A reader recently discussed how Phillips screws and drivers were designed to cam-out, and they called this a myth. Is it? Let’s find out.
If you’re looking for the short answer, patents for the original inventions describe how Phillips screws and drivers were designed to resist cam out.
There are several US patents related to Phillips screws and drivers. For the sake of this discussion, let’s look at patent US2046837A, which details the invention of Henry F Phillips regarding “Means for Uniting a Screw with a Driver.”
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One of the highlights is the “firm wedging engagement between the bit and the recess when the two are brought together.”
The results of such a union are obviously highly advantageous in presenting screws to be driven, either by hand or by power-driven types of tool, to work to be dealt with, especially in places difficult to approach, that is to say, in places where neither hand of the operator can be placed.
They specifically discuss the benefit over slotted screws.
In applying screws of the slotted type to work in any location, both hands of the operator must be applied, one to guide the screw, and then to stabilize the screw during its advancement, and then to further stabilize the driver in a central position with respect to the screw.
The shortcomings of slotted screws and drivers are further emphasized.
Such failure of the slotted screw to retain the blade-driver, especially in power driven operations, is not only dangerous to the operator, but is likewise, always injurious to the work, especially in the construction of furniture and other types of work wherein the elements to which the screws are being applied become badly mutilated when the power driver leaves the slot, usually during high speed operation of the driver which is most difficult to stop in time to prevent injury to the work.
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From a lot of this language, “firm wedging engagement” and retention are a specific benefit.
“Camming” action is referenced in this patent, with emphasis my own.
Another object of the invention is the particular angular formation of the walls of the recess in the screw with respect to the angular formation of the working end or bit of the driver to establish a wedging engagement between the two when united.
This same angular formation of both elements is especially designed to also create what might be termed a camming action during the approach of these angular faces toward one another with respect to any substances which might have become lodged within the recess of the screw.
It has been found by experiment that a downward thrust of the bit into the recess will instantly dislodge any substance within the recess by causing it to move upwardly and outwardly over the walls of the recess.
Interesting – camming action is referenced with respect to substances that might have become lodged within the recess of the screw.
There are additional references to fastener engagement.
Still another object of the invention is the provision of angular faces in such relation to each other that the wedging engagement may be obtained by the mere gravitation of the driver and the operators hand applied to it.
The angular faces, in other words, are so related to each other that even a slight downward thrust of the driver into the recess will cause a firm wedged engagement between the two elements.
Apparently, the Phillips screw recess was also designed to accommodate slotted screwdrivers.
I also wish to point out that my invention provides means in the grooves which are diametrically opposed, to receive the ordinary flat blade-driver such as is now commonly known and used.
This particular feature enhances the utility of the screw by reason of the fact that any blade-driver may also be used to actuate the screw.
Basically, it sounds like the Phillips screw recess was designed to be backwards-compatible with slotted screwdrivers.
A still further object of the invention accomplished by this specific angular relation between the driver and the screw is that only two sizes of my improved form of driver are needed to fit all types of screws in sizes ranging from number 5 to 16 inclusive, instead of six or more sizes of the slotted drivers required to fit the same range of sizes of slotted screws.
That’s also interesting – Phillips sought to replace 6 slotted screwdriver sizes with just 2.
Moreover, by reason of the perfect fit between the driver and the screw, the screws may be driven and removed innumerable times without the slightest indication of mutilation to the head.
This highly desirable feature is made possible by the firm contact of all the angular faces of the driver into the corresponding angular faces of the recess formed at many different equidistant points around the longitudinal center line of both the screw and the driver.
Thus, is provided many times as much gripping area as is provided in the slotted screw. This obviously, gives greatly increased strength and torsion with the result that my screws can be driven into material which slotted-head screws could not be made to penetrate.
The screws were designed for installation, removal, and reuse.
There’s more talk about “camming out,” with emphasis my own.
In other words, space is provided around all points of the bit for further advancement thereof into the recess to accomplish an even greater degree of wedged engagement between the bit and the recess.
Moreover, this slightly spaced relation permits of a camming out or crowding out of any substances which might become lodged in the recess without disturbing the predetermined relation of the driver and screw.
The downward thrust of the converging angular faces of the bit toward the diverging faces of the recess will cause the substances within the recess to be crowded upwardly and outwardly over the inclined walls of the recess.
Hmm. They refer to “camming out” as something that happens to debris or other substances that might be within the recess of a screw head.
