On 2012-04-18, Tim Wescott wrote:
I've got a little 3oz fuel tank (model airplane) made out of thin
tinplate (a Dole Pineapple Chunk can, actually). So, maybe about 10 or
15mil, with corrugations.

I need to drill a 1/2" diameter hole in it, to solder in a fitting. I
know that if I use a regular 1/2" twist drill I'll just rip out big hunks
of tin -- so that's a no-go.

Is the can curved, or do you have a flat place to drill the
hole?

This is a last-minute rework to get me to a contest this weekend, and
I've spent out the modeling budget this month. So I'd like to be able to
do it with tools I have in the shop rather than spending time or money I
don't have to order something, or even nip around to Horror Freight.

I have a nice stepped drill that goes up to 1/2 inch, but it's longer
than the tank. I may just go ahead and drill through and patch up the
far end -- but if there's a better solution, I'm open to suggestions.

If there is no curve, and you can back up with some wood, I
would suggest drilling with a brad point wood drill, which cuts through
at the OD first (not counting the centering brad, of course). This will
probably dull the bit, but it may be expendable.

If you have two of the Unibits, why not cut off the end of one
so you can use the normal one to get up to as far as you can get before
the tip touches the other side, and then use the shortened one to
complete the hole.

If you could live with 9/32", something like my sheet metal
punch pliers (Roper-Whitney No.5) might do. Hmm ... there is another
size, the "Model XX", which can go up to 17/32" hole size -- almost all
the way there.

Here is their web page, in case you are not familiar with these
tools:

http://roperwhitney.com/punching/2-45.cfm

For that matter -- do you have the T-handled tapered reamer? It
will go up to 1/2" (though it is rather long for your can) and I'm not
sure how well it will work in something as thin as your workpiece.

Or -- do you have Greenlee radio chassis punches? They will
work well for this, set the punch on the inside with the points set at
the apex of the curve, and the die on the outside. You'll probably need
about 3/4" to clear the thickness of the die between the ribs of the
can.

Good Luck,
DoN.

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