A slot is a slot on the head of a screw or screw (German: Schlitz - groove, slot), designed to transmit torque to this product from a tool (screwdriver or socket wrench).
Splines come in various shapes and sizes. In this article we will look at the most common types of holes and the bits intended for them.
Straight spline (SL) - the most popular and simplest type of slot. It is a straight groove passing through the center of the head of the fastener. The head for fasteners with a straight spline is called a "spline" or colloquially: "flat", "straight" or "negative". The working end of the screwdriver is a wedge-shaped plate.
The disadvantage of this slot is that due to the lack of clear centering, the screwdriver often flies out of the groove, while the edges of the slot itself “break off,” which is especially typical for high protracted forces. For this reason, the flat spline is poorly suited for assembling mechanisms and precision products.
Phillips slot (PH) - a widespread type of hole in a fastener. The main varieties are the traditional Phillips and the more modern Pozidrive.
Phillips (not to be confused with the Philips brand of equipment) is the oldest and most famous type of Phillips recessed threaded fasteners and screwdrivers or bits for them.
This slot was patented and put into production by a certain Henry Phillips (H.F. Phillips), who, in turn, acquired the rights to the idea from the inventor J.P. Thompson.
In a cross-shaped slot, compared to a straight slot, the grip is strengthened, the moment of force on the axis is reduced, but still, with a “tight” entry into the material, additional efforts have to be made to hold the bit in the product.
Posidrive type slot (PZ) - is an improved version of Phillips, and is used in the production of screws and self-tapping screws for wood. In mechanical engineering and metalworking, posidrive is used much less frequently. A distinctive feature of the spline is small additional recesses, offset by 45 degrees relative to the main axes. They provide greater stability and protection against scrolling, although they do not completely solve it.
Posidrive screwdrivers are not pushed out of the slot when used - a more stable grip is formed, which reduces wear on the bit and the part itself.
Square splineRobertson (S.Q.) - was first produced in 1908 by the Canadian Robertson, who introduced it into production instead of a straight spline. Subsequently, he was in demand by Ford in his automobile industry until Robertson refused to sell him a license to manufacture and sell the spline, after which the sales project in the United States completely failed.
Nowadays, the design of a slotted clamp with a working part of a square cross-section is used for tool heads and in fasteners. The Robertson spline is designed to quickly change hand tool heads with high reliability.
Hexagon spline (HX) - type of slot of threaded fasteners in the shape of a regular hexagon. The angle between the sides is 120 degrees. The head of the fastener is usually cylindrical in shape with a hexagonal recess; to work with hexagonal slots, a screwdriver or a hexagonal bit is used.
Hexagonal screws are used in the mechanical engineering, furniture, aviation and automotive industries.
Spline typeTorx (TX) - type of slot in the shape of a six-pointed star.
This spline is capable of transmitting high torque without deforming the bit or tool. TX slotted fasteners are commonly used in automotive applications, bicycles, brake systems, various prefabricated metal structures, computer hard drives, ATMs, consumer electronics, and fuel equipment.
Thanks to the reduced radial load, tool and bit life is extended. This is achieved due to the fact that the angle between the edges is only 15 degrees. This geometry creates virtually no stress. Unlike cross profiles, TORX does not require any effort to drive the screws, and there is no slipping effect, which is common, for example, in a negative slot. Thus, the force transmitted through this spline will be much greater under normal application force.
Please note that there is a difference between a TORX and a TORX PLUS slot: in fact, it is possible to screw a TORX PLUS screw with a TORX screwdriver, but this will lead to rapid wear of both the screwdriver and the slot itself.
TORX Tamper Resistant (TXH) prevents unintentional screw removal. The only difference with regular TORX® is the hole in the center of the bit and the small pin in the center of the screw.
Spline type 3VING denotes a special “three-bladed” type of slot for threaded fasteners and screwdrivers for them. Keys and screwdrivers are marked 3 V or TW(Tri-Wing). The 3VING slot was originally used in the aerospace industry, particularly for the assembly of wide-body aircraft, but later became used in other types of production, for example in the manufacture of electronic devices. This slot is also used in NOKIA chargers.
