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Broken tap remover

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While tapping a hole in some aluminum stock W I broke off the tap inside the hole. I tried to grip the broken piece with pliers to no avail. Every method I could think of to remove it would destroy the original hole or the threads. A chemist friend of mine suggested that I immerse the part in 50 per cent solution of nitric acid. I tried this and in a few hours the steel tap was completely dissolved and the aluminum was none the worse for wear. If the aluminum piece is too large for immersion, an eyedropper can be used to apply the acid.

John S. Sisson, jr.,WA2GWF.