The photo below shows one of the driving axleboxes being trial fitted on the axle.
The axle is covered in marking blue, the axle box is then placed on and rocked from side to side. When the axlebox is removed, the 'blue' will show the points at which the whitemetal bearing surface of the axlebox is actually touching the axle, high spots can then be removed with an engineers scraper.
The photo above shows an axlebox that has been taken off the axle, the blue marks can clearly be seen.
The blue high spots are scraped off and the axlebox repeatedly tried on the axle until there is an even strip of blue marks 2 - 3 inches wide down the centre of the whitemetal surface. The lower sides of the bearing are scraped away so that they don't come into contact with the axle, allowing room for the lubricating oil to be drawn between the axle and the bearing.
All of the axleboxes have now been successfully trial fitted.