Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant

--
Posted via a free Usenet account from http://www.teranews.com

On Mon, 21 Jan 2008 18:25:07 -0800, Grant Erwin wrote:

I find I have no idea how to shape e.g. a 4" soft aluminum
circle so it will lie close to the OD of a rounded 3D surface like a
tank end.

I've had fair luck with a shot bag and small mallet.

On Jan 21, 6:25 pm, Grant Erwin wrote:
Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant

--
Posted via a free Usenet account fromhttp://www.teranews.com

Hey, Grant.
Did you ever get one of the canvas lead shot bags that Boeing Surplus
had years ago? My son and I found them and each got one. He cleaned
and washed his really well and used it to hold fossils while he
cleaned the stone matrix away. I still have mine in original condition
and don't think I have ever used it.

Paul

You can do this on a flat surface.
-Cut the piece to shape and file or smooth the edge.
-Find a hard flat surface. An anvil or a half inch thick or thicker
steel plate would be good.
-Using as large a radius domed hammer as you have, simply begin
hammering at the center of the piece and make a spiral of hammer marks
out from the center. Be careful not to hit anywhere close to the edges
of the piece.
Stretching will occur anywhere you hit with the hammer, but, since
you are NOT hammering the edges, the stretched (hammered) material will
have to go someplace and it will dome out as you need.
-Don't try to get all the doming you need in one pass. Just work from
the center to the outside, then go back and make another complete spiral
pass, hammering between the previous hammer marks if possible.
-You do need to be a little cautious that you don't overly work harden
the piece to the point where it cracks.

Note that the larger the radius of hammer you use, the nicer the
finished part will look.

Pete Stanaitis
-----------------
Grant Erwin wrote:
Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant

Ah. That would be "raising". I read about that once in a book about how
they used to make copper pans. Thanks, Pete.

GWE

spaco wrote:

You can do this on a flat surface.
-Cut the piece to shape and file or smooth the edge.
-Find a hard flat surface. An anvil or a half inch thick or thicker
steel plate would be good.
-Using as large a radius domed hammer as you have, simply begin
hammering at the center of the piece and make a spiral of hammer marks
out from the center. Be careful not to hit anywhere close to the edges
of the piece.
Stretching will occur anywhere you hit with the hammer, but, since you
are NOT hammering the edges, the stretched (hammered) material will have
to go someplace and it will dome out as you need.
-Don't try to get all the doming you need in one pass. Just work from
the center to the outside, then go back and make another complete spiral
pass, hammering between the previous hammer marks if possible.
-You do need to be a little cautious that you don't overly work harden
the piece to the point where it cracks.

Note that the larger the radius of hammer you use, the nicer the
finished part will look.

Pete Stanaitis


-----------------
Grant Erwin wrote:

Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different
dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant


--
Posted via a free Usenet account from http://www.teranews.com

On Jan 22, 2:25 am, Grant Erwin wrote:
Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant

--
Posted via a free Usenet account fromhttp://www.teranews.com


Spin it using your lathe.

Dan

Grant Erwin wrote:
Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different
dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant

I've done both hand raising and metal spinning but these days I do
metal spinning as it's so much quicker for doing round objects. If you
can turn up a blank to match the inside of your piece then you should be
good to go. For a one off very simple tools can be used depending on
your quality requirements. I would be inclined to join and post here
about details to start with
http://metalspinningworkshop.com/forum/upload/index.php . You can use
traditional spinning tools or for things like spinning a tank end I have
used a cam follower roller bearing mounted on what amounts to a radius
turning attachment. See

http://www.metal-arts.co.uk/~djb/Rol...rollertool.jpg
http://www.metal-arts.co.uk/~djb/Rol...rtoolfront.jpg
http://www.metal-arts.co.uk/~djb/Rol...ertoolside.jpg

I have recently done this on the same lathe, Harrison M300, upto 12"
diameter and may try at max 18" using the face plate as a former.

Grant Erwin writes:

I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

Cast the conjugate shape against the original with Bondo. Or epoxy plus
quartz sand instead of Bondo. Use that as a one-time spinning mold. Or
make a 2nd cast (positive this time) and use the pair in a press to form
the sheet.

Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.


We can combine modern technology with the classic sculpter's wisdom:

1.Chuck a piece large enough to create it in your CNC turning center.

