So You're Telling Me That's Not a Phillips?

Dear Phillip,

Wherever did you hear such a thing? Perhaps you were reading the comments after “ Church of MO” two Sundays ago, in response to Gabe Ets-Hokin’s tortured tales of working on his old Honda? It is rather hard to believe, as one commenter mentioned, that after all these years of mangling Phillips screws on Japanese bikes, more people (many of them professional mechanics) don’t know about JIS screwdrivers – Japanese Industry Standard.

Looking at a JIS tool next to a regular Phillips screwdriver, most people are hard-pressed to tell the differences, but they are definitely there. Ninety-percent of the time, a regular Phillips will work on a JIS screw; but it’s that other 10% that gets us swearing, then throwing things – those tight screws holding on your carburetor float bowls being particularly devilish once they’re past about two decades of non-removal. That’s when the right tool can make all the difference. The right tool is a JIS screwdriver, which just fits better in a JIS screwhead and is designed to let you apply more torque than a Phillips driver.

At Instructables.com, we learn: The Phillips system was invented for use in assembling aluminum aircraft, with the object of preventing assemblers from tightening screws so tightly that the aluminum threads strip. The driver will “cam out” before that happens. The Phillips driver has four simple slots cut out of it, each slot is the result of two machining processes at right angles. The result of this process is that the arms of the cross are tapered and has slightly rounded corners in the tool recess. Phillips is designed so that when excess torque is applied it will cam out rather than ream the recess and destroy the bit.

Japanese Industry Standard: Often improperly referred to as Japanese Phillips. Commonly found in Japanese equipment, JIS looks much like a Phillips screw (and even more similar to Frearson), but is designed not to cam out and will, therefore, be damaged by a Phillips screwdriver if it is too tight. Heads are usually identifiable by a single raised dot to one side of the cross slot.

Most people and companies outside of Japan have absolutely no idea what they are. With the similarity in appearance to the Frearson and the Phillips the screws are often damaged in removing and installing with the wrong tools. JIS tends not to cam out like Phillips. The JIS driver can be used on Phillips quite easily but not reciprically (sic). Drivers are not easily available in North America, try your local RC Airplane hobby shop. Most RC Helicopters use JIS screws to mount the propeller. JIS-spec cross-head screws are generally marked with a single raised dot or an “X”. JIS always fit Phillip fasteners, but because of slight design differences, Phillips drivers may not fit JIS fasteners. (unless the tip is ground down a bit).

The JIS is not a miracle tool for really stuck fasteners on old Japanese bikes, but it can make a huge difference. Luckily, most manufacturers have seen the light in the form of the hex-head fastener and the Torx, and while they can also present problems, they’re nothing like as frustrating as trying to remove a stubborn Phillips-head screw with not-quite the right tool.

Send your moto-related questions to AskMOAnything@motorcycle.com. If we can’t answer them, we’ll at least make you feel temporarily better by thinking you’re talking to somebody who cares even if we don’t. And remember, only the Pope is infallible. But we probably know more about motorcycles.

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