Yes, you drill the hole bigger and tap for the threads on the outside of the helicoil or thread insert. The other main advantage of using one of these over just tapping for a larger bolt is in softer base materials (aluminum, plastic) it will distribute the screw load and prevent it from stripping in the first place, at least to a point or damaging the threads when the screw is removed and reinserted. This is especially important if the screw is one that will be installed and removed every year. I think that there might also be an advantage in preventing a stainless steel screw from seizing/corroding as it will tend to do over time in tapped aluminum, at least in a salt water environment. For that reason, I would tend toward using a solid insert such as https://www.mcmaster.com/catalog/126/3505 rather than a helicoil if putting a stainless steel screw into threaded aluminum where I want to be sure I can get them apart again. We had bolt together reusable aluminum frames at my last job with M16 and M24 bolts and used inserts for threaded holes in the aluminum - worked great and we never had issues with stripping or galling of the threads.
~~~ Nathan Post S/V Wisper On Thu, May 14, 2020 at 10:18 PM Graham Collins via CnC-List < cnc-list@cnc-list.com> wrote: > Hi David > > Yes, allows the use of the original screw, so whatever is fastening to it > doesn't have to be modified. > > Procedure is to drill and tap oversized, and install a helicoil - > essentially a coil of square wire, wound up like a spring. The wire > engages in the new threads and is sized so that the original screw threads > inside it. > > Graham Collins > Secret Plans > C&C 35-III #11 > > On 2020-05-14 10:50 p.m., David Knecht via CnC-List wrote: > > I have seen mention of helicoils several times on this list but I have no > experience with them. I have several stripped screws on my Harken furler > and was thinking they might be useful to repair. What is unclear to me > from what I have read is the reason to use them. I still have threads > there, and I thought the idea was to screw in a helicoil to make the > threads grab again. However, every description I have seen of using them > drills out the hole, taps and then screws in a helicoil. I don’t get the > point. If I am going to drill and tap, why would I use a helicoil instead > of just putting a screw into the newly tapped hole? Is it that you can use > the same size screw as before instead of going to a larger size? Is that > preferable for some reason? Dave > > David Knecht > S/V Aries > 1990 C&C 34+ > New London, CT > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each and > every one is greatly appreciated. If you want to support the list - use > PayPal to send contribution -- https://www.paypal.me/stumurray > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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