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.