Making JIS screw bits

The JIS screws festooning these motorcycles are often mutilated by the previous owners use of the Phillips screwdrivers. Many then replace the screws with allan head sockets after destruction during removal.

Instead of sourcing the original Japanese Industrial Standard driver the modification to make your own is illustrated.

The photo shows the result.

A standard Phillips should have the angles modified to 57 degrees from horizontal. The point that results is then flattened.

Compare the impression mould of the JIS screw for guidance.

Thanks for that info. I have a set of JIS drivers but always wanted one I could tap with a hammer without fear or breaking the handle. Now I'm I gonna modify a phillips with a straight through shank.

Molded impression of a JIS screw head (white) versus the Phillips (PH2) bit commonly found in the tool box on a US penny for size

At the top of the thread is a profile measurement of 57 degrees derived from my plastic mold of a JIS screw.

The following drawing indicates it should be 64 degrees. I presume this drawing is correct.


Also note the screw bit would provide maximum torque to the screw if the wings are fully engaged at the periphery. The slender Philips profile fails.

JIS bit ground for an impact driver