What Is Pozidriv? How Does It Differ from a Phillips Drive? (2020) | Hacker News Reader

What Is Pozidriv? How Does It Differ from a Phillips Drive? (2020)

albanycountyfasteners.com

88 pointswalterbell96 comments

Pozi is most common head in the UK apart from Phillips and slotted! Pozi has a greater surface area which helps with cam out. I have no idea why on earth we still have slotted engineering screws with a cheeky short cylinder on the end to aid initial contact, to hold electrical faceplates onto back boxes.

For big wood screws ie six+ inch no 10s or 12s you really want Pozi but the tip needs to be cleft and the lower thread needs to be toothed to cut in. You'll be using torque that can potentially break or at least hurt your wrist if you are not careful with a big drill/driver so a carefully placed leg to the right can help avoid that by acting as a stop.

For really big wood screws eg joining two sleepers, we generally use hex headed screws and a socket set or a impact driver and some care.

In general the real problem is getting the bloody things out again after 10 years of weathering or other age effects. WD40 and the like is often your mate here and so is being creative on how to apply enough lateral force to ensure that your cyclical force is sufficient to remove the fastening.

> I have no idea why on earth we still have slotted engineering screws with a cheeky short cylinder on the end to aid initial contact, to hold electrical faceplates onto back boxes.

I would assume that it's because in areas where it's possible for the head of the screw to get "gunked up" with paint or dirt, that a slotted head is easiest to scrape away the material and restore function. You generally don't need any special tools for this -- you can use the screwdriver already in your hand.

I noticed this feature when watching some wooden boatbuilding channels that specifically use slotted head screws in places where the fasteners are recessed in the wood and will be filled and sealed with wood plugs. The slotted screws can be cleaned out later if repairs need to be made.

I think it's more that electricians typically have an electrically insulated slotted screwdriver in their hand at all times.

If any electrical device were to require a different screwdriver it would be extra effort to go get a different screwdriver when everything else uses slotted.

Must be regional. Over here I picture electricians with an insulated #1 square welded to one hand and a power driver to the other.

Slotted stands out because it's a wallplate-only screw.

> * the real problem is getting the bloody things out again after 10 years of weathering or other age effects. *

Try putting grease on thread as you drive it in. 90% or so of the bolts and coach screws i've removed from hardwood or treated pine are reusable after 15-20 yrs in Oz climate. They were all greased up by my dad going in. The ones that failed are rusted badly & the grease wasn't coated around the shaft. The good ones have signs of corrosion (we use galvanised), but essence of grease and the thread is still there.

We don't use Pozi, but use hex drivers (coach screws & bolts) or their negative female equivalent (bugles), which an allen key fits into. We also pre drill holes.

"Try putting grease on thread as you drive it in."

I appreciate the advice mate. We have quite a diverse set of conditions to deal with. I live on an island that is N hemi. and temperate. You live on a huge island that is continent sized and S hemi.

Pre-drill holes: me too and I think that is a real win.

My golden rule is that the less stressed fix is a good fix.

It's probably time for me to see me relos down south!

> You'll be using torque that can potentially break or at least hurt your wrist if you are not careful with a big drill/driver

Getting an impact driver for woodscrews was a game changer. I used to do theatre carpentry which mostly involved rapidly assembling stuff that a chorus of 20 can dance on. It frequently involved big timbers and large woodscrews. Even carefully piloted, and clearance holed a 4"x12 (80x12) requires a lot of torque and a lot of weight on the drill in order to prevent cam-out and head stripping, and even with practice it was challenging. With an impact driver there's no issue at all. You just learn very quickly to buy impact rated PZ bits for it!

I share the experience that impact drivers seem to require less downward force to keep the bit engaged compared to a drill or hand screwdriver but I can’t work out why this should be the case. If they exert the same torque then shouldn’t they require the same downward force?

The nature of impact is that it comes in many "hits" vs continuous application, maybe? Just guessing.

> For really big wood screws eg joining two sleepers, we generally use hex headed screws …

Known as “Coach Screws” in the UK, if anyone’s searching for them.

For new screws in my experience pozi outnumbers phillips 20:1 at least, and flat heads even higher. Flat heads I only really see inside plugs which I rarely need to remove, even the outside screw for changing the fuse tends to be a phillips, if the plug isn't moulded of course.

I’ve switched 100% to Robertson for woodworking and Hex for electronics/metal/3dprinting/etc. As far as I’m concerned Phillips are as outdated as flathead screws and ridiculous to consider in anything new.

