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Old 02-12-2020, 07:12 AM
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1/8 NPT Banjo bolt?

Have any of you experience with using a 1/8 NPT banjo bolt? Didn't even know such thing existed.
I'm strugging with the hose routing on my Wilwood calipers. They have 1/8 NPT inlet fittings, and machined surface around the port.
If this works, it will solve my problems.

https://www.ebay.com/itm/Pipe-1-8-NP...53.m1438.l2649

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Old 02-12-2020, 07:55 AM
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NPT is tapered thread .....I'm not convinced there would be sufficient thread engagement to hold pressure on the banjo fitting, I know you're overseas but have you talked to wilwood ??
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Old 02-12-2020, 08:01 AM
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Speaking strictly from a machinists standpoint, I would approach this with extreme caution. As 2old stated, pipe threads are tapered. IF the bolt has a large enough OD and goes deep enough to engage enough full depth threads, then it might work. The fact that the calipers are aluminum makes this critical. I've already had to repair a Wilwood caliper for a guy that stripped his out. They are pretty soft.

Also, you will have to make sure that the bolt does not bottom out on the taper before it provides enough clamping force to seal the banjo.

This would be a very difficult setup to ensure safety. You would be better off, IMO, modifying the caliper to take a standard banjo, if that's the ony thing that will work.

Another option would be to find someone that does machine work and have them make a very short 1/8" pipe "L" fitting. This is entirely doable.

Last edited by Hotrod46; 02-12-2020 at 08:09 AM.
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Old 02-12-2020, 08:31 AM
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After thinking about this, it occurred to me that there is an uncommon pipe thread known as NPS. This is a straight thread that has the same general dimensions as the tapered pipe threads, but no taper. It is intended for parts that seal against a shoulder or gasket instead of using the wedging effect of tapered threads.

I just checked and EBAY lists several 1/8 NPS taps for $10 or less. There is no way to know the actual dimensions of the bolt you listed without actually measuring one with a precision caliper or micrometer, but it is possible that you could tap out the caliper with an NPS tap and get an acceptable mechanical fit. You would need both the tap and bolt in hand to compare and I would probably do a test hole in aluminum scrap to verify the mechanical fit before attacking the expensive Wilwood calipers. This would be a cheap gamble if it works and gets you out of the corner you've painted yourself into. To make a realistic test, tap a piece of scrap with a tapered 1/8 tap as close to the fit of the NPT threads in the caliper and then go in with the straight tap to see if you get good threads. Then bolt up the banjo just as if you were installing it on the car. Yeah, it's a lot of work, but I would rather ruin a piece of scrap and waste a little money than screw up the calipers.

The threads will need to fit together with very little clearance and as deep as possible in the caliper to ensure that they will hold properly. If you are unsure, find a machinist and get them to check out the fits.

Last edited by Hotrod46; 02-12-2020 at 08:42 AM.
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Old 02-12-2020, 08:40 AM
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Yes, NPT(aper) and NPS(traight). OP's link in post #1 specifies "S". His other thread didn't specify which 1/8 thread for the caliper, but he refers to it as "NPT". The NPS threads were used on GM automatic trans oil cooler line fittings and sealed with crush washers. The threaded shank on that part looks long, they would prolly work, assuming it didn't bottom out in the caliper.

Russ
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Old 02-12-2020, 07:58 PM
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staleg....The intention of Wilwood is likely that you would use an adapter to convert to the brake line of your choosing. That could be to convert from NPT to inverted flare, if you were using a hard flared line like 3/16", or to convert to a brake line fitting like AN-3 or AN-4 which would be common to braided stainless steel flexible lines. There could likely be other options as well.


I would say that the flat face of the drilled and tapped fitting attachment port is not intended, in this case, to be used with a banjo fitting. Any banjo fitting I've seen used is held with something like a 7/16" or 10MM hollow banjo bolt and sealed by a crush washer on both sides of the banjo fitting.


I hope this helps.


Lynn
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Old 02-12-2020, 08:52 PM
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If the caliper is NPT, then there would be no seat face machined for a brass washer to go with the banjo fitting.
If clearance is a problem for direct hose connection, you may have to elbow to steel brake line, then invert flare back to pipe or AN then connect to your stainless flex. Using some sort of support bracket at steel line and flex connection to tie it down.
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Old 02-12-2020, 09:50 PM
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staleg...from the ebay link you provided the fitting is stated to be NPS thread in the listing title, NPT in the description text, and one of the photos shows NPT. I would call that a messed up listing. The fittings pictured in the ebay listing has no appearance of tapered threads like would be on a NPT tapped hole, fitting or pipe. Here's a copy/paste of a search regarding NPS vs. NPT threads.


"Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch). However, NPT threads are tapered and NPS threads are straight (parallel). Both threads have a 60 included angle and have flat peaks and valleys. ... While NPT and NPS threads will engage, they do not seal properly with each other."


I sell race parts and just referred to the fitting section of brake plumbing parts. The only banjo bolts listed are 3/8"-24, 7/16"-20, 10MM-1.25 and 10MM-1.5. That was checking the "house" brand of fittings as well as Aeroquip. Just to see if Wilwood used any type of proprietary fitting I checked them too and found nothing. The random calipers I looked at on their website showed to be either 1/8"-27 NPT inlets or one of the banjo bolt sizes I listed above.


