by RS13 » Sat Oct 04, 2008 8:07 pm
To drill through a single layer of sheet, we make a couple of sheet metal (zero angle) drill bits out of normal drill bits of the same size, say 10mm.
You use the first bit (with the angle spigot) to start the hole, and make a 10mm circular recess halfway through the sheet.
Then with the second bit, you grind off the spigot and even slightly "dish" the cutting faces, then drill to the second layer.
And then just work them apart. Its' a pretty time consuming way of doing it, but it'd be a damn sight cheaper. If you don't know how to grind out a normal drill to sheetmetal-spec, any decent engineer could do it easily.
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