Without metalworking capabilities, today's life is unthinkable. It is impossible to imagine modern technology without fastening elements.
For example, automobile wheels are fixed on passenger transport thanks to bolts and nuts - their reliable threaded connection.
In industry, more than one type of mounting thread on metal is used. But more than others, a cylindrical type of thread is popular. Unfortunately, it is not always possible to purchase the necessary parts in the finished form. For self-cutting or updating jammed, damaged parts of the thread using tools for cutting internal and external threads.
In connection with the growth of production volumes, increasing requirements for the quality of threaded joints, methods for processing parts are constantly being improved, and metal cutting technological processes are being updated. Modernizing not only the tool for cutting internal threads, but also other implements of production.
Popular threaded connections must comply with GOST requirements, securely fasten parts and elements.
How to thread
A pair of circuits that are mainly used in threading by cutting correspond to two processing processes: milling and turning.
Basically, to create a thread, methods of cutting, rolling, rolling, milling and grinding are used. In this case, use the tools:
- threaded combs and cutters - for cutting external and internal (from 12 mm in diameter) threads on lathes;
- Sliding and conventional dies - for internal and external threads;
- thread-cutting heads and taps - a tool for cutting internal threads;
- knurled dies - for machine knurling;
- milling cutters - for threaded milling;
- abrasive wheels - for grinding precise threads.
Threading with cutters is a low-performance method. It is used only for precision machining (spindles, calibers) and small batches of parts. The main advantage of the cutter method is the simplicity of the tool and the accuracy of the resulting thread.
Hole threading
The threads are different: single and multiple, have a rectangular, triangular, radius, trapezoidal and other profile configurations, are divided into left and right, internal and external.
Applying threads to the internal surfaces of parts is not an easy task. But for "hidden" manipulations, there are opportunities. Cylindrical holes in such cases are treated with comb cutters, cutters (in isolated cases), sliding dies and taps.
If when choosing a tool on the face of your interlocutor there will be a dumb question about which one is better to choose, name the tool for cutting internal threads - a tap. It is it that is most often used for both manual and mechanized thread-cutting of round holes.
What is a tap
Tap - a cylindrical tool designed for threading inside fasteners, including nuts and pipes.
Various designs of taps make them a universal tool for cutting internal threads. Photos posted on the pages of Internet resources allow us to judge this. The variety of taps design decisions is due to the material of the workpieces being processed, as well as the nature and conditions of the process itself. With all the model diversity, the basic principle of operation and structure of taps remains the same. The tool is threading as a result of screwing.
Tap design
A tap is a kind of hardened screw having protruding ribs with several slotted screw or straight grooves - cutting edges. When screwed into hollow billets of the appropriate diameter, such corrugated ribs cut the chips, removing it from the machined zone of the hole and leaving similar helical grooves on the walls of the part - thread.
A simple thread-cutting device, a tap, in fact, is an iron rod made of high-quality solid steel, with a cutting part on one edge and a square element on the other (for hand models) for attaching a knob used for reciprocating tap movements in the process of work.
The working area of the tool for cutting internal screw threads is conventionally divided into parts:
- the cutting part (intake), providing the main cutting allowance for processing;
- a calibrating section that finally processes the thread;
- feathers (ribs with screw thread);
- grooves for chip output (small taps have 3 grooves; large, with a diameter of more than 20 mm, 4 grooves);
- core, giving the tap rigidity and strength.
Tap classification
Thread cutting tools are classified by size. The quality of the thread depends on the correct diameter of the tap. It should exceed the size of the hole being machined by 0.2-0.3 mm.
Taps are special, prefabricated, die, uterine, nut and hand. This is how the tool for cutting internal threads differs. Types, areas and ways of using taps are diverse. According to the method of application, they are manual and machine. Taps for machine tools are divided into solid straight, nut and fixtures with insertable blades. For consumer use, this threading tool is offered in three varieties:
Hand taps
There are taps that are used as a bench tool for cutting internal threads. They are called manual taps. They are offered, as a rule, in sets of sets of a couple or three pieces. And although all taps have the same diameter, they are different. The first rough tap carries out coarse threading, the second (middle) cuts the smaller layer. Filigree profile processing is provided by a third finishing tap. Achieved smoothness provides ease of connection with bolts and studs.
To distinguish equipped taps on their tail, where the size of the thread is indicated, risks are applied. The finishing tap has three circular risks, the average has two such risks, and the draft one has one. In the layout "draft - middle - finish" layer of material removed by taps is 50, 30 and 20% of the allowance, respectively.
Machine taps
If the thread is cylindrical or conical, has a pitch of up to 3 mm, and it must be positioned in a blind or through hole, it is recommended to use a machine tool or a mechanical device. Although manual slicing is also possible. Machine taps have very large shanks and sizes of intake parts.
If the thread-cutting process is carried out in a high-strength steel part, then a set of a two-set set of taps will be required. For billets of structural steel, the use of a single tap is permissible. This also applies to cast iron parts.
A tool of this kind differs in the profile of the grooves provided for quick chip removal and in the shape of the shank, which is convenient for fixing in a spindle or chuck.
Nut taps
The shortest tools for cutting internal threads are used in the manufacture of nuts.
The small tap length is due to the small hole lengths of most nuts. Such taps are used when threading on automatic nut-cutting equipment. Lathes may also be involved.
A manual or nut tap is in the locked state in the process of being mounted on the shank.
On machines, nut and machine taps are fixed in special cartridges. Cartridges provide safety and self-shut off during overload. The chopped nuts hang comfortably on the long shank of the tap.
Pneumatic thread-cutting machines, manipulators and installations
Modern equipment allows to increase the volume of manufactured fasteners without sacrificing quality. It all depends on what tool is used for cutting internal threads and how the production is equipped.
The main advantages of progressive thread-cutting pneumatic machines, manipulators and installations:
- Improving work efficiency compared to manual threading.
- Lack of marriage.
- High efficiency when processing a large number of holes.
- Increase tool life by about 2.5 times.
- Reduced labor intensity by at least 3.5 times.
In conclusion, I would like to recall some rules for using a tool for cutting internal threads:
- Be sure to use grease to prevent overheating of parts and the appearance of burrs.
- After a certain translational stroke of the tap (several turns), it is necessary to give it a reverse movement in order to remove the chips from the working area and improve the surface quality of the threaded protrusions.
- It is necessary to use taps in strict alternation, according to the marking applied to them.
- After work, the tool should be wiped and kept clean.
No matter what modern equipment is used for threading, no matter what advanced technology the process is carried out and no matter what modern tool is used, these rules always remain unshakable. Successful projects!