Not being a (woodworking) machine user, I don't usually comment on such matters, but in this case I can't resist. Having worked for years in an engineering environment in which a great deal of effort was expended to ensure high plant reliability, there are a few things I've learned over the years that may be worth an airing.
Long-term reliability is usually associated either with simplicity (absolute minimum - preferably no - moving parts), or with regular and intensive maintenance.
The American approach to tablesaw/circular saw safety does surprise me somewhat. Americans are not a stupid people (no more so than the rest of us, anyway), yet in this matter seem almost wilfully blind to well-known contributions to safe use. The riving knife has been in use in the UK and elsewhere - indeed, mandatory in commercial and industrial situations - for as long as I can remember, and probably a lot longer than that. It's simple, has no moving parts so is reliable, and works well; yet it took many years for it be adopted to any extent across the pond. Ditto crown guards - the simpler and more solid, the better, generally.
I was rather surprised a year or so ago by the fuss about the 'saw-stop' flesh-sensing technology device which some seem to want to make mandatory in the USA. It's a very impressive device, but it relies too much on sensors and devices, all of which could fail at the critical moment. It's not simple, and consequently, it's reliability could not be guaranteed. High technology devices are also prone to increased unreliability as the machine they are fitted to ages, especially if the machine is used unsympathetically and gets little cleaning and maintenance. The beauty of the riving knife is that (short of gross damage or physical removal) it will continue to function properly for the life of the machine. (I could see the saw-stop being a useful additional fitment to saws used in, for example, schools; additional safeguards for the inexperienced being generally a good idea, and being an environment where regular maintenance is usually relatively easy to ensure.)
There's a story told (probably apocriphal, as most such are) about the use of ball-point pens during the days of the space race. NASA discovered that they didn't work in zero gravity (they don't work upside-down, either - try for yourself) so spent a couple of million dollars developing a pen that would work in space. The Russians discovered the same problem, but solved it a different way. They took propelling pencils instead.
I wonder if America has suffered a slight case of 'technology blindness' with table saw safety. America is a society so used to technological solutions that (collectively at least), it automatically assumes that a problem must have a high-tech solution. Simple measures (riving knife, crown guard, push sticks, rip fence not extending past blade) have been well known for years, and must be better, simpler, cheaper and more reliable measures to adopt as mandatory fitments to new saws than costly and potentially unreliable flesh-sensing auto-stops.
I'm not taking a pop at anybody, here. I'm just genuinely slightly puzzled that a normally intelligent and pragmatic country seems to have had a slight mental block over this one.
