Oil Drain/Pipe fittings question
05-26-2015, 11:43 PM
#1
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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.
Thanks!
Thanks!
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05-26-2015, 11:51 PM
#2
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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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05-26-2015, 11:57 PM
#3
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.
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.
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05-27-2015, 11:16 AM
#4
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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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05-27-2015, 01:15 PM
#5
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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
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05-27-2015, 04:58 PM
#7
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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
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05-27-2015, 06:17 PM
#8
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
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.
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05-27-2015, 06:22 PM
#9
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
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
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05-27-2015, 06:46 PM
#12
From here: Nominal Pipe Size - Wikipedia, the free encyclopedia
Or maybe I'm misreading something.
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.
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.
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05-27-2015, 06:51 PM
#14
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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05-27-2015, 06:53 PM
#15
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.
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05-27-2015, 07:22 PM
#16
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Emphasis is on "loosely" related.
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
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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