XK120 FHC Fog Lamp Switch location

(Rob Reilly) #21

C.792 is described in the FHC and DHC parts books as “Washer, Plain, behind Clamping Washers”, quantity 8.
Although I seem to have more than 8.
The tapered shoulder thing you see here is C.3225 Washer, Wing Clamping (behind Wing).

On the outside is the chromed tapered washer listed as C.3945 Spacing, on Screwed Extensions, quantity 4.

The difficulty in trying to figure out about the “correct” fog lamp switch position, and also the C.2985 right and C.2986 left fog lamp brackets, is that apparently very few cars were actually fitted with them from the factory. LWK707 is the only surviving car on which there seems to be a good chance of this as an example of a factory installation. But there are many cars fitted with fog lights later by dealers or independent shops or owners, using various other brackets of unknown origin. The significant clue is that they are usually not lefts and rights. The switch position may or may not have ever been specified by the factory, and if so, such a document has not surfaced, and subsequent switch installers may or may not have followed it if they ever had it.
Many people seem to be adamant that what ever they have has been on their car since the 50s and therefore must be correct original. It would be more correct to say “it has been on there since the 50s”.
The only way to really come up with a certainty on this is to find a significant number of unrestored unmolested cars with fog lights on identical style left and right brackets. Then see if the switches are in the same place.
We could ask a second question, “where does it make the most sense to put the switch, what would the factory do?” But there may be disagreement, and even if a single answer seems to present itself, there may not be universal acceptance of the answer.

(Jag-ur) #22

Well said. This was the logic I used when facing the same issue as Wyn. Without a shred of ‘proof’ I looked at the dash of my car a '54 120 OTS and said to myself … what LOOKS right? the spot I chose was the only vacant unbalanced location on the central instrument panel… the location used by the factory on the FHC / DHC for the panel lamp switch. Now I realise this won’t work for everyone as the instrument panels are different…

(Jag-ur) #23

Neither do I Wyn but that is what the spares dept of Jaguar send me in 1978. NOTE FW prefix. so by factory definitions this was a specific part for this application.

(Rob Reilly) #24

Most of the time prefixes mean something.
FW means an ordinary flat washer from any number of suppliers.
BD means Body.
C means Chassis (including engine, gearbox, brakes, axles and steering), and an example is the Shakeproof washers which are all C numbers, probably because they could only come from one supplier, the Shakeproof Co.
Philidas and Pinnacle nuts are other examples with C numbers.
So C.792 was originally chosen for use on the chassis, and such a low number suggests it was assigned during the SS era.
In my spare time (not much of that lately) I have been cataloging C parts in numerical order. Parts C.787 to C793 seem to be extra thick flat washers in increasing sizes. If I find time I’ll see where they were used on SS and Mark IV.

(Jag-ur) #25

agreed… if you look in the back of the 120 SPC the factory description of FW208/T is : 1/2” BSF x 1.125” OD .092 thick BEVELLED steel. it also notes only 6 were used on the car. I can find no other place where these particular washers were used… why 6 ? don’t know.

(Rob Reilly) #26

I was under the impression that beveled meant the hole was beveled, so it would fit against the stud protruding from the C.3943 Screwed Extension for Spring Bar Fixing.
And of course we have more inconsistencies, in that FHC and DHC use only two.
We’ll have to look around and see where beveled washers FW204, 205, 206 and 207 are used; maybe we can get a clue from those applications.

(Roger Payne) #27

Wyn, one day I will provide a comprehensive write up of Jaguar fasteners, with the immediate post-war period, including the XK120, a particularly volatile period given the arrangements that were put in place during WW2 by the British Ministry of Supply, that progressively became enshrined in revised, and indeed totally new British Standards during the 1940s and 1950s.

The particular WASHER you are asking about, is identified in the J.8 SPC as being an FW.208/T Washer, Plain, on Bolts. and note, it is shown as being 6 off.

Now you need to appreciate, the coding FW.208/T is based on the WW2 British Ministry of Supply arrangements, adopted or extended by post-war British Industry including Jaguar Cars, and the various companies making nuts, bolts, washers etc as being a ‘Standard’ fastener. If Jaguar wanted anything else, it was a ‘non-standard’ fastener, which then required Jaguar to allocate their own part number (C-prefix for Chassis related items, and BD-prefix for body related items), and prepare their own engineering drawing detailing exactly what they wanted - it could be simply an otherwise ‘standard’ bolt, but needing a hole drilled in it for a split pin, or a ‘standard’ washer required to have a special finish such as being plated, and not the manufactures own default finish which is another important subject for XK120 fasteners.

