I just purchased a 5 HP compressor pump from Amazon. It seems (seemed?) like a nice pump, but it has some real issues. One of the top ones is the silly elbow fitting they sent with the pump to provide the outlet air. For one, thing, it is far too short to properly clear the pump housing. given that, and its other issues, I will just be discarding it. The next issue is the female port is not SAE: it is metric. I don't know if anyone has tried to get a schedule 80 or equivalent metric pipe and elbow, but I haven't seen anything of the sort. The biggest issue, however, is the female threads in the pump housing (and the elbow, but that no longer matters) aren't pipe threads! They are not tapered. They are perfectly flat. They appear to be m27 x 1.2mm threads. I can make such an external thread on my lathe easily enough in order to mate with the pump housing, but how am I supposed to seal them if they are not tapered? The outlet temperature is reported to be very high - high enough for lead/tin solder to fail if used to solder pipes together at the outlet. That would eliminate epoxy. Even though neither the elbow which came with the pump nor the pump body have tapered threads, I suppose I could still taper the threads on the adapter I am going to make, but I am not sure how well that would work. For one thing, it might well still leak, even though the fitting is tight and sealed with PTFE. Worse, it could fail completely, and a 1" pipe coming off a 200 PSI air port... well, I don't want to be anywhere in the same building, that is for certain. So how should I get a presumably non-tapered, threaded air connection to seal properly?
-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
How do I seal this compressor?
- Thread starter lesrhorer
- Start date
- Joined
- Feb 1, 2015
- Messages
- 9,645
The port may be intended for a seal on a flat face. An O ring could be used oir if high temperature is a concern, soft copper could be used. Such strategies are use on hydraulic lines where high temperature and much higher pressures are encountered,
If you are making/buying an adapter for npt threads an don't ever plan on removing it, epoxy can also be used as a sealant.
If you are making/buying an adapter for npt threads an don't ever plan on removing it, epoxy can also be used as a sealant.
How did the elbow seal? The straight pipe threads I have seen in hydraulic lines use an o ring and what looks like a half nut to seal the threads. The Asian straight pipe threads in metric sizes have to be measured to figure out what they are. Japan’s are different from China’s. It can be very confusing.
- Joined
- Jan 2, 2019
- Messages
- 6,587
Do you have a local compressor shop?
I made friends with the one in Traverse City and they were excellent to work with. Sometimes Amazon isn't the cheapest either when you factor in all the stuff you have to do to make the "bargain" part work. In any case it's worth a trip to the local guy with your fittings to see if they have something in stock.
John
I made friends with the one in Traverse City and they were excellent to work with. Sometimes Amazon isn't the cheapest either when you factor in all the stuff you have to do to make the "bargain" part work. In any case it's worth a trip to the local guy with your fittings to see if they have something in stock.
John
- Joined
- Feb 2, 2013
- Messages
- 3,638
if you were so inclined, you could tap the bores to the NPT equivalent and swap from metric fittings
the work may be worth the reward
the work may be worth the reward
The mating surface is anything but flat or smooth. I thought about possibly taking a file to it to try and get it flat and smooth enough to seal and using a metal o-ring, but I am not sure I can pull that off.
If, as reported, this thing gets hot enough to soften Lead solder, normal Epoxy resins won't work. Maybe there are some resins with high enough temperature resistance? I don't know of any.
Permatex Ultra Red claims to be good to 343C. That is way above the Sn/Pb melting point, and might be good enough. I am trying to find out just how hot this thing gets. I would not expect i o get higher than 300C, but I just don't know.
Last edited: