Screwdrivers date back to the early 15th century, when they were invented to tighten the newly-invented screws used in metal suits of armor and engines-of-war.
However, not much has changed in the technology of screws and their drivers, and the only real developments during the past several hundred years had been an increase in the variety of drives, improvements of metals used in their manufacture, and the design of more efficient screwdriver handles.
Today, much of the success of modern technology and industry depend on the humble screw and its corresponding driver, so if you are planning a DIY project, or are shopping for new screwdrivers, read on, because in this article we will tell you everything you need to know about screwdrivers.
You will learn
- Types of screwdrivers
- Types of Screw Head and sizes
- Uses and applications
- Buying Guide
Phillips Head Screwdriver :
When viewed from the front, the tip of the screwdriver looks like a cross, but in high quality screwdrivers, the actual tip of the tool will be rounded. Tools with sharp, almost needle-like tips will not fit screws made in the West, so do not buy them unless you are working with screws that match their narrower profile.
High quality Phillips screws are almost always marked with a number engraved on the head, and this number denotes the size of the drive required. For general DIY purposes, the #2 Phillips drive is the most commonly used, although this type of drive is available in sizes ranging from 1 to 4, with larger sizes available for industrial applications.
This is the oldest style of drive, and it is merely a slot cut across the full width of the screw. However, slotted screws are becoming increasingly rare, because it of the difficulty in tightening them to high torque values without damaging the head.
Slotted-head screws require a tool with a flat blade, and there are several sizes available to fit screws of different sizes; however, the angle of the tapered tip when viewed from the side is of critical importance, since this determines how well the tip will “grip” the sides of the slot. High quality tools have tips that are very near parallel towards the very tip to prevent the tip slipping out of the slot under high torque values.
Below is a table that indicates the width of the flat blade in relation to various sized slotted screws. It is very important to use the correct screwdriver with each size screw to avoid damaging the slot drive.
|Slot Size||Blade Width|
The Pozi-drive was developed by the Phillips Screw Company in collaboration with the American Screw Company to eliminate the tendency of normal Philips screwdrivers to “cam- out” of the drive because of the angles between the screwdriver and the screw.
In this drive, the angles in the drive is reduced, and the corresponding reduction of the angle on the screwdriver tip ensures improved contact between the drive and the tip. This greatly reduces the chances of the driver slipping out of the drive, which means that higher torque values can be applied to these screws without damaging the heads. The drive is also enhanced by four shallow radial lines between the main recesses to provide additional contact points.
Pozi-drives are not as common in America as they are in Europe and elsewhere, but where they are available, they come in sizes ranging from 1, to 3.
Robertson drive. (Square Recess)
Also known as the Robertson drive, after its Canadian inventor, the drive in these screws is a recessed square. Since there are no angles involved, it is almost impossible for a driver to slip out of the recess, which means that very high torque values can be applied. In fact, it is more likely that the screw will snap off before the square-shaped driver will slip out of the drive. The most common sizes are #2, and #3 drives, but some care must be taken not to use the #2 drive in a #3 screw, since this will damage the both the screw and the driver.
This drive is configured like a six-pointed star, but with the points rounded off. There are no angles involved, and the large contact area between the screw and its driver provides excellent contact, which means that these screws can be tightened to very high torque values.
However , the drives in these screws are relatively shallow, so some care must be taken that there is no dirt, or other solid material in the drive that can reduce the effective contact area between the drive and the driver. Torx drives are available both in internal and external drives, and corresponding drivers are available in sizes that range from T1, to T100.
Hex drives have six even straight sides, hence the name, hexagon drive. However, most hex drive fasteners are bolts, rather than screws, but there are nevertheless screwdrivers available to drive them. The most common use for hex fasteners is in the assembly of furniture, but using a T-handled Allen wrench is often the better choice when working with these screws because it provides for the application of higher torque values than is possible with a narrow-handled “screwdriver.”
Other, less common screw drives.
Some manufacturers of consumer goods have developed special screw drives that make it almost impossible to disassemble their products. This is mainly to prevent tampering with electronic devices that carry heavy electrical currents, but also to ensure that products are not tampered with, in order to ensure the reliability and proper working of the product. Below are two examples of (almost) tamper-proof screws.
This is a similar drive to the Phillips drive, but instead of four recesses that form a cross, this drive has only three, which makes it almost impossible to remove such a screw without the correct driver. While Tri-Wing drivers are available, they are expensive, and not easy to find. Nonetheless, Tri-Wing screws can be tightened to very high torque values, and they come in sizes that range from 1, to 3.
This type of screw drive that is not in common use outside of the electronics industry, consists of two “eyes”, or recesses at the edge of the screw head. The corresponding driver has two “prongs”, much like a pitch-fork, that engages the recesses to provide a means of turning the screw. The fact that no other screwdriver or tool can be used to turn these screws makes them tamper-proof, and they are available in sizes from #4, to #12.
Common Screwdrivers Types and their applications.
Below is a table that lists the most common types of screws and screwdrivers, and the uses to which they are most commonly put.
|Type of Drive||Typical Applications|
|Phillips||Most commonly used in the manufacture of furniture, electronics, jewellery, and in carpentry.|
|Slotted||Previously used in almost all applications, the slotted drive is becoming increasingly rare in mass-produced goods.|
|Pozi-drive||Typically used on a wide range of products for the European market. Pozi-drive is not common in the USA.|
|Square Recess||Typically used in the manufacture of furniture due to the efficiency of the drive.|
|Torx||Typically used in the electronics and automotive industries.|
|Hex||Typically used in the manufacture of furniture.|
|Tri – Wing||Some electronics manufacturers use this drive to prevent users tampering with their products.|
|Spanner||Typically used with electronics, doors for restrooms, and elevators.|
Screwdrivers Buying Guide
The quality of a screwdriver is arguably more closely related to its price than that of any other class of tools, which is why it is very important NOT to buy cheap, unknown brands. The most common problem with substandard screwdrivers is that the tips, regardless of the type, do not fit the drive of the screws properly.
Phillips screws are a good example; some manufacturers in Asia and the Far East make the cross-shaped drive in their screws narrower and deeper than similar screws made in the West, and while screwdrivers made to fit screws of Eastern manufacture work perfectly, the sharper profile of these screwdrivers mean that they do NOT work on screws made in the West , because they do not match the profile of the screw drive.
There are other examples, such as the fact that the tips of cheap screwdrivers are either too soft, or too brittle, which means that can (and do) they break under load, or deform to the point of uselessness before the screw is even loosened. In both cases the screw can be so damaged that it becomes almost impossible to extract it even with high quality tools.
So when you are shopping for screwdrivers, always look for reputable brands, and take along a sample of the screw(s) that you are going to be working with. Test the tip(s) of the screwdriver(s) against the drive(s) to ensure a proper fit, and do not purchase tools that do not match the drive in the screw perfectly.
Below is a short description of the various types of screws, and screwdrivers in common use today.