I generally even replace existing Phillips screws around the house with Hex equivalents as I come across them, just so future maintenance is more reliable and easier.

Phillips was the VHS to Robertsons BETA, yet Robertson has finally gotten a second go at it and seems to finally be winning. Our hardware shops have them in every size and use case now (alongside hex).

As a Canadian it still blows me away that Robertson isn't as ubiquitous everywhere else as it is here. They are far superior to Phillips in every way.

As someone in the US, Robertson is better than Phillips, but Torx/star is superior in every way. Besides the better torque with Torx, the bits don't get mangled as quickly.

My experience with Robertson, where it is the default for pocket-hole screws, is the bit corners get rounded and it then starts to really destroy the fasteners. It's not always easy to determine when a Robertson bit should be thrown away.

In contrast I've had star bits that had multiple chipped edges but it still grabs. Instead of rounding, those bits usually chip off, so it's pretty clear when the bit is junk.

Full agree. Torx is the best. T25 and larger bits are essentially indestructible.

Spot on, I can go through box after box of screws with a Torx bit without it breaking or even wearing visibly. You do want to make sure you have some pressure on it.

Anything smaller than T3 is just asking for trouble, though. I guess they can be seen as tamper evident :)

fair enough, but I guess anything under T3 equivalent in any drive system is pretty damn difficult. What do you use?

The smallest Torx i've used is T5, and even that was very dicey.

Bits only get chipped when torque is still being applied as the driver is being removed. (Or inserted)

Tool makers could easily fix that problem with a sensor that detects pressure on the bit, and if it drops to zero, stop the tool.

This is the side effect of being patented.

They're more expensive to make.

As the article explains several times: Self. Centering. For manufacturing, it's a non-trivial property.

For manual work, also as the article said multiple times, yes roberson and torx are fine, even better.

In Atlanta? I'm surprised to hear that, because I was never able to find Robertson when I lived in the US a few years ago. Robertson is about all you can get here in Canada, but certain screws are also available in Torx (only the GRK brand though).

I've been buying square drive screws(mostly woodworking) for decades in California. Definitely my favorite type.

Only place I've found Robertson in the US (also Atlanta) is "online", which is arguably "not in the US". They are way better than Phillips but you can get Torx now at "big box retail" stores so that's what I use now.

I have baggies of the robertsons stored...somewhere.

Why not torx?

Hex is torx

Wait... Isn't it?

Hex is a 6 sided polygon, torx is more like a sheriff's star.

https://www.wonkeedonkeetools.co.uk/wp-content/uploads/2019/...

You can sometimes fit one bit into the other but that's just a coincidence and you'll probably strip one or the other if you do it hard enough.

Torx is hexalobular. Not the same as hexagonal Allen. You can wedge some sizes of wrench into the wrong fastener but it's a good way to strip the heads.

No, definitely not. Though sometimes (in a pinch, and very bad practice) you may be able to use a slightly oversized hex bit to drive a Torx fastener.

Are you in Canada? I haven't seen Robertson anywhere else but in .ca.

IIRC Phillips was designed to cam out on purpose to avoid over-torquing. I personally disagree with that design decision (inconsistent max torque between users and tools, cam-out strips screws, etc).

Using the "wrong" pairing (pozidric screw + Phillips screwdriver or vice versa) results in easier cam-outs in my experience, without alerting the user that they're using the wrong screwdriver.

I personally like Torx and (less so) hex heads.

Only refined phillips (post-1949) was designed this way. Early on, phillips was not designed to cam out, and instead was designed to have better ability to be torqued than slotted. The whole "phillips was designed to cam out" has been retconned :)

Wikipedia actually goes into this: https://en.wikipedia.org/wiki/List_of_screw_drives#Phillips

The truth is that it was already pretty hard to mass produce a phillips recess (vs a slotted one) back then.

Once everything transitioned to being stamped, and stamping was easy, phillips became the worst choice for roughly every application.

I found the original designs that are part of the patent, it was designed to cam out.

Edit: I guess the very original patent was edited to _add_ the cam out? I may be wrong on this, but my research showed that the automated screwdrivers on assembly lines did not have good torque controls and therefore were wrecking screws (early 1900s?) and so the cam-out feature was added to help with this problem.

What you've found in your research is the common story, but there is not a lot of evidence to back it up, AFAIK. Like if you actually go read the references, there isn't a lot of history from the early 1900's that agrees with the narrative.