“Camming out,” in the context of this patent is used to describe how the “wedged engagement” between the screwdriver and screw ejects “substances which might become lodged in the recess.”
The patent does reference benefits for hand or power driver applications.
My new and improved form of screw especially designed and adapted for co-operative use with the driver…
There could be other patents detailing driver-screw slip or “camming out” in the way most people have been led to believe.
But as this patent describes the “new and improved form of [Phillips] screw” and accompanying Phillips head screwdriver, I’m not sure how much deeper we should look.
This specific patent details the benefits and advantages of Phillips head screws, most significantly the wedged engagement.
Such failure of the slotted screw to retain the blade-driver, especially in power driven operations…
There’s nothing about intentional disengagement, aside for this being a downside of slotted screws, especially in power driver applications, that the new screw type improves upon.
The same patent also includes modified forms of the Phillips screw, with 2, 3, and 5 pronged recesses.
Another patent concerning just the screw – no. US2046343A – discusses other benefits.
Another object of the invention is the provision of such grooves and side walls for the purpose of affording maximum bearing surfaces for a driver of corresponding configuration, and also to provide means for self-centering said driver with respect to the screw, this same means also acting as a positive lock and stabilizer between the screw and driver during all driving operations and under any load conditions imposed upon the screw either by a hand driver or by the power driven type of driver.
Maximum bearing surfaces, self-centering, positive lock and stabilizer. There’s no mention of camming-out in the context of disengagement.
What about a patent concerning Phillips screwdrivers – no. US2046840A?
Moreover, the new and novel construction of our tool produces a screw driver having substantial core portion with equally strong radiating vanes or gripping surfaces for engagement with the grooved portions of the recess in the screw head.
Thus we provide a tool of maximum strength and at the same time one which when used as a punch, forms a punched recess in a most efficient manner, by permitting the proper flow and distribution of the metal without causing any of the disadvantages as above pointed out in reference to other types of punches, broaches and the like.
“When used as a punch…”
They also reference how the opposite end of the shank “may be formed into a suitable shape to provide gripping means for operative engagement with a power driven tool” or “adapted for engagement with punching machinery when the tool is to be used as a punch.”
I’m not seeing anything about Phillips screws and drivers being designed for slip-style disengagement.
That is, based on an examination of the earliest US Patents that discuss the intended benefits of the Phillips screw and driver inventions, “camming out” – where the driver tip slips out of the fastener – was NOT a deliberate feature.
In fact, reduced cam out, at least compared to slotted screwdrivers, was one of the claimed benefits.
Let’s look at one more Patent, no. US2046839A, with emphasis my own:
As pointed out in said prior application, one of the principal objects of the invention is the provision of a recess in the head of a screw which is particularly adapted for firm engagement with a correspondingly shaped driving tool or screw driver, and in such a way that there will be no tendency of the driver to cam out of the recess when united in operative engagement with each other.
That seems definitive.
It turns out, that the popular belief, that Phillips screws were designed for cam out-type disengagement, is not factual.
Thus, Phillips screws were designed to resist cam-out.
See Patent US2046837A via Google
See Patent US2046839A via Google
Andrew
Hopefully this bubbles to the top of the internet, and pops the ‘designed to cam out’ myth.
Thanks for digging into it 😉
Stuart
It’s still possible, but every original patent I looked at thus far directly contradicts the popular belief.
Thanks for bringing it up!!
D Collins
The original patents and original intent, yes.
I thought there are a couple follow ups to the patents where it was *later* listed as a feature.
“It’s not a bug, it’s a feature!”
It’s been a while since I paid that much attention though.
Stuart
I couldn’t easily find any patents where it’s listed as a feature or benefit.
Also keep in mind that Phillips screws were designed to be more secure in a time when slotted screws were standard. Powered drivers were also very large, heavy, and slow compared to modern tools.
D Collins
You are right, it wasn’t Phillips, it was someone else talking about it.
US 2474994, Tomalis, Joseph J., “Screw Socket”, issued 1949-07-05, assigned to American Screw Company
Sal
Yes, slotted screwdrivers, then phillips screwdrivers, now torx screwdrivers. There were also square ones. The ones that I’ve found to be the best are torx. Or “star” screws and drivers. Great material contact and next to no slippage.
