That Phillips-head screw isn’t what you think it is

Here you can see the simple dot on the screw head that identifies this screw as JIS. Kyle Smith

The unsung hero of the automotive world is the threaded fastener. Most people only think about the bolts and screws of their machines when they have to, when the components are stripped, seized, or broken off. That dismissive attitude, however, may cause these components to strip, seize, or break in the first place.

For instance, if you are working on a classic motorcycle, you are probably using the wrong screwdriver—and are setting yourself up for disaster. Hear me out.

screwdriver drawer
All these screwdrivers—and none are the correct ones for my Honda project. Kyle Smith

Let’s talk a bit of history first. Screws were first created using files to grind threads into round stock. Like anything handmade, the process was laborious and the results were inconsistent. With the advent of machinery to roll threads rather than cut them, screws and bolts began to usurp nails in production environments. Threads may be the identifying mark of a screw, but the truly critical part is the design of the head, which determines the tool engagement that imparts torque to drive the fastener into the material (or nut).

Slotted screw heads were the easiest to manufacture, but inventor John P. Thompson thought that a crosshair-style engagement would be a better idea. He patented the idea in 1932 but, unfortunately, he was not a very good salesman. Thompson abandoned the venture and sold the patent to Henry Phillips, who formed the Phillips Screw Company and went about manufacturing and selling the hardware. In 1935 Phillips filed a patent application that modified the Thompson design slightly and tailored it for production lines, in which screw guns were becoming commonplace. The Phillips screw was born.

Phillips screw patent
U.S. Patent Office

That patent for a cruciform, or cross-shaped, screw head expired in 1966. Though the style became generic, the Phillips-head design never lost its uniquely American roots. The cross-haired head was created for ease of assembly and was always intended for production environments, in which efficiency was key. Making a Phillips head requires only two cuts with a tool. The finished head has a rounded profile and tends to “cam out” when high torque is applied to it; Phillips-head screws worked perfectly with screw guns because the fastener was “foolproof.”

However, some countries saw the “speed over accuracy” American production style as crude. Rather than engineer a fastener to avoid over-tightening, the Japanese wanted to shift responsibility for precision from the mechanical component to the craftsman.

This concept brought about a redesign of the Phillips screw, commonly known as the Japanese Industrial Standard (or JIS). This type of screw head looks very similar to a Phillips, with the exception of a single, tiny dot. JIS fasteners may look a lot like a Phillips-head, but the tool engagement is far superior—if you are using the correct tool.

jis and phillips tool drawing

For years, I piddled with project motorcycles in my parents’ driveway or in a storage unit across from my college dorm, often getting frustrated by the screws securing items like engine case covers. The problem wasn’t my technique. It was my tools. I was attacking these JIS fasteners with my Phillips screwdriver out of ignorance. Yes, a #3 Phillips fits pretty good in a JIS 3 head, but once you start applying torque—especially to a screw that is properly stuck—you are far more likely to strip the fastener than if you were using a JIS driver.

Once I realized the error of my ways, I found that JIS screwdrivers were worth every penny. They saved me countless moments of frustration. I am a fan of buying high-quality screwdrivers and keeping them nice: I have a set of screwdrivers that are exclusively for carburetor service, plus a general set for all other tasks. You may think I’m crazy for having redundant tools, but strip out one carb jet because you’re using a worn-out screwdriver, and you’ll change your tune. I’m similarly obsessed with JIS screwdrivers and bit tips in the garage. If you play with vintage Japanese motorcycles, you should be too.

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