Experiments with power and hand sharpening burrs and edges, 12/11/2014

[Query]

I did some experimentation to investigate the microscopic effects of sharpening, using power and hand tools, and the effects of various forms of "deburring". Essentially I wished to determine whether sharpening produces the edge as a simple intersection between the hollow arc and the side of the blade, or whether it creates an over-burr. The results were mixed.

The study is flawed, because I did not consider all possible combinations of blade composition, hardness, and sharpening technique. But the differences are intriguing nonetheless.

---------------------------------------------------------------------------------------------

First, I asked Mike Cunningham, a well respected sharpener who manages "Skater's Paradise", in Waldorf, MD, to sharpen a skate blade, using conventional techniques. He chose a new MK Club 2000 blade, a relatively low level carbon steel figure skating blade. He sharpened the blade using a Blademaster power sharpening tool, using a 60 grit Blademaster sharpening wheel. He used a light oil or polishing fluid, as the sharpening lubricant.

After the initial sharpening process, I examined the edges using a Digimicro USB digital microscope, connected to a small notebook PC. The magnification was approximately 50. The primary edge was clearly created as the simple intersection between the hollow, and the side of the blades. In addition, there was a very ragged and poorly organized burr off to the side, not particularly confined to one plane, in a sequence of varying lengths that alternated with lengths with no obvious burr.

He than rubbed a fine flat sharpening stone along the side of the blade, flat surface against flat surface. This mostly removed ("deburred") the burr, but left a few short stretches small amount of even more ragged burr. The burr was more or less turned upwards (it would have been downwards if the blade were oriented as in skating), but was still not confined to one plane.

He then rubbed a hard rubber stone containing abrasive, purchased from Sid Broadbent's company, at an inward angle. This completed the process of removing the burr. The main edge was also dulled somewhat.

This result is fairly consistent with what most people claim to be the result of figure skate or hockey sharpening, though most sharpeners do not use the final hard rubber stone, and some sharpeners brush the flat stone at a somewhat inward angle.

---------------------------------------------------------------------------------------------

Second, I sharpened an Ultima Matrix 1 Dance blade,  a higher quality and harder stainless steel blade. I used an Edge Specialities "Profiler" hand sharpener, using the "coarse" (diamond dust) sharpening cylindrical stone. I used water instead of oil as the sharpening lubricant.

The created the same type of primary edge as the prior technique. But the sharpening burr was substantially more intact and much flatter. Perhaps better called a "lip" than a "burr".

I then brushed a flat stone along the side surface as in the previous technique.
This bent incomplete lengths of thin lip above the edge.

---------------------------------------------------------------------------------------------

Third, I resharpened the Matrix 1 Dance blade, using the coarse Profiler stone again, and then using the fine Profiler stone. The lip was much more intact.

Then I used the fine cylindrical stone, at an angle, to brush that lip vertical, starting from far away from the edge, brushing towards the end of the edge, using water again. The lip was essentially brought intact into a vertical direction, creating an extremely thin edge extension.  The lip was easily felt before and after the brushing.

This is the type of edge I personally have generally preferred - though it is somewhat fragile - I can not take many steps onto a rubber mat off-ice without risking knocking the lip off to the side. The bent-to-vertical lip is sometimes called an "over-burr".

I speculate, but have not proved, that the lip would obviously act as an extremely sharp edge, that I assume would cut through the ice surface and act to prevent side slippage, but which is thin enough to create little extra drag.

While the final result of this third technique was consistent with what I thought was always produced by a sharpening process, the process was different. In particular, I thought that the lip was created as the knocked-down tip of the edge. That does not appear to be correct. The lip is initially created as a separate entity from primary edge.

---------------------------------------------------------------------------------------------

Three obvious questions arise:

1. Are the differences between the power and hand sharpened result created entirely as a result of the different sharpening and brush techniques, or could it have been affected by the such things as differences in composition?

2. If one used a very fine grit power sharpening wheel, combined with that same altered brushing that I finally settled on in the third case, could power sharpening produce a similar effect to the third technique?

3. Would many people prefer this much sharper edge, which I believe creates more resistance to side-slip and less drag than using a smaller radius of hollow?

4. Would most people find the result too sharp - e.g., too fragile, or too sharp to handle?

[Bill_S]

That's an interesting set of observations.

You have some questions at the end, and I'll add one...

If you skate for a short time, does your preferred burr still remain? It should be an easy task to make observations periodically while you skate on freshly sharpened blades.

Also be aware that I've had trouble receiving products from the Pro-Filer company (Edge Specialties) lately. I won't elaborate here, but since you are using one of their sharpeners in your experiments, it should be noted.

[Query]

If you skate for a short time, does your preferred burr still remain? It should be an easy task to make observations periodically while you skate on freshly sharpened blades.

I haven't really turned a microscope on it before. But I can say that it stays there by feel for maybe 30 or 40 skating hours. But it might depend on many criteria, like burr length, steel type, and ice hardness and roughness. Plus, my jumps are very tiny, and my spins not very good.

I just asked Don Giese, who originally showed me how to do over-burrs, whether he ever tried a speed-skate style edge (using a flat bottom skate instead of a hollow), but with an over-burr (note: he and some other speed skaters like over-burrs, but some speed skaters prefer to completely deburr), on hockey or figure skates. He says no. He thinks it would be faster, but that it would require more frequent sharpening, but that is pure speculation. Speed skaters usually sharpen before every race, sometimes before every heat. However, perhaps this depends on the same factors I mentioned above, and on the fact that speed skaters place a huge premium on having very sharp edges, and skate faster than we do.

Also be aware that I've had trouble receiving products from the Pro-Filer company (Edge Specialties) lately. I won't elaborate here, but since you are using one of their sharpeners in your experiments, it should be noted.

That worries me a lot, because I like Pro-Filer better than the alternatives that I've seen. If you don't want to elaborate publicly, could you send me a message with the details?