Overview of solutions
Makarov VA, Nizhny Novgorod
Association "P C O M E T & W"
Rezboobrazuyuschie rod fasteners: screws, bolts, studs — are progressive fasteners. This volume group, and parts are widely used in large quantities in all areas of economic activity and in everyday life.
In current practice rezboobrazuyuschie or parts used in the holes of mating parts, for fastening the latter on the other parts and assemblies, and to connect the individual pieces in a package in other ways, for example by drilling or screwing element is connected in the package.
The first design rezboobrazuyuschih screws appeared in the XIX century. The first known patent for the invention of the screw rezboobrazuyuschego issued in the US in 1880. In Russia in 1928, it was granted a patent for a type of screw, which by its design resembled a screw. Improved he called self-tapping screws.
In the process of industrial development there was a need to rezboobrazuyuschih screws for different purposes, which led to further improvements.
Study of technical, information and proprietary material revealed the presence of about 600 technical decisions on design details rezboobrazuyuschih, methods for their preparation and tools, most of which are protected by patents.
Depending on the method of forming the thread connecting the individual parts in the package rezboobrazuyuschie parts can be divided into three major groups:
— rezbovydavlivayuschie part or rezbonakatyvayuschie forming threaded holes in the walls of the extruded metal in the radial direction;
— self-tapping screws and parts that connect the individual parts in the bag by screwing and insertion of thread turns in the mating parts;
— Self-tapping part or kraskosnimayuschie forming threads in the hole to form a chip.
On rezboobrazuyuschie parts there are many international standards, government, industry, other technical documentation. Russian GOST 27017-86 «Fasteners. Terms and definitions «rezboobrazuyuschih samples of threads used in the production, with different heads and lead-ends.
There are seven automotive industry standards: OST 37.001.315-88 37.001.321-88 … «Bolts, screws, studs rezbovydavlivayuschie» and TU 37.103.040-96 «Rezbovydavlivayuschie fasteners», under which they are produced verification and acceptance .
There are 12 state standards for self-tapping screws, seven standards 1980 and 1993 five standards: Screws for metal and plastic with different heads and taps of the threaded rod.
Virtually all standards lost harmonization, that is out of date.
The latter were established on the basis of following the DIN 1993
The need to ensure the reliability of threaded connections, reducing metal, and ultimately costs led to the widespread use rezboobrazuyuschih fasteners to automotive engineering. In accordance with the known concept of counting and cost savings in the manufacture and sale of fasteners «In Place Cost» («price on the spot») final criterion are cost reduction assembly work on a conveyor installation of fasteners in a particular node.
Rezbovydavlivayuschie fasteners nakatyvaya metric threads in the holes, can not only combine the assembly with mechanical treatment, eliminating threading operation, but also provide a locking screw connection. By their nature, they are also the caulking, making high-strength screw connection. It is basically a part with a curved cross-section of the threaded rod with the arcuate projections deforming, blending smoothly into the arcuate part, or parts with projections along the thread turns on its side surface at the top. The protrusions are arranged on the thread or on the lead-in portion of the rod or across its entire length.
The former include fasteners under the trademarks Taptite and Duo-Taptite, received the greatest popularity and applicability in the world market of fasteners. On the basis of the thread Taptite created a number of new designs components for different materials and operating conditions. The second group may include, for example, threaded fasteners, widely known under the trademark Swageform, and several others (1, 2, 3).
Traditional imports of fasteners in Russia in recent years — is to import self-tapping screws, and in large quantities.
Russian industry is not paying this kind of fasteners sufficient attention, and appeared on the market emptiness fills the import of fasteners.
The largest importer of self-tapping screws and screws for the past many years, is Taiwan.
The first production of fasteners in Taiwan occurred in 1949 in the province of Kaosung. In the 60s, during the Vietnam War, the US Army supply services identified Taiwan, a major supplier of fasteners and sent their technical expertise and equipment for mass production and quality assurance of Taiwanese fastener on US standards.
In 1978, Taiwan was launched the first modern plant with full metallurgical cycle. The highest flowering of Taiwan’s hardware industry reached in the early ’90s, when the Government has made significant investments in its development both within the country and outside — in neighboring countries with cheap labor (China, Malaysia, Thailand). It was built many modern factories for the production of fasteners, wire, has created its own metallurgical and machine-tool industry, we prepared the highly skilled staff.
Currently, Taiwanese experts are leading developers of fasteners, hardware and tools in the world and Taiwan Institute of Industrial fasteners (Taiwan Industrial Fastener Institute) is a key link in the development of the industry development strategy in the region. In Taiwan, more than a thousand companies — manufacturers of fasteners. The basis of their — small and medium-sized companies (10 to 50), which accounted for about 80% of the issue.