Spline typeTORQ- SET denotes a special “four-blade” type of slot for threaded fasteners and screwdrivers for them. Keys and screwdrivers are marked 4 V or T.S.. The 4V slot is used only in the aerospace industry, although 4V screwdrivers are commercially available.
Spline typeONE- WAY(CL) - denotes a special type of slot in threaded fasteners and screwdrivers for them, intended only for tightening. When you try to unscrew the slot, the bit cam immediately pops out of the groove. However, there is a socket that can unscrew the CL spline. If such a “stray” is not at hand, all that remains is to drill out a screw or, after drilling two holes in it, unscrew it with a 2P bat. ONE-WAY slotted fasteners can be used in public areas to protect structures from vandalism.
Secret slot type fork wrench (2P) - with two rectangular cams, also known as "snake eyes". The slot is not designed to transmit high tightening torque, and the force is transmitted here only through two pins, which does not allow overtightening the screw.
This type is used in elevator panels, in some waiting rooms, in subways, and also for tightening cleats in some types of shoes.
There is also a variation of the bat - with three pins, which, for example, is used in clutches of bladed weapons and firearms.
Round Head Hex Slot Type Hexagon Balldrive (HB) - allows you to reach hard-to-reach places at an angle of up to 25 degrees. They are quickly and completely inserted into the recess and reduce the problem of “breaking” edges.
Spline typeSpline (SP) - slot in the form of a twelve-pointed star. The tightening force is evenly distributed across all rays of the star, providing the ability to transmit a high tightening torque.
Therefore, this type of spline is widely used when tightening cylinder heads and other motor connections.
A feature of the SP type is a tight fit and maximum coincidence of the contours of the bit and the product, therefore, if dirt and dust particles get inside the bolt, the bit deviates from the axis and can cut off the inner edges of the product and its teeth.
Triangular head slot (TR) - a type of security slot used by railways, fire services, and also in radio electronics.
The design is an equilateral triangle. The spline is not designed to transmit high torque due to its small area.
This is a simple but at the same time important question. Most home craftsmen do not know how to match a bit to a self-tapping screw. And often they cannot buy self-tapping screws for the bat they already have.
This leads to people complaining about bits or screwdrivers. They say it's raw meat and it's impossible to twist.
Self-tapping screws for PH and PZ
How PH self-tapping screws differ from PZ is something every craftsman who does housework needs to know. Not to mention the installers who cover the balconies.
Most self-tapping screws have a cross head. There are two types of cross holes in the self-tapping screw PH and PZ.
How to understand which screw needs which bit?
The self-tapping screw can be small or large, with a hidden head or an external one. There is an instruction on the head of any self-tapping screw.
If there is a regular cross on the head, then you need a Ph bit.
If the cross has the characteristic four notches at 45°, then this screw needs a Pz bit.
Two types of cross bits
PH stands for Phillips. It has the shape of a regular cross. Good idea. There are practically no cons. It was first developed by Phillips engineers.
PZ - stands for Pozidrive. It has the shape of a cross with characteristic notches between the edges.
The Ph bit is more versatile. It can be used to tighten both Ph and Pz screws. The only thing is that it hangs in the Pz screw. Because it has less completeness.
With a Pz bat you can only spin Pz; it doesn’t fit into Ph and breaks off the edges.
Bit marking
Each bit is marked. Either a sticker has been pasted, or the value for which screw it is suitable for has been punched out with a press. That is, the same Ph or Pz and its dimensions 1, 2, 3. About the dimensions a little lower.
Bit size
Bit lengths are 25 mm, 50 mm, 70 mm, 90 mm, 120 mm, 160 mm, 200 mm.
But besides length, they also differ in numbers. The Ph bits are marked as Ph 1, Ph 2, Ph 3. The Pz bit is: Pz 1, Pz 2, Pz 3.
As a rule, sizes smaller than Ph 1 and Pz 1 are not used. There are no screws for them.
They can be used somewhere in radio engineering and electronics. There are also no bits larger than Ph 3 and Pz 3. Larger screws have other types of bits, for example, a star or hexagon.
Why does a self-tapping screw need its own bit?
The bit or screwdriver must fit the screw. By the way, recently screwdrivers also indicate which screws it fits.
Why is it so important to choose the right bat?
