Without the possibilities of metalworking, today's life is unthinkable. Modern technology cannot be imagined without fasteners.
For example, car wheels are fixed on passenger vehicles thanks to bolts and nuts - their reliable threaded connection.
In the industry, more than one type of fastening thread on metal is used. But more than others, the cylindrical type of thread is popular. Unfortunately, it is not always possible to purchase the necessary parts in finished form. For self-cutting or updating worn, damaged threads, use tools for cutting internal and external threads.
Due to the growth of production volumes, increasing quality requirements for threaded connections, we are constantly improvingmethods of processing parts, updated technical processes of metal cutting. Not only the tool for cutting internal threads, but also other production tools are being modernized.
Popular threaded connections must comply with the requirements of GOST, securely fasten parts and elements.
How to cut threads
A couple of schemes that have received the main distribution in the creation of threads by cutting correspond to two machining processes: milling and turning.
The main methods used to create threads are cutting, rolling, milling and grinding. In this case, tools are used:
- threaded dies and cutters - for cutting external and internal (from 12 mm in diameter) threads on lathes;
- sliding and regular dies - for internal and external threads;
- tapping heads and taps - internal threading tool;
- knurling dies - for machine knurling;
- cutters - for thread milling;
- abrasive wheels - for grinding fine threads.
Threading with cutters is a low-productivity method. It is used only for precision machining (lead screws, calibers) and small batches of parts. The main advantage of the incisive method is the simplicity of the tool and the accuracy of the resulting thread.
Threading holes
Threads are different: single and multi-thread, have a rectangular, triangular, radius, trapezoidal and othersprofile configurations, divided into left and right, inside and outside.
Threading the internal surfaces of parts is not an easy task. But there are also opportunities for "hidden" manipulations. Cylindrical holes in such cases are processed with comb cutters, cutters (in isolated cases), sliding dies and taps.
If, when choosing a tool, a dumb question arises on the face of your interlocutor about which one is better to choose, call the tool for cutting internal threads - a tap. It is he who is most often used for both manual and mechanized threading of round holes.
What is a tap
The tap is a cylindrical tool designed for cutting threads inside fasteners, including nuts and pipes.
Different tap designs make it a versatile tool for tapping internal threads. Photos posted on the pages of Internet resources allow us to judge this. The variety of design solutions for taps 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 the structure of the taps remains the same. The tool cuts the thread as a result of screwing in.
Tap design
A tap is a kind of hardened screw that has protruding ribs with several cut helical or straight grooves - cutting edges. When screwing into hollowworkpieces of the appropriate diameter, such corrugated ribs cut chips, removing them 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 hard steel, with a cutting part on one edge, on the other - a shank with a square element (for manual models) for fastening a wrench that serves to return - translational movements of the tap during operation.
The working area of the tool for cutting internal screw threads is conditionally divided into parts:
- cutting part (fence), providing the main cutting of the processing allowance;
- gauging section that finishes the thread;
- feathers (ribs with screw thread);
- chip grooves (small taps have 3 grooves; large taps with a diameter greater than 20 mm have 4 grooves);
- core, giving the tap rigidity and strength.
Classification of taps
Threading 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, ram, master, nut and manual. This is how the tool for cutting internal threads differs. Types, areas and methods of application of taps are diverse. According to the method of application, they are manual and machine. Taps for machine tool applicationssubdivided into solid straight, nut and fixtures with plug-in blades. For consumer use, this threading tool is available in three varieties:
- manual;
- wrench;
- machine.
Hand Taps
There are taps that are used as a bench tool for cutting internal threads. They are called hand taps. They are offered, as a rule, in sets-sets of a couple of pieces. And although all taps have the same diameter, they differ. The first rough tap performs rough threading, the second (middle) cuts off a smaller layer. The filigree processing of the profile is provided by the third, finishing tap. The achieved smoothness ensures ease of connection with bolts and studs.
To distinguish complete taps on their tail, where the thread size is indicated, put risks. The finishing tap has three circular risks, the middle one has two such risks, and the draft one has one. In the "roughing - middle - finishing" layout, the 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 is necessary to place it in a blind or through hole, then it is recommended to use a machine or a mechanical device. Although manual cutting is also possible. Machine taps have very large shanks and pick sizes.
If the threading process is carried out in high strength steel parts, a set of two sets of taps will be required. For blanks made of structural steel, the use of one tap is acceptable. This also applies to cast iron parts.
This type of tool features a flute profile for quick chip removal and a shank shape that is easy to clamp in a spindle or chuck.
Spanner taps
The shortest internal threading tools are used in the manufacture of nuts.
The short length of the tap is due to the short hole lengths of most nuts. Such taps are used when cutting threads on automatic nut-cutting equipment. Lathes may also be involved.
Hand tap or wrench tap in the process of work are in a fixed state in the collar, mounted on the shank.
On machines, nut and machine taps are fixed in special cartridges. Cartridges provide safety and self-shut off when overloaded. The cut nuts hang comfortably on the tap's long shank.
Pneumatic threading machines, manipulators and installations
Modern equipment allows you 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 pneumatic threading machines,manipulators and settings:
- Improve work efficiency compared to manual threading.
- No marriage.
- High efficiency when machining a large number of holes.
- Increase tool life by about 2.5 times.
- Reduce 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 lubricant to avoid overheating of parts and burrs.
- After some forward 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 markings applied to them.
- After use, the tool should be wiped and kept clean.
No matter what modern equipment is used for threading, no matter what advanced technologies the technical process is carried out on, and no matter what modern tool is used, these rules always remain unshakable. Successful projects!
