Brake hose copper crush/sealing washers.

[DerekS]

Evening all. I'm maybe being too finickey here but I have a set of Goodridge brake hoses waiting to go on my 1500 Spitfire; however the copper washers supplied with them are, to my mind, too big an internal diameter. Mic'd up, they are all 10.4mm as opposed to 3/8", a difference of around 40 thou in old money, a sloppy fit around the thread. What concerns me is that if they don't end up central to the fitting then they are liable to fail. I've been in touch with the supplier and they are adamant that they're right but I would be happier with 3/8" i.d. ones. This is where the fun starts... I've now had deliveries from 3 different suppliers of supposedly 3/8" washers but on inspection they are all the same, 10.4mm. When I've spoken to the suppliers they all say that 3/8" and 10mm are the same size. When I was working in engineering, we had boxes of Imperial and boxes of Metric, small differences but the size was important. ( Sit back and wait for the wisecracks...) So, can anyone point me in the right direction for the correct sizes please, or am I wasting my time? My apologies if this has been discussed before.

[Pete Lewis]

3/8"  =  0.375    =  9.54 mm 

Washers have a clearance so expect internal diameter to be a tad larger

The problem with brake fittings is there is often an undercut at the end of the thread to  ensure it fully tightens against the faces

and not be thread bound . This gives you the extra sloppy fit you have ended up with

Doesnt solve it but gives some clues why its happening

Understanding your feelings of reliability I would feel the washers will be fine despite some off centre results,  

Pete

[Colin Lindsay]

I took my hoses to a local motorfactors and we fitted a selection until we got ones that were a correct fit; the ones that came in the boxes (Goodridge, as well) were far too big.

[DerekS]

Yes, there is an undercut on the thread and the washers are a sloppy fit on the threads as well, the two factors combined give a load of clearance. It also effectively reduces the area of the sealing face. Not good. That's a good idea re the motor factors, Colin, thankyou. 

[Pete Lewis]

Loctite make a hydraulic sealer , designed for high pressure threaded fittings

We used it in manufacturing on brake fittings , impressive its a gotu for life once its set ,,  it wont come apart without a fight.

Pete

[DerekS]

Food for thought there Pete, I have a tube of Omnifit in the garage, it is good stuff, used in industry shall we say, but can be, err... permanent.