Firstly, using the wrong tool, you constantly tear off the cross hole in the screw. This makes it difficult to unscrew the fastener in the future.
Second, you wipe down the edges on the bat itself. Thus quickly rendering it unusable.
In my childhood, the choice of tools was very limited - a hammer, a saw, a wrench, or better yet, a universal bicycle “family” wrench and two types of screwdrivers, flat and Phillips. Then it turned out that any of these instruments is divided into entire families of different instruments. Hammers come in light, heavy and sledgehammer types; with a sharp edge, chisel and nail puller; carpentry, joinery and geological; There are forged, cast, powdered metal, wood and even rubber. There are even special hammers for working in zero gravity that have no recoil! Saws were divided into dozens of types, tooth directions and for different tasks. And even wrenches, it turns out, come in not only open-end wrenches, but also socket wrenches, socket wrenches, combination wrenches, adjustable wrenches, adjustable wrenches, pipe wrenches, and the hell else!!! In general, life turned out to be much more difficult than I imagined =)
However, screwdrivers in my world have long stuck to the concepts of “phillips” and “flat head”. In various sets of screwdrivers that I found at different times, there were some inscriptions, such as PH or PZ - my brain somehow explained this to itself as foreign markings and I did not delve into these designations. But one day I suddenly understood the essence of these designations and, frankly speaking, I walked around for a week amazed at my insight!!! It seemed to me that this was some kind of secret knowledge that no one knew. The world of screwdrivers suddenly went from 2D to 3D!
Types of splines
First, a little about a flat-head screwdriver
Screwdrivers with a straight slot are marked with the letter SL, which stands for “Slot” and is literally translated as “Slot”. The number in the marking indicates nothing more than the width of the slot in millimeters. SL No. 6 is a 6mm wide flathead screwdriver - it's very simple. A straight slot is the first and simplest type of slot in threaded fasteners, known since the 15th century.
This slot is very simple to implement, however, during the times of scientific and technological progress during the mass assembly of cars and airplanes, it developed a serious drawback - due to the lack of clear centering, a screwdriver or screwdriver easily slips out of the slot, while the edges of the slot itself “break off” which is especially typical for high protracted forces, and the screwdriver leaves scratches on the part and the installer’s hands. In addition, such a slot allows for the transmission of a fairly large torque, which contributes to stripping the threads on the screws and breaking the screw heads themselves. For this reason, the flat spline is poorly suited for assembling mechanisms and precision products.
A moment of history
The flat slot did not immediately transform into a Phillips slot. There was also a transitional option. The first splines suitable for automated production were invented by Canadian Peter L. Robertson in 1908. The slot is patented under the name Robertson - a square cutout in the head with a chamfer on the edges and a cone-shaped recess in the center. The Robertson screw had a number of undeniable advantages: inexpensive to manufacture, allowing the screwdriver to be firmly centered in the square recess of the head, it made it possible to work almost with your eyes closed, by touch, at a minimal angle. The applied effort decreased in proportion to the increased productivity. For some time, these screws were used by Henry Ford in the production of the Ford T and Ford A models, saving 2 hours on assembly time! Given the mass assembly line, this was a phenomenal breakthrough. But Robretson did not want to give the rights to Ford, just as he did not want to license other screw manufacturers, so this slot did not gain popularity. Today they are used mainly only in Canada. By the way, Robertson is one of the best splines, and much better than Phillips.
Phillips PH
In 1933, American John Thompson developed screws that effectively solved the disadvantages of the flat spline. They automatically center the screwdriver blade and push it out when the screw is tightened. However, all his attempts to introduce his invention into factories led to nothing. The next year, chance brought him together with engineer Henry Phillips. He bought Thompson's patent and founded the Phillips Screw Company in 1936. Henry Phillips (who is not related to Gerard Phillips, the creator of the Philips brand of household appliances) developed the technology for producing such screws, but he also encountered difficulties in introducing his invention widely. Phillips actively sought out customers willing to buy his screwdrivers and screws, but was rejected after rejection. Meeting Eugene Clark, president of the American Screw Company (the company that was the largest manufacturer of hardware in the United States), radically changed the situation. Clark liked Phillips' invention so much that he allocated $500,000 to re-equip the production of his enterprise. Despite the objections of the company's top engineers, Clark threatened to "fire anyone who said it couldn't be done." We might not see any PH/PZ in our lives.