Franck
Thank God for P.L. Robertson screw and manufacturing process. Another great canadian invention 😉
Bonnie
Truth. I always reach for robertson over phillips or torx (except for large lag fasteners) and stock my shop even down here in the states with robertson.
Goodie
I’m south of Canada, and reach for my Robbies first. They and the DeHavilland Canada aircraft are on my list of favorite Canadian originated products. Glad to have Canada as neighbors.
Marvin L McConoughey
Concur. We in the United State ae fortunate to have Canada as our northern neighbors. I hope that we will always treat Canada and Canadians with all the respect that they merit.
Amatts
Popular belief well because every screw butcher with a cordless drill that is too stupid to use the clutch duh
Frank D
Popular belief? Since when? Where? How?
Because one person said it on the internet???
Stuart
Everyone on and off the internet.
S
It’s always been my understanding that it’s nature to resist over-tightening and camming out at full torque was a major reason Henry Ford introduced them on his then-newfangled assembly line process.
Articles I recall about it specifically discussed how it prevented fastener over tightening, or damage to the work surface, which ultimately led to increased production times, with more consistent end products, and cemented the Phillips screw as the new standard in fasteners in america of the time.
Grokew
Then there are other articles that talk about how P.L. Robertson and Henry Ford had a disagreement, so Ford went with the Phillips screws and drivers.
J . Newell
Whether or not the driver cams out depends a lot on the pressure (downward force) applied to the driver and the amount of torque applied.
Stuart’s research is brilliant (and very interesting reading) but the wedge-shaped blades will cam out unless the necessary amount of force is applied axially to the driver.
A W
Thanks for looking into it. I have certainly heard the urban legend that came out was a design feature.
Jared
Me too.
Plus I like this kind of content. Maybe Stuart can do a Phillips vs JIS article next and settle the debate of whether modern Phillips negates the distinction.
Or explain why Americans use Torx on their deck screws instead of Robertson like God intended.
Bonnie
I’ll second that. I’m a sucker for patent research and history.
Saulac
Did I miss the mentioning of JIS slot screws with less pointed head and there for less come out?
Assume come out is not desirable, at least in most cases, then the only reason for “non-pointed” heads such as Torx and hex not more popular is due to cost? How harder to stamp those head?
MM
I think this might explain where the misunderstanding comes from. The Phillips drive isn’t intended to cam out, though it can and does if the torque goes high enough. Other later screw drive designs were designed to have less potential to cam out. It’s easy for someone to misunderstand statments like “JIS is designed to better resist camout than Philips” as “JIS is designed not to camout while Philips is”. In other words, it is the comparison between Phillips and later designs like JIS (for example) that made people think that.
Bonnie
This. Also the timeline of all these different designs being both created, and becoming popular, which may not even happen in the same decade.
Nathan
It’s a long running mechanic myth.
I always heard the primary purposed for making them was easier machine installs. Or assembly line. While also being backwards compatible
fred
Thanks Andrew and Stuart for helping to set the record straight
Hard to dispel what you have made clear is a myth.
It is easier to follow the advice given in the movies (The Man who Shot Liberty Valance) – “When the legend becomes fact, print the legend”
And no lesser authority than Google helps promote it. Once again it goes to show us something about both the benefits and foibles of the Internet. Here is what’s said on Wikipedia:
https://en.wikipedia.org/wiki/Cam_out
John
I love this! Maybe next you could do the myth that there’s a difference between square drive and robertson?
fred
But there is a difference! Just like the difference between “star” and Torx.
The difference in naming can be traced back, not to any change in geometry, but more to avoiding trademark infringement. The name “Phillips” is trademarked as well – but perhaps has become so synonymous with the style that trademark infringement lawsuits don’t threaten copycats. BTW the Phillips Screw Co. also owns the trademarks for POZIDRIV, TORQ-SET, TRI-WING, ACR, MORTORQ, AND DECKMATE.
J . Newell
Robertson missed a huge opportunity! If he had thought differently about the relative benefits of licensing vs. retaining exclusive rights, his name might be a household word south of the 49th parallel. 🙂
Bonnie
Unless this is also a myth, he’d been badly burned by a very similar deal to the one Ford offered, and was not unreasonably unwilling to license out his design to another new manufacturer with the capacity to (pun intended) screw him over.
MT_Noob
Great research. Thanks for digging into the facts.
The next myth that needs busting is the one about “locking” a keyless chuck by tightening it and then loosening it one click.
