After a over a decade of meaning to get around to piping my dust collection system, I finally started making somewhat of an effort. Between being busy building my second shop, and commuting from Asia, things happen at a relatively slow pace in my life.
Anyway, I ordered some 6" flex pipe from Wynn Environmental to use on the transitions between my S&D PVC ducting and the machines. The problem, as I was to find out, is that the O.D. of the S&D pipes is about 6-1/4", and the flex duct is made to fit a 6" pipe. As hard as I tried, I could not get the 30 mil flex duct over the S&D pipe. I read about some people getting it to work with difficulty by using hot water to soften the flex duct, and others have cut slits in the green pipe so that they could squeeze it into the flex duct. Neither of these methods appealed to me, so I came up with a trial and error solution that I hoped would work. Below is an account of the steps I took, and the results (which I am very pleased with).
First, I started out with a piece of black pipe that was in my garage. I have no idea how it even got there -- I think it came with the house. It was rusty, but just the right size for me to work with. It had an O.D. of 6-5/8" and a 1/4" wall thickness. It would barely fit in my little Jet bandsaw, but I managed to rotate it a number of times until I cut off a piece 2-3/4" long.
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Next, I mounted the pipe, which wasn't very round, on my 1948 Logan 14" lathe. I cleaned up the end, the inside, and a little of the outside. I flipped it, and matched up the ID to the other side. I took the whole outside down until it was .100" thick. This was just a ballpark guess at a size that would retain its shape, but would be flexible enough to bend by hand. The full 1/4" would not have been flexible at all. In the end, the thickness turned out to be just about right.
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Once I got it finished on the lathe, I took it back to the bandsaw, and cut it lengthwise. I did some math to determine the final circumference that I would need on the ring. I determined that I needed to lose another 3/8" of circumference, so I flipped it upside down in the bandsaw (so that the vise was holding near the cut), and cut a parallel cut to the first one (from the inside out) 3/8" to the side.
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Next trip was to the welder. I welded on two pieces of angle iron and a couple of hand holds. Pardon my welds. I was trying to pump this out quick, so I didn't take my usual care in producing nice welds. You can probably see where this was going by now.
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At around this point, I decided to take the MAPP gas torch to a piece of S&D pipe as a test to see how easily it got soft. I probably should have tried this first, because the green pipe did NOT like the torch at all. I was kind of like taking a torch to a marshmallow. It just turned brown, bubbled up, and burned it (without even being close to getting soft. At this point, I figured that I just wasted all of my time and efforts building my compression clamp. What was I thinking? Anyway, out of the blue, I got another idea, and as luck would have it, it actually worked. I'll get to what I did in a couple of more pics.
For right now, I took a piece of S&D pipe to the router table and made an inside chamfer using a ball-bearing chamfer bit. This was to smooth out the transition in the air flow direction.
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My compression clamp/collet in place on the pipe
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Next step was the difference between this idea working, and being the disaster that I thought it was going to be after my failed torch attempt. The trick was to heat the clamp -- NOT the pipe. If the flame hits the pipe, it will burn, but if you keep the flame on the steel and keep it moving, the steel will distribute the heat uniformly. I just kept moving the torch around and every minute or so, tightened up the bolts with a socket on a long-extension ratchet, and a wrench. Eventually (it probably took maybe 5 minutes or so), I could tell when I was at the right temperature. The bolts just turned down very easily until they were tight.
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Here is what it looked like tightened down with the clamp fully closed. You can see the nice, smooth transition inside the pipe.
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continued...
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Originally Posted by Dan Hintz
