Sep 142013

The lock barrels are of the wafer tumbler design where five sprung loaded wafers protrude at the top of the barrel. They align with corresponding slots in the handle’s push button and stop the barrel from being rotated inside the push button.

A retaining pin then stops the barrel from being withdrawn from the push button.

The profile of the matching key is such that, when it’s inserted, it draws the wafers inwards until they are all flush with the barrel’s circumference. The barrel is therefore able to rotate unhindered within the push button.

Another feature of this design is that it is not possible to remove the key when the wafers and slots in the push button are not aligned. The wafers need to be allowed to protrude in order to release the key. In effect, they are clamping the key within the lock.

The return spring fitted to the lock barrel ensures the lock always returns to the position allowing the key to be removed A spring is fitted to the inner end of the lock barrel which ensures it always returns to the aligned position, allowing the key to be removed.

Slotted on to the rear of the lock barrel is a profiled plunger which has two ‘ears’ at its base. The plunger is not attached to the barrel but its movement of travel, both rotationally and in/out, is limited by the shape of the rear of the lock barrel.

The plunger serves two purposes; the operation of both the door latch locking mechanism and the door latch release lever.

Operation of the Latch Locking Mechanism
The rear of the lock consists of a spring between two washers, the lock operating lever, lock end housing and plunger fixing screw. The operating lever and housing both have a hole matching the profile of the plunger.

The fixing screw ensures that the ears of the plunger are positioned in line with the end section of the lock barrel (when the button is not pressed).

In doing so the plunger is always engaged in the hole in the lock operating lever.

When the key turns the lock barrel, the plunger ears will come into contact with the edges of the lock barrel. At this point the plunger and operating lever will also turn.

The installed door lock with the latch release lever immediately behind and the sprung linkage to the latch locking leverA sprung linkage is attached between the operating lever and the locking lever of the latch mechanism, mounted below on the rear face of the door. Therefore the latch lever will either be pulled (unlocking) or pushed (locking), depending on the direction of rotation of the key.

The purpose of the spring is to provide some resistance in the rotation of the operating lever and engaged plunger. As a result, when the key is turned to lock the door, the operating lever and plunger will remain in the locked state when the key is released which affects the operation of the latch release lever, describe below.

Operation of the Door Latch Release Lever
The hole in the lock end housing allows the plunger to pass through when it is correctly aligned, which is when the door is unlocked. At which point, the plunger ears will be engaged with cut outs in the end of the barrel. Pressing the button will push the barrel inwards and with it the plunger. The plunger passes through the housing until it hits the latch release lever allowing the door to be opened.

In the locked state, the plunger ears are aligned with slots running the length of the rear part of the lock barrel. This time, when the button is pressed and the lock barrel moves inward, it simply slides past the plunger and the release lever is not activated.

Rebuilding the locks
The first issue was only one key was provided which only operated the drivers door and not the passenger door or glove box. So the both door locks must have been changed at some point in time. I could live with having a separate key for the glove box but it would become annoying for the doors.

Unfortunately replacement sets of matching lock barrels haven’t been available for a number of years. After quite a bit of searching I found a classic car lock specialist who could replace the wafers to produce a pair of matching barrels. A couple of days after sending them, a match pair were returned.

By chance, a month or so later, a friend contacted me asking about replacement locks on behalf their friend who has an E-Type out in Harare (their car was first registered in Zimbabwe on 6 January 1970, only 5 days after mine was registered!). I mentioned they’d been unavailable for some time and the hassle I’d had with the locks. When he made some enquiries with SNG Barret, complete barrel sets including the boot and glove box were available and had just come back in stock, for little more than I paid to get mine matched – another case of poor timing on my front!!

With the lock internals removed, the handles and push buttons were sent away for re-chroming. Overall I was pleased with chroming work, except for the handle and push buttons as the plating process had deposited too much material (I think this is quite a common problem). This stopped the buttons from moving once inserted into the handles and also stopped the barrels from being inserted into the buttons.

They were sent back but even when the returned the fit wasn’t good so I carefully removed some material from the inside of the handle with a Dremel. Not only that but I’d accidentally left one of the retaining pins in the button for safe keeping. It was then firmly re-chromed in situ and was not that easy to drift out. I can hardly complain about that as it was my fault!

Stoneleigh is a great place for picking up obscure parts such as a new lock housingOther immediate issues were one of the alloy lock housings had broken around one of its mounting holes and the inner washer, inserted before the large spring, was missing.

To my surprise I found a stall at the Jaguar Spares Day at Stoneleigh that were selling reproduced alloy housings so that issue was easily resolved. As yet I’ve not sourced a replacement washer which I have subsequently found out causes a problem.

The operation of both locks had started to suffered due to a build up of dirt and greaseBoth locks had become clarted up with dirt and grease over the years. One so much so that it was difficult to rotate the key.

I think the problem is that grease and heavier oils tend to pick up more dirt. I’ve used Lock-Ease graphited lock fluid when putting the locks back together which will hopefully reduce the build up in future. It’s also designed to reduce wear and keep them working in freezing temperatures.

I rebuilt a lock without replacing the missing washer to see if it was absolutely necessary. The lock worked fine which was good news …. until I’d operated it half a dozen times and it began to seize up. The washer sits between the two springs within the lock. Without it the springs start to entangle. I now suspect this was why one of the locks was harder to turn rather than just a build up of grime.

I’m a bit stumped on how to resolve the issue as I’ve not been able to find a replacement yet …..

  2 Responses to “Operating door locks once more …. well, one lock!”

  1. Chris,

    I think this is the most thorough explanation of the Jaguar locking mechanism extant. This will no doubt be an invaluable resource to a lot of us.

    As for the washer that is missing, and chance you could fab one yourself? Find some shim or sheet stock of the right thickness (maybe 303 stainless steel – easier to machine than 304), drill or machine the center bore to size, cut the external dimension roughly to size with a band saw, then chuck it up on mandrel to turn the outer dimension on a lathe? But maybe that’s a lot of work for a washer…

    In the US we have McMaster-Carr ( for nearly all of our fastener needs. Anything like that in the UK? Maybe there’s a common washer of this size or close enough to be modified with hand tools…

    Not sure I’m saying anything you haven’t thought of yet, but my gut tells me you’ll get it worked out 🙂


    • Peter,

      Thanks for your comments. Unfortunately I haven’t got access to a lathe at the moment but it is something that I have my eye on. It would have been so useful if I’d have taken the plunge and got one at the start of my restoration.

      There are a couple of UK suppliers who might have them but it’s an outside chance. It’s not a common size so if the supplier don’t have them, I’ll nip down to the local machine shop.

      Fingers crossed!


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