A broken stud can frustrate even the most experienced mechanic if he does not have the correct tools to remove it. Unskilled extraction of a broken stud can seriously damage a cylinder head or an engine block.
A stud extractor, or easy-out, extends a broken stud so it can be removed using a wrench or tap holder. The extractor engages with a hole drilled into the centre of the broken stud and grips tightly as it is unscrewed, drawing the stud with it.
Tapered stud removers, either straight or spiral, are common; straight cylindrical extractors, which engage uniformly with the broken part, are sometimes preferred. Sets of extractors, formed from high-strength tool steel, often include correctly sized drill bits and guides.
A professional quality set of five tapered spiral easy-outs with left-handed drills retails for about £26. A corresponding five-piece cylindrical extractor set without drills has a suggested retail price below £13. (Prices are as of February 2011.)
It is important to drill the hole exactly in the centre of the broken stud; an off-centre hole increases the chance of damage to the head or block. Drilling sometimes loosens the seized thread, and a left-handed drill can turn the stud and remove it without an extractor.
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