Were Phillips screwdrivers designed to "cam-out"?

There has long been a popular belief that this was actually a deliberate feature of the design, for the purpose of assembling aluminum aircraft without overtightening the fasteners.

The section in the patent update that talks about it isn’t as clear as wikipedia makes it out to be, either.

It’s more of a “hey, isn’t it neat that they cam out?”

PSA for some scenarios is that if you’re having major issues with cam out/stripping, you may not even be working with a Phillips head screw. A lot of Japanese equipment uses JIS screws, and a Phillips screwdriver can make an absolute mess of them (learned that on an old trail 90).

Pozidriv is another variation that will cause issues. You see a lot of them in higher torque applications, ski bindings being the ones I’m most familiar with.


phillips is just horrible…
when we get rid of the wuhan, phillips should go to

I’ll second that. They suck. Torx head screws with a torque limiting driver is the way to go.


That’s what I was thinking after poking around a bit on Wikipedia.

It’s not neat. Torx or star drive is the way to go. Just finished setting/replacing/repairing a few fence posts and panels… If camming out on purpose is true, a shitty idea for the general public. Only phillips head screws I buy are for drywall. Best tool in my box is a cordless 1/4 drive Dewalt impact driver, drives 3 1/2" star drive coated screws into treated wood with ease. The tan screws with the cutting tip, no predrill.


Anybody run into JSA standard phillips head screws. They are guaranteed to round out if you use a standard SAE screw driver. If you ever wondered why mostly electronics components you can never find a screwdriver that fits this is it.

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Back in the 70’s I bought a CL90 while in Yokohama. Learned the hard way. But not a big deal as long as you grind the tip off the Phillips driver.

From “One Good Turn - A natural history of the screwdriver and the screw” by Witold Rybczynski.


In all the years I’ve used them I never knew I was using a Robertson screw

If I come across a phillips screw I usually bin it and replace it with pozidriv, interesting video about screws:

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Interesting and informational, left out star drive though. Must buy good quality bits.

Torx (“star drive”) screws are indeed great, and most of the high-end electronic manufacturers I deal with are going to them. The trick is to use a driver with settable torque so you don’t break 'em going in and can properly deal with an overtightened one coming out. Pozi-drive is the best of the “phillips” varieties in my experience, but Torx is better.
You DO have to know when to heave out a bit that’s worn out, though - they don’t last forever!

Seems like a rather obscure subject to have that particular book on your shelf. Is it just coincidence, did you just pull it from the “fasteners” section of your library?


Answering the original question, it doesn’t seem the Phillips system was designed to cam out. If it was, why wasn’t it noted in the patent application?

After using all the above mentioned screw systems ( and also Reed & Prince) my vote goes to the square-drive/Robertson screw as the best. Why these haven’t supplanted all other screw systems I have no idea.

I first saw them used for marine carpentry back in the 1980s. Simplicity itself: the drive is square. Another great thing about them: the screw will stay on the bit when held at the horizontal, or even a few degrees down-inclination. Which other system does this reliably? Which is why marine carpenters loved square-drives. They just put a self-drilling screw on the bit in a cordless drill motor and “shot it” it into bulkheads quickly. A time saver.

But instead torx has taken over the segment of the market that square drive should have occupied. A mystery to me.

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Robertson screws were invented by a Canadian which explains their popularity in that country. I think both Robertson and Torx screws are superior to all others and a matter of personal choice depending on the project.

Torx VS Robertson.

From my library. For some reason I own two copies too. There was a time many moons ago when the thought occurred to me that most of my adult life was spent to varying degrees locked in a struggle with the mighty screw thread. Finding out more about the beast seemed a good idea at the time. Highly recommended for coverage of the development of machine tools - think Maudslay, Brunel, Whitworth etc. - the notion of precision, the Antikythera Mechanism and other interesting tidbits.


Robertson and torx are great screws in the right hands, but I think that Philips and Pozidriv are the most popular because you don’t need as many different sized screw drivers for them compared to torx and robertson. A lot of consumers are lazy and just want whatever screwdriver they have to fit.

Also that video I posted mentions that roberston screws aren’t very self-centering in wood, I think it is the same for torx, that is because the end of the screw drivers are flat. Phillpis and Pozidriv have pointed screw drivers so there is more self-centering of the screws into wood, they are less likely to starting going in squint if you are working quickly and carelessly. You can also get a large amount of torque with a pozidriv as it has 8 points of contact versus 4 points of contact with a Robertson.

I would prefer that Torx or Pozi-drive had become the most common before Phillips. I’ve done a lot of work on yachts, and Phillips has been the norm, except for Hatteras. Oddly, my co-workers and I grumbled whenever we ran across Pozi, because none of us had a stock of screws to replace missing, broken, or damaged fasteners. We didn’t normally have drivers for them, either.
The sound of Phillips drivers camming out and ruining the head was common and referred to as “theft-proofing” the fastener :face_with_raised_eyebrow:
I do have a nice selection of specialty tools to remove damaged screws, though.
My favorite:

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