Many people still believe that a screwdriver blade can only be of two types:
- splined - Ps
Popularly referred to as “minus” - flat.
The very concept of slot (schlitz) is translated from German as a groove or slot.
- cruciform
Moreover, as some believe, they differ from each other only in size (width and thickness of the tip) or diameter.
In fact, the shape of the cross-shaped profile also plays a significant role.
Moreover, the “cross” itself appeared much later than the slot. Due to the massive introduction of screwdrivers, using a straight slot with these devices has become not entirely convenient.
Therefore, we gradually switched to a cruciform shape. It centers better and is much easier to work with.
Screwdriver profile Ph
The cross-head slot we are used to was invented back in the 30s. A few years later, the patent for this invention was bought by the enterprising Henry Phillips.
G. Phillips patent for Ph profile
This profile was named in his honor - Ph = Phillips. Just don't confuse the Philips company from the Netherlands (with one L) with the Phillips Screw Company founded in the USA.
We know the first one well from televisions, cassettes, high-quality lighting devices, etc. But the second one gave us variety in threaded fasteners.
At first glance, Ph is a simple cross, narrowed to the base and nothing more. It would seem that there is nothing to invent and patent here?
But this is not true at all. The Ph profile is made strictly at a certain angle of 55 degrees and with an inclination of the side surface of each face.
Thanks to this, if you start tightening screws or screws with extreme force, risking overtightening them, the bit or sting will simply pop out of the head of the screw or screw without damaging the fastener itself.
As you know, this was not done by accident. In this way, a certain tightening torque was achieved when using the tool on flow assemblies of the automotive industry and aircraft manufacturing in the USA.
Subsequently, with the invention of torque ratchets, screwdrivers and screwdrivers, as well as increased requirements for precise tightening torque, this began to work to the detriment.
In practical terms, this means that you don't have to mutilate the Ph bit if it starts popping out of the fastener. It turns out that the limit of the screw's tightening ability has been reached and there is no need to turn it any further.
PH2 bits: description, purpose
Until 1933, screwdrivers with a straight cut (flat) were used in production, which could easily damage parts, and they turned out to be unsuitable for mechanical tightening of screws. The invention of Phillips screws and the same bits was revolutionary. Henry Phillips bought the patent, and the bits began to be called after him - PH or Phillips. Depending on the size, a number from 0 to 3 is added to the marking. PH2 bits are used in everyday life, the features of which are:
- slot in the form of a cross with a bevel angle of 550;
- the ability to screw screws into soft or thin material;
- When working with a screwdriver, upon completion of tightening, the tip of the bit is pushed out.
Profile Pz - main differences
In 1966, the same Phillips company modernized its earlier invention and introduced the Pozidrive slot - Pz (Pozidriv) to the world.
Its distinctive feature is:
1Additional edge located in the quarters of the slot.
The bit turns out to be 8-spline. Four main faces, four additional.
At the same time, the heads of self-tapping screws and screws received similar notches. All this allowed for even better centering of the tip.
2The edges of the working surface in Pz, unlike Ph, are made parallel to each other, and not at a narrowing angle.
With Ph, this taper is made specifically so that at the end of the twisting operation, the bit pops out of the head. The so-called self-pushing effect.
When Pz was invented, they abandoned this, shifting the responsibility of limiting the force to the screwdriver or torque tool itself.
3 Ph bits and screwdrivers have a slightly different sharpening angle - 50 degrees.
Thanks to all these modifications, the spline began to fit much deeper into the mounting hole of the fastener. Which led to increased tightening of self-tapping screws.
In simple words, we can say that Pz is a reinforced cross-shaped spline.
Features, sizes and where to use
Pz is used mainly in furniture assembly and construction.
It is not as common in machine manufacturing or metalworking. This is explained by the fact that due to the greater depth, the posidrive fasteners must have slightly larger heads. Otherwise, their strength decreases and they break off.
Well, a larger size always means more weight, which is often unacceptable in some critical industries.
Moreover, both splines have 5 main dimensions, rigidly tied to the diameter of the fastener.
The most common numbers are 1, 2 and 3. Both Ph and Pz.
The most popular of them is the Pz2. It’s not for nothing that in sets of bits, this size is usually included in 2 pieces. It is used most often and, as a result, wears out most often.
Walking into a hardware store, a knowledgeable buyer immediately tells the sales consultants: “I’d like a set of two Pozidrive bits, please.”
Amateurs and non-professionals usually call them “double plus”! Be literate in such seemingly small but important issues.
However, the correct name is not the key to success. Having the same names, bits from different manufacturers may differ.
The highest quality brands are Wiha, Wera, Milwaukee.
If with the Ph profile everything is still more or less smooth and not everyone can mess up, then with the Pz profile a real disaster happens. Chinese bit manufacturers simply do not follow the sizes and standards.