Small businesses are complemented by large, being part of the whole economy of the country, successfully working in small niche markets.
Over the past five years there has been rapid growth in the production of fasteners in China. Many firms in the USA, Taiwan, and other countries have built their factories in China, which have become a high-tech, efficient enterprises.
The volume of production of fasteners for the past five years has increased by 15-20 times. Today, the Russian industry is unable to compete with Chinese imports (more than 70% of all imports — from China and Taiwan). Niche domestic fixture firmly behind China. Go deliveries from
Poland and Germany. Spain and other countries.
Although Russia has a number of modern production self-tapping screws, such as Urals Precision Alloys Plant, «MMK-Metiz», a number of small enterprises, the old production, mainly working in the automotive industry, with outdated equipment and technology, unable to compete with the Asian market fixing. Besides the need of automobile factories in low self-tapping screws. So, OAO «GAZ» consumes about 50 tons per year, which is less than 1% of the annual total of fasteners, JSC «UAZ» consumes about 15 tons per year, which is also less than 1%. KamAZ consumes only 3.2 tonnes per year 0.05% of annual volume. And only of «VAZ» uses a significant amount. Of 1.75 billion. Pieces fasteners on the self-tapping screws have to 135 million. Per year, or 7.72% of total fastener (4, p. 26).
In 2003, 60% of the total supply of fasteners for imports accounted for self-tapping screws and screws. In 2005, imports amounted to 60 thousand. Tons — more than 50%. In 2007, imports of screws slightly decreased and amounted to about 40 thousand. Tons. In the next two years in Russia, sharply increased the demand for self-tapping screws in the building, which clearly leads to an increase in imports. Only 25% of fasteners required by the market, produced in Russia, 75% — by imports.
By its design, technological features and methods of using self-tapping thread is significantly different from each other. By design features, they differ on the profile of the screw threads, the thread pitch, the height, the number of screw thread form Zachodni areas, etc. By means of the application may operate as threaded holes in soft materials and alloys (without chip removal) or as separate parts in the connecting package.
According to the Norwegian standard NS-959-03-1982 Skruer, muttere og tolbexor («Fasteners. Terminology») metric thread there, and self-tapping wood screw n. N … 2.1. 2.4. Screws with self-tapping thread for all forms of lead-divided into several types, the most important of which A, B, AB, p. … 24.1 n. 24.6.
— Type A — carving wood screw with a larger step with a sharp tapered threaded lead-end, full height.
— Type B — thread is normal, zahodnye 2-3 round cut on the cone, the end obtuse.
— Type AB — thread type B with a sharp tapered threaded end, full height.
— Type C — metric thread, blunt end, zahodnye coils are cut on the cone.
Thread design and types of lead-ends are shown in Fig. 1. There tapping screw with grooves (stripping) n. … 26.1 n. 26.7.
A striking example of self-tapping screws are fasteners with a triangular cross-section of the rod, based on thread Taptite.
Powerlock — Self-self-tapping thread, US Patent number 3426820 NCI 151-22. Designed for use in hard but brittle materials such as gray iron, or easily deformed materials such as aluminum alloys. The latest cuts easily carving, crashing into the wall of the hole of the parts.
It has a high resistance to loosening. Screw connection in cast iron is formed by the insertion of the thread part in the pre-threaded in the hole.
Profile threaded coil at the tip configured with an angle of 30 °, the base angle is 60 °.
Plastite — self-tapping thread for use in viscous plastics, nylon and similar materials. It has a high resistance to tear-out and destruction under variable loads. It has several versions of the profile of the threaded coil. The thread profile 45 °, 48 °, 60 °, single- and double flighted, low and high.
Pushtite — resistant thread US patent number 3865006 NCI 85-44, with an increased pace.
The core part is hammered into the hole axial force. The presence of acute trailing edge at the coil prevents samooslableniyu connection. The screw is turned out freely.
Under the trademark HI-LOW, it has been widely used, especially in the construction and finishing works, for fixing plasterboard and gypsum boards, metal profiles, plastics and other soft materials.
Tapping screw thread design, developed by the American company Illinois Tool Works Inc., protected by many patents, including British patent number 1080482 IPC F 16 25/00.
The design is characterized by a double thread on the rod uneven profile with a big step.
The end of the rod may be either blunt or sharp, provided with special recesses (Fig. 5). The parts are made from soft carbon steel and stainless steel.
On screws HI-LOW developed standards, such as the company Fiat Italy № 01540-1987.
