[R-390] Phillips screws and drivers [WAS: bracket]

[Charles Steinmetz]

gary wrote:

> I can only assume that, while the #1 can, as you noted, being careful, work on a #2 screw, a #2 screwdriver will not work with a #1 screw  *  *  *

Be very careful about identifying Phillips screws as to size.  There are 
precious few #1 Phillips screws in anything the size of a 390.  Almost 
all of the screws are #2.  And even "being careful," using a #1 driver 
is doing damage to them every time you use it.  There are even some #3 
screws in a 390 (the green module retainer screws come to mind).

This is a mistake North Americans are *VERY* prone to making.  Note that 
the shaft of a #2 driver is considerably larger (50% to 100%) than the 
heads of many (most) #2 screws.

Always try the #2 driver first, and only break out the #1 driver if the 
#2 driver just doesn't fit.

The "JIS B 1012" (Japanese) standard drivers are the most compatible 
with the three most common standards of Phillips-head screws (Phillips, 
Pozidrive, and JIS B 1012).  From Wiki:

"The JIS B 1012 is commonly found in Japanese made equipment  *  *  * 
Superficially it looks like a Phillips screw with narrower and more 
vertical slots, to give less tendency to cam out. The bottom of the 
recess is flat, and the point of the driver has to be blunt.  *  *  *  A 
correctly sized JIS driver will engage at full depth into a Phillips or 
Pozidriv head screw slightly loosely, but without damage. JIS heads are 
often identified by a single dot or an "X" to one side of the cross slot."

Note also that both hardware and driver manufacturers have made 
non-standard screws and drivers that to not conform to the international 
standards, in which case all bets are off. This is besides a whole raft 
of *other* (non-Phillips) cross-point screw standards (Reed & 
Prince/Frearson, Phillips II, Supadriv, etc., etc., etc.).

No doubt more than many wanted to know, but there are two take-home points:

[1]   When shopping for Phillips drivers, look for tools conforming to 
the JIS B 1012 standard ("JIS drivers," for short).

[2]  Always try the #2 driver first.  Looks are deceiving.

Best regards,

Charles