In 1937, General Motors pioneered the use of Phillips screws and screwdrivers in the production of Cadillac models. The results exceeded any expectations, and by 1940 all American automobile manufacturers had re-equipped their factories, and hardware manufacturers literally lined up to get a truly precious license to use the gold-bearing “cross.” During World War II, such screws began to be used in the production of military equipment.
It is noteworthy that it was the war that allowed Phillips screwdrivers and screws to spread throughout the world, and since then, manufacturers in all countries have been actively using them in the fastening industry. The “cross” came to Russia thanks to American B-29 long-range bombers. In 1944, these American planes, which bombed Manchukuo and Japan, made emergency landings in the Soviet Union. In accordance with the Russo-Japanese non-aggression pact, the bombers and their crews were forcibly left in the USSR. It was from them that the overseas propeller was copied. This is how the Soviet Tu-4 appeared with a fundamentally new fastener for our country. The crusade of the updated screwdriver around the world ended with the global expansion of Phillips’ “cross”.
With such widespread adoption, Phillips Screw Company management was unable to track all the illegal uses of its patent, and the patent was canceled in 1949. And in 1958, at the age of 68, the inventor of the Phillips screwdriver himself, Henry Phillips, died, leaving behind an invention to the world that gave a significant impetus to the development of the entire world industry. A push that is not inferior in its significance to the invention of the conveyor belt. The name of the inventor of the Phillips screwdriver remains forever immortalized in the name of the Phillips slot.
Despite the fact that many experts today consider the Phillips cross to be outdated, it is still considered the de facto standard.
Advantages of the Phillips slot (PH)
Holds the fastener and screwdriver exactly centered relative to each other, compared to a conventional straight slot.
When using a screwdriver without adjusting the torque value, its tip is pushed out of the fastener slot when the maximum torque value is reached to avoid damage to the thread.
Disadvantages of the Phillips slot (PH)
It is impossible to obtain a large torque without applying significant axial force (pressing the screwdriver against the fastener).
Self-ejection increases mechanical stress on the spline, which increases wear on the spline and the likelihood of its damage (the so-called “breakdown”).
Phillips slot PZ
This spline was patented in 1966 by the same Phillips Screw Company, 33 years after it received a patent for the Phillips spline, which had expired by that time. PZ stands for POZIDRIV. Pozydrive is an improved version of the Phillips cross-head and is used primarily in the production of screws and self-tapping screws. In mechanical engineering and metalworking, Pozidrive is used much less frequently. Unlike the previously invented Phillips slot, the deep edges of the side surfaces of the Pozidriv screwdriver do not become thinner, but run parallel to each other. In this case, the axial force pushing the screwdriver out of the slot is insignificant - the screwdriver is practically not pushed out - a more stable grip is formed, which reduces the wear of the mating elements and the likelihood of the screwdriver slot and the fastener breaking off. It also becomes possible to apply more torque to the tool.
Advantages of the Pozydrive (PZ) slot
Reduced spline wear due to more stable grip.
Possibility of achieving high torque.
Disadvantages of the Pozydrive (PZ) slot
External resemblance to a Phillips slot - because of this, they can be easily confused and when using a screwdriver that does not match the slot of the fastener, incomplete contact of the working surfaces occurs - this significantly increases the mechanical stress on individual sections of the splines, leading to their premature wear (mainly in screwdrivers) or damage.
The slot is significantly deeper than Phillips, so it is used only where screws have large heads for reasons of strength - in construction and furniture production.
Size range of bits and screwdrivers
Screwdrivers with PH slots have numbers: 000 (1.5 mm), 00 (2 mm), 0, 1, 2, 3, 4.
Screwdrivers with PZ slots have numbers: 0, 1, 2, 3, 4.
The international standard for Phillips splines is ISO 4757:1983 (our GOST 10753-86). The screwdriver standard for it: ISO 8764-1:2004 (GOST R 52785-2007 “Pipe screwdrivers for screws and cross-head screws”), however, it does not describe sizes smaller than 0 (such as PH000 and PH00).
