helicoil in heads
Tips for Helicoils in heads:
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Things to think about with Helicoils.
Make sure that you set them deep enough so your bolt doesn't bottom out on the flat tang on the bottom when putting everything back together.
Since the tang should be broken off when the helicoil is properly installed, this is a moot point. The tang should NEVER be left intact after installation. You leave the helicoil high enough so you can snap off the tang with a small punch. NEVER use the bolt to snap it off. Helicoils are very hard and can damage the threads on a Grade 5 bolt very easily if the tang does not cleanly snap off.
The flat tang at the bottom is used to drive the Helicoil into the hole and then stake it in when you back out the installation tool. You can sometimes hear it snap when you do.
Yes, the tang is used for driving the helicoil in, but you do not stake it in place, you snap it off.
If you use it on the straight through holes with out a bottom, cut the tang off and use some strong Loctite or equivalent thread locker to keep it from coming out. If you have to cut the tang before installing it, use a thin nut at the top of the installation tool to drive the Helicoil into the hole. Sometimes the end of the bolt has to go past the end of the Helicoil.
DO NOT use loctite in helicoils!!! There is so much misinformation about how to install these useful items, I can't beleive it!
You use the tang to install it no matter if the hole is blind or not. Always snap off the tang after installation, then using a small punch, stake the TOP of the helicoil. That, plus the fact that it is stretched lengthwise and compressed in diameter will hold it in place.
If the hole is threaded deeper than one Helicoil, use two to get enough thread depth and cut the tang of the top one as described above.
Not really necessary. The helicoil is designed for the particular diameter bolt you are working with and should be fine to hold torque with only one if you properly drill , tap & install the helicoil.
Take my advice. I spent 10 years in the automotive machinist business and was ASE ceritified. I installed a lot of helicoils and fixed a lot of improperly installed ones.
