Hi,

I have a 16" x 48" piece of 304 Stainless Steel 1/8" perforated sheet
metal, about 1/16" (.065) thick. I want to bend it into a 15"
diameter x 16" high cylinder. Is this something that can be done
(manually) without any special machinery?

The method I had in mind would be to obtain a 16" length of 15"
diameter pipe (or perhaps bolt a few 15" diameter wheels together to
form a 16" high cylinder). This would be bolted or clamped to a fixed
object. I would then clamp one (16") side of the sheet metal to the
pipe with a piece of bar stock and a couple of c-clamps. Another
piece of bar-stock would be clamped to the other side of the sheet
metal, and I would then slowly bend the 48" length around the pipe.

But then, what can I do to retain the cylindrical shape? I assume
that 1/16" stainless will want to spring back with a vengeance. I've
considered clamping it in place and then hammering and/or heating it.
I've considered using a smaller pipe and bending slightly past the
diameter I need. But I don't know how much smaller a diameter to use.
I need to have a reasonably "perfect" circle, and I don't want any
kinks.

Is this a practical thing to attempt, or should I try to make friends
with someone who has a slip-roll forming machine.

Any advice would be appreciated.

To form a cylinder from sheet, you need to first bend the few inches on
end of your sheet to the correct curve, using either a press brake or
cornice brake, then use a slip roller to roll the rest of the sheet
into the proper curve.
Doing it any other way is just too much damn trouble.

You could have this done by a sheet metal shop for maybe $20 - $30.

You could form the cylinder in 2 pieces by using over length pieces,
bending them around a curved object with a smaller diamter than your
finished size, and then cutting the curved bits from the middle of each
bend.

It is always better to over bend and then un-bend than to under bend
and then try to force the edges together.

For a 15" diameter curve try something 12" - 13" diameter.








In article , cdg
wrote:

Hi,

I have a 16" x 48" piece of 304 Stainless Steel 1/8" perforated sheet
metal, about 1/16" (.065) thick. I want to bend it into a 15"
diameter x 16" high cylinder. Is this something that can be done
(manually) without any special machinery?

The method I had in mind would be to obtain a 16" length of 15"
diameter pipe (or perhaps bolt a few 15" diameter wheels together to
form a 16" high cylinder). This would be bolted or clamped to a fixed
object. I would then clamp one (16") side of the sheet metal to the
pipe with a piece of bar stock and a couple of c-clamps. Another
piece of bar-stock would be clamped to the other side of the sheet
metal, and I would then slowly bend the 48" length around the pipe.

But then, what can I do to retain the cylindrical shape? I assume
that 1/16" stainless will want to spring back with a vengeance. I've
considered clamping it in place and then hammering and/or heating it.
I've considered using a smaller pipe and bending slightly past the
diameter I need. But I don't know how much smaller a diameter to use.
I need to have a reasonably "perfect" circle, and I don't want any
kinks.

Is this a practical thing to attempt, or should I try to make friends
with someone who has a slip-roll forming machine.

Any advice would be appreciated.

I have a 16" x 48" piece of 304 Stainless Steel 1/8" perforated sheet
metal, about 1/16" (.065) thick. I want to bend it into a 15"
diameter x 16" high cylinder. Is this something that can be done
(manually) without any special machinery?

Almost. To hand form this without tools, you need a 16x96 inch sheet of sheet.
Aren't you glad you asked us AFTER you bought it?

You can make two 16 inch high by 15 inch diameter cylinders this way, or one
good one that's just about perfect.

Take a sheet of computer printer paper and roll it to a diameter of 2 inches by
8 1/2 inches long. See how the metal goes around more then once?

Now roll it as tightly as it needs to be rolled so that when you let it go, it
can be jigged for "welding" with a very weak 2 inch diameter rubber band. You
have just accomplished

Springback Compensation

but only for the end INSIDE the roll. To get the other end straightened out,
you should first cut off whatever length was damaged by your fingers making a
new roll tightly on the outside, then reroll with that end inside, such that
the whole thing unrolls to 2 inches.

