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Oil Drain/Pipe fittings question
I took a brass fitting out of my oil pan and it fits into a 3/8" brass female at the hardware store. I ordered a 3/8" NPT to -10AN aluminum adapter with which to replace it, and it doesn't fit the hole. Threads are the same, but it looks like it's about 0.5mm too thick?? I tried the Al one at the hardware store and it fit into a 1/2" compression female. Did they send me the wrong damn thing or am I missing something here? Educate me about some-a those there pipe fittin's.
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Its a tapered thread so the size of the hole and the brass part depends on how far the tap was wound in and the die was would on. I'd file a slightly steeper taper on your brass and persevere or grab a tap, check that it won't hit your oil pickup inside your pan and tap a bit deeper.
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3/8 NPT is small for an oil return. I'd do 1/2" NPT minimum. I personally ran 3/4 NPT to -12AN for a drain. IE both are 3/4" ID. What you are doing is going from 10 AN (~5/8", which is fine) to 3/8" which is tiny.
I do run 3/8" fuel line though. :) If it won't thread in, threads probably need to be cut deeper with a 3/8 NPT tap to answer your question though. |
Thanks everyone. Woohoo, an excuse to get a new tool! I hope I can tap a larger hole (1/2" NPT as per the suggestion, then get a new fitting) while the pan is on? I've never used a tap & die set before. I'll do some reading - I know there are lots of resources floating around about oil pan tapping.
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Originally Posted by patsmx5
(Post 1235071)
3/8 NPT is small for an oil return. I'd do 1/2" NPT minimum. I personally ran 3/4 NPT to -12AN for a drain. IE both are 3/4" ID. What you are doing is going from 10 AN (~5/8", which is fine) to 3/8" which is tiny.
Blargh, if you want to read about NPT, here's a couple links: http://en.wikipedia.org/wiki/National_pipe_thread http://www.engineeringtoolbox.com/np...ads-d_750.html --Ian |
Well most pipe fittings, the size is the ID, that's how pipe fittings are spec'd. It's a minimum ID. Perhaps some are larger, but not all 3/8 NPT whatevers are going to measure 1/2".
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Originally Posted by patsmx5
(Post 1235292)
Well most pipe fittings, the size is the ID, that's how pipe fittings are spec'd. It's a minimum ID. Perhaps some are larger, but not all 3/8 NPT whatevers are going to measure 1/2".
Regardless, 5/8" hose with a barb using 3/8" NPT threads is what most of the turbo kits out there use and it works fine. --Ian |
Originally Posted by codrus
(Post 1235404)
NPT is not "most pipe fittings", the spec is for OD because that's where the threads are. 3/8" NPT is spec'd as 0.675" OD pipe. Wall thickness varies with the material and requisite strength, but pretty much any 3/8" NPT fitting you find is going to have an ID that's much closer to 1/2 inch than 3/8. Schedule 40 steel pipe, for example, specs 3/8 pipe has having a 0.49 ID.
Regardless, 5/8" hose with a barb using 3/8" NPT threads is what most of the turbo kits out there use and it works fine. --Ian Pipe fittings sizes are close to the ID for schedule 40 pipe. That's how the naming convention was created for pipe. It does vary depending on wall thickness, but the convention is related to ID, not OD. Pipe = ID, tubing = OD. |
Originally Posted by codrus
(Post 1235291)
FWIW, 3/8 NPT isn't actually 3/8" in any dimension. The 3/8" NPT hose barbs commonly used in FM/etc kits are 1/2" inner diameter.
Blargh, if you want to read about NPT, here's a couple links: National pipe thread - Wikipedia, the free encyclopedia NPT- National Pipe Thread Taper- ANSI B1.20.1 --Ian Nominal Pipe Size (NPS) is loosely related to the inside diameter of Schedule 40 pipe |
3/8 npt drain is fine. 3/8 npt shed 80 is .49 Id. You are misreading wiki again pat.
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I was taught Pipe is ID, Tubing is OD a looonnnnnggggg time ago. Did it change?
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From here: Nominal Pipe Size - Wikipedia, the free encyclopedia
Based on the NPS and schedule of a pipe,[5] the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M. For example, NPS 14 Sch 40 has an OD of 14 inches and a wall thickness of 0.437 inches. However the NPS and OD values are not always equal, which can create confusion. For NPS ⅛ to 12, the NPS and OD values are different. For example, the OD of an NPS 12 pipe is actually 12.75 inches. To find the actual OD for each NPS value, refer to the tables below. (Note that for tubing, the size indicates actual dimensions, not nominal.) For NPS 14 and up, the NPS and OD values are equal. In other words, an NPS 14 pipe is actually 14 inches OD. The reason for the discrepancy for NPS ⅛ to 12 inches is that these NPS values were originally set to give the same inside diameter (ID) based on wall thicknesses standard at the time. However, as the set of available wall thicknesses evolved, the ID changed and NPS became only indirectly related to ID and OD. |
I think you've got it bolded on the end there, the discrepancy is a lot larger on smaller pipe fittings. Fittings themselves are not set to a standard either, like the I'd of hose barbs and the like.
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To stay on topic, I never ran a 3/8 Drain but if everyone does that and it works, go for it. I would recommend a larger one myself as more won't hurt. I ran my GT3271 unrestricted with a 12AN drain and it didn't smoke, though I did in fact put a restrictor in down the road.
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Originally Posted by deezums
(Post 1235447)
I think you've got it bolded on the end there, the discrepancy is a lot larger on smaller pipe fittings. Fittings themselves are not set to a standard either, like the I'd of hose barbs and the like.
I run 1/4 NPT fittings on my WI and they are all .25-.3" ID brass, but a steel fitting I bought was larger ID for 1/4". Wall thickness diff. But none of the fittings are smaller than advertised in my experience. Maybe Schedule 120 would be but I've never used that on a miata. |
Originally Posted by patsmx5
(Post 1235436)
From your link 2,
I think what's going on here is that this is an old standard that was based on a previously-existing even older standard that's gone through major revisions over the years. Yes, at one time those numbers corresponded to physical dimensions, but at this point they really don't any more. --Ian |
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