PVC pipe furniture is popular as ever. When wood dust become cancer causing agent, working with PVC is even more attractive. With a roller cutter, you don't need an expensive saw table to cut precisely, and there is even no saw dust.
However, I have been looking for non-PVC, environment-friendly alternatives. All the metal alternatives are expensive to very expensive, especially the fittings. EMT conduits are comparable in price to PVC, though, but the fittings are too bad or too expensive. These fittings just don't fit like PVC.
People have been looking for low-cost fittings for low-cost EMT. I would say they all fail, until now.
I invented the use of 4 EMT clips to function as a cross in EMT terms. Finally, I have to admit partial failure because the two holes in an EMT clip is not symmetric. It may be a good reason to hold the EMT tight on a base but the result of a cross over is not square enough.
I'm surprised to find a Kickstarter project to manufacture fittings for EMT - the Maker Pipe project. Because EMT manufacturers aren't interested. There's always the Kee Klamps, rather expensive but a lot less than rigid conduits. Recently, Lowes has a complete system of metal pipes and fittings that are close to Kee Klamps. Basically, there is a whole spectrum of metal alternatives to choose from and if you want cheap you can always go back to PVC.
Honestly, I have been looking at all type of pipes, their inner diameters, and outer diameters. I wanted to strengthen PVC pipes with EMT pipes inside. But I never find any way to fit EMT cheaply.
One day, it dawns on me that I never looked at schedule 80 PVC. A quick look shows that a 1/2 EMT can fit inside an 3/4 Sch. 80 PVC pipe with less than 1mm gap. I was so excited when I went to the hardware store to check it out. A EMT pipe can fit in some PVC pipes but not others. I thought there must be debris blocking the tiny gap. So I picked one PVC pipe, went home, hammered an EMT pipe in, and failed.
I thought it was another failure to find cheap fittings but then I wondered how EMTs can fit inside some of the PVC pipes in the hardware store.
On further analysis, there is a less than 1 mm nominal gap. However, the tolerance of the wall thickness is large. The tolerance of the OD of PVC pipes are much smaller, and I think it would be true for EMT pipes too. The fittings depend on the tight tolerance of the OD's.
In summary, an EMT pipe (1/2) can fit in more than half of the Sch. 80 PVC pipes (3/4) statistically. The same relation holds for 3/4 EMT pipes and 1" Sch. 80 PVC pipes, with an even smaller nominal gap.
First, it's a neat way to reinforce PVC with EMT inside, or EMT with PVC outside, depending on how you see it. It allows you to use thinner pipes, stronger, probably cheaper and better looking.
More important, now you can make EMT structures using PVC fittings, almost the same way you use pure PVC pipes and fittings. You just need to cut half an inch of PVC pipe, push it into a PVC tee, and use it on EMT.
OK, the PVC tee can slide across an EMT pipe. But this is an advantage. There is less cutting of the EMT pipes. Sometimes you want something that can rotate and slide, which is not easy in PVC.
There are many neat ways to hold the tee in place. Because the gap is so small, you can use most glue so the tee cannot slide. More secure is to drill the tee with a thread maker and tighten the EMT inside with a machine screw. If the tee is load bearing, you can drill through the EMT and put a sheet metal screw in it. The other nondestructive method is to use hose clamps on one or both sides of the tee to prevent it from moving at all.
A 3/4 tee is less than 1/5 the cost of a Maker Pipe Tee.
However, I have been looking for non-PVC, environment-friendly alternatives. All the metal alternatives are expensive to very expensive, especially the fittings. EMT conduits are comparable in price to PVC, though, but the fittings are too bad or too expensive. These fittings just don't fit like PVC.
People have been looking for low-cost fittings for low-cost EMT. I would say they all fail, until now.
I invented the use of 4 EMT clips to function as a cross in EMT terms. Finally, I have to admit partial failure because the two holes in an EMT clip is not symmetric. It may be a good reason to hold the EMT tight on a base but the result of a cross over is not square enough.
I'm surprised to find a Kickstarter project to manufacture fittings for EMT - the Maker Pipe project. Because EMT manufacturers aren't interested. There's always the Kee Klamps, rather expensive but a lot less than rigid conduits. Recently, Lowes has a complete system of metal pipes and fittings that are close to Kee Klamps. Basically, there is a whole spectrum of metal alternatives to choose from and if you want cheap you can always go back to PVC.
Honestly, I have been looking at all type of pipes, their inner diameters, and outer diameters. I wanted to strengthen PVC pipes with EMT pipes inside. But I never find any way to fit EMT cheaply.
One day, it dawns on me that I never looked at schedule 80 PVC. A quick look shows that a 1/2 EMT can fit inside an 3/4 Sch. 80 PVC pipe with less than 1mm gap. I was so excited when I went to the hardware store to check it out. A EMT pipe can fit in some PVC pipes but not others. I thought there must be debris blocking the tiny gap. So I picked one PVC pipe, went home, hammered an EMT pipe in, and failed.
I thought it was another failure to find cheap fittings but then I wondered how EMTs can fit inside some of the PVC pipes in the hardware store.
On further analysis, there is a less than 1 mm nominal gap. However, the tolerance of the wall thickness is large. The tolerance of the OD of PVC pipes are much smaller, and I think it would be true for EMT pipes too. The fittings depend on the tight tolerance of the OD's.
In summary, an EMT pipe (1/2) can fit in more than half of the Sch. 80 PVC pipes (3/4) statistically. The same relation holds for 3/4 EMT pipes and 1" Sch. 80 PVC pipes, with an even smaller nominal gap.
First, it's a neat way to reinforce PVC with EMT inside, or EMT with PVC outside, depending on how you see it. It allows you to use thinner pipes, stronger, probably cheaper and better looking.
More important, now you can make EMT structures using PVC fittings, almost the same way you use pure PVC pipes and fittings. You just need to cut half an inch of PVC pipe, push it into a PVC tee, and use it on EMT.
OK, the PVC tee can slide across an EMT pipe. But this is an advantage. There is less cutting of the EMT pipes. Sometimes you want something that can rotate and slide, which is not easy in PVC.
There are many neat ways to hold the tee in place. Because the gap is so small, you can use most glue so the tee cannot slide. More secure is to drill the tee with a thread maker and tighten the EMT inside with a machine screw. If the tee is load bearing, you can drill through the EMT and put a sheet metal screw in it. The other nondestructive method is to use hose clamps on one or both sides of the tee to prevent it from moving at all.
A 3/4 tee is less than 1/5 the cost of a Maker Pipe Tee.
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