Looking for a way to swage a hole to weld in a fitting for an aluminum fuel tank

What about a greenlee punch that electricians use?

I am not sure. but it seems to me all you are asking is how to make 3 different size holes in .090 aluminum sheet.

Mark the center point and drill a 1/4" pilot hole. (Clamp on to a drill press if you can.) Now use a fly cutter with a piece of 1/4" drill rod as the pilot.

See:

It might be a good idea to cut the size you want on a piece of scrap to be sure the cutter is set to the proper diameter.

Go gently and keep all body parts out of the way in case the part grabs and spins. It is also a good idea to back up the part with some wood if you can.

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"Ebby" wants a flanged hole, per thread in rec.aviation.homebuilt, eg

-jiw

It'll work. Put a radius (fillet) or chamfer on the hole in the steel. You don't want a sharp corner there.

Guy Lautard had some tooling designs to do this sort of thing in one of the Machinist's Bedside Readers, don't remember which one. Basically an outer die with the desired flange radius machined into it and a taper plug that was threaded axially so it could be drawn through the under-sized hole to form the flange. This was designed for pipe and clamped around same, you'd have to figure out how to hold things together on your tank. You'd need at least a lathe to make the tooling, if not a mill. If your tank is curved, the die will have to match the curve where you want the flange and you'd have to have a set for each hole size.

Another alternative is to turn/mill flanges out of some compatible weldable alloy, punch your holes via Greenlee punches and weld your flanges in place.

I suppose if you had access to the inside, like before you put the tank together, you could use hardwood dies and hammer your material into shape, punch/flycut/drill an undersized hole first. You'd want to practice first.

Stan

I made something like that. But much smaller*). Needs a little experimenting to find the right sizes. It consistet of two parts: a) the die: it is just some kind of tube (thick-walled). Make a smooth radius where the die sits on the work and the "jet" will get pulled in. Through the center of the die goes a pulling screw from the ... b) punch: It is conical shaped. The flater the cone is, the better. Around 5° if you have the room. But 15° work too. Out of the tip of the cone the thread is coming out. Polish that cone.

Drill a hole through the work, apply some cutting oil onto the punch (well, it doesn't cut, but do quite some bending), put the threaded bolt through the hole in the work, slip the die over the bolt and pull the cone through the work (with a nut). Of course, you did some math that the hole in the die + 2 times the work-thickness equals the big diameter of the punch's cone. You'll get some burr at the formed "jet" that you will have to file off.

Here's a picture for clarification:

On the lower right is the cone (hardened drill rod), left of it the die (also hardened drill rod), on top the pulling bolt. Couldn't make the punch and bolt in one piece to get it all into the tube. On the left, you see the tube. The pulling bolt is M2. :-))

HTH, Nick

Ok so he wants a thicker hole. Easy way to reinforce the hole is to have a wide flange on his fitting and weld both sides. I really don't see an advantage to the process he describes. The way to do it however would be to make a set of dies and use a press. He could probably get away with mild steel for the onsy twosy project he is building.

Correction 10..15° is OK.

nick