Tag: sharpening

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.

References

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.

This is the anchor for a series of posts about skate sharpening.

When you get your skates sharpened, the skate technician passes your blade across a grinding wheel in a sharpening machine. In most machines, the grinding wheel is parallel to the skate blade, like it is in this video:

The video mentions dressing the wheel. This means that, before the skate is sharpened, the edge of the wheel is shaped to a portion of a circle with the desired radius. This is called the radius of hollow. About half an inch is common for both freestyle and hockey. Figure (i.e., patch) hollows start at an inch and go up from there. A larger radius of hollow produces a shallower groove on bottom of the blade that feels less sharp. A smaller radius of hollow produces a deeper groove that feels sharper.

Patch skates, which have a shallow hollow, feel very dull and tend to skid, but glide very well and produce few flats (double lines, which occur when both edges touch the ice). This is desirable behavior for figures. Freestyle skaters prefer a deeper radius of hollow, which lets them grip the ice better, making it easier to land jumps and do other tricks.

The optimal radius of hollow depends on the skater’s size (a larger skater should use a shallower hollow) and the ice conditions (a deeper hollow is better for harder ice). The width of the blade also makes a difference. Ice dancers with dance blades generally prefer a smaller radius of hollow (typically 3/8″) because dance blades are narrower than freestyle and patch blades. The narrowness of the blade means a deeper hollow is necessary to get the same bite angle, which is what you feel when you skate. It’s the angle at which the edge hits the ice.

A seemingly small difference of 1/16″ in the radius of hollow can make a big difference in how the blade feels. When you can’t stop after getting your skates sharpened, it may be because the radius of hollow is just a little smaller than what you’re used to. If your blades still feel dull, it’s possible the radius of hollow is a little larger. Or your edges could be uneven.

As the person in the video notes, it’s important for the sharpener to align the blade so that the hollow is centered. If it’s not, the edges will be uneven and have different bite angles. When this happens, your skates may feel ok at first, but soon you’ll be skidding off one edge while the other grips the ice very hard. You can check the levelness of your edges by holding the skate upside down and putting a quarter or other flat object across the blade. If it’s perpendicular to the blade, your edges are level. If it tilts, you need to get your blade fixed. There are also special tools, like this one, for measuring edge levelness.

Next time you get your skates sharpened, ask what radius of hollow your sharpener uses. Then, you can keep asking for that number to make sure you get the same thing every time. Or, you can try changing it to see what works best for you. If you want to really get into the details, read Sid Broadbent’s Skateology: A Technical Manual for Skaters Regarding Skates, Skating Fundamentals, Skate Sharpening. It’s available on his website.

Skate sharpening has changed over time, and future posts will focus on different aspects of sharpening. The radius of hollow needed its own post because it’s so important.