Factory «Krasnaya Etna», Nizhny Novgorod, in 2000, developed and mastered several designs of self-tapping thread and single bifilar blunt and sharp end of the rod with different heads under the building products company «Avangard-Knauf», including HI- LOW. Dimensions 3.6, 3.9, 4.1, 4.25, 10 steel, 20 kn.
Manufacturing technology of the past has been protected by a patent for an invention, Russia, №2179419 IPC B21 H 3/06, developed specifications for the manufacture of TU 1280 … 2000
Widely known self-drilling self-tapping screws, which appeared in the mid XX century and quickly spread around the world. This piercing, single and dvuhperovye self-tapping screws or metric that can drill a hole in it and form threads in the metal thickness from 1.5 to 6.35 mm. Odnoperovye screws, for example, French Patent №1337151 IPC F 16 B 25/00, dvuhperovye screws, the most famous Teks, US Patent №3125923 NCI 85-47, Wingteks (Fig. 1), Drill-Kwick, US Patent №3395603 NCI 85 -47, piercing screw with sharp point such as a nail, German Patent №1475016 IPC F 16 25/00. Known drilling screws type Wingteks combined with thread — metric at the drill and self-tapping at the head.
The license for the production of a self-tapping screw odnoperovogo thread HI-LOW, and self-drilling screws Teks dvuhperovogo USSR was purchased for the plant «Mosmetallokonstruktsiya» Vidnoe, Moscow region, from Italy.
-Tapping screws, stripping
The most time-consuming operation in the assembly of the car and other dimensional articles provided with threaded holes or nuts is the compound of parts after coating them with ink, clogging the threads. Requires an extra cleaning operation threaded holes from welding paint and sagging, which leads to additional material costs. Basically, these works are carried out metchikovaniem.
It is known, for example, that on cars VAZ one body takes about 40 types of weld nuts, and that about half of all fasteners. In the middle of the XX century in the West, this problem was solved by using the Self-tapping screws or rezbozachistnye. Standard thread — metric that allows, if necessary, replace the screws on rezbozachistnye ordinary and vice versa. Based on technological grounds tapping screw must provide low torque screwing, complete cleaning of the threads from dirt and paint, a low cost of manufacture. Application details rezbozachistnyh cancels the cleaning operation taps threaded holes, thereby reducing the complexity of the assembly work. By tapping screw design features can be divided into three groups:
— screws with longitudinal grooves along the entire length of the rod;
— screws with longitudinal grooves in the entry area of the rod nom.
— bolts with notches of various shapes and slits for lead-section of the threaded rod.
The screws with the grooves along the entire length of the rod operate primarily as-tapping and then later as a rezbozachistnye. The grooves on the rod can be from one to several, different shapes and lengths. The larger grooves, the lower the screwing torque, the more easily threaded into the hole.
Unfortunately, the weaker and less reliable threaded connection, as the grooves may occupy a fourth part of the circumference of the threaded rod.
The spiral arrangement of the grooves and the lead-in portion of cone rod provide a gradual and uniform screwing into the hole of the mating parts.
On the approach may be incomplete thread profile. Details with grooves along the entire length of the rod should be used in less demanding nodes.
Pat Russia №731107 IPC F 16 and 25/00 on the circumference of the threaded rods are made of six helical grooves perpendicular to the screw turns. French Patent №1118057 IPC F 16 B 25/00 on a threaded rod provided with two diametrically opposed grooves.
Fig. 6 shows an example of a bolt with five grooves along the entire length of the threaded rod, die company Hilgeland for rolling such a thread in a single pass of the thread and the spiral grooves.
In 1993, JSC «VAZ» was developed by drawing on the bolt MB with six helical grooves for the striker, seats, models 2105 and 2121, steel 35. The width of the groove of 0.85 mm, depth 0.7 mm, the angle of the spiral grooves 15 ° . These screws are produced by the «Elektroshchit» in Samara.
Table. 3 shows the recommended dimensions of grooves for screws with the grooves along the entire length of the rod
The depth of the groove is determined by the formula d — d1 / 2 where d — outer diameter; d1 — the diameter of the cone at the end.
The width of the groove at the screw 6 is taken equal to 0.5 mm depth, at propeller than 6 mm groove width is equal to its depth. Helix angle is selected within 13-15 °. The length of the tapered approach is S-diameter rod, and its angle in the range 10-15 °. Material screw — steel cemented or thermally enhanced.
Mechanical control methods are tested on screwing, twisting and stretching.
When threading in the control plate screw thread must not be deformed. Torsional loads must be equal to the minimum torque at the break.
