Skye Poier wrote:
>
> > WARNING, another 'story'
>
> Keep them coming Neil -- I enjoy them!
>
> SKye
Bedtime Story For MG Nuts. ( Original from Roger Furneaux
MGCC 'T' Register, UK.
Modified by Neil Cairns!!)
It all started in 1915, when Hotchkiss, a FRENCH manufacturer of
machine-guns, moved to England to get away from the Bosche, who were at
that time winning WW1. Hotchkiss built a new factory in COVENTRY, with
finantial aid from the UK government. The guns were a vital part of the
armament supply to the troops, but a safer base was needed away from the
advancing Hun.
After WW1, ( England 1, Germany 0,) the firm found itself with no work,
so they approached William Morris, for whom they built a copy of an
American engine under licence, for the Bull-Nose Morris Oxford and
Cowley. The firm had never made an engine in its life, but their
expertise in machines was a great asset. They did such a good job of the
engines and gearboxes, Morris brought them out, lock stock and barrel so
to speak, in 1923.
It was common in the early Industrial Revolution for companies to have
their own theads on nuts and bolts. In the UK three had eventually been
standardised for the motor industry, British Standard Fine, BSF; British
Standard Whitworth, BSW; and British Standard Pipe Thread, BSP. All used
the Whitworth thread form. The USA was developing its ANF and ANC
system, but the European Continent had mant variations of metric
threads, that would eventually lead to the ISO Metric system. There were
other threads, British Association, BA, a tiny system used in
instruments, and some UK firms were coyping the Americans, but calling
the system UNF and UNC, Unified Coarse and Unified Fine.
Hotchkiss had their own metric thread system for the manufacturer of
their guns. They continued to use these taps and dies on the engines
they made. But as time advanced, the more logical system on a 'Unified
Common Thread' for all machines was developed. In the UK the heads of
ALL the nuts and bolts were made BSW sizes. This was handy as the BSF
head size for the BSW equivalent was the next size down. This mattered
not, as the mechanic only needed one set of spanners. Even BSP used the
spanner sizes, ( on sump plugs, etc.)
Morris's Nuffield Empire was not to be left behind, Morris Engines
Branch, as Hotchkiss became once purchased, use BSW heads on their
unique metric nuts and bolts. So Morris engines could be stripped and
rebuilt with those normal set of spanners.
Now, not only Morris used Morris Engines Branch Engines, so did Wolseley
and MG. It would have cost a small fortune to re-engineer the automatic
thread cutting machines of Hotchkiss, so these old French Metric threads
were used on Morris until 1954, MG until 1955 and Wolseley until 1956.
In the MG context the XPAG engine and its gearbox were the last to use
these odd metric threads, the XPEG being the same, but bored out, unit.
Are these old metric the same as modern ISO? Well, some are and some are
not. The ancient metric threads were in two pitches, ( distance between
the tops of the thread,) these were standard & fine. The standard
Hotchkiss thread DOES match the modern ISO, especially in the common
sizes. The fine does NOT match up, though the most common 8mm x 1.0mm is
still available. The thread angles are 60 degree throughout.
Mad Metrics, the bolt supply specialist run by Roger Furneaux, can find
you the nuts & bolts you may need. These 'Mad Metric' threads are used
in the MG;- TA, TB, VA, SA, WA, TC, TD, TF, YA, YB, YT; Wolseley;- 4/44,
Ten/40, Twelve/48; Morris;- Eight, Ten, Twelve, Fourteen, Twenty, Series
'M', Minor, Minor series MM, sv Cowley and Oxford.
In the XPAG;-
Dia & pitch equivalent location BSF spanner size
5mm x .8 ISO metric fan blades 8mm or 5/16"A/F
6mm x 1.0 ISO metric Oil pump bolts 1/4"
Tappet chest cover or 5/16"
8mm x 1.0 ISO fine Front of sump,
long head rear of sump,
long slotted head, rest of sump,
Bell housing,
Gearbox remote studs,
Rocker shaft small,
Small water pump studs,
Back axle casing,
Manifold studs,
Timing cover,
Little end pinch bolt, all 1/4" or 5/16"
10mm x 1.5 ISO coarse Cylinder head studs 3/8"
Rocker shaft large 7/16"
12mm x 10.5 no equivalent Main bearing stud 1/2" or 9/16"
10mm x 1.5 ISO coarse brass plug in sump 1/4
12mm x 1.5 special, no equivalent Oil gallery plugs
with screwdriver slot.
.383" x 28tpi 1/8" BSP Oil pipe block to head 7/16"
.518" x 19tpi 1/4" BSP Oil filter pipe bolt. 1/4"
And for information...at chassis number TD12285 the wheel studs,
driveshafts, and back axle threads were changed to UNF, ( ANF.) The rest
of the chassis continued with BSF threads. UNF uses A/F heads.
Roger is on UK 01932 243534, phone & fax.
Neil.
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