It occurs to me that with the short tube spanner with the square end, we may be looking at the wrong and of the horse.
Perhaps it’s not a tube spanner, but a socket, and the square end is for a standard 1/2" drive fitting.
That’s a thought, but Tool Kit includes a small 5/16" dia tapered Tommy Bar (C.34), for the 5/16" dia tommy-bar hole in the middle of the C305 Box Spanner, as per pic below.
Yes I can see the reasoning Ed, use with any 1/2" drive socket. I cannot
think of a 1/2" square female plug etc on a ENV.
For the 9/16" BSF perhaps the Hartfords,arm to chassis/axle, on a 100
Peter B.
Of course there’s no reason a socket couldn’t also be turned by a tommy bar-. Multi-functional
And /or possibly the tools weren’t specifically for Jaguar but already were used on another vehicle.
And so cheaper to use existing tooling
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You mean it could have been used with a square drive handle.
Like these I inherited from my wife’s grandfather.
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Rob
Exactamundo
Ed
In the absence of any other probable explanation for the 1/2" x 1/2" square end, there is good merit in your suggestion Ed, and at this stage only feasible explanation.
But that’s the 1/2" x 1/2" square end.
What is the .580 AF Hexagon end for on a C305, if the square end is an alternate drive to the Tommy-Bar, then the hexagon socket end must have a specific purpose, especially being a non-standard AF size.
The “.580” couldn’t be .600"" could it and be for 3/8 " BSF?
I wish.
Its shown on the Engineering drawing as .580" and two originals that I have measure to be the same, +/- .002 across all three AF positions on both box spanners. As before, an odd ball, and the only SS/Jaguar box spanner that has no sizes stamped on anywhere.
I’m currently having a ruthless purge of magazines but trying to retain a few that might interest me in the future. Anyway, in Jaguar Driver October 1996 Allan Crouch describes the spanners in the MkIV tool kit. He describes C305 as “Box spanner for rear axle bolts 3/8” BSF at one end and square at the other for the clutch taper pin."
I can’t think what the clutch taper pin is but I presume Allan will be able to identify it.
Peter
p.s. It might be the pin C.568 securing the “C” shaped lever to the release shaft.
C.568 is the threaded pin both on the clutch release bearing fork, and on the outer end of this same shaft where a lever arm connects to the pedal shaft, and is certainly tapered. It is also drilled through on the square head for a wire tie. But the square head is 5/16" so this C.305 doesn’t seem like the right size.
Have to say, all the tools in an SS-Jaguar tool-kit were supplied predominantly for specific-purposes on the road/ or routine maintenance jobs, and I think accordingly, totally improbable for anything that was part of a major repair job. I just cannot see Tool-Kit box spanners being supplied for clutch jobs, removing shock-absorber mounting bolts or any such similar major repairs.
Drain Plugs, filler plugs, brake adjustors, sparking plugs, wheel-changing equipment, all are road/routine maintenance jobs, with a set of open-enders thrown in for good measure.
What is interesting is that the C.305 described as being for Rear Axle, was supplied to SS-Jaguar and Mark IV/V that had both ENV and Salisbury rear-axles.
The C178 was supplied to 2-1/2 and 3-1/2 litre SS-Jaguar and Mark IV only, not 1-1/2 litre and not Mark V.
So quite a deliberate deployment, not that Jaguar never made errors with tool-kits - the small Allen-key handbrake adjusting wrench as required for early 1961 E-types only, was still listed and supplied to 1962-4 E-types with self-adjusting handbrake, and indeed although deleted from 4.2 E-type tool-kit listing was still in fact supplied in 4.2 E-type tool-kits. Starting to think the guy responsible for the E-type handbrake wrench listing, may have learnt his trade from his father who did the C305 listing 
Although SS1 tool kits had specialised spanners for adjusting the bearings inside the diff centre. Probably as major a sit gets
Sorry to keep on about this, but still exploring possible uses for the C.305 Box SPanner for Rear Axle.
I have just located an old reference that said the C305 was a 7/16" x 9/16" Box Spanner, which is wrong - the C305 has a 1/2" x 1/2" square end and a .580" internal hexagon the other end, and the C178 Box Spanner for Shock Absorbers is 7/16BSF x 9/16BSF.
But any way, says its use if for the ENV Rear Axle Dip Stick. Photos I see show the rear-axle as having a hex-headed plug o top of dipstick, but I don’t know size. Can anyone advise hexagon size, and if possible a good photo of dipstick and one of its Hexagon plug. That’s the type of service application that may well warrant a tool-kit tool.
The other end was claimed to be for nuts securing rear axle to springs - most improbable I think, but as above, who knows - nothing else obvious.
The U bolts , rear axle were a BSF thread , The fronts are UNF but with a Whit sized hex But the size varies on different models. I think some 1/2" some, 7/16"
SS1 were smaller than later OHV Jags
A tube spanner may be right as you have to wind the nut up the U bolts often against the spring tension.
Hi Roger,
The dip stick head is 7/16" Whitworth. 0.825" across flats.
The filler plug is 1.32" across flats.
Peter
Roger,.
I use 4 rear axle U bolts (origin `37 21/2 saloon) on my car.
They are 3/8" dia with 3/8 UNF not BSF threads.
Each U bolt has 2 full nuts and 2 locking half nuts, all are 3/8 W /7/16 BS
socket/spanner size.
BTW when stating socket/spanner sizes Whitworth or BS helps.
Sometimes you do sometimes not.
Peter B
Dipstick plug
takes a 7/16W 1/2BSF spanner
Square drain plug
takes a 3/16W 1/4BSF spanner
Differential housing nuts
take a 5/16W 3/8BSF spanner
Filler plug
takes a 1-5/16" socket
Rear axle leaf spring clamps
take a 5/16W 3/8BSF spanner
Square brake adjusters
take a 3/16W 1/4BSF spanner
So I’m coming up blank on what the C305 could be used for.
I know you said you had a drawing, but is there any chance it has been misidentified? A drain plug would make the most sense.
Many thanks Rob for all your pictures, and those with marked spanners in hand - perfect. I will digest for answers and relevance.
I agree though, I still cannot confidently place any probable use for a C305 Box Spanner that was supplied to all 1938-40MY SS Jaguar, as well as Mark IV and Mark V. Whether the C305 factory drawing is correct or not, its advised dimensions of 1/2" x 1/2" external square one-end, and .580" across-flats internal hexagon the other end is physically as per original C305 box-spanners are - I have three, and have checked several others.
Maybe the factory drawing was in error, but I doubt it - as it is the only box-spanner that deliberately specifies ‘non-standard’ size ends, and indeed the only box spanner where the sizes were not required to be stamped on to the spanner - and were not in practice. Maybe it was intended to fit something that ended up being changed, but the C305 spanner wasn’t modified/changed. I still think the male 1/2in x 1/2in square end looks like being intended for a female 1/2in x 1/2in drain or filler plug, so maybe ENV changed their design/supply to Jaguar. But that’s a guess, and still doesn’t explain the .580" hex-end, another non-standard size. Ed’s suggestion of the 1/2 x 1/2 suiting a socket-drive is improbable, but the best idea I have so far, but still there is that .580" hex end! Maybe that’s why all C305 box spanners I have and have seen are UNUSED!
Many thanks Peter for the Dipstick photos. Shame the hexagon is not .580" across-flats, not that I thought it would be looking at photos.