Helicoil
A brand of coiled wire thread repair insert used to restore stripped or damaged bolt threads in metal components.
A Helicoil is a precision-formed coiled wire thread insert made of high-quality stainless steel, used to repair stripped, damaged, or worn internal screw threads in metal components. It is commonly used in aluminum engine parts, such as cylinder blocks, cylinder heads, and transmission casings, where steel bolts can easily strip out the softer aluminum threads during tightening.
The repair process involves drilling out the damaged thread, tapping the hole with a special oversized tap, and winding the Helicoil insert into the tapped hole using an installation tool. Once installed, the Helicoil provides a permanent, high-strength internal steel thread that matches the original bolt size. The insert is held in place by radial expansion forces, preventing it from backing out.
Common automotive repairs that utilize Helicoils include fixing stripped spark plug threads, oil pan drain plug threads, and cylinder head bolt holes. If a bolt cannot be torqued to specification because the threads have pulled out, a Helicoil is often the most cost-effective and reliable solution. It restores the original structural integrity without requiring expensive component replacement.