How do you hollow?

[sampaguita]

Liked 7/16" as a beginner, and hated 1/2" (wouldn't grip at all!). Took ice dance, was recommended 3/8", and never looked back. Holding an edge became a breeze.

[skategeek]

Mine was ½" (default; no real thought went into it) until I switched techs about two years ago.  He asked some questions about my skating (specifically, whether I had trouble stopping right after a sharpening) and decided to move me to ⅝".  Now I'm wondering whether I should reevaluate that now. 

[Query]

It's not really "sharpness," it's "depth" as in shallow or deep.

If you think about it, it's even more complicated. Because many (most?) sharpeners deliberate dull (round off) the tip of the edge, to make it more durable and less prone to being bent over, and so people don't notice as much the change in sharpness after sharpening. Rounding affects the depth of the hollow associated with a given ROH too. And it definitely affects effective sharpness.

The hollow creates a fairly specific "edge angle" - though if the blade is side honed (e.g., with a dovetail shape, widest at the bottom), that alters the edge angle that a given ROH generates. Edge angle is a big component of effective sharpness.

I prefer to repoint and polish the sharpening burrs into thin foil edges, which act very, very sharp - but are not very durable at all. But, while I worked at a rink, I sometimes gave up on foil edges, and dulled my edges instead, because I didn't always have time to put on blade guards, so the edges took a beating.

On top of that, the grit of the grinding wheel (or sharpening stone, if you do it by hand) has a profound effect on effective sharpness. Fine grit makes blades feel a lot sharper. I'm not certain I completely understand why.

But the o.p. may not have a lot of control over all these other factors, especially if they don't let him/her interact directly with the sharpener, to specify degree of rounding, deburring vs creating a foil edge, grit size, etc. So while ROH alone does not determine effective sharpness, it sounds like the only way the o.p. can affect effective sharpness may be to specify ROH.

One could argue that unless the prior blades were significantly thinner or thicker, the ROH on the prior blades might be a good starting point, because that is what he/she is used to - unless he/she wants to adjust ROH to make spin entry stronger (lower ROH) or to make the spinning friction less (higher ROH).

[FigureSpins]

From your experience, does a deeper hollow (smaller ROH) make it easier to enter the spin, easier to maintain the spin once established, or both?

YMMV, but to me, the deeper hollow makes it easier to hold the FO edge on the entrance and hook the spin more quickly.  Staying on the sweet spot and proper body alignment maintains the spin moreso than the ROH. I can maintain spins on 1/2" but they're easier on 3/8" because the entry is more controlled.  Sharp skates with any ROH for good camels and laybacks.

[tstop4me]

YMMV, but to me, the deeper hollow makes it easier to hold the FO edge on the entrance and hook the spin more quickly.  Staying on the sweet spot and proper body alignment maintains the spin moreso than the ROH. I can maintain spins on 1/2" but they're easier on 3/8" because the entry is more controlled.  Sharp skates with any ROH for good camels and laybacks.

Thanks.  Those are the premises I've been going by as well for scratch spins.

[skategeek]

OK, I think I'm confused...  if a deeper hollow/smaller ROH makes it easier to hold edges, why are patch blades usually sharpened with a bigger ROH??

[Bill_S]

Patch blades need flow, so the push takes you around further. A larger ROH helps with that.

The edges talked about are much deeper edges (more leaning into the curve) than you find in patch.

[skategeek]

Patch blades need flow, so the push takes you around further. A larger ROH helps with that.

The edges talked about are much deeper edges (more leaning into the curve) than you find in patch.

That makes sense.  Thanks!

[Loops]

Patch blades need flow, so the push takes you around further. A larger ROH helps with that.

The edges talked about are much deeper edges (more leaning into the curve) than you find in patch.

Also, patch blades are wider than freestyle blades.  So a 1" or 1.5"(like I have on mine) don't translate to a 1"or 1.5"on a freestyle blade. 

[FigureSpins]

Now I have to go look at my Silver Test blades.

[Bill_S]

Just some data FWIW,

My current Coronation Ace blades - 0.162" thick blade

My old Coronation Aces circa 2003 - 0.161" thick blade

Jackson Ultima Synchro blades  - 0.157" thick blade

Measured with a Starrett 1" micrometer with the circular anvil flush with the skating edge.

[Meli]

Original sharpener was a 1/2 kind of guy. Worked for me.

The sharpener at my new rink did a mystery ROH on me, was super grippy. I was afraid of just getting stuck in the ice. Rink owner toned it down for me. Not sure what he took it to.

Rink owner is a 7/16 kind of guy. Wanted me to try it. Tried it. No bueno. Too grippy.

Back to 1/2. For my plus-size pre-bronze self on coronation ace blades, it works.

[Query]

In what I tried of patch, I couldn't glide long enough. No doubt my pushes aren't strong enough, and my balance isn't good enough, to glide forever. But flatter blades (longer rocker and hollow radius) than I used should let you glide longer. 

But why are patch blades thicker?

[sampaguita]

But why are patch blades thicker?

I also wonder why hockey blades are thinner (I believe). Is it speed vs. control kinda thing?

[Query]

I also wonder why hockey blades are thinner (I believe). Is it speed vs. control kinda thing?

I'm not an expert on this. But here is some speculation:

I'd be willing to bet the biggest reasons is weight. Good hockey players sprint up to speed very quickly, and they take a lot of strokes doing so, so the energy required to lift the leg (and the boot with it) might be more important. In professional hockey, players often only stay on the ice about 45 seconds or so, because sprinting literally tires them out that fast. So every little fractional ounce matters. You see this in the boots too - modern hockey skates are very light, compared to most figure skates. That said, hockey players wear heavy padding.

Thinner blades seem to be faster. I can't tell you why, but speed skating blades are very thin.

It might have something to do with durability. I think figure skating blades are expected to last a lot longer than hockey blades, because hockey sharpeners remove a lot more metal with each sharpening, to get rid of nicks, and because many hockey players sharpen blades once/game or more - though that isn't universal. But there may be something wrong with my theory here - if you watch aggressive hockey play, they put extraordinary sideways stress on blades, especially when they stop and change directions. You might think that would mean they would need stronger and therefore thicker blades... OTOH, hockey blades are shorter, so that reduces the stress somewhat, whereas the toe picks on figure blades have more of a lever arm to increase the torsional stress.

It used to be true (and still is in school figures = "patch") that figure skating judges would look at the ice tracings in detail. A thicker blade should make required edge changes a little bit more obvious. But I don't know how much that usually matters, especially outside school figures.

A thinner blade can change edges a more quickly. I believe that is one of the main reasons ice dance blades are ground a bit thinner than freestyle blades - there are a lot of fast edge changes in ice dance. Aggressive hockey play also involves very rapid edge changes, as part of direction changing.