Then, use several bands of paper cut from the piece you removed to retain the
paper in a roll exactly 2 inches in diameter. Test fit this roll where the
finished product must be used. Mark and cut a single straight line with
non-curling nibblers, (ok, you do need a hand tool) along the line, leaving
uncurled edge. If you use scissors on the paper or sheet metal snips (even
aircraft snips) you'll curl the edge and ruin your work.

Now you have a roll of stainless steel (if you followed the instructions at the
desk, then went into the shop), about half an hour of wasted time, a nibbler,
and something ready to be joined. You can apply tape to the paper roll, or go
back and make an overlap, then glue it, and you can stitch weld, or TIG (GMAW?)
weld your sheet steel butted edges, or braze them if you set up a small
overlap.

And it cost you twice as much as the sheet, which the company that runs the
roller knows, which is why they charge approximately the same as the original
sheet cost to do this for you. They know about the hand method, but why should
they tell it to you? You're going to spend twenty bucks either way.

Doing it without a roll machine, with the sheet cut to L on one edge, and pi *
D on the other, requires a lathe with capacity D to turn a forming cylinder, a
large flat place to work, like a clean floor, and MANY expensive, tedious cuts
to make the forming cylinder come out right. You can save on cuts by
calculating the springback using Young's modulus, the percent elongation before
plastic deformation, and the thickness of the sheet. And then after you make
this HUGE cylinder and roll the sheet with it, there will still be an end that
won't lie down flat.

Next time, post your requirements (a sheet steel cylinder 15 inches diameter
and 16 inches long) and let US figure out what you should buy, and what labor
you should pay for, in which process you will determine whether you want to own
a pair of nibblers when it's all over, a couple bits of useless sheet steel
that won't lie flat every again, or a receipt from the sheet metal rolling
company. Me, I'd go with the nibblers, but I am getting the feeling you are
going to end up with a receipt.

The method I had in mind would be to obtain a 16" length of 15"
diameter pipe (or perhaps bolt a few 15" diameter wheels together to
form a 16" high cylinder). This would be bolted or clamped to a fixed
object. I would then clamp one (16") side of the sheet metal to the
pipe with a piece of bar stock and a couple of c-clamps.

Use angle iron for more stiffness than bar stock.

Another
piece of bar-stock would be clamped to the other side of the sheet
metal, and I would then slowly bend the 48" length around the pipe.

And if it springs back on you, you could get whacked in the face with a heavy
pice of bar stock. Ouch. Get some friends for this part.

But then, what can I do to retain the cylindrical shape?

You figure the Young's modulus, % elongation, and sheet thickness before hand,
then build a form smaller than 15 inches, but 16 inches long. Try finding a
piece of pipe that's 13.725 inches diameter or whatever the calculated value
happens to be. Good luck. That would be a coincidence of high order. You could
adjust your thickness to make the form come out to be a standard size, but you
already bought the sheet. Tough titty there.



I've considered using a smaller pipe and bending slightly past the
diameter I need. But I don't know how much smaller a diameter to use.

Mark's Standard Handbook of Mechanical Engineering, or our favorite,
Machinery's Handbook, will probably tell you.

I need to have a reasonably "perfect" circle, and I don't want any
kinks.

Perfection costs (1/tolerance) ^ k where k is something like 5.

Is this a practical thing to attempt,

NO. You'll be injured

should I try to make friends
with someone who has a slip-roll forming machine.

At least you probably know some folks who own leather gloves. Start there, and
see if the three of you can scare up someone with a slip roller.

Any advice would be appreciated.


Sorry if I have been a bit harsh, but I don't want you to be hurt. I hope
you've learned something. There will be a quiz at the end of the thread. Five
questions, two true-false, two caculation, and one essay. Submit medical
treatment bills to your insurance company, not to me. All I did here was talk.

