what can we use to test blades that need to be sharpened?

[marc]

I've been wondering for a long time how you can test a skate that needs sharpening.
for the moment I'm using the fingernail technique but I don't really like it (and I wouldn't have enough nails!).
Before having my own machine, I didn't ask myself all these questions, it was roughly every 40 hours, but now that I have the machine I do it for my daughter every 20/25 hours).
but I would like to have a serious technique...
And I would love to have your ideas or advice.
Hello to you enthusiasts of the south of France!

[AlbaNY]

My main coach used the fingernail method and assured me I was good to go still with 80 hours on my first ever sharpening.  I also have never found it to make any indication compared to how I felt while skating.  Perhaps my nails are soft (they are,) but it just never seemed like a useful test.

I routinely have gone that long between sharpenings, but I do enjoy the secure feel if done by a bit over 40 hours.  Even if I had the option for 20 hours I'd be reluctant in order to save blade longevity since I guess I can get away with the handling.  My main coach hasn't had his blades sharpened in over two years now but has great edges.  Dullness forces you to use pressure.
Without a trusted tech here I went from June to February without any sharpenings (  )
It's a very personal experience thing as far as sensitivity to sharpness and how it feels.

As to the question... I find a careful look will tell.  You just see the obvious nicks and general lack of sharpness in the edges or in how light gleams on them.  Obviously I am a not scientific minded person but go by senses.  I bet Kaitsu and BillS will have more precise answers. 

[Bill_S]

I used nothing scientific when I skated. I always went by feel. One thing that I noticed was that the more advanced my skills became over the 23 years that I skated, the more tolerant I became of edges becoming dull.

I would venture a guess that most skaters, except for beginning skaters, can tell when their edges start to slip. That's when it's time for a sharpening. For the inexperienced, they won't have deep edges to worry about and an approximate number like 40 hours will suffice.

Unless there is impact damage, 20 hours seems too short and could impact blade life. A few minor (and inevitable) nicks won't hurt anything, so don't chase perfect edge condition at the expense of blade life.

[tstop4me]

I've also tried several proxy methods.  To test for a sharp edge, I've used the fingernail test.  Even more sensitive for me is the fingertip test. If I run my fingertip across (not along) a really sharp edge, I can feel it and also see traces of shaved skin fragments left behind.  This works only if my fingers are thoroughly dry.

I also have a HDI (Hollow Depth Indicator) gauge, in which I swapped out the stock dial indicator for a higher-resolution digital indicator.  I thought maybe if I tracked the decrease in depth of hollow as the edges wore down, I would get a proxy for when sharpening was due.

None of these methods were successful.  Mainly because I touch up my edges with burnishing rods.  So I can maintain a sharp edge, but the edge angles vary and the degree of bite varies.

So ultimately I know it's time for a sharpening, even after repeated rounds of burnishing, by actual performance (starting to slip).  For me, primarily reduced control on back cross-overs and entrances to one-foot spins are the early indicators.  I do keep a log of hours of skating after a fresh sharpening.  But it's only a rough guide, because it depends on what moves I'm concentrating on:  different portions of edges get worn down more quickly than others; and different portions of edges are more critical than others.

[Query]

FWIIW, many skate techs say once every 40 hours on the ice is typical for figure skaters.

But there is a lot of variation.

Not just by skater, but by the type of ice you skate on. Rough ice, and dirty outdoor ice wear out blade edges a lot faster.

I currently sharpen more often, maybe every 8-15 hours, because I love sharp edges, but I use hand tools (mostly Pro-Filer) that remove a lot less metal than powered machine tools, I think because they reshape the steel somewhat more than remove it - the blades still last me for years, and probably well over 100 sharpenings. But about 30 sharpenings seems roughly right for sharpening using powered machines. Maybe worse if you are still having a bit of trouble centering the blade position on the wheel when sharpening.

Is your daughter old and safety oriented enough to learn to sharpen her own skates? It might encourage her to take good care of her blades. (Or not. ) I've watched a lot of kids run off the ice onto the rubber mats surrounding the rink, and out to the lobby or bathroom, with no concern for their blades, secure in the knowledge that their parents will get them sharpened and replaced as needed. Of course, some adults aren't much more careful.

I've also seen some who don't dry their blades after use, leave their blades in blade guards between uses, or store their skate in a closed bag, box or trunk. All of those increase corrosion and shorten edge and blade life. Hopefully your tool experience means you have explained to your daughter what she should do to preserve her blades as much as she can.

[R45]

As mentioned already, the tolerance towards dullness of the edges is a personal preference.
Many skaters are under the impression that edges are not allowed to slip. But controlled sliding is part of skating.
Dull edges have a bit the same effect as a more shallow hollow: you have no choice but to learn how to control your edges more effectively.
I sharpen my skates once a year, mainly to get the nicks out.