So far I'm defining a fine tooth ratchet as one that will interfere with me reversing the ratchet lever depending on the angle (when it's on a fastener). For instance, comparing two different ratchet adapters, one that is 24 tooth doesn't get stuck in any position, and the other 36 tooth one will (sometimes), as will any ratchet I have with 36 or more teeth (unless there's some trick to that, besides turning the handle to a different angle or removing it from the fastener).
Actually now I'm not sure about this being a simple matter of tooth count, just that it tends to happen with ratchets that have higher tooth counts (70-, or 80-something). I checked another one that hasn't gotten stuck on me, and it looks to be a 40 tooth (I was assuming it was lower, because it's el cheapo), so maybe this has more to do with the switch on those, or is a combination of the two. As far as I can tell, it doesn't matter where one's made... wait, are there ratchets by
Swiss watch makers?
I don't know, is it just me, or do fine toothed ones get stuck easier...

At least some are much harder to turn at times, if not technically stuck, and I'd have to use the other hand to switch it, rather than the one holding the handle (maybe it's the angle of the handle too, and all the socket connections can wobble somewhat adding to that). In that case I think it's hit and miss as to which ratchets are always easy to switch, yet they all seem to work consistently without pressure on the mechanism.
Yes, that's it. I just tested out the 24 tooth ratchet adapter on a heavier sliding T handle, and it switches easier when the weight is balanced, by having the handle in the center, then it becomes more sticky when the handle is slid to one side. It's mostly about weight distribution then, I'm pretty sure. Just that the 36 tooth adapter on the same handle is not designed to switch as easy from either position, as it happens. Those two switches are in different locations on the adapters. The one on the front switches better, probably because there's less weight acting on it as a result (I think the other one gets sandwiched in there under load). My 40 tooth ratchet that's never gotten stuck is only an 8 oz handle. The other fine toothed ones are heavier. So it must be a leverage thing, because the ratchet switch is a lever of some kind, as is the handle (and sometimes the handle wins). For sure, a heavier 30 tooth ratchet behaves the same way. I hadn't compared it until now, and didn't get any of those based on tooth count, but that was a false assumption too (well, one of these coincidences had to be true, if not several of them). Maybe that's obvious, but you never know, some things work better under heavy load, like the brakes on a commercial vehicle (not that it was on my mind in particular, but I must have been over thinking some of this based on some of that, as if fewer ratchet teeth were so dynamical). I'd say they're more comparable to a clutch now (or that of manipulating various levers to facilitate shifting), as the ratchet adapters have a neutral or direct drive position, which is easy enough to switch into under higher torque, just not out of. I suppose it depends on the size and stability of the fastener too, how well balanced a particular ratchet might end up on there. Less is more though, on this kind of mechanism for working precisely, besides the tooth count.
Also I found that a flex head ratchet with a heavy enough handle to get the selector switch stuck from a 90 degree angle can be temporarily angled straight out to balance the weight better, and switch the lever (72 tooth by the way). I've got this thing fingered out.
