Monday, June 26, 2017 Detailed Auto Topics
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The cross-headed type screw is everywhere. They replaced slotted screws, in all automotive applications. Many people are frustrated trying to tighten or loosen them. Stripped heads, and gouged work and sore fingers abound. The key is in knowing, that a Phillips screw driver may be the wrong tool.

Cruciform-screws have the familiar "+" shaped recess in the head. While many people call these Phillips' screws, that is only partially correct. Several designs exist, and each has a unique driver.

History

J.P. Thompson invented the actual Phillips screw. Henry F. Phillips bought the idea, refined and patented it in 1936. Originally, they designed the recessed cross-drive for automated driving machines. The advantage was a self-centering screw, which would "cam out" or slip, before it was over tightened. This was a big plus in preventing screw and tool damage on an assembly line.

In 1939, Cadillac is the first major vehicle builder to adapt the new technology. By 1940, the industry assembles virtually every U.S. car with the Phillips screw. A huge exportation of U.S. goods, during World War II, spread these screws all over the world. Phillips became synonymous with the cruciform design.

Many similar designs have evolved over the years, and not all are compatible. Worse, they are very hard to distinguish. They have ceased using most designs or they never found their way into automotive use. Two notable exceptions exist, and these create most of the problems.

Three screws, using cross-drive, are in common use.

Three common screw types in automotive use

The Phillips screw is widely used on domestic vehicles. The familiar cross shaped recess and no other marking are the way we identify these. Asian vehicles, often use a JIS or Japanese Industrial Standard screw. These are very similar in appearance, and a small dimple near the drive opening is the clue. European vehicles often use a third design. They call this screw a Pozidriv, sometimes misspelled as Pozidrive. Four hash-marks, one at each of the four corners of the cross, identify this system.

The Japanese Industrial Standard

JIS and Phillips screwdriver comparison

The JIS screw driver will work with a Phillips screw, as both share common 57 degree points. A Phillips driver will not work on the JIS and will round the head out, without removing the screw. This is because of the flutes, machined into the Phillips design. Tool makers do not design the JIS to cam-out when tightened and it is not compatible with Phillips.

Though close in design, these screwdrivers do not interchange

Looking closely, telling the designs apart is hard. They invented the Phillips screw to slip out of the drive before damage occurs. Machines angle the flutes along the drive blades, when they build it. The Japanese do not make the JIS to slip, as automated torque-limiting drivers were common by the time they invented it.

Most people in the U.S. and many technicians are not aware of the difference. Folks who do not know may falsely accuse screwdrivers of being worn out. Selecting the wrong driver will damage the fastener. Anyone working with Asian vehicles, should have a set of JIS screwdrivers available. An owner of such a vehicle might wish to ask their shop about this. Knowledge of this standard is an indication of the commitment to quality of the service facility.

European Pozidriv fasteners

small hash marks identify the Pozidriv, on the right

The Pozidriv screw is most common with European vehicles. The small hash marks, at each corner of the cross, identifies this design. Producers machine a small square into the opening, when they build the fastener. This prevents the cam out of the screw, when tightened. A Phillips screw driver will work with this type, but the Pozidriv tool will not work with a Phillips screw.

To prevent problems, watch for the small signs and multiple designs. Using the right tool is the key every time.





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