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The only major setback so far is a broken plastic thread section of what I think is a vacuum hose connection. OReilly's Auto says a left handed screw extractor will work fine so we'll see how it works for me. Does anyone have any other suggestions?
Many threads cover the procedure and the problem. Often, the screw extractor breaks off. The steel used in extractors is very hard, which makes it difficult to do much with it outside of a machine shop.
Here's what I do:
0) Soak for a few days in penetrating oil.
1) Use a center punch to indent the center of the broken screw/bolt. This is where the hole will be, so be careful and get it right. If the screw broke at an angle making this almost impossible, use a grinder ball on the end of a Dremel first. Get it in the *center*.
2) Buy a set of left hand drills. Harbor Freight sells them for about $15. Those are acceptable. Better ones can be found at many places, including at McMaster Carr.
3) Find the angle of the screw. Drop a thin rod or use a threaded rod in one of the holes parallel to the broken screw. Hold your drill at that angle. You're going to be holding that drill for a long time, so find a position where the weight is supported and you are guiding.
4) Use cutting oil or motor oil to lubricate.
5) Drill down the length of the broken screw using the smallest drill. Use moderate pressure and keep under 200 RPM or so.
6) Stop every two to three minutes. Be sure that the tip of the drill is not hot. If it is, use less pressure or slower speed. If it isn't warm, use more pressure/speed. Add oil and continue.
7) Repeat until you are through the length of the screw, or until the drill chuck is almost interfering with the screw or surrounding metal. It could easily take an hour.
8) Change to the next large drill and repeat. This will go much faster. The cutting part of the drill has something to cut into.
8) Keep using larger drills.
9) Eventually, the screw will give up and spin out. That is the reason for using left-hard drills. The screw is held in by a combination of corrosion and pressure against the female threads. Penetrating oil + heat from drilling + vibration from drilling will fracture the soft rust. As the core is drilled out, the screw will slightly shrink into itself, relieving the tension. The drill will rapidly speed up and the hollow screw will spin out.
10) Chase the thread with a tap.