2.Remove everything that does not look like a domed disk.


--
Dennis

In article ,
Grant Erwin wrote:

Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

Carve the shape you want in a wooden block. Beat aluminum into it. try
"dapping" for a generally smaller scale application of the concept.

You can also work it over a suitable sized ball from the other direction.

Or - work the aluminum on a shotbag, more or less freehand.

In either case you can use soot or chalk to mark the wooden form where
you need to cut it, or the aluminum where you need to beat it, unless
you really want the mess of using prussian blue, which is overkill - but
the mark and cut process is very similar in concept to the same process
in machine scraping.

Also look up "raising sheet metal" and "raising sheetmetal".

If your aluminum is not dead soft, you'll have a much happier time if
you get it to dead soft before you start trying to shape it.

--
Cats, coffee, chocolate...vices to live by

this is a 4" disc, with not much concavity, does it have to be aluminum,
does it matter how thick it is? oftentimes (if the project doesn't have a
heavy time restriction on it) i'll just keep my eye open for objects at the
local recycling center/dump. how about *getting* a tank end and cutting
(plasma, jigsaw, etc.) a 4" disc out of it already pre-formed? sometimes i
get lucky and find exactly what it is i need at the dump.

sorry grant if this doesn't help you at all.

b.w.

(at first i thought you were talking about making a whole weber style dome.
i tried to find a link i used to know about a guy making a expansion pipe
for a two stroke motorcycle by hydroforming it, wondered how big of a dome
you could blow up before it started wrinkling
http://en.wikipedia.org/wiki/Expansion_chamber (see links at the bottom)
there are other better links on the web about this. it surprised me how
smooth the blown up shapes can be.)

William Wixon wrote:

this is a 4" disc, with not much concavity, does it have to be aluminum,
does it matter how thick it is? oftentimes (if the project doesn't have a
heavy time restriction on it) i'll just keep my eye open for objects at the
local recycling center/dump. how about *getting* a tank end and cutting
(plasma, jigsaw, etc.) a 4" disc out of it already pre-formed? sometimes i
get lucky and find exactly what it is i need at the dump.

We don't seem to have dumps like that where I live. We have "transfer stations"
and people do drop metal off there but no one is allowed to pick through it.
That is a vanishing way of life in the Greater Seattle metropolitan area, sad
to say.

I have decided to make a different kind of vent - a tube with a top-mounted
vent. I know how to hold a tube vertical and scribe it to a curved surface.
Then I'm going to cut out the tube and grind it until it fits the tank end
closely, then hold it in place and scribe around the tube and cut a bit inside
the scribe line, then smooth the cut a bit and then weld the tube in place.

The surface isn't regular is the problem - it will have to be off to the edge,
and the tank end isn't spherical. Unless the surface is regular a rotating
disk Weber-style vent won't work.

Grant

--
Posted via a free Usenet account from http://www.teranews.com

On Jan 23, 1:04*am, Grant Erwin wrote:
...
I have decided to make a different kind of vent - a tube with a top-mounted
vent. I know how to hold a tube vertical and scribe it to a curved surface..
Then I'm going to cut out the tube and grind it until it fits the tank end
closely, then hold it in place and scribe around the tube and cut a bit inside
the scribe line, then smooth the cut a bit and then weld the tube in place..
...
Grant

Then put a Diesel rain cap on it.

Jim Wilkins

Grant Erwin wrote:
Picture the little aluminum disk riveted to the top of a Weber kettle. It
closely matches the profile of the domed kettle top.

I want to make something similar in concept, but with different dimensions.
I find I have no idea how to shape e.g. a 4" soft aluminum circle so it
will lie close to the OD of a rounded 3D surface like a tank end.

This is for making a smoker vent ..

Grant


A friend of mine has been making domes with hydraulics.

He forms 321 stainless into headlight reflectors,and similar domes,
using his grease gun, and a quick-n-dirty jig. Basicaly a flat plate
with a grease zerk, a layer of stainless, then a ring of appropriate
size. There is a ring of 1/4" bolts around the rim if the ring.

With a 4 inch diameter ring, he says he can get a little less than
half that in height, before the grease ends up all over his shop.

Me, I'd cheat, just like some manufacturers do, and build the vent as a
flat assembly, and weld it into a cut out hole.

Cheers
Trevor Jones