Steve,
Fitting the slider to the feet, the way I learned,takes the "slack" out by the bottom of the slider bearing on the bottom of the slot in the feet(which is a little proud)while this forces the slider up to bear on the bottom of the slot in the base.This takes out the tolerances necessary in manufacture,and it is easier to fit, since you are not filing blind in a slot.The slot in the feet being proud of the slot in the base is what forcrs the ring down.In fitting the slider,tapping it into the slot with a drift and small hammer,and fileing where the drag marks show interference,takes out the slack.Milling the slot in the feet, results in a slot parallel to the top of the base, and the slider needs to be parallel, to insure maximum contact and not wedge in so tight it is hard to remove the scope.The top of the base has been "skim"milled to make it level and parallel to the water table.The area that sits on the top of the base(which has been leveled)has been milled parallel, while milling to adjust the height, and usually "spotted in" to insure even bearing (one of the reasons the feet should be clear of the barrel).This "milling"can be done by fileing, but the fitting will take a lot of time and will be highly dependent on the skill of the workman.Mounts can, and do, sometimes get loose after 50 or 60 years of use;but it is much easier to correct this by replacing/refitting the slider.If the slot in the feet is not proud of the slot in the base, you can't refit it with just a new slider.
Mike
