I have an opposite opinion of pneumatic vs manual.
I've never used a "regular" manual squeezer, only the Cleaveland one (this one
https://www.cleavelandtool.com/collections/all/products/main-squeeze-model-22). I've been told it is easier to use, and I believe it
I bought it because I had a couple of close calls and mini-disasters using the pneumatic one. My main issue with pneumatic is that there is no room for mistake.
There are two scenarios where I had troubles guaranteeing the outcome:
1. Riveting various ribs and spars together. Generally, there is some access, but there are all kinds of flanges and other ribs you need to carefully work around. Or maybe there are some other shop heads sticking that a die will happily grab onto while squeezing.
2. Dimpling in the tight corners where you need to "pre-squeeze" first in order for dimples to fit (ends of the ribs, for example).
I tried to feather the trigger, but I wasn't able to master it. There is still some small chance that my finger will twitch at the wrong moment. And the cost of mistake is kind of high (figure eight hole or smashed flange or something like that). In some places I even removed the spring from the squeezer to position it over the hole, which is both not very safe and also cumbersome.
So, I bought the Main Squeeze and I loved it. Even for AD4 rivets the force is tolerable. Yes, usually it does require an extra hand, but it's less of an issue for larger parts. Also, in a pinch, if I don't have a helper, I can push one handle against the table (or even against my belly
).
I started using it more and more, and now I don't even bother setting up the pneumatic one most of the time (unless I need to mass produce a line of dimples / rivets). I also found that I don't have to set it up perfectly. I guesstimate the dies to use, start squeezing, and if they are too tight, I will see shop head becoming too flat and I can stop at that moment. With pneumatic one, you can't really err on the "tight" size.
Oh, and also the pneumatic one I have has a trigger safety (you need to slide the trigger "up" before you are able to press it) which I disabled early on. I just wasn't able to hold the thing (it's kind of heavy), keep it perfectly positioned over the rivet and then slide and press the trigger simultaneously. Which is also a safety issue. Again, likely a skill issue.
So, in the end, for me, the end result of using manual one over the pneumatic is:
* It is safer
* It is easier to set up
* It is actually smaller and in some cases can reach the places where pneumatic won't fit (although, I think, I had cases where opposite was true as well...)
* The downside is that on average I need one more hand
* Doing dozens of AD4 rivets is tiring