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Ditto on Dell’s assessment of the machining method to straighten the hole. As a Tool & Die maker, I can tell you that a drill will follow the same path as a previously drilled hole. To straighten it, you need to bore it out or plunge with a milling cutter. Hence the need for the milling machine. Another threaded insert, of whatever design, will only yield a crooked bolt hole with good threads. Another option, similar to what Joe had suggested, is to drill and tap it to an oversize bolt diameter. (Once again, dependent upon enough material being present!) Tap the hole close to the bottom as you can using a taper tap. Get yourself some threaded rod of a suitable material, and turn it in until you start to encounter some resistance. Mark the depth that it entered and remove it. Clamp it into a vise, and use a hacksaw to cut about halfway through it a distance equal to roughly the threaded rod diameter above the depth that you could turn it in. Get a couple of nuts, and lock them together above the cut. Coat liberally with permanent Loctite, and turn it in. using a wrench on the upper nut, you just keep cranking it in until you end up shearing the threaded rod off. This forces the end of the threaded rod into the lower portion of the threads that have not been cut to full depth by the tap. I’ve used this numerous times to “move” dowel holes in stamping dies, and it will never pull out. Now finish up the exposed portion with a grinder, and follow what Joe has said. If you decide to go with Joe’s plan, (excellent point on the .002” undersize lead in!) I might add the suggestions of putting the pin in the freezer for a while before driving it in, and try to have the block at a warmer temperature. Also add some cylindrical bonding Loctite.
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