But an FW.208/T Washer is a ‘Standard’ washer according to the British Ministry of Supply, as used by Jaguar and as recognised/used by the various British suppliers of washers, and was incorporated into relevant 1940s/50s British STandards that were revised/updated from time to time.

But immediate postwar, this FW.208/T ‘Standard’ washer part number, can be decoded as follows…

Fx. = BSF thread. (This effectively tells you that the nominal Bolt diameter is as per BSF specifications, and in the case of standard washers effectively tells you the nominal hole diameter)

xW. = a standard Washer. (that’s straight forward, but later codes tell you more about the type of Washer)

So far, all we have is the FW. prefix means a generic 'nominal BSF Washer - and no Rob it does not mean ‘Flat Washer’. The body of the code now gets specific…………

.2xx = for a Washer the 2 denotes being a heavy-duty plain washer. (a 1 denotes being an ordinary plain washer).

.x08 = the size of the washer, in this case the 08 is 1/2 inch nominal BSF bolt size with the actual hole diameter having set tolerances (the British Standard says for a 1/2" BSF washer, the actual hole diameter must be 0.515" to .520" thus I have adopted my own system of showing these nominal sizes as being in this case 1/2" Ф )

So now we know our simple ‘Washer’ as referred to in the SPC is in fact a nominal 1/2"BSF heavy-duty plain washer. Now the British Ministry of Supply, and indeed the relevant British Standards tells us more exactly what that is.

A heavy-duty 1/2"BSF (nominal D) washer is 1-1/8" Outside Diameter (dimension C), with a 0.515" - .520" Internal Diameter (dimension B) and an ‘approximate thickness’ (dimension A) of 13 S.W.G (British steel gauge that equates to 0.092")

(now it should be noted that heavy-duty washers were one Outside Diameter increment larger than their equivalent ordinary plain washer - in the 1/2"BSF size a plain washer is 1" OD, and depending on size may also be one gauge increment thinner, albeit in the 1/2" BSF size still a plain washer is still13 SWG)

Now as Godfrey has pointed out, there is a most useful table on page 99 of the SPC which indicates that all FW.208/T washers are ‘Bevelled’. This in fact is not correct, and I can quote the source from the British Standard …….
15. Plain washers…………………… They may, at the option of the manufacturer, have a chamfer of approximately 30 degrees on one face.

Note ‘at the option of the manufacturer’.

This of course explains why those who have closely studied actual XK fasteners will be aware that although there are many uses of FW.2xx series heavy duty washers, although always of one diameter increment larger (for the nominal bolt size), they are regularly found ‘bevelled’ or ‘flat’ without any bevel, so no surprises finding flat FW.208/T washers on an XK120. There are other manufacturing characteristics not specified in the British Standards, thus for those that care about pedantic detail, should seek out and restore the correct original fasteners, rather than buying new - with the new ones not necessarily to 1950s dimensions/tolerances nor indeed manufacturing characteristics.

Re the topical FW.208/T their are two residual aspects…….
The /T suffix denotes the material used, and in the case of a plain Washer /T denotes STEEL. The British Standards will specify the exact grade of Steel, being a pretty basic uncontrolled strength mild steel, somewhat inferior to the 45/55 ton /D grade steel used in bolts and setscrews. (Washers used by Jaguar can also be found in grade /X = Spring Steel, /E = Copper and /C = Brass)

The final detail is what finish is applied to the steel washer, if any.

As per my introduction above, if Jaguar had wanted these washers to have any special finish then they would no longer be a ‘standard’ fastener, but a ‘special’ fastener required/supported by a C.xxx prefix part number engineering drawing So they are NOT plated, as is say the C.793 Washer, Spacing shown Chromium plated in the photos.

For standard Washers all the 1951 issue British Standard requires is…….

" The bolts. screws, nuts shall be cleanly finished, sound and free from defects" (Washers don’t rate a specific mention)

What that means is you got whatever the manufacturers ‘default’ finish was, depending on item and how they made it. Normally in practice, things were either left bare-untreated steel, often given a basic protective ‘blackening’ process, which during the XK period was invariably one of the many proprietary hot chemical-conversion bath processes that gave a black-oxide finish, and indeed as students of XK120 BEES bolts will appreciate, sometimes a simple red-lead dip. My observation of ‘standard’ XK washers however, is those not over-painted in an assembly, were most probably black-oxided. And if Jaguar was not happy with that, then all they needed to do (but didn’t) was instead buy these in as ‘Special’ fasteners with a Cxxx part number, and nominate their required additional surface finish treatment.