How to identify a bit type
Besides the fact that almost all bits and screwdrivers have markings, it is not difficult to visually distinguish these two types. PZ bits have additional rays running in the middle between the working splines. This design feature immediately catches your eye, unless the bit has a number lower than PZ1. In the PZ0 and sometimes PZ1 bits these rays are not expressed. If you look closely at the edges of the bit, you can see that the PZ bits have parallel slot edges, while the PH bits have trapezoidal edges.
Accordingly, the heads of the PZ screws also have diagonal rays. And sometimes there’s also a stamped letter Z for added significance.
Varieties
“The further into the forest, the more firewood” - this proverb can confidently be applied to screws! Phillips screws, at the time of their invention, solved the shortcomings of straight splines. Firstly, the screwdriver installed in the recess did not fly off when rotating. Secondly, when a certain force was reached, the screwdriver was pushed out of the screw, thanks to the rounded internal corners of the slot. Now this seems like a very stupid idea, but at that time the tool was bulky, and adjusting the torque was unthinkable, so it was the only way to prevent thread breakage during installation.
In general, all of today's attempts by manufacturers such as laser notches, ribbed surfaces, diamond or carbide coating, etc. This is just an attempt to at least somehow compensate for the initially inherent technological feature of Phillips splines. This happens when a flaw gains popularity too quickly and others are already forced to adapt.
In addition to trying to improve Phillips, more than a dozen different Phillips splines were invented. Half of them are owned by the Phillips Screw Company itself. And almost all of them are designed to minimize push-out and improve torque transfer. If you try to cover all the varieties, you will have to write an encyclopedia of slots! But within the main topic, we will consider the directions for improving PH and PZ splines.
The Phillips slot currently has three varieties, in addition to its original state:
Phillips II is an improved version of Phillihps. Cross-shaped slot with inclined notches against ejection (ACR technology - anti-cam-out recess; distinctive marking - ACR2). Designed to meet increasingly fast assembly processes that may cause the screwdriver to be ejected from the screw, resulting in damage to the surface of the part. It facilitates tightening in difficult installation positions and reduces pressure on the spline, resulting in reduced worker fatigue. Screw heads with such a slot have characteristic double notches along one of the diagonals, but are quite compatible with regular PH.
ACR RIBBED PHILLIPS- Cross-shaped slot with notches perpendicular to the axis of rotation. (Distinctive marking - ACR, anti-cam-out recess). The manufacturer emphasizes that this bit reliably holds the screw on the blade of the screwdriver, which increases worker productivity. This bit is compatible with all Phillips screws and the screw heads are no different from regular PH. In the photo on the left, the two bottom elongated bits labeled S2 PH1 and S2 PH0 are ACR bits, the top ones are regular PH. Now almost all PH ACR bits are already in stores, i.e. with notches.
PHILLIPS SQUARE-DRIV - Phillips combination with a square drive. Cross slot with serrations (ACR technology), combined with a square slot. (Distinctive marking - PSD - PHILLIPS SQUARE-DRIV). Allows significantly higher torque. Just three screwdriver sizes cover the most popular size ranges. The screw heads have a double notch in one diagonal and a single notch in the other. The manufacturer claims that this bit/screw pair can be installed and tightened with one hand. The screw sits so tightly on the screwdriver that it is practically impossible for it to fall. Moreover, these are non-magnetic bits! The screwdriver is not compatible with regular PH screws, but PSD screws can be unscrewed with a regular screwdriver.
The Pozidriv spline itself is improved compared to Phillips, however, this spline also has one variety:
POZISQUARE-DRIV is a combination of the classic Pozidriv with a square slot. Perhaps the manufacturer made a typo somewhere in the description, but this bit looks and is marked exactly the same as the PSD. In general, the advantages of this slot are similar: it allows for significantly greater torque, holds the screw perfectly on the bit, and reduces worker fatigue. But, in addition, it is compatible with Canadian square screw systems!
Frearson (Fr)
PH and PZ are not the only Phillips splines. There was also Frearson - a rather rare and almost forgotten type of slot. Also known as Reed & Prince. Similar to Phillips, but has a sharp end and a larger V-shape angle (75°). One advantage over Phillips is that one screwdriver fits all screw sizes. Found in imported marine equipment. The lack of fillets in the cross slot allows for more force to be applied, unlike the rounded conical shapes of Phillips, which were designed to push the tool out at high torque. This spline was developed by English inventor Frearson in the 19th century and was produced from the late 1930s to the mid-1970s. In 1987 the company went bankrupt.