S
I have not heard of that one.
I’m curious of the core principle of the idea. Are they saying that loosening one click somehow digs the jaws deeper into the bit, same as tightening it another few clicks?
I can’t say I’ve ever had an issue with any chuck loosening, but have had the torque requirements change while drilling, which results in slippage later on in the process
MM
I haven’t heard this myth either. At first I started typing that it didn’t make any logical sense and I didn’t know why anyone would repeat that. But, now that I think about it, I have noticed that sometimes it takes considerably more torque to loosen a keyless chuck compared to how much it took to tighten it. Perhaps someone noticed that behavior and assumed that it would clamp harder if one loosened it enough to feel the higher torque by hand, but not enough clicks for it to fully loosen?
MT_Noob
There were a few youtube videos about the “trick” going around a couple years ago. Eventually it seemed to die down once a few videos were made debunking it. AvE did one called “secret drill trick?” and clarified it.
J . Newell
I wonder if there’s an interesting sequel to be written about the origins and variations of blade-type screwdrivers. Most are slightly tapered, and will certainly cam out based on factors such as width and thickness of the end of the driver and the amount of axial and rotating force. But there are hollow-ground drivers that provide parallel driver surfaces that are much less likely to cam out but still subject to how well the driver blade matches the slot in the fastener.
That topic seems like one that would be a lot less likely to have authoritative documentation available (like patent records).
MM
I’d be curious about exactly when the old “turnscrews”, which were often strongly tapered to a sharp edge to the point that someone might confuse them with chisels, transitioned to the more modern style of slotted screwdriver where the blade is not actually sharp.
David Vande Berg
I didn’t have time to read it all, but a thought occurred to me; Would a ‘notch’ the width of a flat blade work better than a full width cut out?
Jonathan OAF
Thank you for the article. That’s a fun & educational read.
Jerry
The advantages of the Phillips head screws are obvious to anyone in any kind of production environment over flat head screws. They are ‘self centering’ in that in a power driver you don’t get it off center and ‘wobble’ like you do a slotted screw. In addition, (and this is where I think the cam-out myth got started) it allows for the driver to be slightly ‘crooked’ in comparison to the screw, and still engage. This is again good for production, as you can start the screw much easier, but when not held quite straight, it cams out much easier. A flat blade will cam out as soon or sooner when not held straight, but looking at the screw, it is obvious the tip is not engaging properly, but not so much with a Phillips.
It has been my experience that a Phillips screw with a properly fitting bit held at a right angle to the screw will be less likely to cam out than a flat blade screwdriver. However, add a bit of wear to the screwdriver, and it gets bad very quickly. While a flat blade driver can be touched up when it rounds off a bit, a Phillips really can’t, which adds to the myth – Grandpa’s old flat driver (that has been reground a dozen times) still holds good, while the Phillips in the same set slips easily.
fred
I’ve always thought that it was important to recognize that most tools wear. Some (but not all) can be refurbished (cleaned, ground, sharpened etc.) to like-new condition – but with others you need to bite the bullet and replace them when worn. Most quality Phillips screwdrivers now feature hardened tips to resist (but not prevent) wear. Bits also can be hardened, laser etched or costed to prevent slip. Bit hardness and screw hardness sort of do a dance with each other. I think of screwdrivers as closer to being consumables than many other tools – not as bad as razor blades cutting wallpaper – but nowhere near the longevity of an anvil.
Ryan C
I mean, the tip of a screwdriver *could* be considered “something which has become lodged in the recess” and therefore designed to cam out. 😂
Good dig, very informative read. Thanks for sharing!
ElectroAtletico
The perfect screw doesn’t exist
fred
But manufacturers keep trying to invent new drive style. Here’s what’s said about one of the newer styles called Aster Recess:
“The ASTER™ system offers the best performance in torque capability for one-sided installation threaded fastener systems. • The specific geometry is designed to reduce radial stress in the fastener providing higher torque transmission.”
I don’t know – but when we encountered them – our toolroom guy did a bit of cussing about needing new l-keys that were then very hard to source.
Jason
The ‘cam out’ phrase could also be a result of language creep. Over years and decades (and different regions), words and phrases can change meaning, so what we refer to as ‘cam out’ today may not be what ‘cam out’ meant when the patent was filed.
Stuart
The last patent discussed had a reference of the driver resisting “cam out of the recess,” suggesting congruent usage.
