Stew, there is more to this, and it is the evolutionary aspect
Vickers Carden Loyd built the predecessors to the carriers we know. VCL was a British company, who would naturally use British engineering standards. Pre war they were working with the French, in development work. I cannot recall for sure and could well be corrected here, but I think that is where the metric sized plate came from. If not, It is where VCL sourced their plate from.
Many things have rolled on through. As an example, the petrol cap on the Carrier fuel tanks was the earlier engine oil filler cap in the Vickers tanks. The Vickers tank track Became the standard from which Australian carrier track came, which later became the basis for Windsor track. I would suggest the Americans had a close look at the construction of the Australian LP1, and transferred features to the T16.
The metric steel plate went right through the carrier family (as far as I know)
If you want to check into the threads further, from memory the British thread will have a 55 degree included angle with a flat root, and radiused crest, while the American threads will typically be 60 degree included angle with a flat root and crest.
As Paul has eluded to, BSP ( particularly tapered) is a a very common thread form used all around the planet, more common that NPT.
Michael R has cleared this up for me, as I had previously disregarded BSP as a contender for the axle thread.
This little line is great:
The greatest cause of non observation, is preconceived opinion

Here is another thing to think about. The British inch, and the American inch were different lengths until about 1941, because they each arrived there by different methods. (If your machinists book has a green cover, Stew, it might be in there. mine is about 5 or 6 thousand kms away)

Yes mine has a green cover and that is why most women :salute: do know what six inches really is!

British pipe sizes are designated BSP.Tr for tapered threads, and BSP.Pl for parallel threads. Pipe sizes are the same both sides of the pond, and there is no 7/8 pipe.
There is however a BSP.F thread that is similar to our NS(National Special) series of thread. The BSP that is being referred to for the spindle threads is the BSP.F, 7/8-14 which has a O.D. of 1.189in. The BSP.F series of thread uses the same nominal diameters as the British pipe schedule, but have added a few sizes in between the standard pipe sizes to give a better range of thread sizes.

Perry

Hi Perry,
Being in England and working in engineering for over 40 years, I am well acquainted with British Standard threads and use them every day at work still. The designation BSP.F means BS Pipe Fitting thread. One of my old reference books, is dated 1946, a Mechanical Engineers handbook, and it lists all the diameters of BSP thread sizes through the range, inc. the 7/8" which has been discussed. A trap that some may be falling in is that certain sizes like 1/4", 3/8", 1/2" are internal pipe sizes, as for water and gas, etc., with some thread sizes not relating to a standard pipe internal diameter. But pipe threads are also used in hydraulics and compressed air and may not be used in conjunction with external threading of pipe, but for other uses. It may be confusing with the size not relating exactly to the thread diameter, but those who use this thread are well aware as OD is shown in the thread tables. With the wealth of metric and US thread forms in the world today, we have to check TPI and angles on unfamiliar applications at times but BS is an excellent thread form and far superior to the rest ..... in my long experience.

Im a hydraulics engineer and you dont want to get into thoes threads!!!
In hydraulics for example, 1/4" BSP thread to 1/4" hosetail (on a fitting) are completely different!!
Think about it, 1/4" is roughly 6.5mm (tail size) but the threads are about 10mm (guessing as no guage with me in office!) :doh: :bang: :fry:
JIC used to get me at first then it all fell into place! Some people use thread sizes but also can use DASH sizes
1/4" is -4
5/16" is -5
3/8" is -6
1/2" is -8
5/8" is -10
3/4" is -12 etc

With JIC its a case of

7/16" is -7
1/2" is -8
9/16" is -9
5/8" is -10
3/4" is -12
7/8" is -14
1 1/16" is -17
1 3/16" is -19 etc:wacko:

man I need to brush up on all this engineering magic :confused.
I sometimes measure parts using both metric and imperial, so something could be 14"3mm. my brain doesn't work well in imperial.
I hope the penny drops one day

rick

Paul, You never stated why the disparity in sizes. It is because those sizes refer to a bore diameter, because of flow volumnes.
Re the JIC fittings, where I have worked we have refered to them (rightly or wrongly) as "bar" 8 (1/2"), or bar 12 etc. and the one you left out Bar 16, (1 inch) (obviously in 16ths, hence Bar 20):wacko::ergh::blink
Perry, how ever it's designated in your book, BSP T or Tr, and BSP P or BSP Pl, it still stands for taper or parrellel.

26 years and never come across a 1" jic mate!
Had jic with fine threads!
Your bar sizes are same as dash sizes
Nov also same as SAE and UNO