Ascot Forum
'Round The Campfire => General Technical => Topic started by: J6G1Z on November 01, 2013, 01:39:44 pm
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Ever wonder why those Phillips headed screws were so hard to remove without stripping out the head?
Turns out that they are not really a Phillips head screw to begin with. They are what is known as a J.I.S. headed screw, or Japanese Industrial Standard head screws. A J.I.S. screw driver will fit both a JIS screw head or a Phillips head screw, but not the other way around. Here is a bit of information that I found on an eBay listing.
The Phillips is an American design created and patented by Henry Phillips in 1936. It went onto the production floor first at the Cadillac factory in 1940. One of the attributes that Cadillac engineers liked about the design is that the driver would "cam-out" after a certain torque was reached and not allow over-tightening of the screw. The design offered other advantages like self-centering and the tool, screw engagement was quick, with never more than 90 degrees of rotation needed before the tool started working.
Japanese engineers developed their own cross-point design, but did not view this "cam-out" feature as an advantage. They wanted the benefits of self-centering and quick tool, screw engagement that the cross-point design offered, but torque and over-tightening would be addressed at the operator or tool level, not at the screw tip.
After learning this, I bought a set of JIS drivers & impact bits. Here are the listings for them in case you want to stock up your tool box also.
JIS Impact Bits: http://www.ebay.com/itm/380748854776?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_2077wt_919
JIS Screw Drivers: http://www.ebay.com/itm/181199638855?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649#ht_212wt_1141
Good luck on breaking loose those screws now that you know the difference.
J.
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Quite right, I have a proper factory screwdriver ( t handle) which is invaluable, a crack on the end with a hammer often frees a screw without needing the use of an impact driver, years ago I saw a technician from Honda Japan doing that. I also have some screwdriver shafts from genuine tool kits, on which the wider one is right for these screws. Not that my bikes have many, because most had the 8mm headed bolts fitted from the factory but there are odd cross head screws in some areas.