Retaining Screws for MKV Rear Window Trim

Hello Friends,

Just a quick question, hopefully!

I have replaced almost all the Phillips Head screws in the interior of my MKV but am wondering if the correct engineers head screws had cup washers under them or not? I understand the logic of fitting cup washers under those holding the timber work in place but am unsure about those in the chrome rear window trim? I imagine it is the same on a MKIV?


Here are the original BD.539/1 screws from my Mark V saloon rear window or backlight.

I would not have used the terms Phillips nor engineers head to describe these, although I understand there may be different terms in use in Australia than the USA. Here we call these slotted oval head; Phillips means a cross head.
They are 3/4" or about 19mm long and appear to have been chrome plated although it is all gone now. The thread diameter measures 0.115" and the head is .225" which makes them pretty close to the US #4 size designation. The parts catalogue page 99 calls them raised head #4 x 3/4" chrome plated.
The factory did not use cup washers with them in the window frame.
I have not been able to locate them in stainless with a slotted head, although McMaster-Carr has them in cross head as part 90315A409.

Those screws Look the same as used on later models, including the MK2. Hence replacements shouldn’t be too difficult to source.

For Mark V saloons, BD.539/1 Screw, securing Frame to Body for the rear window/backlight are as Rob describes and were used without washers. I have not found indication in Spare Parts Catalogue Feb., 1958 of what was used to mount the coupe backlight.

For most of the Mark V fasteners, slotted screw heads were normal. Phillips screws were helpful as self-aligning, and popping the screwdriver off the screw head when torqued sufficiently, for the screw/screwdriver during manufacturing and were faster to assemble but their use did not spread across the pond widely until the early 1950s. The only Phillips I remember seeing in Mark V are in Lucas equipment, e.g. the windscreen wiper motor.

Roger’s assessment agrees with what we have found in research on the XK120, Phillips is only found on the wiper motor cover. It probably associates with the gradual introduction and use in industry of electric screwdrivers.

For the DHC, we are only gradually arriving at a consensus on the shape of the window, let alone the screws, but since they go into the other side of the chrome frame I would expect them to be BA thread rather than self tapping. XK120 OTS people could help us there as it was probably the same screws.

Hi Rob,

Thank you as always.

They are definitely self-tapping with slotted heads (as I knew they would be). I have stainless steel slotted head screws ready to go, it was just the issue of cup washers or not.

It remains an area of considerable frustration for many owners that when cars have had interiors and the like replaced, the restorers seem to find it easier to use cross head screws instead of slotted head screws. If you wander around most Jag car shows you will no doubt see what I mean.

Best wishes,

Hi Tim.
Have only seen cup washers used when up against wood.
Never seen them on those holding chrome or brass trim.
Classic Fasteners in South Australia have them available in chrome or stainless.(called raised head countersunk by them. Also heard this type referred to as instrument head screws)
Cheers, Graham

Hi Graham,

Yes, I’ve only ever seen them used when up against wood too. Nevertheless I thought I’d ask just in case some pedant said, “They should have cup washers under them!” :wink: I have the screws already, purchased from Classic Fasteners (they are great) some time ago. Once I have changed these then all the screws will be correct.

The car is running really well but boy is it hot in the cabin when the outside temperature goes over 30C! :hot_face: Definitely a cool day car.

Thanks again,

I think Standard Vanguards had the same cup washers and self tapping screws holding the inner front windscreen trim in.

23 cents AUD each in stainless, $1.10 AUD each in chrome. They even have a currency converter.