If the area around the inlet port is machined, I would suspect Wilwood just spot faces the surface for a professional, finished look. Try a known actual NPT fitting or threaded pipe to see if it threads in freely at first and tightens up as the taper tightens up in the caliper inlet.


The ultimate answer regarding the thread types they used for various calipers would come from Wilwood. If my suggestions prove incorrect I offer my apology in advance.


Lynn
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Old 02-13-2020, 02:54 AM
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Thank's for the information. I have given up this project.
The calipers will be used as door stoppers or dust collectors.

My own fault, as I didn't do enough homework before I bought them, and bad luck that I painted them before I discovered the hose routing problems, so I Speedway won't accept a return.

The photo shows the common plumbing for them, but this interfere with the lower A arm at full turn and top end point of the suspension.
I know many would live with that, and if it was the flexible part of the hose that hit the A arm, I wouldn't mind either, but it's hard end that interfere.

Another possibility is to switch around the brake hose and the bleeder.
I prefer not as you have to loosen the caliper and turn it upside down when bleeding the brakes.
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Last edited by staleg; 02-13-2020 at 03:02 AM.
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Old 02-13-2020, 07:21 AM
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staleg....mayby there's a solution available. I don't know how much more clearance you need but perhaps a 90 degree 1/8" NPT X AN-3 or -4 adapter like this would help tighten things up a bit for clearance? It could be used with a brake line with a straight end to keep everything closer to the caliper.
https://www.jegs.com/i/Allstar-Perfo...50018/10002/-1

Another possible solution would be a brake line with a forged end rather than a sweeping elbow version as you have pictured. One like this?
https://www.summitracing.com/parts/aaf-all46402-18/
The one in the link is a AN-4 line, 18" long, but they're available in various lengths and also in AN-3 fitting and line size.


Just a thought. Sometime just a bit more clearance is all that's needed.


Lynn
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Old 02-13-2020, 07:45 AM
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Quote:
Originally Posted by lake_harley View Post
staleg....mayby there's a solution available. I don't know how much more clearance you need but perhaps a 90 degree 1/8" NPT X AN-3 or -4 adapter like this would help tighten things up a bit for clearance? It could be used with a brake line with a straight end to keep everything closer to the caliper.
https://www.jegs.com/i/Allstar-Perfo...50018/10002/-1

Another possible solution would be a brake line with a forged end rather than a sweeping elbow version as you have pictured. One like this?
https://www.summitracing.com/parts/aaf-all46402-18/
The one in the link is a AN-4 line, 18" long, but they're available in various lengths and also in AN-3 fitting and line size.


Just a thought. Sometime just a bit more clearance is all that's needed.


Lynn
A tighter turn on top of an AN3 to 1/8 NTP adapter will interfere with the lower sliding bolt, making it impossible to loosen the caliper without removing the hose and because of that, bleeding the brakes.
And The Allstar hoses are not DOT approved.
The 90 degree adapter in your link is not possible to fit, because there are not enough space around the inlet port to screw the adapter in place.
Besides that, using this adapter would also turn the AN fitting in a direction that would increase the risk for it to be loosened by the up-and-down spring movement. To avoid this effect, one can add a small bracket close to the caliper end of the hose, but with sliding calipers this bracket would have to be fastened in the caliper itself, which is not possible.

But thank you for trying.

Last edited by staleg; 02-13-2020 at 07:55 AM.
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Old 02-13-2020, 08:38 AM
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The key is that a banjo bolt will tighten against the caliper, crushing the copper washers on either side of the banjo fitting. The seating area on the caliper would be machined square to the threads and there should be small annular ridges machined to cut into the copper washer between the banjo fitting and caliper.
NPT would seal by mechanical interference between the threads as it is tightened , the interference increases as the fitting is tightened. This could make clocking problems if you were to use an elbow.
There is BSPP british straight parallel pipe, I believe has the same dimensions as NPT & NPS thread, but has collar nut to tighten against the caliper after the fitting is positioned (clocked). This requires a small chamfer at the lead thread, were an o'ring is squeezed into, as the seal. If it lacks a chamfer, there are steel washers to contain the o'ring while the collar nut is locked down.
BSPP would also require that there be straight thread in the caliper and that there was a flat area around the hole. But would cure any clocking issues for an elbow.
If you dont use an elbow, then there is no clocking problem. A NPT fitting is adequate for the pressure in the system and should be fine except you would have to use a steel fitting. Brass fittings tend to crack at the base of the thread.
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Old 02-13-2020, 10:13 AM
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You could spot face the caliper and drill and tap the existing 1/8 npt hole for 7/16-20 threads making it possible to use standard banjo fittings ....
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Old 02-13-2020, 06:27 PM
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Staleg could you post a picture similar to the the one you post in #9 but showing the full suspension
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Old 02-14-2020, 06:04 AM
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This is how I would get over the problem.The Purple is a bracket welded to the top arm to hold the Green Bulkhead fitting.The Yellow is a bend fitting. The Red is a 180 dec fitting. The Blues are flexible hose crimped to the fitting.
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