Brake pipe union threads

[craman]

Yes, Taupe, I've been reading your posts too! I will just have to pick either one, as I'm re-building from scratch, I might as well change the to metric because where I live, both UNF and BSF are extinct anyway! So let's create a 3rd version, right, wrong, metric. ;-)

Cheers.
Chris

[Nickol]

To be precise and rather pedeantic, it is not metric but SI - Systeme international. The Name never really caught on since ist inception. places which previously used the metric System hardly noticed any Change and the British did not like it much because........perhaps I had better not say.

[philthehill]

You can find 'Unified', American National Fine (ANF) and British Standard Fine (BSF) threads on the brake system of a Morris Minor.
Throughout its production there were changes made to the brake pipe fittings of the Minor and unless you know the Chassis/Com number and that the brake system has not been touched since it left the factory you will never know what you have fitted until you check the threads of the pipes you are having to deal with.
In the early BMC workshop manuals under 'General Information' there used to be a comprehensive description of the threads used and how to identify them

[oliver90owner]

Thread gauges are cheap enough to buy and should last a lifetime if looked after. An alternative is to buy one (pair) of each thread fitting, and retain these as comparative examples.

Clearly, if plumbing from scratch, using the modern, internationally unified (apart from the US!), metric, SI, simple system should be the sensible choice. Unfortunately, the connections at the ends of the pipes may well have to be the old, outdated, superceded, imperial, or unified US system type. Think here master and slave cylinders.

RAB

[philthehill]

Imperial and/or Unified threads are not old outdated or totally superseded - far from it - they can be currently found in a diverse selection of equipment from cars to mowers.
Each thread has its purpose and use/application.
It make no sense to depart from the original specification unless those parts are not available - It is not as if the Morris Minor brake pipe unions both male and female of what ever persuasion are not available.
Departing from original specification can lead to confusion and the application of the wrong part/thread which could lead to brake failure.
Just as important as the threads on brake fittings is the shape of the nipple on the end of the thread - as alluded to above - the nipple on the end of the brake pipe has to be the right form. If not the right it can lead to leakage of the brake fluid and ultimately failure of the brake system. Concurrently with that - the end of the brake pipe nut has to be the right shape to seat on the nipple.
Brake pipes should be fitted/shaped so as to eliminate any stress at the point of entry into the union/cylinder/nut otherwise there is a good chance of a pipe fracture.
There is more to fitting brake pipes than just thinking about threads.
Phil

[IslipMinor]

Chris,

I don't understand what you mean by ' I might as well change the to metric '?

The brake pipe fittings screw into either the master cylinder, wheel cylinders or brass fittings - they are all imperial threads, either BSF or UNF and cannot/must not be fitted with a metric threaded pipe fitting. Please explain what you mean?

[craman]

Hi Guys,

Thanks Phill and Nickol, I fully understand what you all meant. Was just fed up with all the various combinations available. Am sticking to plain vanilla as they call in IT, which is, what it was out-of-the-box.

Richard, what I meant to changing to metric or SI, was the BSF of the M/C remains, there would not be a banjo as I will connecting that to the inlet of the servo (Lockheed type LE72696), will remain. The inlet to the rear cylinders which is BSF shall remain. Unless I change the 4-way front and 3-way rear, and yes, I will have to add another 3-way from the servo outlet to the rear and front brakes, I could determine that those pipe ends could be in SI.

So there will a mix of 3 BSF plus the rest in Metric, owh, not to mention the UNF which will go into the Marina front disc calipers as well!

Rest assured, have decided it will be as-they-were.

Thanks for all your input.

Regards,
Chris

[bmcecosse]

So - you are now going to make even more of a pig's ear of it all by fitting in some Metric pipe connections?? This makes no sense at all and could lead to disaster - perhaps not with you if you remember what is where -but with a future mechanic/owner. I strongly advise to keep it standard and NOT get involved with metric fittings for the brakes.

[craman]

Nope bmcecosse, I was not serious about the pig's ear although the innards are great in a stew.

It's standard fittings as you stated and not taupe's original sketch which is pre-1957 or on a Series 1 & MM setup.

It will be all UNF except the outlet from the M/C, and from the rear 3-way outlet (2-ports) and into the rear cylinder will be BSF. No more changes, period.

Thanks for the feedback and concerns!

Chris

[bmcecosse]

And the brake pressure switch T piece....... Rover made a mess of the later Mini (and probably others in the range) by using M10 x 1 fittings in some places and UNF in others - but at least they dropped the BSF. UNF and M10 are particularly dangerous because it is just about possible to convince yourself that an M10 fits into a UNF with drastic consequences for the threads - and possibly on the road if the connections hold together that long.....

[craman]

I agree on the UNF = M10 which is a no-no.

For the brake pressure switch, I have just received a new T-piece 1/8 NPT all 3 sides (1 male, 2 female) which should fit as standard. A question on this, I have noticed the Minis had a braided oil pressure pipe connected on the engine end and to a straight connector where a copper pipe would connect to the gauge. Is the braided pipe there to absorb any vibrations from the engine or could I just connect a single copper pipe from the engine (T-pipe) to the pressure gauge, with slight looms to ease pressure off the pipes compared to a straight through connection.

Cheers
Chris