And I believe that in this country, that freedom is guaranteed, and I
appreciate the efforts of our enlisted and officers who keep it that way.

Oh, if you have a tree handy, you can adze it to the right diameter and chisel
a slot to put the metal into, then tie it all up with lots of ropes tied with
blood knots, then weld it, but that would kill a tree, so unless it's YOUR
tree, and you need to make more than one, please don't go there.



Yours,

Doug Goncz
Replikon Research (via aol.com)

Recent Original Posts:

http://groups.google.com/groups?scoring=d&q=+-Re+dgoncz

(1,150 and counting)

glad you got your cylinders made. i've been thinking of making my own slip
roller. Not that i need one right know. Any chance you could put photos of
your one hour model up in the dropbox.

--
Doug Arthurs
Kent Bridge, On

Check out my website at http://www.netrover.com/~arthurs/
"cdg" wrote in message
om...
Hi,

I have a 16" x 48" piece of 304 Stainless Steel 1/8" perforated sheet
metal, about 1/16" (.065) thick. I want to bend it into a 15"
diameter x 16" high cylinder. Is this something that can be done
(manually) without any special machinery?

The method I had in mind would be to obtain a 16" length of 15"
diameter pipe (or perhaps bolt a few 15" diameter wheels together to
form a 16" high cylinder). This would be bolted or clamped to a fixed
object. I would then clamp one (16") side of the sheet metal to the
pipe with a piece of bar stock and a couple of c-clamps. Another
piece of bar-stock would be clamped to the other side of the sheet
metal, and I would then slowly bend the 48" length around the pipe.

But then, what can I do to retain the cylindrical shape? I assume
that 1/16" stainless will want to spring back with a vengeance. I've
considered clamping it in place and then hammering and/or heating it.
I've considered using a smaller pipe and bending slightly past the
diameter I need. But I don't know how much smaller a diameter to use.
I need to have a reasonably "perfect" circle, and I don't want any
kinks.

Is this a practical thing to attempt, or should I try to make friends
with someone who has a slip-roll forming machine.

Any advice would be appreciated.

"Doug Arthurs" wrote in message ...
glad you got your cylinders made. i've been thinking of making my own slip
roller. Not that i need one right now. Any chance you could put photos of
your one hour model up in the dropbox.

I'll take some photos as soon as I can find a camera.

(Dan Caster) wrote in message om...

Relax, have a beer. Quit thinking the world revolves around you.

Thank you, and cheers! I have not expressed any such a concept, nor do
I think it.

You didn't have to pay anything for the ideas, so what is the big deal.

I asked a simple question. No one was required or coerced to respond.
Two members provided helpful advice. Another was simply abusive. I
thanked the first two, and I told the third that his input wasn't
helpful, appreciated, or accurate (as presented).

And while you may only want one cylinder, someone else may search for
ideas in the future and need two cylinders. Hell, I might even try it
someday to make some stove pipe that is heavier duty than what is
available in the stores.

Be my guest. If you can construct any number of cylinders based on Mr
Contz's response, you are far more innovative than I.

I always appreciate replies to my questions even if the replies are
not something I can use.

As do I, if they are decently presented.

Someone took the times to reply and gave you an idea of how to do something in a way you had never considered.

The reply to which I objected did not endeavor to, or accomplish, that
goal. Nor do I believe it was intended to do so, but rather to scoff
and strut.

How terrible can that be.

Terrible enough that I've received numerous supportive emails from
other members of this newsgroup that were equally or more critical of
the post in question.

Even the replies that are obviously posted in jest are entertaining.

Some of us did not find the post in question amusing, helpful, or
informative.

I agree that metal is not paper, but it can be formed into a cylinder
without using a form.

Please supply usable details of the procedure involved (which your
colleague did not --- he simply suggested rolling it up very tightly,
without a hint as to how this was to be accomplished --- which was the
question he was supposedly addressing). And, when you suggest a
procedure, remember, the material we are (or were, or should have
been) discussing is .065 thickness 304 stainless, not paper, nor
aluminum flashing. The 1/8" perforation will make it somewhat more
flexible, but it is still quite rigid.

