There are four (more or less) flaring styles in common use for brake
systems. British cars have a bubble flare (aka Girling flare) backed up with
a male swivel nut or a 45 degree double flare backed up with a female swivel
nut. Metric cars have ISO bubble flares, where the pipes and threads are
metric sizes rather than inch. Detroit iron has a 45 degree double flare
backed up by a male threaded nut. Most (non-British) race cars are plumbed
with AN (aka JIC) type single flares - a 37 degree single flare with a
backup sleeve and inch threaded swivel nut (some people make a double flare
here, which is useless overkill and may lead to failure; see below). Lastly,
some brake fittings use tapered pipe fittings.

Take the easy one first: tapered pipe fittings are not really a positive
seal under adverse conditions. They may do the job for a street car, but
they certainly have no place on a race car.

The bubble flare is used with a male swivel nut, and seals at the bottom of
a drilled and tapped hole, with a nice angled bottom. While it can usually
be resealed, it has a limited lifetime - there's no good way to get back the
deformation that was crushed out for the first seal, short of remaking the
flare from scratch.

Making such a flare is easy: if you are in possession of a standard 45
degree double flaring tool, the bubble flare is what results after the first
half of the operation. Simply stop there, and you have the bubble flare
which will seat nicely at the bottom of the hole. If you continue, inverting
the form tool and finishing the job, you *then* have the more familiar
double flare used by Girling and the US automotive industry.

REFERENCE:
http://www.dimebank.com/BrakePlumbing.html
--
Shawn Feller
Ohio
www.carboncow.com