Radius of Hollow v.s. 'name'

[Rusty Blades]

Can ya'll give me the different 'names' for different types of sharpening (like "freestyle", "combination", etc.) and the actual Radius of Hollow that corresponds to each?

It seems like different names mean different things to different people and I would like to get a "range" of RoH for the different names.

Thanks!

[Skating Jessica]

I can't speak for every type of sharpening, but the guy who sharpens my skates offers two choices: freestyle and low freestyle. The difference is that the regular freestyle sharpening is a little deeper. Beginner skaters (those working on mainly single jumps or basic skills) tend to get the low freestyle sharpening. Sorry, but I'm not too certain about the ROH for each though.

[Bill_S]

A sharpener at an Ohio rink gives 1/2" as a standard sharpening, and calls a slightly deeper 7/16" radius a "Duke special".

...well, you asked!

[Virtualsk8r]

Same here ..... 1/2 inch is a standard freeskate sharpening, 7/16 inch is a sharper freeskate and 3/8 inch is a dance sharpening or a really sharp freeskate (if your sharpener will do it).

I use a 7/16 for most of my skaters, and 3/8 if they skid their jumps. I find a 1/2 radius just doesn't cut it for doubles and triples. The harder the ice (hockey ice) the sharper the blade, and sometimes if the ice is actually figure skating temperature, the 1/2 inch might do.

[dbny]

Same here ..... 1/2 inch is a standard freeskate sharpening, 7/16 inch is a sharper freeskate and 3/8 inch is a dance sharpening or a really sharp freeskate (if your sharpener will do it).

I use a 7/16 for most of my skaters, and 3/8 if they skid their jumps. I find a 1/2 radius just doesn't cut it for doubles and triples. The harder the ice (hockey ice) the sharper the blade, and sometimes if the ice is actually figure skating temperature, the 1/2 inch might do.

I would stick with the numbers and go with the guidelines from Virtualsk8r.

[Isk8NYC]

Sharpeners in NY/NJ that I've used in the past use these equivalents:

Recreational = 5/8"
Competitive = 1/2"
"Deep ROH" = 3/8"

[Skate@Delaware]

Sharpeners in NY/NJ that I've used in the past use these equivalents:

Recreational = 5/8"
Competitive = 1/2"
"Deep ROH" = 3/8"
Wow! must be the difference (hoagie vs. sub; soda vs. pop) thing...

1/2" here is recreational (or hockey <g>)
3/8" is dance
7/16" is 'AGGRESSIVE'

freestyle is whatever you tell them (even if it's 1/2"

[AgnesNitt]

Here's what I've skated on in the last year after consultation with my skate technician (who has far more grand customers than me--including a couple of former national champions). As far as I know, I am his only figures oriented customer.
He based my ROH first on my ability, then on the ice I normally skate on. This appears to be his common practice.
When I was a baby beginner on hockey ice, 1/2. Then I was not satisfied with my hang in my edges so he took me down to 7/16 (on hockey ice). That got me through the learning curve. Then I told him I wasn't happy with my glide in my figures. I'm now on 9/16 (still on hockey ice). We're planning on shallower cuts as I get more experience.
The first couple of minutes on the ice with 9/16 ROH after months with 7/16 were scary, And for some reason I lost my 'feel' of the blade. I had to actually go back and spend an hour retraining certain elements. I find that I have to focus to keep my edge, and it really forces me into correct body positions---ie. it's a lot less forgiving of sloppy habits.
So based on ISK8NY's comment, I'm creeping my way up to a recreational cut (5/8==10/16). Is that what they use on rentals? Maybe that explains why no one wearing rentals can keep their feet under them. ;)

[Zac911]

i think 1/2 and 7/16 are pretty common. too much bite can be a bad thing. i have seen some sharpeners in the Bay Area do 5/16... makes me shake my head. those real deep hollows take away speed and will make you fatigue much faster ( and when your legs are tired you are more apt to wreck/injure yourself ).

[Isk8NYC]

Three different sharpeners told me that 5/8" is the factory standard. Is that true, Zac?

Also, just for the record, do all skate sets come pre-sharpened?

(I understand if you can only speak for Riedell/John Wilson.)

[vesperholly]

Sharpeners in NY/NJ that I've used in the past use these equivalents:

Recreational = 5/8"
Competitive = 1/2"
"Deep ROH" = 3/8"

Wow! must be the difference (hoagie vs. sub; soda vs. pop) thing...

1/2" here is recreational (or hockey <g>)
3/8" is dance
7/16" is 'AGGRESSIVE'

freestyle is whatever you tell them (even if it's 1/2"
We really need the metric system in the US. I'm pretty dumb with math, but I can't tell what the difference is from 1/2 to 3/8. :giveup:

[Isk8NYC]

We really need the metric system in the US. I'm pretty dumb with math, but I can't tell what the difference is from 1/2 to 3/8. :giveup:Funny but (sadly) true!