Furthermore, what about the "springback compensation" with which your
colleague was ostensibly so concerned, while rolling his 8.5 x 11
sheet of computer paper and magically producing a metal cylinder from
it? How did it suddenly disappear, as we are rolling twice the
material in an even tighter circle?

Nice to see that you are open to learning about tools even if not relevant to YOUR problem of the moment.

I am open to learning about anything, if the material is presented in
an amicable matter.

Dear cdgoldin,

I checked my Statics and Strength of Materials to see if there was a formula
for bending sheet metal around a curve. The best that was there were the
parabolic deflection beam formulas. I don't think they apply. However, with a
distributed load on a straight beam, the apex of the parabola does have a
computable radius after the material gets bent.

So let's say the Young's modulus of your stainless is known. Use the Young's
modulus calculator, the bend radius, and the sheet thickness in:

http://www.allmeasures.com/Formulae/...gs_modulus.htm

to get the force required to hold the material in a 16 inch diameter circle.
Apply an adjustable strap, slowly working up to that much tension in the strap,
more or less, and your desired bend radius. The strap should be right down the
middle. Use one of those endless hose clamps, available in lengths of up to 10
feet, if you don't have a two ladder lock buckles and a 5 foot length of nylon
webbing. Use your judgement.

Then apply something a little stronger and resistant to heat, like two pieces
of 3 mil aluminum tape 2 inches wide, and at least a foot long, along the
edges, over the joint. The extra length is so the adhesive at the ends remains
strong while the brazing or welding is done. Remove the center strap, if you
used nylon, or leave the endless hose clamp in place. Either way, your choice.

Then, tag weld the seam, be it lapped or butted, one half the way from the
center to the edge. Two weld nuggets about 1/8 inch diameter should do. I don't
weld much at all. I am probably not as good a welder as you.

If having the seam lapped and then having the upper layer stubbornly remain,
say, 1/16 inch from the lower, preventing a sound weld, is a problem, then
clamps must be applied to a bar over the seam, leaving the weld area free, and
using a more or less identical bar diametrically opposite. For instance, I'd
think two pieces of 1x1 inch steel 18 inches long with a 1/4 inch hole through
at each end 3/4 inch from the end would do, in combination with two pieces of
1/4-20 threaded rod about 18 inches long, and four matching nuts.

Once two tag welds are made, you can make several more to hold that edge down
if it is a lap joint, or a few more if it is a butt joing, and then grind them
all smooth. After that, my choice would be to braze rather than weld. Handy &
Harman will provide a small sample of stainless compatible braze filler, about
3/16 inch diameter, which is an excellent color match and very strong. You'd
use a hell of a lot of flux for stainless and try to work quickly, because the
chromium in the steel becomes chromium oxide, a ceramic, at brazing
temperatures, and even a large amount of, say Anti-Borax brand flux can only
dissolve so much chromium oxide before turning black and forming an insoluble
glass. This is an indication that the flux has been "burned". The material is
very tough.

If you finish the joint and the flux is insoluble, you can add lots more flux
and reheat the work to dissolve the chromium oxide. Then, soaking the seam in a
tub of hot water overnight will dissolve all the flux. If necessary, set up a
tray with vinegar and water or a solution of hydrochloric acid. This will
dissolve the remaining flux.
Be careful with HCl, you already know it's dangerous ****.

Now to finish this, you can use a sanding belt to smooth the braze and remove
oxides from the metal that got hot but wasn't protected by the flux, and you're
done.

I switched to decaf all day yesterday, at well, did a little work, and felt OK.
I'd still like to know if when you read my first post in reply to your original
post, whether you got the impression I had had too much coffee?



Yours,

Doug Goncz (at aol dot com)
Replikon Research

Replikon Research researches replikons, which are self-reproducing
configurations of non-living matter in environments that support replication,
analogous to organisms living in ecologies.