I downloaded a thompson linerar bearing and rail from cbliss.com. After racking my brain with the layout Im working on I decided to check the parts I downloaded.
The bearing mounting holes have the correct center to center dimensions however the dimension of the edge of the part is not centered about the part. Also the bearing is not centered about the part. 1.687 x 1.00 dimensions for 4 holes are correct but they are skewed to one side, as is the bearing center where the rail slides on. I discovered this because I mounted two together which should result in a 2.00 center for the 2 rails and it was 2.062.
The rails seem to be drawn accurately.
Perhaps someone can correct the part for future users.
Just wanted to alert all of you.