Technical M10 x 1 into 1/8 NPT- safe?

Hi all,

this is my first post on the site but I am a long time lurker.

I’ve been working on my project, more specifically replacing a blown brake proportioning valve (not fit by me)- this was a ****ty Amazon one, incorrect fitting for the union on the pipes I discovered only after dis***embling it but failed quite suddenly presumably under pressure with the servo that’s fitted through the actual dial before I could find that out the hard way. I don’t think the car was a actually driven by the previous owner who fit it.

i took the plunge and ordered a Wilwood prop valve supplied with adapters-I am new to working on brakes which is where these issues have come from as I wasn’t sure about sizes.

to put an already drawling story short I inserted an m10 thread (flared copper pipe) into the prop valve with little resistance (1/8NPT) and the gap between the Union and pipe (important to note NOT between union and valve) spurt fluid everywhere as I’ve realised, in retrospect, it didn’t create a seal as it had nothing to squash against. I somehow got the brake Union (which was m10- I didn’t know at the time) into the supplied 1/8 /27 NPT to 3/8 UNF adapter (don’t ask, I still don’t know how) and this created a seal, for a while, before the fluid blew out of the other side which I had left as the m10 Union floating about in space- again, my understanding of brake fittings was far less than it is now but this worked for a minute before I realised it was wrong.

I understand now what needs to be done- buying a 1/8npt to m10x1 with a conical interior fitting so the flare seals.

I am wondering if the integrity of the thread is something to be concerned about? the side that I fit the supplied 1/8 NPT (the valves input) adapter into, after inserting the m10 Union into it prior, sealed very well (will still put the m10 into the correct adapter and refit) but I am wondering if anyone has done similar and how it held up? should the valve just be replaced? it was approx £60 so would rather take £10 in correct adapters than buying an m10 valve for a further £60.

 

I’m not actually understanding what you want to do, I’m sure another will though.
But I’d contact Wilwood and ask

“I have this valve of yours, pn “**xzzz” and I need to adapt it to “ this size line. “ Can you let me know what I need”?

Just a suggestion.

 

M10 is smaller in diameter and has a small pitch difference to 1/8 npt. the smaller diameter would prevent the pitch from seriously compromising the thread form over a short thread depth. I doubt it has harmed the existing thread.

 

Reading this has my head spinning.

 

sorry for the lack of clarification but the whole situation as it happened was as complicated as I’ve articulated:

it boils down to, is threading M10 x 1 into a 1/8 NPT slot going significantly compromise the thread if I then reinsert the correctly sized 1/8 NPT- I am asking if it will still hold the necessary pressure it is required to or if it will leak

 

Gee, there is a lot of pucker factor if you loose your brakes....but I guess not as much as loosing steering.
https://www.engineersedge.com/hardware/pipe_thread_installation_13424.htm
The link shows a torque value on a 1/8 NPT fitting at 7.0 inch lbs
I would just put the correct fitting in (maybe cut a flair end off and insert the nut over it so you can use a socket on your inch lb torque wrench)
and tighten it to like 9 inch lbs and see if it volunteers to strip out the internal threads.
and really, I don't know if this is good advice or not.....

 

Get some of the really strong Loc-***e and screw in a 1/8 NTP to 1/8NPT extension. The Loc-***e will lock the first thread into place, the other end can then be used as needed. You can dis***emble if needed without removing the Loc-***e end.

 

Yes. The integrity will absolutely be compromised.

It will leak, too.

You are headlong into harm here. Don't.

 

The hydraulic function of the brake system is under a lot of pressure. If you forced (even lightly) a fitting with the wrong threads into any brake part, those threads in the part are junk and the threaded part needs to be replaced. I wouldn't trust anything less the replacement. If some fool pulls out in front of me and I need to slam on the brakes, I want to be sure the system is up to the task.

When you replace the part with the screwed up threads with the new part, find out exactly what fittings are suppose to be used with the new part. There are several different brake fitting sizes and end configurations for the seat design on the market these days, you have to have the correct diameter, thread count, and seating design for the part you have. Brake fittings are not something you want to guess about.

I've been playing with automotive brakes for a lot of years. I just can't recall any system that used NPT fittings anyplace on the brake line system.
It could be a new thing, or something I just haven't seen or don't remember, but it would surprise me.

 

hint on pictures....take a picture of the damaged area of the part, so we can see what you can see.

It's a Wilwood thing. They use 1/8" NPT on most of their aftermarket calipers and such.

