Hi all, first post with a new account. I'm Chris (used to be iti_uk on here but couldn't access that account since I forgot my password and the email account it was registered to was deleted a long time ago )

I have a situation where I need to join an M12x1 double flare brake hose to a M10x1 double flare brake hose (male-male).

My car has this union block from the factory (M10 - M10) (pic courtesy of random ebay ad). In my mind, I would be re-machining this block, or fabricating an equivalent to accept M10 and M12 double flare lines.
[img]https://i.ebayimg.com/images/g/Ec8AAOSw58Njot44/s-l960.webp[/img]

Does anyone know any good contacts who can do this? Or even whether adapters like this already exist?

The reason for all of this is that I'm using a non-standard brake booster and master cylinder in my car, and the only master cylinders I can find in the correct bore and mounting flange (I don't want to use adapter plates) come with M12x1 brake line ports, whereas my car uses M10x1. The car already has a factory brake line "break" block (I believe where a proportioning valve is otherwise installed in other markets) and this seems to be a natural transition point for the brake lines without increasing the number of joints in the system (this is why I don't want to use M12 male - M10 female afapters if possible).

Hope that makes sense.

TIA

Chris

Maybe another possibility - considering the brake lines are 3/16 (4.75mm), would anyone be able to comment for/against using these;

https://www.rallydesign.co.uk/product_info.php?cPath=562_85_1923_1210&products_id=9956

First I've heard of a fitting allowing a 3/16 line to connect to a M12x1 fitting...??

No reason not to use the M12 pipe unions on 3/16 pipe, such unions have been around for years, pretty sure some fitted as OE. But would that not mean your block

Link to image

would now need to be 12mm to 12mm - dunno if such connectors exist, I couldn't find any?

Oli at Furore products could make you a replacement hose with whatever ends you want on it to give a direct male to female joint for far less than any specialist machining.

Link to custom hoses

I'm thinking that this M12 would be the connection on the master cylinder, with the 3/16 line coming out of it which would then be attached to that block using the standard M10 fittings.

Thanks for that contact, I'll make contact soon .

As long as there is no problem with the 3/16 line flare dimensions and the normally-1/4" line port then I will go with that as the simpler more-off-the-shelf solution.



edit: breaking out the verniers, the ID of the 3/16 line is around 3.1mm, the port internal diameter on my stock M10-based brake components seems to be ~2mm, and the port internal diameter on my M12-equipped master is ~3.5mm. The "outer diameter" of the seated portion of the flare on the line (if that makes sense) is ~5.4mm. So, with a 3/16 line, of the 1.15mm mating surface of the flare, with an M10-based fitting you get all of the 1.15mm, whereas with the M12-based flare, you get 0.95mm mating with 0.2mm inward-overlap of the line's flare into the port. Not sure how that compares with using the 1/4" line as I don't have a sample to check, but I think ~80% mating contact of the standard M10 fitting would be... okay??

[Edited on 14/10/24 by ChrisCope]

Can't you just put m10 on one end of the pipe ans m12 on the other?

quote:

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Originally posted by adithorp
Can't you just put m10 on one end of the pipe ans m12 on the other?

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