: Not sure what a blade truing disc is, but, if it's the large flange/washer
: that goes under the nut, yes by all means get one. All saws should have
: that included when purchased. They stiffen up the blade considerably. Try
: to keep it close to the same size as the backing plate the blade rests on.
: Anything larger or smaller by considerable may tend to push/warp the blade
: when tightened down.

LV's blade truing disc is an "advanced" version of the big washer/blade stabiliser you're talking about. It contains a number of set screws machined into the sides of the discs, and use can use these to press against the blade. The idea is that it will take out any wobble or misalignment of the blade on the arbour.

coop