Turning pipe

I'm not a pro on this and I'm sure someone can improve on it, but I'd use a somewhat higher speed than normal and take lighter cuts with a slower feed rate.

THEN you can always touch it up with a file (very lightly) and even finish that off with some fine grit emory cloth.

If that doesn't do it try some rouge.

W.W. Grainger is only ONE of many sources of polishing compound/rouge. Here is their url

Looks like you might have to copy the second line (it'll probably split) click on the top part and then paste in the extension. Or, I should have done a tiny url! ;-)

McMaster Carr is probably another good source.

? Enco, Grizzly, etc.

I had the same problem turning mild steel plate into flywheels.

I received an email from a reader who suggested grinding a tool to take a shear cut. The way mine ended up is like a small roughing tool with high rake angles laid on it's side.

I was able to take .005" cuts and get a beautiful finish. I also tightend up the gibs and locked the axis that I wasn't using. I used a slow speed and feed, trying to make sure that I didn't heat things up and work-harden the stock.

It takes turning it slightly oversize and then spinning it while holding on a pneumatic belt grinder (Dynabrade type) to take it the last coupla thou and finish it at the same time. There are special tools made for finishing pipe but they are real spendy.

They just make pipe up from rolled flat bar, and the rolled flats are most likely coming from remelted steel, with a somewhat loose tolerance on the recipe, so my guess is that pipe steel will vary quite a bit. If you have a lot of it to do, you might consider using DOM tube instead of pipe. Ex:

Grant

I got a decent finish, used a new insert (carbide) and took light cuts.

A bit of spinning with some emery cloth to finish it off worked out fine.

Wes

I wanted to make a bigger column for my cheapy drill press and found some pipe almost the right size in the hardware store's offcut pile, needed about .030" taken off it. Unless it's D.O.M. or seamless stuff, pipe's made from soft strip steel rolled and welded with a nasty seam left. Mine had 4 distinct corners on it when I started. I ended up "machining" it on a belt grinder, round and round from end to end, I had no pipe centers large enough to take it. Had a nice ground finish and no lobes when I was done. Took a lot of checking and a steady hand, most of a Sat. afternoon. So that's a possiblity for you, roughly machine to size and grind to finish. If you use sulphur- based cutting oil, your finish might improve as well as using sharp HSS tools. Hone after grinding.

If it's for some load-bearing application, remember that plumbing pipe is MADE to be bent.

Stan

Did Gerry every tell us what type pipe he was working with? I don't recall it. That could make a difference.

It's not really a big deal to grind up a HS tool bit. The first time takes a bit longer, but after that it's just touching up. With a bit of radius on it I'd bet you'd get a better finish, too. I'm not saying you have to do it for this or anything, but it's an ability well worth picking up for home shop stuff.

Thanks for the comments everyone. The project I have in mind is a paddlewheel type flowmeter to set on the top of an open chute. I intend on using reed switches potted inside steel pipe triggered by wheels with rare earth magnets that will spin on the outside of the pipe. The wheels will have UHMW poly bushings to spin on the pipe, There will also be an air purge comingfrom inside the pipe to form a cushion for the wheels to float on and to keep mud out. Final version will likely be stainless but my second and third versions will be using plain old black 1/2" schd 40 pipe. Again, any comments will be welcomed

The black iron pipe is a magnetic shield, and will short the magnetic field out, keeping the reed switch from working. Brass, copper, plastic, or stainless steel would be better.

Brass and especially copper could be a problem if the paddlewheel turns too fast, as the magnets will induce eddy currents in the metal, which will impose a drag on the paddelwheel. (Try dropping a rare earth magnet down a copper tube - the magnet falls very slowly.) Plastic or stainless steel would be better.

Given that the final will be stainless, it would be best to start with stainless.

Joe Gwinn

It is my intent to mill a window in the pipe directly above each reed switch. When the internals are potted in place the window will be filled with potting compound

Speaking of copper, a few years ago I saw something really surprising. It was a varible speed drive using magnets and a coper disc. Magnets were on one plate parrallel to the copper plate As one turned the magnetic field turned the other. The speed could be changed by increasing or decreasing the distance between the two. Looks like a cheap and easy varible drive to me. It was capable of transmitting 100 HP to a centrifuge without any energy consumed

An eddy current drive. While at first glance it may appear to be a lossless system, it's really just a slipping clutch. The motor always runs at full speed producing enough torque to turn the load at a lower RPM. The power in is proportional to torque x motor RPM; the power out, torque x load RPM. Since the torque is the same on both sides of the coupling, the difference between the motor RPM and load RPM represents a loss.

Ned Simmons

According to Gerry :

Well ... the stainless (if a non-magnetic alloy) will probably work, but you really expect to get magnetic fields through the walls of a mild steel pipe? I strongly doubt that you will get anywhere near enough to sense with anything other than an amplified Hall-effect sensor -- if that.

Good Luck, DoN.

Pipe will be milled away in the area of the reedswitches. When the switches and air tube are potted in place, the potting will come out to fill in the milled out area to the same contour as the pipe origionaly was

???????? I'm not too sure I understand.

There is no such thing as a "loss." What we perceive as an energy loss is actually a transformation into something else, usually heat. In other words, a slipping clutch gets awfully hot awfully fast. So, in this system, where does the energy go if there is a significant difference between the drive RPM and the load RPM?

Jerry

It goes into heating the copper disc. The energy dump is proportional to slip rpm x transmitted torque.

Randy

Heat, which is usually considered a loss in a mechanical system, unless you have a use for the heat and a means to capture and utilize it economically.

Ned Simmons

According to Jerry Foster :

[ ... ]

[ ... ]

Into heating the copper disk via eddy currents. Even though the resistance of the copper is very low, the currents are very high, so it is enough to significantly heat the disk.

Enjoy, DoN.

OK. What had me going was your comment that "it may appear to be a lossless system." In the example given, 100 hp applied to a centrafuge, I would expect the quantity of heat to be very great and so the heat loss to be substantial and very obvious.

Jerry