Phillips S
Specifications and standards do not apply to splines smaller than No. 0, however, there are a great many tiny screws in modern equipment. Especially in Japanese. That is why the Japanese have supplemented their spline standard (JIS B 1012) with size S. This type of spline is used for screws with a diameter of up to M2 and, if the screw head is small, then no more than M3.
Type S is different from type PH, although outwardly it can be confused. Moreover, in Japan itself there are two standards defining S-type splines: the already mentioned JIS B 1012 and JCIS 8-70 (Japan Camera Industrial Standards - industrial standards for Japanese cameras). In fact, it is a cross with minimal rounding of the internal corners. The splines of both standards are almost the same, with the exception of a narrower tip, tighter tolerances for JCIS and another difference in the length of the working part of the splines. S slots are found in cameras and accessories, various small electronics, and radio-controlled helicopters. Thus, Japanese screwdrivers of standard size PH0 differ from screwdrivers according to the ISO or GOST standard, since they are made for their “native” S-type slot. In the photo on the left you can see that the heads of the S-type screws have more straight internal angles than those of the PH. The top picture is the battery compartment of a Japanese Canon EOS camera, the middle photo is the autofocus motor of the lens of a Japanese Olympus camera and the bottom photo is the battery compartment cover of a Chinese toy.
Bits for screwdrivers and screwdrivers: understanding the markings
Which bit will fit which screw? The most popular types and types of bits used in hand and power tools. Marking bits and their differences...
Since the advent of electric screwdrivers and hand-held screwdrivers with interchangeable attachments, the production of bits for unscrewing various fasteners has also begun to develop at an active pace.
At the moment, the industry produces a large number of varieties of bits. This article will highlight only the main, most popular types of these attachments.
A standard bit is a hex shank designed to be clamped into a chuck or held in an adapter; the shank, which goes into slots of different standards, is paired with a specific type of screws or self-tapping screws.
Types and types of bits
PH - (Phillips standard)
The PH standard is a Phillips spline with an apex angle of 55°. Each of the four splines has an extension towards the shank.
Bits marked PH can have different slot diameters and are marked from the small PH 0, designed for small diameter screws, to PH3, capable of holding large screws.
Bits marked PH 2 are the most common, as they are used for tightening so-called self-tapping screws for thin metal, or (black) self-tapping screws that have a simple cross-shaped slot in the head.
The PH standard is more universal and can be used with other screws.
PZ - (Pozidriv standard)
This standard is suitable for self-tapping screws that have slots in the Pozi standard head.
The Pozidriv standard is a kind of improved version of the previous type of bit.
PZ bit - represents a cross-shaped slot, having the same thickness of each edge with an apex angle of 50°.
A significant difference between the PZ bit is the “double cross”. The placement of additional small splines between the main splines made it possible to increase the holding force of the bits.
PZ standard bits are also available in different sizes and can be marked PZ1, PZ2, PZ3.
PZ standard bits are used for such self-tapping screws as UP (universal countersunk), which has an average thread pitch, as well as for other self-tapping screws with a Pozi slot.
SL - (Slot - Straight slot)
The well-known flat spline also has its own marking, such a bit is called SL.
The SL standard is a straight spline (flat) that can have different widths.
The width in millimeters is indicated after the SL marking - for example, SL 5, from which we understand that we are dealing with a bat that has a flat slot 5mm wide.
Torx - (Six-pointed star)
This slot, when viewed from the end of the bit, is a six-pointed star; the differences lie in the diameter of the star.
The slot number is indicated on the bit and comes after the inscription Torx or simply the letter T, for example Torx 10 - which corresponds to approximately 2.74 mm. Torx has its own numbers for different bit sizes.
Torx slots are used where high torque is required when tightening fasteners. Such a slot can be found on powerful self-tapping screws.
In addition to marking the slots, the bit may have a different shaft length or a limiter that will not allow you to turn the screw in the drywall further than necessary.
