The EAA states that building your own airplane is educational. Well I'll
say!! I spent the day down in my shop working on the swedging problem. I
am pretty sure I have the answer to what needs to be done. As the alloy is
5052 and .090" in thickness, it seems to hve good workability.

I ended up making a device very similar to a regular Greenlee chassis punch
except instead of cutting a sharp edged hole, the male portion of the die
has relieved edges and has a diameter equal to the slug I want to weld into
the aluminum. Before I use the device, I cut a hole in the aluminum with a
bi-metallic hole saw slightly smaller than the finished hole size. It is
smaller by twice the length of the swedge flange. A 1/2 inch bolt goes
through the female die (oak plywood block nailed to another plywood block
which has been drilled to finished hole size plus twice the thickness of the
metal plus twice the bend radius for .090" aluminum) then through the
aluminun sheet then the male die. A large washer is placed over the male
die then the nut goes on. I spray WD40 on the threads and start to torque
the nut. I was surprised at how nicely the aluminum deflects downward. I
continue to wind the nut down until the male die is pulled through the piece
of aluminum. Originally I was using oak as the male die but it didn't hold
up. Then I switched to UHDPE. The PE went through fine but compresses
slightly so the hole ends up undersized. I ordered a piece of 3" steel bar
which I will turn down on a lathe to make the male dies. At this point I
think I have the problem solved. A lot of work for five holes. But as I
started my message it's all educational. Thanks Ernest!

Ebby


"Ernest Christley" wrote in message
.. .
Ebby wrote:
Ernest,

I think I understand your description. I am going to send you a picture
of how I interpret your instructions. To me it seems like the tool you
describe is similar to a radio chassis punch. Is that correct? Instead
of punching a hole, your device pulls a slug of aluminum through a hole
in the plywood 2x4 side of the aluminum.

Also are you saying that once the tool and aluminum are all clamped
together the hole dug out of the hole saw will press through the aluminum
sheet creating the swaged hole? I do have to mention that the swage will
result in a flanged hole that I can use to weld my finger strainer and
sight gauge fittings. Should a hole larger than the 1/4" hole you
mentioned be drilled in the aluminum first so the male swage block will
pull down through easier to create the flange.

I'm all ears to solve this fabrication problem.

Ebby

I think I answered you with direct email, but for the greater audience....
I'd use the "chasis punch", as you describe it, to make the swage and then
use a step drill to cut the hole. That will help avoid unwanted cracks
around the hole from the stretching. You can make a larger hole, but
remember that you're stretching the aluminum. Keep the hole as small as
possible.



"Ernest Christley" wrote in message
...
Ebby wrote:
Dear All,

I am starting to build my center section fuel tank and need information
about how to swage holes in the bottom of the tank so that I can edge
weld the six fittings specified in the plans. Four of the fittings are
finger strainers and one is for the sight gauge. There is one more
hole on the top for the filler. As there are only six holes in three
different diameters, I was thinking about doing it using simple hand
techniques rather than expensive tooling.

Here is my idea. The tank is .090" 5052. I planned on drilling holes
(.180+flange dimension) undersize in the aluminum. Then centering the
holes over 3/8" steel plate with holes .180 oversize, then use a
polyethelene bossing hammer to swage the edge of the hole into the
female die hole. The holes in the female die would have the edges
relieved to accomodate a bend radius. It might be time consuming but
educational.

Any advice or previous experience to share

A piece of 1/2" plywood and a couple chunks of 2x4. Tack plywood to one
of the blocks and use a small hole saw with a 1/4" centering bit to cut
the inside diameter of the swage. The piece that you dig from the hole
saw goes on one side of the aluminum. Use a bigger hole saw, centering
on the same 1/4" hole, cut the outside diameter of the swage, then drill
the 1/4" hole all the way through the block. Drill a 1/4" hole through
the other block. Drill a 1/4" hole where the swage will go.

Thread a sufficiently long bolt through a fender washer, the block with
the plywood attached, the aluminum, the piece you dug out of the small
hole saw, the other 2x4 block, then another fender washer. Spin a nut
down to extrude the swage.

I don't know if this will work on .090, but I've used this technique on
thinner material.