Tensile load must be sufficient to achieve the minimum tensile force.
Table. 4 shows the test parameters on tapping screw screwing, twisting and stretching.
Screws with recesses in the lead-in portion of the rod (Fig. 1, type F, BF and Fig. 7) working as a rezbozachistnye.
French Patent №1151215 IPC F 16 B 25/00 five symmetrically disposed grooves angled koshi rod in French Patent №1520416 IPC F 16 B 25/00 embodiments are landing on transitions cylindrical lead-through with two opposite grooves parallel to the axis of the rod. Belebeevsky plant «Avtonormal» in 2000 patented a few useful models stripping screws with different heads. At the end of the rod is provided with two and three grooves parallel to the axis of the rod.
The factory «Krasnaya Etna» developed and tested at JSC
«GAZ» flange bolts M 6 … M 10 with four grooves 90 ° parallel to the axis of the rod, the material — steel 20G2 R.
Screws with slots and cutouts of different shapes at the lead-in portion of the threaded rod and operate as both-tapping kraskosnimayuschie depending on the type of the thread (Fig. 1, type G, BG.T, VT, 17).
Used in soft alloys, plastics, wood, sheet metal. Japanese Patent number 54079158 IPC 21 K 1/46 considered the design and method of landing toggle landing lead-end machine with an oblique cut from the butt of the rod axis with a cutting edge (Fig. 1, the type of T or BT).
Wrapping thread flat dies — the most common way to thread rolling. Set of dice for rolling threads on the screws (Fig. 6) has a fixed plate with grooves to form a thread and movable with the projections that form the profile of the grooves on the rod parts. The formation of the thread grooves and occurs simultaneously.
Rezboobrazuyuschie screws of various designs are produced by various companies around the world.
Of particular interest to a group of companies INDEX Fixing Systems, Spain, manufacturers of construction fasteners fastening-systems of different types: concrete, brick, plaster boards, fibroblast-elementwise, metal panels and profiles, wood-based materials.
A significant share of production volume of the company take-tapping fasteners. All products are standardized. To DIN 7981 … 7983 made screws for metal and wooden structures, and plastics. Thread 40 °, lead-end of a sharp (15-25 °), different heads.
According to DIN 7504 are made dvuhperovye self-drilling self-tapping screws. In the nomenclature of the company and products are available with thread HI-LOW, sizes 3.9, 6.5, 7.5. Thread 30 ° to 60 °, with the setting of 25 °, under gipsokar-ton slabs, with stops at 15 °, aluminum and plastic windows. Threaded 60 ° with the grooves on the wrap, a concrete structure.
There-tapping screws stripping MB, with metric thread and seven helical grooves along the entire length of the rod.
Tayvaskaya firm Diing Sen Fasteners Industrial Co. Ltd. It produces self-tapping screws of different sizes of carbon steel and stainless steel. Some parts available in inch version, such as screws HI-LOW.
Rezboobrazuyuschie details rightfully belong to the progressive fasteners.
Using rezbovydavlivayuschih screws eliminates threading operation and its control, create robust and reliable connection, tapping screw to rule out tapping operations and its stripped holes in metchikovaniem by pollution, increasing productivity on a conveyor assembly, reduced manufacturing costs and production costs.
Application rezboobrazuyuschih screws in mechanical engineering, especially in the construction of tapping very profitable. This fully confirms the international experience.
Russian industry is mounting needs serious reforms. The question arises, stoitli develop the production of self-tapping screws in Russia? Probably yes, although there are some difficulties with the metal and input costs.
Development of small and medium-sized production able to compete with manufacturers from Southeast Asia.
Should I refuse to import? Of course not.
The Russian market of fasteners loses 75% self-tapping screws. The introduction of fees is not restricted to lower this figure, but affect Russian consumers. Disappear competition among manufacturers remain monopoly enterprises. All remain at square one. You should be created equal conditions for normal development of the production of fasteners in Russia.
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2. Makarov VA, Khokhlov EN, Bunatyan GV Self-fasteners. Bolts and screws rezbovydavlivayuschie // «Hardware», № 2
(18), 2008, pp 76-80.
3. Bunatyan G. Khokhlov EN, Strokina MP Taptite — rezbovydav-Lebanon fasteners // «Hardware», № 3
(19), 2008, pp 48-50.
4. Musin RA, Gamahmetov T. S. Development of advanced designs self-stripping bolts // «Hardware», №03 (10), 2005, pp 56-58 (p. 26).
5. as self-tapping screws // «Hardware», №02 (21), 2009. P. 78. «Hardware», №03 (19), 2008, pp 12, 32.