Pro-Filer Users: What's the diameter of your cylinder?

[tstop4me]

I haven't heard of anyone else using a honing steel. Usually a flat stone, and/or a hard rubber "stone". I also haven't seen anyone else use a belt sander. But whatever works for someone, is good.

I was shown how to use my first Pro-Filer by the pro shop manager, Don Giese, who sold it to me. He usually did leave the re-pointed burr, even on machine sharpenings, which is one of the reasons his results felt sharper than most of the others. Don coached, speed, hockey and figure skating, and I think he used to be a top ranked U.S. ice and inline speed skater. But he did a lot of custom work, and sometimes shortened or removed the burr for skaters who didn't take good enough care of their edges to deal with the burr, which is quite fragile. He is now largely retired.

The person who used to manage the pro shop at Bowie Ice Arena also left a long repointed burr, creating very sharp edges.

(Edge Specialties' instructions for Pro-Filer used to describe sharpening using a reopinted burr, but I rhink they have now removed most of the details.)

But most skate techs produce less sharp edges. E.g., Mike Cunningham, a respected sharpener at Skater's Paradise, with many high profile clients, mostly deburrs, by default. (He and I looked together at blades he sharpened under a microscope.) His theory is that the skater should not notice a significant difference in the way a blade feels after sharpening, as long as he/she sharpens reasonably offten. But, like any good skate tech, he too does custom work, and will do what the customer asks for.

Many skate techs who think they deburr, actually leave some repointed burr, that you can feel, or see under a microscope.

Blackstone Flat-Bottom V sharpening equipment grinds an edge that resembles a repointed burr, but I think the "V" is a little thicker than a repointed burr. I don't know any figure skaters who say they've tried it. Anyway, the entire shape is built into the way they dress the wheel, so is produced differently.

BTW, I think I got "over-burr" from the knife sharpening community, not the skate sharpening community. And I should note that I have yet to see a sharpening burr that is a clean, well-ordered sheet. Edges and burrs are usually quite uneven, under a 50-100x microscope.

In knife sharpening, the term "burr" is common.  I've never come across the term "over-burr".  I did a Goggle search of "over-burr", "overburr", and "over burr" and did not come up with anything on point (lots of references to Aaron Burr).  In knife sharpening, burrs remaining after sharpening with an abrasive stone are straightened with a honing steel.  A fine abrasive stone will reduce large burrs left by a coarse abrasive stone, but will itself leave fine burrs that can be further reduced by a honing steel.  Hard rubber is too soft to straighten burrs.  If you inspect edges under sufficiently high magnifications, you'll of course invariably find defects of some sort.  I've seen images of knife and razor edges taken with an SEM (scanning electron microscope) at 5,000 X and greater.

[Query]

The article that mentioned "over-burr" is no longer on the web. A number of articles talk about "top burr" and "wire burr".

In this video, it is the sharpest part of a steel blade, the "apex", after the grinding process has pushed it over to one side, and possibly lengthened it. See the picture at the start of

  http://player.mashpedia.com/player.php?ref=mashpedia&q=tiIsAn1ZGkw

In knife and razor sharpening, it is common to create such a burr, then switch sharpening sides, and grind on the opposite side, until the burr has moved to the opposite side, many, many times. This creates a very fine, well polished edge, that acts very, very sharp. E.g., see

  http://devilsfoodkitchen.com/2016/04/01/101-knife-sharpening/

The first video talks about removing the burr. But it looks to me like he "removes" it by the same process as he creates it - i.e., he moves to sharpening on the opposite side, but only long enough to take the burr to the top, but not to bend it over again.

Skate grinding also only sharpens and polishes on one side - the hollow side. Then you use the flat stone to polish the opposite side. If you want to genuinely deburr, you can do so by drawing the stone somewhat across the edge, say at a 30 - 45 degree angle relative to the side. This effectively cuts off the burr. E.g., that's what Mike Cunningham does, unless the skater requests otherwise, though at the final step he uses a hard rubber "stone" to do it instead of a grinding stone.

Here is an article about the wire edge

  http://www3.telus.net/BrentBeach/Sharpen/wireedge.html

which the author claims occurs when the the grinding process removes the crystal structure (a form of "tempering"), so that the steel is no longer hardened. But since he is talking about cutting tool use, he feels that such a soft edge is useless, and he wants to remove it.

Some skaters and skate techs feel that the burr, moved to the top (the bottom when you orient the skate for skating) is still useful in ice skating, because ice, at ice rink temperatures, ice is fairly soft. They (including myself) feel it is thin enough not to create much drag, but deep enough to create lateral resistance to skid, and makes it easier to push. OTOH, many speed skaters prefer to remove it, because they feel the drag is more important than the improved push. If you know any speed skaters, you know that they sometimes debate the advantages of each style.

OTOH, now that I sometimes work as a rink guard, and volunteer as a skating instructor, it wastes too much time to constantly take of and put on the skate guard, when I come on and off the ice, so I no longer want the blade that sharp. Supersharp edges are just too fragile for walking on the rubber mats, because they sometimes bend over and become worthless.

[Query]

If anyone wants to see some really pretty pictures of burrs, using an electron microscope,

  https://scienceofsharp.wordpress.com/2015/01/11/what-is-a-burr/
  https://scienceofsharp.wordpress.com/2015/01/13/what-is-a-burr-part-2/
  https://scienceofsharp.wordpress.com/2014/04/16/the-honing-progression/
  and other links from https://scienceofsharp.wordpress.com

The pictures are much better than my cheap ($30) USB microscope produces.

Though it should be noted that the author is removing, not using burrs. I think cutting hair with a razor is harder than cutting into the ice. In particular, it only takes a few minutes of shaving before a razor ceases to be good for future shaving.

In contrast, as near as I can tell, skates more or less hydroplane across the ice, over the flat (speed skate) or hollow (figure and hockey skate) region, but the edges on the sides slide (?) a limited distance into the ice (water?) to create lateral resistance. They aren't cutting anything all that hard, unless you are skating on ice that is very, very cold, or on fake "synthetic ice" (more or less greased plastic, which is really, really hard on blades).

Incidentally, last I knew, the experiments that indicated that all ice has a surface fluid layer (and presumably intermediate semi-fluid layers) were under conditions somewhat different than occur in skating. In particular, I think there was no pressure or contact from a metal blade, let alone a moving blade, and the expirements were static. Further, if I remember right, they were (x-ray?) diffraction experiments, which did not directly measure the mechanical properties of the ice surface. So the interaction of skate blade with the ice hasn't really been well defined. Without a better model of the moving ice/air/steel boundary layer, there is no way I can think of to come up with an accurate numerical model of how blade and edge shapes interact with skater motion. I think that the money that would be needed to do it "right" exceeds what anyone is willing to pay to study it. Substantially less money, for example, than has been made available to study the interaction of naval ships with water - yet many elements of that area are still poorly understood and modelled too. And perhaps less money than has been made available to understand tire hydroplaning, especially when you consider that tire designers seek to to eliminate hydroplaning rather than enhance it, which means that tire tread design principles may not be altogether applicable to skating blade and edge shapes.