I recently ran across an explanation of how to sharpen skates from March, 1919—just over 100 years ago.
Don’t try to draw file at first, … Cut right across the runner first, filing in the usual manner and watching closely the file marks, see that they do not cut down over the corner of the runner. In this manner work down the entire length of [the] runner until all the rounded corner has removed; then take the file in both hands and draw file all the cross marks off. This will enable you to see exactly what you doing to the skate runner; show where to file and where not to.
Perhaps it may be well to file and then draw file two or three times in succession before the skate has been sharpened to suit. By working alternately thus the skate runner can be brought down to a straight or slightly curved bottom, with square, sharp corners, so much desired in skates to enable the skate to `bite’ the ice. The skate may be grooved with a round file if desirable, but skates so grooved, while good for beginners, are not capable of making as much as when worked off flat on the bottom.Hobart 1919, 12.
I think it’s interesting that hollow grinding, which is so important to skaters today, was considered only suitable for beginners. This goes all the way back to Robert Jones, who says “fluted skates” are “so bad, that they are not fit to be used” (37). Today, only speed skaters have their skates sharpened flat across the bottom.
Hobart continues with a little more advice:
…when you can sharpen skates with a file you may regard them as not being first class skates The runners of really good skates are so hard a file will not touch them and the sharpening must be done with a grinding wheel of emery, carborundum or something similar. But you can use the same method of alternate cross and lengthwise grinding so as to ‘see what you are doing’ to the runner, and not to grind off too much at one place and little at another.Ibid.
Using a grinding wheel is the modern technique, but cross grinding (grinding with the wheel perpendicular to the blade instead of parallel to it) is generally frowned upon because most cross-grinding wheels are of a very large diameter. Cross-grinding makes the blade’s radius of hollow equal to the radius of the grinding wheel—something like 5 inches—which is generally not what modern skaters want. The parallel grinding wheel then puts the right radius of hollow on the blade. This process takes off a lot of metal, which shortens the life of the blade. But if the grinding wheel has the radius of hollow you want (and back then, people wanted large ones), it’s less of a problem.
James F. Hobart. 1919. “In a Clay County Smith Shop: An Article about a Blacksmith Who Didn’t Want to Do Automobile Repair Work Because it Interfered with His Regular Business.” The Blacksmith and Wheelwright 79.3:10–12.
R. Jones and W. E. Cormack. 2017. A Treatise on Skating. Edited by B. A. Thurber. Evanston, IL: Skating History Press.