XJ6 & XJ12 Series I, II & III 1968-1992

The difference in Jaguar Phillips head screws

Old 02-06-2019, 04:32 PM
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Default The difference in Jaguar Phillips head screws

I came across this recently and was amazed that I had never heard of it in over 50 years of working on British cars. Did you know that the screws on our classic Jaguars are not actually phillips head but actually something called Pozidrive? I knew that a lot of the screw heads on my cars were damaged by the screwdriver slipping out. Turns out that is because people used a plain phillips screwdriver instead of the correct Pozidrive bit.

Now the good news. I looked in an old kit of driver bits I had and bingo, there were the three sizes of Pozidive bits. This is one of the very cheap kits with screwdriver bits, little hex and tork bits in a cheap plastic case. Probably $10 for dozens of different types of drive bits. I have heard they sometimes sell them in the Dollar store.

I found this gem of wisdom is a great book that is a free download on the internet. It is called Experience in a Book by Kirby Palm. It's written about XJ-S and specifically the V12 but maybe half the information pertains to the XJ6 as well. The book is over 700 pages long! So I just skipped the sections on V12 engine, convertible top, etc. A fantastic resource and it mentions several of our Forum gurus. A great (did I mention free) book to pass the winter months.

Here is a web page with info on phillips vs Pozidrive.
What is the Difference: Screw Bits - Phillips vs. Pozidriv - Fine Homebuilding

What is the Difference: Screw Bits - Phillips vs. Pozidriv - Fine Homebuilding

Despite their similarities in appearance, the Phillips and Pozidriv bits are not interchangeable. Learn how to distinguish between these two useful systems.

The following 3 users liked this post by Yellow series3:
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Old 02-06-2019, 08:58 PM
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I've seen the screws, and the bits. Until now though, didn't know the significance.
Old 02-07-2019, 05:16 AM
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I have been aware of pozidrive since the 1990s and i have a case kit like you describe purchased at BIG LOTS.
my kit has 6 sizes of posidrive bits.
For very large pozidrive screws, I have a Volvo screwdriver which is also pozidrive. They were used to screw the hubcaps in Volvo 122 in the 1960s.
Old 02-07-2019, 08:00 AM
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Pozidriv is pretty widespread outside of the US. Ever put together anything from Ikea and stripped the heads with your Phillips screwdriver? That's why.

Many screwdriver kits that come with multiple bits include a couple of Pozi (I recently got a kit from Amazon that did).
Old 02-07-2019, 12:02 PM
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I have a couple of those "bit" boxes. Both from HF, as I recall. POZI is a tad better than Phillips. A more secure bite.

I will confess to using a Phiillips driver on POZI fasteners...

Worst are slotted fasteners. I don't think any are left on my Jaguar...

Not quite true. Two odd ones on the odd frame holding down the battery..

Old 02-07-2019, 01:37 PM
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Pozidriv was actually invented by Phillips when their patent ran out. It was used early on by Jaguar, and by Tektronix, USA maker of oscilloscopes. The rest of US manufacturers never picked it up and retained the original Phillips design, much like they never picked up metrication. But, in contrast, most of the world did. As a result, folks outside the US never see Phillips--all of their screws are Pozidriv. Some products in the US, like air tools, are primarily of Chinese origin and you will see Pozidriv in these, even if brand new. OTOH, various alternative head styles, like torx and triple-square, have become ubiquitous and have replaced both Phillips and Pozidriv in many applications. IMHO.
Old 02-07-2019, 02:58 PM
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Yes, Pozidrive screws/screwdrivers are significantly better than the Phillips - much less chance of slippage and damage. Another superior type of screw/screwdriver (not used on automobiles) which is virtually unknown in the US is the Robertson square system -a bevelled square indentation in the screw head and a square-head drive on the screwdriver. A Canadian invention (amazingly, invented by a man with the surname Robertson!)...it almost achieved fame by being used on very early Fords...in the end (not a pun), Henry Ford decided against it - I think because of something to do with supply. Or perhaps Canadian screws were considered a security threat.
The Roberston screws are almost the norm in Canada. As a result, most of us don't have a screw loose -but there always exceptions.
Old 02-07-2019, 03:15 PM
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my kit has Robertsons too. They are quite positive, getting Robertson-head screws is not difficult, they are used in commercial plumbing fixtures.
Old 02-07-2019, 09:27 PM
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Being a Toyota Supra enthusiast, I many years ago bought Japanese Industrial Standard screwdrivers in #2 and #3. The difference between the JIS and Philips screw is barely noticeable, but functionally quite striking. The story I read was that the Philips screws were invented back in the 1930s when manufacturing was being automated with air powered tools. Today, every cordless drill has a clutch mechanism so you can set the maximum torque, but back then they didn't have that yet. The Philips screw and bit was designed to "cam out" rather than break off the head of the screw if the factory worker got careless. It prevented stopping the assembly line and delaying production while a broken screw was extracted. Who knows, probably helped win WWII. So it was great for putting the stuff together in the first place, but quite lousy for taking things apart later after the threads got a little corroded. The JIS system, like pozidrive in contrast is designed NOT to cam out. Who knows, maybe it hobbled the production of "Zeros" at the same time. But I'm not working in a 1940s war factory. While the Philips screw is still designed to be mated to a Philips bit, the JIS bits happen to fit a Philips screw head just fine and are far less likely to cam out. So now the JIS is the only + shaped screwdriver in my tool cabinet that I ever actually use.
Old 02-12-2019, 06:38 PM
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I've bought several of these kits from Harbor Freight through the years.. They come with multiples of several different sizes of pozi drive bits... And cheap enough that I don't feel so bad when I loose one...
Definitely a must for getting some of the screws out...

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