Shakeproof screw?

What is a “shakeproof screw” such as BD20780/3? One of these is used on each door lock assembly along with three UFS.419/3H (#10 X 3/8" long slotted pan head) screws.

Dave Christensen

They look like the below

I think a shake proof screw would be one that had the shake proof washers as posted by Denismo above attached permanently. Try looking here:

I last touched my door lock mechanisms 20 years ago and forget which type were used.

I just checked my parts and service manuals re the door locks and there is confusion I see. The lock that attaches to the door has 4 screws on it and they are all the same. I am not sure why the parts diagram shows 6? I do not see where the shakeproof screw goes but here is an image from the service manual that shows the 4 screws that hold the lock to the door.

I have both the parts and service manuals. I think they are both correct. Each door lock is attached with four screws - 3X UFS.419/3H (#10 X 3/8" long slotted pan head) screws (6 total as per the SPC) and one BD.20780/3 Shakeproof Screw (2 total as per the SPC).

It seems that the shakeproof screw is probably the same as the other three screws except it has a captive shakeproof washer. I am putting them together with all four screws the same. (When I lose points at a Concours for that I am sure the judge will have the definitive answer and documentation. :crazy_face:)

Dave Christensen

Can you tell us what parts manual and service manual you are referring to? I don’t see BD.20780/3 anywhere but in the spare parts pricing guide. And it doesn’t shop up in the Bentley nor in the J37.

Page 173 of the Spare Parts Catalogue for Jaguar 4.2 “E” Type.
As shown in JCarey’s picture above, the service manual references four screws per latch with no part number reference.

You need to just flat or recessed pan screws (I forget what that head is called), and unfortunately Drew’s McMaster link doesn’t show any screws with that head. The washer doesn’t absolutely have to to be integrated with the screw. You can just slip over close fitting external tooth lock washers. As you tighten it, the washer will become conical and take the shape of the recessed hole and work fine.

Also make sure you use the proper cheese grater shim behind the striker. I didn’t know about them at first and it was a nighmare. No matter how tight I made the screws, it would start to move within a week.

Got it. You’re right about there being two separate screw types. The same thing shows up in the 3.8 parts manual. Hopefully someone on the forum can look at their car and tell us which position of the four the “Shakeproof Screw” goes into. It’s a special screw so it may be longer/shorter, have a different head, etc.

By the way the 4.2 2+2 has a different latch altogether.