These cause more hassle then they are worth, used twice, snapped twice!!!yes there just like a reverse tap, but tapered, your suposed to drill a small hole and insert the tool, but as you already have a hole then no drilling,
http://www.screwfix.com/p/screw-extractor-5-piece-set/18643?kpid=18643&cm_mmc=Google-_-Product Listing Ads-_-Sales Tracking-_-sales tracking url&gclid=Cj0KEQiAot_FBRCqt8jVsoDKoZABEiQAqFL76Kdvy4HJTsKiDR_6BOHwQJKswvWr5I4hP8IJaF-XmucaAgZj8P8HAQ
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