It’s happened to a lot of us. If you’ve ever bought a secondhand bike, then you may be extremely familiar with the pain of finding screws with heads so chewed up, you have to resort to means other than a screwdriver to get them out. What kind of screws were they before they got so damaged? Sometimes, the damage is so bad, you can’t even tell from a visual inspection.
If you’re working on a Japanese bike—or Japanese carburetors, or other parts made in Japan—then chances are excellent that the poor, obliterated screw that’s giving you a massive headache is a Japanese Industrial Standard (JIS) screw. “Wait, there are more than flathead and Phillips screws?” I hear you asking. Yes, there are—and getting your hands on a JIS screwdriver or two (they come in different sizes, just like Phillips) can save you a lot of difficulty on a many DIY projects, not just motorcycles.
See, way back at the beginning of the 20th century, plenty of hands-on people saw the inherent flaws in flathead screws. After all, your screwdriver can slide right out of them so easily that they can be a pain to loosen, or to tighten as much as you want. There had to be a better way, didn’t there?
Unsurprisingly, different people in different regions of the world came up with multiple solutions to the same problem, each involving a cross point designed to keep the tip of the screwdriver seated more securely in the head of the screw. However, each of these cross-point designs varies slightly—and also results in different behavior when you insert the screwdriver and begin twisting and/or applying pressure.
How The Phillips Standard Developed
1933 Thompson screw patent
1936 Phillips screwdriver patent
In 1932, an inventor by the name of John P. Thompson first applied for a patent on his latest creation, a cross-point screw design. In 1933, the US Patent and Trademark Office approved his application. The text of the patent describes the aperture in the top of the screw in detail, as well as variances that may be made as practicality for a specific application dictates. Together with Henry F. Phillips, the duo subesequently formed the Phillips Screw Company, which then went on to bring this screw design into mass production.
In 1935, Phillips and co-inventor Thomas M. Fitzpatrick filed a patent application with the USPTO for a screwdriver to be used with the cruciform screws first envisioned and elaborated upon by John P. Thompson. That patent was granted in 1936, and the standard went on to become common in the US. However, one common issue with Phillips screws is that they were designed to cam out to avoid overtorquing.
JIS and Pozidriv: Two Different Cross-Point Standards
In the late 1950s and early 1960s, inventors in Japan and the United Kingdom both came up with ideas to improve upon the perceived weaknesses of the Phillips standard. In Japan’s case, the Japanese Industrial Standard evolved. To the naked eye, the screw heads (and screwdriver tips) look very similar.
However, as you can see from the diagram, there are significant differences that allow the JIS driver to fit more snugly into the screw. The video above also illustrates this effect quite dramatically. If you’ve used a JIS screwdriver, then you’ve already felt how much more securely it fits into screws, allowing very little play and giving a much surer feel to any loosening or tightening you may attempt.
The subtle shape differences between JIS and Phillips allow greater precision when using JIS screws and JIS screwdrivers. However, since Phillips drivers do not fit deeply enough into JIS screws to completely engage them, it makes them much easier to inadvertently strip out—thus resulting in a whole lot of swearing and sadness when the next person (or maybe even you, later down the line) goes to remedy the issue.
Over in the UK, GK Screws and Fasteners came up with yet another cross-point design that they called Pozidriv. However, it at least does DIY folks the favor of instantly being recognizable as something different than a Phillips screw. Pozidriv also has a cross-point as the main design, but then it adds what appears to be an X that lines up directly with the center of that cross-point. A later standard evolved from this as well, which is called Supadriv. Both those standards frequently show up on European hardware (and the drivers for both are interchangeable) but are not nearly as prevalent in the motorcycle world as JIS.
Gallery: Ask RideApart: What's A JIS Screw And Why Should You Care About It?
If you’re going to work on motorcycles that are either Japanese or have Japanese parts, do yourself and the next owner a favor and get yourself some JIS screwdrivers. Your wrenching life will be much easier, and did we also mention that they can be used on Phillips head screws, as well?
Of course, JIS screwdrivers can come in handy for much more than just motorcycles. Electronics, cars, bicycles, and plenty of other equipment made in Japan will be much easier to work on with the right tool in your hand. Since most DIY motorcycle enthusiasts tend to be DIY about other things as well, that’s just another reason why these tools belong in your toolbox.
In 2023, a number of companies offer JIS screwdrivers at varying price points. The set you can see in these photos is made by the Japanese company Vessel, which is the oldest manual screwdriver maker in the country. (As a side note, I’ll mention here that these are drivers I purchased with my own money, and that this post is not sponsored in any way.) They have magnetic tips and are probably some of the nicest hand tools currently in our garage.
That said, you don’t need the fanciest JIS screwdrivers to get the job done right—you just need to make sure they’re both JIS and halfway decent, like you probably expect from any hand tool you use. Find a decent JIS screwdriver (or set) that works with your budget, and happy wrenching.