Thread: Trying to plumb my brake system?

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Hi Guys,

I'm trying to plumb my brake system and none of my fittings.....fit. The residual valves, proportioning valve, brake switch all were ordered with 1/8 npt fitting. So natuarly I ordered 1/8 npt to 4 AN fittings from jegs. Well I get maybe 1 turn and the fitting just stops. I need fittings for the Wilwood calipers a well and the instructions state the thread pattern is 1/8 27 npt. So I went to my hose and rubber supply and was told that all 1/8 npt are 27 thread. They gave me one of their fittings and it's the same story, 1 turn and just stops.

My last resort is to order the Wilwood brand 1/8 27 fitting which are $5 a piece betting the a 1/8 27 npt is different than 1/8 npt. But I thought I would try here first. Anyone have any experience with the 1/8 npt to AN fittings? Am I suppose to just get a wrench and start turning? I would hate to strip my new calipers.

Any Ideas?

Dust
a

I would go to the hardware store and pick up a random 1/8 pipe fitting or plug and see how that fits. That will tell you whether it's a adapter or valve problem. Seems like our pipe thread is the one thing the Chinese can't duplicate, probably cause they don't care.

Since pipe threads are tapered, it doesn't take much to cause the results you are having.

It seems to me that the standards for manufacturing of these threads are all over the place. There is also something known as "tolerance stackup". All manufactured things have a high and low range on their acceptable size. Get one part on the small side and another on the big side and you get just what you are experiencing. There are also different classes of fit for all threads. Some are intended to fit better than others.

If you are sure that both parts are 1/8 x 27 pipe, then you may have to buy a 1/8 pipe tap and tap the threads a little larger. I've had to do that many times. Just be very careful. Pipe thread size can sneak up on you. Very easy to get the female part oversize. Just take care not to get metal shavings inside what you are tapping. Grease packed in the flutes of the tap will help trap cuttings.

I know that sounds bad considering that both parts are supposed to go together, but that's the reality of building anything, especially cars. Many parts that are supposed to "bolt on", simply don't. That's a fact of car building life.

Here's an example. I have 2 parts out in my shop that are listed as fitting a stock Mustang II front end. One is an aftermarket spindle and the other is an aftermarket adjustable ball joint. They are by different manufacturers. Both parts will work on a stock front end just barely, but they will not work together. I'm going to have to ream the spindle to fit the ball joint.

Reposted after I re-read the thread.

Get a thread pitch guage you might have a metric thread or something silly like that.

All the Wilwood calipers I've seen were 1/8" tapered threads. I just checked the Wilwood site and even their most expensive calipers are listed as 1/8-27 NPT.

Here's a link to a chart that shows how much thread engagement is considered correct. Remember, just as Denny indicated, the threads should reach the desired engagement when tight enough not to leak.

Also, be very careful with thread sealants, like Teflon tape. Be sure to keep it on the threads only. Don't let it roll over the end. It can tear off an get into your system. I like a Teflon based paste type sealant painted sparingly on the threads.

teflon tape should not be used any where in brake or fuel systems!!!!!!!!!!

Originally Posted by jerry clayton

teflon tape should not be used any where in brake or fuel systems!!!!!!!!!!

I agree. Ask me how I know.
.

Can't argue about the tape, Jerry is absolutely right, but have to admit I have used on occasion in a pinch. The dry stuff applied to some fittings from the factory is probably the best.

Yes, as I'm sure Tech eluded to, I've had to pick out of places it shouldn't be.

Hey thanks guys. I think im going to try and tap them, maybe clean up the threads. I checked and the fittings I bought from both jegs and my local supplier are NPT fittings which are tapered. I would assume that since we know the calipers are NPT It would make sense the rest of the brake components would be.

Still may buy one from wilwood just to see if perhaps the quality may be the reason.
Dust

Hotrod46 did you attach that link? I missed it.

So it turns out I have a tap and die for this so I ran my fitting through it. As you can see by the discoloration, I was only able to get it half way up. So I pulled my caliper and took a couple of measurements. It's around 10 thousands thicker at the top of the thread. I guess it's not meant to fully seat. I also attached a pic to show how much I'm getting before it stops. Hope this is enough. It looks like hell but maybe I'll just start plumping and hope for the best? Won't know if it works until I'm done is the bummer.

Originally Posted by 6696

Hotrod46 did you attach that link?

Sorry, I guess it would work better if I included the link.

Normal Engagement Length of NPT Thread in Inches (A) - Technical Reference - Technical Literature - JGB Technical Information Center - JGB Enterprises, Inc.

Best pipe thread sealant ever made:

No. 5(R) Product Datasheet

Rectorseal - used it in the Air Force on high pressure hydraulic lines and fuel lines.

Originally Posted by glennsexton

Best pipe thread sealant ever made:

No. 5(R) Product Datasheet

Rectorseal - used it in the Air Force on high pressure hydraulic lines and fuel lines.

Thats what I use, especially when teflon tape is not applicable.....

Looking at those fittings - wear pattern - it looks like enough threads are engaging.

Rectorseal, we always called it rectumseal... immature.. but still kinda funny.