"vincent Brannigan" wrote in message
...


Keith Willshaw wrote:



The cost of boring
(drill the main center tube) and turnign (trunnions) is the same.

However the machinery required to cut rifling in a cannon
bore is of an entirely different order from the simple boring
process adopted for a smoothbore.

no it is not. you still advance the cutterbut you synchronize the
forward and rotational action. its called a "screw cutting"


Yes I know

There's a good reason
why rifled cannon didnt appear on the battlefield before
the 1850's and the rise of the machine tool is a large part of it.
It wasnt until 1841 that the first standardised screw threads
were introduced by Whitworth for example.

Does not affect cannon. all you need for cannon is a precisly cut tool
feeding controller. Cannon barrels did not require the precision that a
machine screw required.


But without screw threads how do you make your "precisly cut tool
feeding controller. "

Such devices were made possible by Whitworth and his colleagues
and the simple fact is the maching of a rifled barrel requires a fair degree
of accuracy if you are to have consistent accuracy which is rather
the point. After all until 1745 cannon were basically hollow cast
with maching being confined to cleaning out the bore.

Moreover the Parrott's were reinforced with wrought
iron hoops on the breech.


Sure, but they did burst. a lot, because the thermal effects werenot
well understood.


Its more to do with the fact that cast iron is a poor material
under tension.



It being softer thats hardly surprising.

but you could also make guns lighter than an equivalent Iron gun. which
is why iron was preferred for naval and caost defense gusn and bronze
for field guns.


Actually bronze guns were preferred for all uses until such time
as iron was available in adequate quality as well as quantity.
They lasted better and were more consistent but the huge
reduction in the cost of producing iron and increases in quality
around 1776 with the introduction of the use of coke
made them very much cheaper

Keith