The setup is carried out according to the instructions for the machine and working tools. It would be a good idea to reinforce your pipe cutting skills with video lessons.
2. Next, based on important rules and recommendations, work is done to create a thread with the required parameters.
3. The cleanliness of the resulting thread depends on the correct placement of the working tool and its movement relative to the workpiece. To achieve the desired result, it uses a template installed parallel to the center of the turning device on the workpiece. The projection of the cutter and the template are superimposed on one another and the clearance is checked. The cutting tool must be positioned strictly on the center line of the lathe.
4. To cut internal threads, use a curved working tool. If you take a mandrel, you can also use a straight tool. External cutting is carried out mainly with bent, but sometimes even, cutters. Cutters are selected based on the type of material being processed and the thread performance requirements.
5. The location of the working edges of the cutters depends on the profile to be made. Triangular ones provide for the production of cutting at an apex of 55 or 60 degrees for inch and metric threads, respectively.
6. The selection of the rake angle of the cutter is made based on the workpiece material. It can range from 0 to 25 degrees. In this case, a smaller angle is chosen for harder and more brittle materials.
7. The lateral angles of the tool at the rear must have such parameters that when cutting, the lateral elements do not touch the surface of the thread. In most cases, the left and right sides are the same. So, if the thread angle is more than 5 degrees, the side angles will be 6-8 degrees, or 3-5 degrees if the thread angle is less than 4 degrees.
8. Internal grooving is done after boring or drilling a hole. During processing, the metal is subject to deformation, which is why the diameter of the hole should be chosen slightly larger than the internal diameter. For a brittle metal, add 0.02 to the value, and for a tough metal, up to 0.4.
9. Sometimes the pipe threading machine requires you to complete the cutting with grooves. The internal diameters are made 0.3 millimeters smaller compared to the same thread parameter.
10. When using a pipe cutting unit in order to obtain high-quality cutting at the end, make a ledge of 3 mm (no more), without changing the diameter. This protrusion will mark the finishing pass of the cutting tool. When the job is complete, the ledge can be removed.
11. Roughing using a cutting head is carried out at a speed of no higher than 30 m/min. Finishing allows the head to rotate at speeds of up to 55 m/min.
12. Working with cast iron involves passing the cutting threading head at a speed of up to 25 m/min. For carbide materials this figure is up to 150 m/min.
13. If the thread pitch is less than 2 mm, the work is performed at higher speeds, but decreases with a pitch of 6 mm.
14. The thread is cut on a lathe using several approaches. Upon completion of each approach, the cutting tool returns to its starting position.

  Chuck for tapping threads on a drilling machine

Thread is a necessary element of many designs and parts. Therefore, cutting threads using lathes should be approached as competently as possible. This will help you avoid common mistakes.

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

How to cut a thread with a die?

If it is necessary to manually cut external threads for a pipe connection, make a stud or bolt for a nut with a metric thread, a simple but quite effective tool is most often used - a die. The thread preparation process is quite simple if you follow the instructions below exactly.

Preparing to cut threads with a die

Before cutting a thread with a die on a rod or pipe, you need to select a tool of the required diameter and pitch. The die itself is a nut with conical cutting teeth with holes for fastening in the collar.

The dies can be solid, split, sliding, round, square or hexagonal.   

First of all, you need to select the material and tool of the required diameter.

Below is a table of correspondence between the most popular diameters for metric, imperial and pipe threads with an example of selecting a workpiece for an M6 thread

As we can see from the table, to cut an M6 thread we need a rod with a diameter of 5.8 mm. For larger thread diameters, there is an acceptable minimum and maximum value for the rod thickness. You cannot violate it - if the diameter is exceeded, you risk breaking the die; if the value is less than the minimum, you will get a weak thread.  

Before you start cutting external threads with a die, in addition to the tool itself and the workpiece, you need a driver suitable in shape and size, as well as machine oil. After this, you can proceed directly to the cutting itself.

Thread cutting order

Before cutting, it is necessary to chamfer the outer part of the pipe or workpiece at an angle of 45°. This is necessary to facilitate the first turns and fix the die.

Further actions:

• Secure the pipe or workpiece in a strictly vertical position. The best option to avoid distortions is a bench vise, but you can also use a gas wrench.  
• Lubricate the tool with oil.
• Place the die on the head of the rod in a strictly horizontal position and start with the first few circles.
• If there is obvious misalignment in the first laps, remove the die, tap the workpiece and start again.
• When rotating on the first turns, simultaneously press evenly on the handles of the driver to begin the cutting process.
• After the first few turns, check that the thread is cut correctly. This can be done by checking the horizontality of the dies and the knob, which can be checked with a level. Next, with the correct position of the tool, you can continue cutting the pipe thread with a die to the entire required length.
• When approximately the middle of the length is reached, the pressing force can be weakened, then the self-tightening process begins.
• After one or two turns, it is necessary to turn the die half a turn back to remove chips. 
• After cutting to the desired length, simply return the tool back along the finished thread. 

It is necessary to take into account that the die can have several numbers, most often 2. In this case, after cutting the rough thread, it is necessary to go through each of the numbers in turn to finally form the thread profile.

Source: https://mekkain.ru/stati/kak-narezat-rezbu-plashkoj.html