I bought some of the Exact Rail 36" wheel sets to use on my Micro Trains heavyweights. I added them to a trio of NP coaches, but the wheels bound and didn't roll well. Hmmm. Out with the micrometer, The outside face of the wheels are 0.457" And the space in the truck frame is only 0.4335" !! Ah ha! So, out with the #11. I make a gentle cut at both ends of the area I wish to remove. This little cut acts as a stop so as I shave delrin away, it is easier to control. This pic kind of shows how much material I had to remove, And a before and after. The left truck is modified, the right truck is not. The difference is obvious, and the free rolling is great!