Also, slotted screws (that they were using) actually cam out before phillips (and aren't self-centering).

It's more likely the self-centering part was more useful to the automated screwdrivers back then.

I am really surprised people are calling this a story or narrative. I found factual statement made by the designers in their own patents that "throw-out" (their phrasing similar to cam-out) is intentional to protect against wrecking screws or tooling with use with clutched automatic screw drivers.

Sections 7.35 to 7.55 discuss this here:

https://pdfpiw.uspto.gov/.piw?PageNum=7&docid=02474994&IDKey...

Edit: As a side note, they point out that _all_ screws have throw-out, and the only way to not is to have "zero vertical angle is used on all engaging driving faces or the friction between the driver and the recess walls is greater than the axial component of the driving torque." (Section 7.15 in the link above)

They acknowledge that it's possible, but it's not done in their design intentionally.

That isn't the original patent. That is a modified post-1940 version, as i mentioned.

The original patent is the JP Thompson patent #19008081 (screw - 1932) and patent #2046840 (screwdriver - i forget when)

I agree, here's their original patent:

https://patents.google.com/patent/US1908081A/en

The designers own statements of requiring "zero vertical angle" to avoid cam-out/throw-out is proof Phillips was designed with it to begin with.

The patent change later only added _more_ cam-out/throw-out, it did not introduce it in 1942.

Also, the 1942 patent represents the modern Phillips (which is what everyone would acknowledge is the problem screw), where the original 1932 patent looks more like a Reed and Prince.

Edit: Previous comment should read -- "...is proof Phillips was _NOT_ designed with it to begin with."

It's a good design decision, and a terrible choice to have used that design where it was used.

The design was intended to be used in industrial automation settings where you'd very much rather cam out and possibly destroy a single fastener rather than having it destroy your entire part, or jam your line, or possibly blow up your tool.

> industrial automation settings

In what context are you doing industrial automation, but have to worry about overtorquing a fastener? Wouldn't you almost always solve this problem by having a pilot-drilling + tapping step and then using machine screws? In what industry do machines drive self-tapping screws into things?

(I suppose you could dramatically overtorque a machine screw and end up shearing the head off or something; and that this could have been more of a concern before there was any sort of torque limiting built into drivers. But torque-limiting drivers have been around as long as electric drills/screwdrivers have been.)

Just because torque limiting drivers are available, does not mean they are used, or used appropriately, or used outside the OEM factory.

See also: the JIS/ISO type crosshead standard which are different from both Phillips and from Pozidriv — a.k.a. the reason people strip all the screws some times when repairing their old laptops and game systems and stuff:

- https://bike.bikegremlin.com/10583/phillips-vs-jis-vs-pozidr...

Or if you work on old Japanese cars. Old Honda cars and motorcycles used them. I stripped out tons of screws before I learned about it, it was super frustrating. JIS screws can be differentiated by a dot stamped onto the head of the screw.

And JIS has been discontinued now so if you need to get those screwdrivers/bits, get on it! The nice thing is that a JIS screwdriver can be used on Phillips screws and works better whole a Phillips screwdriver just doesn’t work.

Yikes! I'm glad I grabbed some JIS drivers a few years ago. I've repaired multiple Nikon and Canon cameras and they're loaded with JIS screws (which is to be expected, really).

JIS may be "discontinued" but the screws are still widely available. I buy and use them all the time. I've heard tell that DIN 5260-PH/ISO 8763-1 describes the functional replacement.

I wrecked all the fasteners on an old Yamaha reciever because of this difference.

Bought some JIS drivers and I like them for regular US Philips screws better- more bite.

Note that Pozidriv screws are common in IKEA products.

Once I realized that there was a difference between Pozidriv and Phillips, I started using Pozidriv drivers when assembling IKEA furniture. It made more of a difference than I expected.

Ongoing loosely-related thread:

Robertson vs. Torx screw drives (2021) - https://news.ycombinator.com/item?id=31958512 - July 2022 (69 comments)

Later refinements to phillips head screws made them designed to cam out (early ones did not have this as a goal) so they could be used without over-torquing in the automotive context.

Pozidrive is unfortunately commonly adopted in the screws that come with cabinet hinges.

I immediately throw them away and replace them with torx or robertson.

Honestly, the most impressive part of phillips screws is that they figured out a way to produce them efficiently in the 30's

Do you know the screws used in electric outlets that looks like crossover between Phillips and flathead so it can be driven by both? (or even Robertson #1) Recently I learned that there are screwdrivers that fit those screws perfectly by being flathead with Robertson #1 in the middle.