So it turns out that some bits are thicker, others thinner. The same goes for fasteners. Unfinished notches in the head of a screw or self-tapping screw are completely commonplace. As a rule, this is observed in the smallest sizes up to 20mm for Pz1, Pz2 and Ph1 bits.
In this type of fastener, the tip of the bit already rests against the notch, but there is no edge of the bit yet. As a result, the screw begins to dangle like a metronome. Therefore, when purchasing in bulk from a store, it is advisable to immediately try on the bit with the fastener head.
Recommendations on what to look for when choosing bits
In order for the work of a screwdriver to be both efficient and effortless, it is very important to install a bit of the appropriate type. To do this, you should first of all pay attention to the following points:
- Material. If the part is not made of tool or carbon steel, chromium, vanadium, molybdenum or tungsten, it is better to find something of better quality. It is interesting that often information about the material on the nozzle cannot be found. Many manufacturers prefer not to disclose trade secrets and not give out their alloy. Then there is only one option - to trust the opinion of sellers, reviews on the Internet, brand reputation, and finally.
- Protective covering. This is perhaps a more important criterion than the material itself. In theory, a bat with a protective coating will last much longer than without it. In addition, the coating protects against corrosion and natural wear of the metal. You need to focus on the golden color characteristic of titanium nitride or the shine of the tip with diamond chips. Other reliable coatings are nickel-tungsten and chrome-vanadium.
- Integrity. A bat consisting of several pieces is an abnormal phenomenon. You shouldn't expect anything good from working with such a part. It must be complete and homogeneous.
- Relation to tangential load. When twisting the hardware, it experiences resistance from the surface material and can slow down. At such moments, there is a high risk of fastener failure and damage to the bit splines. Torsion bits handle tangential loads best.
Another useful tip. It is best to immediately buy a set of standard bits for a screwdriver. It usually includes all standard sizes of the main types:
- with flat slot;
- crusades;
- improved crusades;
- hexagons;
- stars.
Set of attachments
There may also be rarer types - anti-vandal, for example. Usually the kits are produced by well-known brands, so you can be sure of the quality of each attachment. However, it is better to check them all before purchasing if you have the opportunity to unbox the kit.
By the way, the brand name, as elsewhere, plays a key role, but not a determining one. You shouldn’t consider all more or less cheap options to be low-quality or fake by default. Everything needs to be checked and compared. At numerous flea markets, the selection and quality of bits are usually no worse than in specialized stores, but they can cost significantly less.
Electrician's screwdriver for vending machines
As for electricians, it is no secret for competent specialists who have been working in this field for a long time that bus bars, cross modules, automatic machines, relays and other equipment have special screw terminals Pz +/- or Ph +/-
Moreover, it was for electricians that manufacturers began to produce special screwdrivers with a Pz/fl or Pz/s profile for automatic machines.
And also Ph/fl or Ph/s - for busbars, starters, relays, etc.
The designation for this spline (Fl or S) is different because until recently, it was not standardized. So they called him whatever it was more convenient for him. Although the essence and form were the same.
Currently it is standardized only in France and the USA as Pz/sl and Ph/sl.
For sockets and light switches, in 90% of cases the first number is needed, and for modular machines, number 2 is required.
The screw clamps of such devices have not only the usual cross with notches characteristic of Pz, but also a wide slot for a flat-head screwdriver.
On the one hand, they are made this way so that even those who do not have the appropriate tool can tighten everything with a regular flat-head screwdriver. Or, when the working slot was already “killed,” you could at least unscrew the screw one last time, then pull out the wire and replace the machine.
But on the other hand, if you twist them with a simple Phillips Pz or a regular spline, then the bit will still slip at the last moment, without tightening the contact with the required force.
And the universal combination screwdriver Pz/Fl or Pz/Sl is just right! However, be careful when choosing manufacturers. There are a lot of negative reviews of such profiles on the Internet.
In them, the corner of the flat slot breaks off first. Especially in the first issue.
Using screwdrivers and bits with incorrectly selected fasteners leads to wear of both the screwdriver itself and the head of the screw or self-tapping screw.
In this case, the worst thing happens when they try to tighten the Ph profile with a Pz screwdriver. The contact of the edges in this case is minimal.
From the first revolutions, as soon as a significant load begins, you are guaranteed to break not only the fasteners, but also damage the edges of the bat itself.
How to choose a quality screwdriver
You shouldn’t expect good metal and an ergonomic handle from cheap products; it’s better to initially choose screwdrivers from well-known brands. This is 2-3 times more expensive, but then you can use one screwdriver for many years, which is better than changing Chinese products every six months. The screwdriver should fit comfortably in your hand and not press on your palm. Even the slightest inconvenience during the work process can reward you with bloody blisters. When applying a lot of force, a low-quality steel screwdriver will quickly lose its shape and begin to spin on the slot of the screw head. It is quite difficult to check the quality of steel when purchasing; usually, the more comfortable the handle, the higher the quality of the steel. The price is appropriate.
