From a conversation on LinkedIn in the Piano Tuners & Technicians group:
I have had good results using CA glue as a pinblock repair. The first time I employed it was actually for a Steinway A3, owned by an elderly couple living in modest circumstances. Too many pins weren't holding. All alternatives involved too much labor (money) and too many question marks. And selling it or rebuilding it were not options.
Tom McNeil was newly-moved to Vermont around this time and he had come to Boston to give a technical, which included stories of saving similarly far-gone instruments up in wood-stove country. So I tried it and my customers were thrilled to once again have use of their somewhat decrepit but deeply-loved instrument.
I love this repair, in spite of the smelly synthetic chemical aspects. It works passively, reinforces the weakening area around affected tuning pins, and basically does its magic by adding more surface contact between block and tuning pin. If applied moderately and let dry overnight, more can be added as needed, extending the life of an aging but essentially healthy pinblock indefinitely.
Heavy duty plastic (large garbage bags) will contain it if it leaks through. You should definitely remove a grand action and carefully cover the keybed. A spot repair for one slightly loose pin might be OK on the fly, but I would suggest chasing it with accelerator. Uprights tend to lean their pinblocks toward us and present a potential mess - be careful.
I have mostly sold the CA solution as a global repair, which for uprights involves rolling up the carpet, putting down some strategically-sized pieces of protective material, using a tilter, and administering the repair with the piano on its back, garbage bags protecting the floor from possible drip-throughs. The watery CA is what works best, and if there is an opening, it can follow that through to wherever... Don't let it puddle, as it can smoke or self-ignite.
Another hazard is tapped pins: if coils are close enough to or touching the plate, surface tension on the glue can prevent it from wicking down to where it is needed. And if it hardens as a collar between pin, coil, and plate, it will prevent access for a second attempt. I only went through this scenario once. And it was a hassle. But, it was the only failure out of the 50 or so times I've used it. CA can even work in pin-dope polluted circumstances. In my experience, it is not a temperamental glue.
The CA pinblock repair has been the first step for me in many partial restorations that would not have otherwise been sensible. I would warn my customer of the possibility of a failure and it would seem a reasonable risk, compared with the costliness and somewhat short-termedness of alternatives. Applied carefully, it can also even out loosish pins in a young pinblock. Oversized pins, which were popular pre-CA, at best gave a 20-30 year solution and at worst...? Also, they required a lot of work, they could act as wedges to extend and worsen hidden cracks, and even if a good new piano warranty might be 10 years, having a restringing job fail after 10 or even 20 years probably does not a happy customer make. No need to discuss the demerits of "pin tightening fluid".
With good sense in the selling of the job and the application of the repair, it is a great repair - great for the piano owner and great for extending our range of work and profitability!