Screw heads: Phillips/Slotted vs ECX

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Stephen Tashi
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TL;DR
Why have ECX style screw heads become standard on electrical switches and receptacles?
(In the USA) recently purchased swtiches and receptacles are held to electric boxes with screws that don't work well with either Phillips or slotted screwdrivers. ( e.g. https://www.homedepot.com/p/Leviton...RCH=REC-_-pipsem-_-301447034-_-100026991-_-N& ) I understand this type of screw head is called "ECX". When did this type of screw become standard? - and why?

Electrical switches once came with screws that were a compromise between Phillips and slotted and did work with either type of screwdriver.

Although the ECX screws can be driven in a clumsy way with a Phillips or slotted bit, neither of those bit types really fits them.
 
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ECX does OK with phillips but also works with a square drive. The square drive works very well and I must admit is better than phillips IMHO. So get a few square bits (I think #2 is the one of choice...provbably 2mm)

Correction: apparently ECX is not the same as a combination., But I think a normal square bit will drive them. I do like the square better than phillips in general. Progress!
 
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My electrician friend that I occasionally help has half chewed my butt because I didn't have a square drive when working in a panel or making up connections. Yes we're still on good terms over it. Lol
 
From your image, the ECX head looks more akin to a Pozidriv head than to a Phillips head. Does a Pozidriv screwdriver fit it?

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As I recall, Phillips were introduced in the US for automated manufacturing - the driver was supposed to self align. In reality, the flanks of the driver are slightly tapered and the driver easily climbs out of the "slot", especially when using a manual driver. The flanks are quite thin. I curse whenever I buy something today which uses Phillips screw heads and I keep my Phillips drivers well separated from my Posidriv drivers so I don't use them by mistake.

Pozidriv was then introduced by GKN, a British company, to overcome this problem. The flanks of the driver are thicker and are not tapered - they are square to the faces in the "slot" making it much less likely that the driver climbs out of the slot and much less likely for the screw head to become mangled. Pozidriv screw heads have "tick marks" between the slots identifying them as different from Phillips. A Phillips driver will go into a Pozidrive slot of similar size and likley damage the slot. A Pozidriv driver's blades are too wide to enter a similarly sized Philips slot. They may be less common in the US.

Alternatively, is it a Phillips/square screw drive, also known as the Quadrex or Pozisquare?

I would be tempted to use a square drive - the slots look pretty poor.

Edit: I have just tripped across Screwdriver Bit Head Design – Effect of Phillips, Straight, and a Hybrid Design on Torque, Axial Force, and Effort Ratio

Edit 2: Posidriv corrected to Pozidriv
 
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Frodo said:
From your image, the ECX head looks more akin to a Posidriv head than to a Phillips head. Does a Posidriv screwdriver fit it?
In my extensive collection of screwdriver bits, I havn't found a bit that fits it. Whether any of my bits is officially a Posidrive, I don't know. (Phillips/square bits that fit deck screws don't work. I think ECX is a proprietary design made by the Milwaukee company and I haven't seen it for sale in local stores. ) I agree that, from photos of a Posidrive bit, that bit is a good candidate. However, if that's the answer, I find it strange that local hardware stores don't sell packs of Posidrive bits for power tools - because installing electric outlets and switches is such a common task.

When it comes to finding driver bits of various sorts, it's easy to find the interchangeable kind that rely on magnetism or shallow notches to hole them in tools. But these bits are inconvenient because they tend to stick in the heads of screws and pull out of the tool. The convenient type of bit has prounounced narrowing of the shaft that locks into mechanism of drivers. Packs of bits like this for T25 Torx and Phillips are easy to find in stores.

I would be tempted to use a square drive - the slots look pretty poor.
I tried a small square drive bit on the screws for receptacles and it worked a little better than a slotted bit or a Phillips. However, I couldn't find a square bit that worked with the similar shaped screwheads on a the bracket for a ceiling fan that I was installing last night.