So my advice to anyone wanting to restore their XK120 to the most authentic standard possible, and in a no-maintenance show condition, read the J8 SPC carefully (and don’t jump to wrong conclusions), but you cannot go past these exposed ‘standard’ fasteners having a black-oxide finish - and never plated.

(Rob Reilly) #28

Thanks, Roger. Always fascinating to learn new stuff. So F means Fine but still works with a BSW screw. Gee, I would never have guessed that the government got involved in assigning ID numbers to washers. I see AW must mean a washer that works with a BA screw.
I found FW204/T Bevelled (Steel) washers are used on Mark V door chrome moldings, headlamp pod chrome motifs and the chrome trim between the front wings. I guess they wanted a larger surface area in contact with the body panels, but I don’t see any bevel on them.
What about this bevel, was it on the ID or OD, and why? Washers are usually just stamped out in a punch press die. Was this an allowance for the punch and draw deformation around the edge?

(Roger Payne) #29

The clue to all of this was the WW2 period where the British Ministry of Supply took over control of who can manufacture what, and supply to whom during WW2. A huge issue was the interface of American equipment supplies and support crews in Britain, with the total difference between the American SAE system and the British Whitworth system which resulted in a number of measures being put in place to better control manufacturing of anything likely to be impacted, and thus the development of the Ministry of Supplies coding system for ‘standard fasteners’, and the rapidly developing associated British Standards.

In the coding system with a two letter prefix being standardised initially (later it added three letters),
the first letter denoted the thread system…

Ax. = BA
Fx. = BSF
Wx. = BSW
Nx. = ANF
Cx. = ANC
and later after the introduction of the new Unified thread series (UNC and UNF) also …
UNx. = UNF
UCx. = UNC
with these latter two seen in XK150 SPCs

The second letter in the two letter prefix (and third letter in the three letter prefixes) denoted the type of fastener………
xB. = Bolt
xS. = Setscrew
xT. = Stud
xW. = plain Washer
xN. = Nut
xU. = Wing Nut
xG. = Spring Washer

The letter association is my best guess, which although sound enough for the more common fasteners, gets a little tenuous at best for the more obscure fasteners, like Wing Nut - and there are more than the ones I have shown.

But its the body of the code that gives you the details/sizes etc, but different protocols for the different class of fastener.

The use of F (BSF) for plain Washers W - thus FW prefix, is more a case of aligning with confusing changes with the development of the 1920s/30s Automotive Whitworth system into what is now called BSF as being a fine thread version of the original Whitworth only system, that was now seen as the course threaded BSW. The constant was the actual incremental diameters of the bolt shank, regardless of BSF or BSW thread, and regardless of the respective hex head size associated, that did change. And you wonder why the Americans were confused in the WW2 period operating in the UK - thus the British Ministry of Supply initiative settling on washers having a hole size to suit the nominal BSF bolt diameter, and not the larger same nominal size BSW bolt diameter.

If your still confused - just trust me. I spent many many hours a lot of years working this all out, and now decoding understood I have my spread sheets prepared, and its been 100% accurate ever since. But you need a good handle on the several different associated British Standards, and all their regular updates and revisions. I was lucky with Australian industry being based on British Industry, and indeed the Melbourne Technical Library has a near complete set of British Standards, issue by issue, up dates and amendments, back to when they started in the late 1800s - and several days searching and photocopying, now has me a collection of everything relevant to XKs.

Now one word of warning - what I have said here relates mostly to XK120/140 exactly, but minor evolution into XK150 period. But also reasonably accurate, indeed good enough for Mark IV and V.
But your 1938 SS-Jaguar will not be exactly relevant, as there was considerable changes in the Whitworth system during the 1930s, prior to the WW2 American confusion (WW2 actually started in Sep1939 for England, Australia, NZ and Canada etc, but not until Dec1941 for USA), and thus the British Ministry of Supplies efforts to sort it all out.