It's called Milwaukee ECX #1

Other variants are PH/SL1 and PZ/SL1

Pozidrive are probably the most common screw here and i hate them. They still cam out really easily and it is not immediately obvious what size Pz bit goes with what screw. Maybe they were once a improvement over Philips but there is no reason for them when we have torx.

Now I think about it, that is actually weakness; it's really easy to use the wrong sized bit. Too small a bit works, until it starts stripping your screw head.

Hold a screwbit upside down, put the fastener on it, tip it over. If the fastener falls off before you hit the 45 degree point then it's the wrong bit, the right one will probably stay wedged way past that point to where you are wondering if it is going to fall at all.

It's almost always PZ2. One screwdriver/bit can be used for 90% of the fasteners around the house.

With Torx 15/20/25 are common. So I need to switch bits all the time.

Does anyone know of better options than Philips / flathead for screws that can be used tolerably with a somewhat-wrong-sized driver? In particular, I carry a Leatherman that has a single Phillips and three flathead sizes that in practice work quite well to remove a large variety of common screws, and I don't think it's possible to produce a similar tool in a Torx world.

This is pretty niche but in a home workshop it's much easier to make something with a slotted head than posidrive, torx or hex. You can do it with no special tooling. Heck, you can even do it with a Swiss army knife.

The best solution for more complex shapes I've seen for that is a rotary broach, a device clearly powered by witchcraft[1].

The problem is that rotary broaches are not cheap tools for an amateur so if I have to make any kind internal fastener socket myself, for now, it has to be a slotted head still despite being clearly inferior.

I had a new found respect for simple stuff like screws, bolts and fasteners, that cost pence or less, once I started making things in a workshop.

1. Actually rotary broaches are really simple but weirdly fascinating devices once you know how they work.

The article says (near the end): "The Robertson, or square, drive is quite common especially throughout Europe."

Is it? I'm in Europe and I've never seen Robertson. From what I read Robertson is very ubiquitous in Canada and is hardly used anywhere else. Is that right? Can some people from different countries share their experience on Robertson in their region?

They're almost the standard in New Zealand. I've also seen pozisquare screws around, which can be driven with both pozi and square bits.

Canada's PicQuic multi-bit screwdrivers have optional Pozi bits, along with Robertson and other common drive formats, http://picquic.ca/.

Picquic bits are 3" and can be used in standard drills/drivers.

I first learned about Pozidriv in the early 80's. HP, Agilent, Keysight use Pozidrive screws in all of their equipment. You might be able to get away with using a #2 Phillips, but you also might strip the screw head while trying.

HP adopted Pozidriv after the Pozidriv patent expired.

Once the Torx patent expired then HP migrated quite a bit to Torx starting in the 1990's when the HP instruments became Agilent.

Robertson > *

I have never had a Robertson (square hole) screw strip out or have any problem, and it's impossible to use the wrong size screwdriver, which is not the case for philips head or posidrive.

Since Robertson is better yet so much simpler, I can only imagine it was hard to manufacture in the old days or they would surely be more widespread.

I haven't seen anyone claim that it was hard to manufacture. Sadly, the answer seems to be that Robertson screwed up the initial licensing so badly that the technically worse Phillips took over the market. Here's an account: https://www.thomasnet.com/articles/hardware/robertson-screwd...

Some people try to argue that Phillips was actually superior, since it cams out rather than breaks, but I feel like they are just making excuses. I'm confused why Robertson/Square is still so hard to find in the US. I don't think my local Home Depot carries any. Torx (which is just about as good) occupies the niche it would otherwise have.

Henry Ford seems to come off lightly in that article. Legend has it that his terms were almost exclusive, so Robertson walked:

https://www.youtube.com/watch?v=R-mDqKtivuI

> Some people try to argue that Phillips was actually superior, since it cams out rather than breaks, but I feel like they are just making excuses.

To be honest I like that square heads just break as I can simply hide the hole and drill a new one instead of trying to remove the stripped head.

I’ve never had a Robertson head strip out either, and in fact the drivers grip the heads so well that the few failures I have experienced were all due to the threads binding in the material followed by me overtorquing it until the heads just twisted right off the top of the screw shafts.

They can strip when the driver bit is worn on the corners.