 

First - Welcome!
Second - Can you tell if the NPT threads are damaged or cross-threaded? If so, start over. In any event, if it was my car, I’d be getting a new valve.

 

Sounds like you need a 1/8 npt to m10x1 male/ male adapter (see torques uk on ebay, you talk £'s so I'm guessing UK) and then use an m10 female tube nuts on the lines. You may or may not need to replace the valve if it leaks but if you do it's a like for like swap. Dunno if Wilwood talk metric for a valve with m10. I doubt it as the npt is tapered and so doesn't have a seat to bear on, but the metric fittings aren't tapered, so nothing for the flare to fit to. You have to have adapters, which are mainly male / male.
Chris

 

None of us can tell you if your particular situation did enough damage....or not to make it unusable other than if we could visually see cross threading. You could try running a tap into the part and see if it cleans a minor amount of material...then clean it and see if the proper part screws in correctly. Its really about trying the new parts but not forcing anything..........then testing it. Thats the only way to tell.........or you can just **** it up and buy the new one and chalk it up as a learning experience. I've had LOTS of learning ($$$) experiences..........

 

thank you everybody for the replies- I am first purchasing an adapter from 1/8 27 npt to m10 x 1 with a concave seat for the flared pipe fitting I have as the first and foremost problem of the flare not seating on anything and floating in empty space inside the valve

this is based on the evidence of the leak coming from the lack of seal between the union and pipe itself, not from the fitting

the m10 was not threaded in far so fingers crossed I can rethread the 1/8 and it seats nicely- this will be rigorously tested and at any sign of leakage the valve and adapters will simply be replaced in their entirety but I believe it will hold as evidenced by the other side holding

 

NO.

 

sounds like you're figuring it out.

Any flare fitting with a nut needs a seat for the flare.

Any straight threaded fitting that takes a washer needs a flat surface to fit onto.

Any tapered threaded fitting needs to mate with a tapered thread fitting.

Then you can get into the different sizes, threads, etc.

Might see if you can take a picture of the threads that are bunged, to show folks how they look.

I wouldn't be automatically scared of them like some guys, but then I like to drive old cars with their old brakes. And there's no MOT here.

 

Rule #1 DO NOT CUT CORNERS ON BRAKES. EVER.
Rule #2 DON'T **** AROUND WHEN PEOPLE'S LIVES ARE AT STAKE.
Rule #3 SEE ABOVE.

Cue the *****s saying: "I did it and I lived." "Don't be a *****." "****ty brakes are traditional", etc.

 

Personally, I have never seen NPT on OEM brakes.
It appears some of the aftermarket does use them.

 

You mention your lack of brake knowledge. The tubing is and must be a double inverted flare , NOT a single

 

I am using a off topic master in my 46, after converting the rear to an off topic axle and using a disk brake conversion. The master has M10 fittings. I bought the nuts for them, used that when I flared the tubing and I have no leaks.

 

Unread.

 

The way I read is you need an adapter to go from 1/8npt female [on valve] to M10 inverted female. I bought some years ago from Aeroquip dealer but I think I have seen them @ Russels, Earl's, ect. Physically they would be 1/8npt male on one end and M10 female flair nut on the other end.

 

Guys....he knows he put the wrong threaded metric fitting into the 1/8" female port. Now he is asking if correcting the problem by installing the RIGHT fitting into the 1/8" female port will be ok or if the port threads were damaged by the wrong one. It's really simple...look at the threads. Look ok? Install correct fitting and see how it feels. Tighten nicely? Remove it, clean and dry the threads, reinstall with a bit of loc***e and run it. Any mushy or funky feeling business when tightening....don't run it. If you don't understand these type of things and are scared, don't run it.
I'd run it.

 

Much like @squirrel I wouldn't automatically throw it away, if the proper fitting threads in and doesn’t leak once the brakes are finished I would happily drive along. But I too drive old cars with old brakes and have been accused of trying to kill the general public…

 

M10-1.0 has 26 TPI, 1/8 NPT has 27 TPI, M10 has a diameter of .3937" , 1/8 NPT is .405"
Both very similar in size and thread count.
Couldn't have done all that much damage, run a pipe tap down the hole and go with it.

 

I have only seen on the fitting for a hydraulic brake light pressure switch.

Those are customarily 1/8"NPT, and are largely too unreliable to use, save for the Harley-Davidson ones.

 

I used to do a lot of hydraulic plumbing on machines I built.
Even with Teflon Tape, NPT wasn't great. We always used quality components, but....

 

That's funny. We usually use a VW one because the HD ones fail so often.