Tip & How-To about Cars & Trucks
A backyard machine shop technique I used recently worked perfectly on a piece of brass pipe corroded into a cast iron steam radiator, but the procedure is labor intensive. Use a hand electric drill or a drill press to drill a small hole reasonably centered. Perfect centering is not desirable, as you shall see below. Then drill the hole out with progressively larger drills, shifting to 1/64th " increments in drill size as you approach the threads. If you have complete letter and fractional drill sets you can get less than 1/64th" increments for some steps. Clean the hole well and inspect carefully for signs of the threads showing up after each increment of drilling. Stop drilling as soon as you can see any sign of threads.
At this point, it's difficult to peck the remnant of the stud loose from the threads with a sharp punch because it still resists collapsing inward due to the full circles remaining in the threads. To make it collapse easier, use a triangular needle file to file two longitudinal grooves in the thicker side of the remnant until the thread barely shows at the bottom of each groove. The two grooves should be about 30 to 40 degrees apart on the thick side of the remnant.
Now use your sharp punch to knock the section between the two notches inward from the threads. The strength of the thicker metal left due to imperfect centering of the drilled hole is actually beneficial here because the piece will be strong enough to come loose as a single piece, rather than just the top thread breaking loose. Last time I did this (a week ago) I was able to grab the section knocked inward with needle nose pliers and pull the whole remnant out with a twist.
Depending upon your finesse, this can leave a thread essentially undamaged except for a small divot at the point you punched. Run a tap down the hole to clean out the corrosion and clean up any damage done. Strength of the threads should be unaffected unless you were really clumsy.
Posted by Crofter on
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