Material characteristics and bit coating
An important component when choosing a particular bat is the material from which it is made, as well as the coating that can withstand various influences.
On the construction market you can find bits from different manufacturers with a wide price range. The durability and ease of working with a bat depends on the grade of steel used for their production.
Probably the most common are bits with the steel marking Cr-v (chrome - vanadium), there are also bits made of chrome - molybdenum steel, etc. In addition to the steel composition itself, some bits are coated with a protective coating.
Manufacturers are competing for consumers and more and more new technologies are being used in the production of bits.
For example, a bit that has a nickel coating, on top of which a second chemical compound of tungsten carbide is applied, has increased corrosion resistance due to the nickel layer. And tungsten carbide, which is the outer shell, enhances the strength of the bit, which increases its service life even compared to a diamond-coated bit.
There are bits with a titanium coating, which gives the bit increased hardness and corrosion resistance.
Very often, especially in inexpensive sets, there are bits whose steel strength is highly questionable. Such a bit is usually enough to drive several screws, after which its edges are torn off and the bit becomes useless. A low price for a bat is not always an indicator of poor quality; on the construction market you can also find decent examples at fairly affordable prices.
The permanent address of the article is http://site/articles/443
Even in ancient times, when decorating the interior of buildings, people used the predecessors of modern ceramic tiles - thin flat bricks cut from natural stone, each of which had a pattern...
Once upon a time everything was simple: a flathead screwdriver, a Phillips screwdriver and a set of hex wrenches for a hex nut/bolt. That's all! Now, looking at sets of bits for a screwdriver, my eyes widen. However, despite the large selection, in everyday life the most popular are still only a few types of bits.
There are a great variety of sections of screw/screw/nut heads, including exotic and exclusive ones, which some manufacturers use in their products in order to make it difficult for “casual” craftsmen to access the insides of the product. They say contact the service center and they will have the necessary tool to disassemble your device. Here we will not consider these types of sections, but will talk about more or less serial and used ones, which are usually included in standard sets of bits. And there are probably only 5 main types of these: straight (flat) slot, Phillips Ph, Phillips Pz, internal hexagon, internal sprocket.
1. Flat slot; 2. Ph (Philips); 3. Pz (Pozidrive); 4. Hexagon (HEX); 5. Sprocket (TORX).
Straight spline This is the most classic type: a cut in the head of a screw or screw for a flat-head screwdriver. They differ from each other only in the depth and width of the cut.
Next in popularity is the cross Philips standard cross section or by marking name Ph. Naturally, especially from the Soviet past, there may be cross slots that are somewhat different from this standard, but for almost any of them you can choose the most suitable bit. According to the standard, Ph implies a cross-shaped slot, at an angle to the top of 55 degrees. The side working surface of the cross is not straight, but seems to taper slightly towards the end. The sets are usually marked as Ph1, Ph2, Ph3, which corresponds to their size.
Next comes cross section Pozidrive or Pz, which resembles Ph, but has additional notches on the head of the screw and, accordingly, additional antennae on the fore-end of the screwdriver or bit. In addition, the side working surface of Pz, unlike Ph, has the same thickness along the entire length, and does not taper towards the end. The angle at the apex is also different - it is 50 degrees. This type of section has a weaker buoyant moment than Ph and allows you to apply more force and transmit more torque.
Of course, you can try to wrap the Pz screw with a Ph bit and even vice versa (which will be completely inconvenient), but with the slightest careless movement this will lead to the notches on the screw breaking off and rapid wear of the bit itself.
The next type of section is internal hexagon (HEX), which is most often used in furniture tie screws. It is worth noting here that when using cheap bits and/or screws, the slightest discrepancy in size will either lead to the bit turning in the screw head, or to the fact that the bit simply will not fit into the screw. But not everything is so terrible, and here you can try to screw in the recalcitrant tie with the following type of section.
Sprocket section (TORX) Most often used on screws or for high torque applications. But a couple of times it was these, not often used, bits that came to the rescue in unusual situations, as in the case described above with a hexagonal section.
Separately, it is worth mentioning the bits for the impact wrench, but everything is quite simple here. Most often, hex bits of different sizes are used, but they are also found with a quadrangular and even triangular cross-section. Designed for loosening and tightening nuts and bolts.