Until I watched a video on YouTube about it a year ago, I didn't even know it was a thing. I'm in France fyi.

https://youtu.be/R-mDqKtivuI

It's a solid design but is it better than Torx? In what ways?

Honestly I think part of the reason is because in 95% of cases, a Philips is going to be easier. Wrong depth, wrong size, wrong gauge, still works in most household cases. Robertson is not as forgiving

Except that there are only three common sizes of Robertson that are impossible to confuse, and the drivers are always colour-coded (a "red robby" is a #2 Robertson, green is #1, and yellow is #3). Nearly all screws will be #2 #1. #3 (huge) is uncommon and #0 (tiny) is very uncommon.

Honestly it’s the same with philips. #0-#4 will cover 99% of cases. But in a pinch, a thin #2 will unscrew all of them.

> impossible to confuse

Read that part again. It's definitely not true of Philips.

(*) Works until you discover you've slowly stripped the screw and can no longer turn it.

Yup and it happens but my guess is most screws only need to go in or out once or twice. Again, technically speaking I think Robertson is better but the reality is most people can accomplish what they need with a #2 philips regardless of what size is actually there.

I want to know why we continue to put accursed Phillips head hardware into everything. It's clearly inferior and large percentage of manual interactions will result in a cam out.

The cost of buying a new set of screwdrivers really isn't that high, so what gives?

Phillips head screws are everywhere, and they really shouldn't be.

They’re ubiquitous for things like wood screws and they really, really shouldn’t be. I’m actually kinda glad that Robertson heads are common in Canada.

The only time I encounter Phillips is drywall screws here in Canada. I’m only one person, but yeah, Robertson is the majority of what I find here.

Having just been in the fastener section at my local Home Depot... almost all the wood screws are Torx. Drywall screws are still Phillips, but all the deck screws and almost all the interior screws seem to be Torx, and they almost all come with a driver bit in the box. I now have a nice little pile of leftover Torx drivers for my impact driver...

The article is hilarious. It notes that torx and robertson are superior, but still recommends phillips.

As I read it, it recommends Phillips for manufacturing due to self centering and perhaps cam out; and Torx and Robertson for manual applications. I guess it draws this particular contrast with "manual" applications to highlight that it in fact means automated manufacturing.

I find that for smallish construction screws like M5x60mm typically used a lot in GB Posidriv is better than Torx because an impact driver will destroy any Torx bit smaller than T25 the first time you use it. For bigger screws, Torx is the winner. T10 Torx bits shear off or get twisted quite easily as I discovered when trying to unpack some windows that were secured to the pallets with a bunch of small Torx screws

> Torx because an impact driver will destroy any Torx bit smaller than T25 the first time you use it

There is a regulator on your compressor, you should probably use it!

Cheapest makita 18v driver doesn’t have this.

Any recommendations for US/Canada online retailers of screws with steel strength labels (e.g. Grade 8 Alloy Steel, low/medium carbon, or any ASTM rating) and country of origin? Amazon is a lottery on both metadata and whether the received screws will match the metadata.

McMaster Carr is best in class. Their website allows you to easily and quickly drill through these categories.

Their site won't provide shipping prices, but its reasonable, and if you call they'll estimate it. My favorite thing about them is they were founded by a stationary engineer (think a ship or train engineer but stationary, such as: big buildings/campuses) over a hundred years ago. I'm a working stationary engineer myself.

They now provide shipping costs, at least in the Los Angeles area.

Much of the shipping work is done by private contractors like DGC. I get same day deliveries, often for $7-10.

Was looking for strong lag screws for wood. Like most places, McMaster-Carr has only regular steel for lag screws, but they have Grade 8 lag bolts. Eventually found Grade 5 lag screws from SPAX, https://spax.us/resources/blog/spax-powerlags-vs-conventiona...

Sigh, yet another effort to design the best fastener head to save us all from the existing ones, once again by those who have apparently never researched the joys and superiority of the Robertson. Lather, rinse, repeat.

https://wikiless.org/wiki/Robertson_screw

Doesn't look all that superior: https://pedriana.wordpress.com/2021/02/03/robertson-vs-torx-...

Especially old stripped screws and bits look nasty.

You'll likely see what I mean by reading through the great comments on the Robertson in another thread:

https://news.ycombinator.com/item?id=31958512

I always regarded Pozidriv to be a joke, a homeopathic design. Does it _really_ does better than Philipps? On paper, yeah. Does it feel in the real world like that? Nope, not at all.

Torx all the way!

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