Originally Posted by jmckinley
Problem with the split washer is that it may, on installation, dig into the bolt head or nut as it is being torqued.
No, that does not happen, it only digs in on removal.
HOWEVER, I did find two other issues in my research.
The first is that the split washer is a spring, thus it may tend to 'Fool" the torque wrench, basically the same problem you report but a different cause.. With a flat washer you torque a bolt to say 200 Foot pounds (to pull a number out of thin air) and that translates to a specific force holding the plates together, With a spring washer,,, They plates may still be able to "Wiggle" due to compression of the spring. With a flat washer, This does NOT happen.
The second issue is that they do NOT gouge in when fully compressed, instead they slide, not holding the nut on the bolt at all.
The best solution, per at least one source, is my favorite one... Locktite.
As I said, it goes on like it was oiled. comes off like it was welded.