But you bevel washers as I said before - a 30 degree bevel on the outside diameter only was optional, so you could have both standard plain washers and heavy-duty plain washers with or without a 30 degree bevel. Still a ‘standard’ plain washer, albeit in my experience usually with heavy-duty washers, and not standard plain. The two round washers under the Cylinder Head dome nuts on an XK140 are FW.207/T - and they always have a bevel. I have extensively surveyed and recorded XK140 fasteners, but not XK120, so cannot immediately comment on where you will find heavy duty plain washers on an XK120 - and then its only physical observation that will confirm whether bevelled or not. (I have done this for XK140)

The J8 SPC advises that on an XK120 OTS (at least, and given 1950 publication date I would say prepared from finalised Aluminium XK120 stock take), there are 4 only FW.204/T, 4 only FW205/T, 2 FW206/T, 4 FW207/T and six only of the current topical FW208/T to be found on an XK120, so shouldn’t be that hard to locate application in the SPC, and then go and physically check whether bevelled or not. The six FW208/T are all on this front bumpers set-up, and seem to all be non-bevelled. (Others can comment), but yes, manufacturing method certainly comes into it.

Non-bevelled washers appear to be simply punched out of sheet steel, but bevelled washers appear to be machined from steel rod.

Re Body items, just remember, Jaguar did also used special body washers, both excessive large diameter, and also the rectangle with oval ends style - but these have Cxxxx part numbers, as they are not ‘standard’

And I too have seen washers with the internal hole bevelled - but these are ‘specials’ and not ‘standard’.

(Jag-ur) #30

Hello Roger isn’t this fun ? All I can go by is what Jaguar sent me back in 1978 when I ordered these as part of a massive order of whatever I could lay my hands on NOS from the factory. May I suggest that we see if we can find known unmolested 120s which we can then deduce which style of washer is found on them ? What I received were bevelled black oxide washers 4 of which are now on the car… the rest of which I am sure I still have in their original packet… somewhere in a box of all sorts of other NOS 120 spares. I am still building my new house so a lot of these things are seriously buried. I’ll be the first to acknowledge that the washers I received may be of later manufacture… but they do correspond with the factory description in the SPC. Whether or not the ‘option of the manufacturer’ was exercised may be moot… surely for judging purposes we need to follow the SPC ?

(Roger Payne) #31

You said it Godfrey - it really is of minimal (but not zero) relevance what you claim Jaguar sent you in 1978 whether with or without original packaging showing FW.208/T part number. This is some 35 yeras after the XK120 original FW.208/T washers were made. A more graphic example of the danger of presuming same use of the same part number 35 yeras later, I suspect no one will disagree that an original C993 Tyre Valve Extractor tool as included in an XK120 tool kit was made of BRASS; yet the C993 Tyre Valve extractor supplied to E-types etc, and as a NOS spare part from 1962 onwards was now made of YELLOW PLASTIC. I am not suggesting you think a yellow-plastic C993 is ‘authentic’ for an XK120 tool kit, nor indeed are you likely to have one in your own XK120s tool kit. But same logic and position applies.

AS you say, if you want a better idea, you need to check several original XK120s built over the 1949 to 1954 period to see whether they are the same, or a mix of bevelled and not bevelled flat washers.

It’s a personal satisfaction thing, as neither out local Australian ACJC Concours, nor indeed my understanding of either the American JCNA system, nor the British system would care, so long as there was a flat washer there, and it wasn’t chrome-plated!

But your NOS Washers should at least measure up as per the dimensions I have advised as decoded from the standard part number FW.208/T as exactly detailed in the in the 1951 British Standard. But then whose to say if something hasn’t changed in a later revision of the relevant British Standard that would have been in place in 1978. Let me know what exact dimensions you get, and if different from the 1951 dimensions, I do have the later revised standards and can check.

But what a shame that back in 1978 you didn’t also get a NOS pair of C.2985 and C.2986 optional XK120 Fog Lamp brackets. Several period photos of XK120 OTS and FHC now confirm their general shape one-piece ‘L’ shape, and scaling can give some indication of certain major dimensions; but I would love to get a caliper onto real ones, even 1978 NOS replacements. But with some solid leads now, as there are a number of the cars with period photos of their Fog Lamp brackets, known to still survive - if not yet any within North America - but they will turn up, even though much rarer than the easily found and non-authentic for XK120 ‘Universal Two-Piece’ brackets as widely sold with a universal Fog Lamp kit by Lucas, to after-market customers for many years.

(Wyn Laidig) #32

Thank you Roger for this illuminating discussion and very valuable information.