MATT RENTZ
The JIS bit drivers work great for me and if you tap the screw on the counter while mounted on the bit it will grab it and you have the best screw starter.
Donald Scott
I recently purchased some JIS Screwdrivers. I want to make sure I have the right tool for whatever application I’m working on. To be honest, I don’t see any difference between standard Phillips Screwdrivers and the JIS Screwdrivers.
What about Pozidriv? Do I need to find a set for that now as well?
Thanks! Rascally
Stuart
JIS and Phillips have been converging, with some brands such as Vessel making all-in-one cross-style screwdrivers.
If you’re installing Pozidriv screws, such as with IKEA furniture, absolutely pick up Pozidriv screwdrivers or bits. In my experience, Phillips drivers can be used, but they slip a lot; Pozidriv tools make the assembly process so much easier with better results.
ParamountPaint
Every cabinet hardware brand I’ve come across uses #2 pozi drive screws for the hinge adjustment…Blum, Grass, etc.
Thus, I have a wera #2 pozi in my tool bag. Makes a big difference.
bob
I’ll preface my comment with, I have no incite about the manufacture of screwdrivers. As with many things ORIGINAL design and intent doesn’t dictate subsequent iterations. Maybe it wasn’t MR Phillips intent for his screwdrivers to cam out, but maybe others make theirs that way.
What about screw manufacuters’s designs?
I’m not trying to be contrarian, I judt don’t think referencing the original pantent is the definitive answer on whether or not phillips screwdrivers are MADE to came out under force.
Rx9
It’s nice to know the real truth about this. That said, even if philips heads are designed to resist camming, they are terrible at it. I prefer torx.
Rx9
Somewhat tangential to this, I had to remove some very tight screws holding in the brake discs on an Asian automobile. I was told they are JIS head screws, which should be handled with JIS drivers, often confused for Phillips. I ended up blasting them out with a manual impact screwdriver and a small sledgehammer.
processwrench
John P Thompson actually invented and patented what we call the Phillips, he sold everything to Phillips. So maybe there were some changes by Phillips in order to sell the idea.
eddiesky
Having a past technical position of a large computer company (well, I was authorized), the screws that were P00 or P000 would cam-off if you were a gorilla. You do not crank down on screws in electronics, else you damage the PCB or component. I also think that a fastener is designed for its application: torx permits a specific hand torque. Robertson or Square-drive can have alot of torque, as some star bits (see GRK) also have more surface area and are rather large (no T5, more like T20 up to T30).
Phillips bits tend to strip out if the fastener is less hard than the bit material, as well as the incorrect bit. Take PoziDrive fastener with a Phillips bit – it WILL strip/cam out. Because its the wrong bit. (now I see Stuart’s comment…)
MFC
It’s such a common myth that I came into here thinking that you were one of the proponents for it being made to cam out! Good to know that you haven’t bought into the nonsense. Mainly just youtubers/tiktokers that I’ve seen stating it.
The only intentional screw head for cam out, that I’m aware of, is the security heads that are made to not be removable. They certainly force the driver tip to “cam out” if attempted to be used in reverse, though maybe there’s a better term. I am sure all of us have seem them in urinals, along with the poorly scribbled notes telling us to do other unspeakable things. The fools, with more time than brains, have managed to remove one or two every once in a while, but they seem to prove mostly reliable in defeating ne’er-do-wells’ foul intentions.
Charles
Then, of course, there is the question of how many current manufacturers of both screws and drivers adhere to the original design and is that the reason why some drivers tend to cam out more – because either the driver or the screw no longer conform to the patented design?
Missing Link
As a boy from the States in the 60’s who was absorbing everything mechanical, I was taken aback by the strange screws in the Powassan wooden boats we used every year when visiting Ontario. (amazing boats, by the way) So I developed an affection for Robertsons, even though they were often tough to find in the States for the configurations I wanted.
But like everyone else that has used Robertsons, I began to see the inherent weakness in the design. The amount of material “missing” from the screw head to allow for the driver just makes the heads too weak for high-torque applications. It also seemed to me that Robertsons became even harder to find with the rise in power driver use.
Another thing that has always made me wonder… Did the surviving members of Robertson’s family somehow settle in Elkhart, Indiana? Of course Elkhart is the self-acclaimed RV capital of the world, and every RV I’ve ever worked on (many) has been built with Robertsons.