The Difference Between Phillips And JIS Head Screws

Do you own a Japanese motorcycle or any bike fitted with Japanese hardware? Then you are likely using the wrong tool for the job of tightening cross-type screws. Today on MC Garage we are going to talk about JIS screws and screwdrivers.

Ever notice how easy it is to round off or damage the cross-type screws on your motorcycle? Notice I didn’t say Phillips—that’s because chances are those screws are JIS screws. Have you been using the wrong screwdriver on your motorcycle?

JIS stands for Japanese Industrial Standard, and while similar to Phillips, the shape is slightly different. It was designed to behave differently than a Phillips when sufficient torque is reached. A Phillips is engineered to “cam out” once the screw is tight, whereas JIS is locked in and the torque setting is up to the user. It all comes down to the shape of the screw and bit.

With the naked eye it’s tough to tell the difference between the two. But if you look really close, you can see that a JIS bit has much tighter radius at its cross section; it’s nearly perpendicular. The JIS is also shallower, and the Phillips has more of a point.

This is a JIS Megadora Impacta P2X100 screwdriver from Vessel Tools. It is really the only one you need in the toolbox for the most part, as it's the most common size. It is basically the equivalent to a #2 Phillips. This one is cool because it is also serves as an impact driver to loosen stubborn screws. Inside the handle is a mechanism, so each time you hit it with a hammer, it turns the screw 12 degrees to the left. There are more sizes and styles out there and a parts and tool company like Sudco usually has these in stock.

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What happens if you put a Phillips in a JIS screw? It won’t bottom out and also won’t grip the cross securely. Since Phillips is designed to cam out, you can imagine what happens on a JIS screw, especially if it is secured tightly. You get rounded off screw heads. Not fun.

So how do you know if the screw is Phillips or JIS? Super simple—just look at the head. A JIS screw will have a little dot on it. The neat part? A JIS bit will work just fine in a Phillips head screw.

For me this is a required tool for any motorcycle toolbox. At around $12 to $15, it’s cheap insurance that you won’t have to struggle with screwed-up fasteners. See what I did there?