Stew,
In my opinion, while you can get away with not being as precise by using Nylatron or Teflon washers, that's not MY reason for not using them. My reason(s) are the facts that Nylatron wears fairly quickly, often times it will pick up bits of grit and score...and just generally require replacement much more rapidly that Bronze. I absolutely hate using Teflon washers.....it's soft, meaning it deforms, it picks up and grit/dirt and holds it, it wears very quickly, and as it "loads up" with grit/dirt, the action on the folder gets "gummy" and gradually more difficult to work.
Consistency of thickness on both Nylatron and Teflon is terrible. I've purchased sheets to cut my own washers, as well as actual sets of washers..... Of the two materials, Nylatron is the closest to being consistent, but I often find that there is a .001-.003 variance in thickness between the washers in a set, or in a sheet of the material. Teflon is WAY out there....I have a set of washers here in the shop that vary .004" from one side of the individual washer to the other!
At first I thought it was just a "freak" instance, but as often happens with knifemakers, I got anal and took the calipers to every set of Teflon washers and all the Teflon sheet I had in the shop....it was shocking. Two different sheets of what was suppose to be .015" material measured from .012" to .018! That's completely unacceptable. Maybe that's not common, but that, combined with the other "issues" convinced me to make the move to Bronze.
I'm in no way suggesting that those who use Nylatron or Teflon are doing anything wrong.....I just believe that Bronze is an overall far better choice for folder washers. When I first moved to bronze washers, it was frustrating, because at first, the folders made with them would not "work" as well as I was used to...I quickly figured out that by using bronze washers, it was forcing me to become more precise in every aspect of building a folder. No longer could I get away with +/- variances in parts....everything had to be pretty much "dead on". So in reality, making the switch to bronze washers has made me a better knifemaker...just by forcing me to be more precise.
Prior to going to Bronze washers, it was not uncommon for a client to return a folder within a year or so, with "action problems", in nearly all cases, replacing the Nylatron/Teflon washers solved the issue(s). At the time I just figured that was the way it was...and that having to do that maintenance was "normal".
Those washers were always full of dirt/grit, embedded in the washers. Since switching to bronze washers, I cannot recall a folder ever being returned for action problems.
For me a simple switch in washer material was a major revelation in my knifemaking career.