Speed skate blades are very thin, just 1mm wide and are flat ground, usually by hand. This means that they have no hollow in them at all, and the skater needs to learn to use the blades correctly to cut an edge on the ice. Since the skaters only ever turn left during a race, the blades may be offset to the left to allow the skater to lean deeper into the turns.
Hockey blades are usually made from stainless steel of around 3mm thickness. Some low end blades may be carbon steel, which is a harder metal, but prone to rusting if left wet. Higher level blades may be constructed from 2 different metals, an aluminium upper for lightness, and a steel lower section for hardness where the blade contacts the ice. Hockey blades are mounted in a plastic holder, the higher level ones having replaceable blades.
Generally made from carbon steel of approximately 4mm thickness, figure blades have a toe pick at the front and a short tail at the back. Higher level blades will have bigger toe picks and may be case hardened ( ie higher carbon content in the outer skin. When the blade is heat tempered, the outer shell becomes much harder than the main body, but the blade remains flexible and not brittle.
Dance blades are very simular to figure blades however the tails of the dance blades are shorter. This tail is only used for stability when landing jumps so in dance this is no longer needed. The toe on top level dance blades is rounded off, meaning the pick is no longer sharp and can be used for other technical movements rather than taking off to jump.
If you were to cut through a properly honed ice skate blade vertically (not recommended), you would find that the base of the blade has a curved groove ground into it.
This groove is formed by a spinning abrasive wheel which has been dressed so it forms part of a circle, the radius of which is known as the Radius of Hollow (ROH)
Skates can be ground to anywhere between 1/4” ROH and 1” ROH, and even 2” in some extreme cases.
The ROH has a major impact on the feel of the ice skate on the ice. A small ROH (1/4” to 1/2” will give good sideways grip, at the expense of glide performance because the blade cuts deeper into the ice.
A larger ROH, 3/4” to 1” will give better glide performance at the expense of sideways grip because the blade does not cut into the ice so deep. This is more suited to novice skaters who are still learning how to stop on skates. A shallower hollow will make it easier for the blade to skid sideways, and since stops generally involve skidding one or more of the blades over the ice, stops are easier to master The blades will also need sharpening more often as the blade will dull quicker.
In the days of true figure skating, ROHs of 1” to 2” were favoured as the skaters were given marks for the pattern they cut on the ice. If both edges cut in on a curve they would lose points, hence the desire for a wide, virtually flat blade. Nowadays it is very rare for anyone to skate with a hollow greater than 9/16”
If the blade is left against the abrasive wheel for too long it will overheat and when it cools, the metal will detemper (soften). If your blades come back with areas which look to have a blue sheen, then you can be pretty sure that they have been overheated.
Damaged drag pick
Good ice skate sharpening will avoid the drag pick altogether. No metal at all should have been removed from the drag pick during regular sharpening. It is possible to re-align a worn drag pick, or raise it slightly to compensate for over sharpening of the base of the blades, but this is a highly skilled operation and must be carried out by a competent technician.
Unless the sharpener is being very careful, it is easy to round the tail of the blade off. The blade edges should run all the way to the back of the tail, and not round off.
Most sharpening wheels will leave a pattern on the base of the blade that looks a little like woven fabric. This should be almost invisible, if there is deep weave cut into the blade, it will introduce unnecessary drag and make the blade run more slowly than it should.
John Wilson and MK blades have developed a carbon fibre topped blade called the Revolution. The benefit of this blade is the reduced weight, less weight means more height on jumps.
The toe pick is machined diagonally, which gives little pyramid shaped sections at the sides of the picks. This gives more bite on the ice, and reduces the likelyhood of the blade slipping when the skater is performing toe assisted jumps.
The blades have concave sides machined into them from top to bottom. This creates a more acute angle at the edges where the blade meets the ice, so the skater gets more bite on the turns without adding extra friction on the straights.
Some blade manufacturers have developed blades made from Titanium, which is very light weight but strong. These blades have steel runners, as it is not possible to sharpen Titanium on a grinder’s wheel.