1/2" = 4/8" -- does that help when comparing?

5/8" = Shallow ROH
4/8" = Deeper ROH
3/8" = Deepest ROH (of my examples, lol)

Now, let's throw in a metric monkey wrench. My patch blades are 1-1/2" ROH. I'm confused?!?!?

[singerskates]

Ok, it's pie time.

1/2 is half a pie.

3/8 is just under half a pie (1/8) because it would take 4/8 to equal 1/2.

7/16 is even closer to 1/2 than 3/8 because 3/8 in /16's would be 6/16's which is 1/16th farther than 7/16 is to 1/2 = 8/16.

5/8 is closest to a whole because in /16ths it would be expressed as 10/16ths which is really flat.

5/16's has a very deep hollow and is 3/16's deeper than 1/2.

[Isk8NYC]

C'mon - tackle 1-1/2" (mainly because I don't quite get it myself, lol)

Oh wait, I can still do math. 1-1/2" = 3/2 = 12/8"

Nope, still don't get it. To me, that says the ROH would result in a blade with the edges higher than the center.

Edit: Okay, I just figured it out now. I was confused by the pie analogy; it's really a SECTION of a circle that we describe as "Shallow" or "Deep." The larger the ROH (1.5" for example) used in sharpening, the more shallow the hollow will become.

[vesperholly]

1/2" = 4/8" -- does that help when comparing?

5/8" = Shallow ROH
4/8" = Deeper ROH
3/8" = Deepest ROH (of my examples, lol)
Yes. :mrgreen: It's the jumble of divisions that screw me up. If I get a baseline denominator - fractions out of 8 or 16 - I can compare just fine. It's when we're going 7/8 to 5/16, I'm all, "whaaa???" 14/16 and 5/16 make more sense to me, because I only have to compare the numerator. I get that the bigger the fraction, the flatter the hollow; just like the bigger the rocker, the flatter the blade.

Go metric system!

[BuggieMom]

Ok, it's pie time.

1/2 is half a pie.

3/8 is just under half a pie (1/8) because it would take 4/8 to equal 1/2.

7/16 is even closer to 1/2 than 3/8 because ...........
You had my attention when you started talking about pie, then you had to go getting all technical and stuff...;) :lol:

If my sharpener offered me pie instead of fractions, I'd be there every week!

My dd's typical ROH is 7/16, that is her Freestyle edge. I have read/heard/been told that most children will like a sharper blade (deeper hollow) because they don't have the weight to force the edges to grab the ice on a shallower edge...I guess that makes sense

[Rusty Blades]

Three different sharpeners told me that 5/8" is the factory standard.

NONE of the good blades come "factory sharpened" so there is no such thing as a "factory standard".

The reason I ask is because I have started sharpening skates for other people, mainly coaches. I have been doing my own and my coach's skates for about a year and I DIDN'T want to get into the sharpening business but there is nobody else in the area people trust.

I would have thought that people who were so precise about their skating (like high level coaches) would know the actual dimension of the RoH but apparently many don't. They only have a name (like 'combination') which tells me absolutely nothing! And one VERY high level coach who's skates I did yesterday had gone so long without sharpening that there was no radius left that I could measure!

Since there is no standard nomenclature, I need to make up my own "cheat sheet" so when somebody asks for a XYZ sharpening I have some idea what they expect.

[Bill_S]

NONE of the good blades come "factory sharpened" so there is no such thing as a "factory standard".

Hmmm...Both sets of Coronation Ace that I have purchased have come with a factory sharpening. The blades purchased in 2002 were sharpened just fine - so much so that I skated on them for a month before resharpening them.

The newest blades purchased last year weren't sharpened as carefully from the factory, but I could have done fine for a couple weeks on the factory edge.

You can even see the hollow in this photo:

http://oak.cats.ohiou.edu/~schneidw/skating/images/remove_strip_sml.jpg

[Isk8NYC]

NONE of the good blades come "factory sharpened" so there is no such thing as a "factory standard".I asked about skate sets, which are boot and blade combinations like Jackson Freestyles and Riedell Medallions. Since Zac is from Riedell, I thought he could give me a definitive answer to clear up the confusion.

Riedell lists (on their website) a variety of 5/16" and 7/16" as their standard ROH for Freestyle and Advanced Freestyle blades.

[RachelSk8er]

My rink does light freestyle, freestyle and dance.

I do dance and freestyle in the same pair of skates. I'm a sharp skate person to begin with, and I find that the dance sharpening works best with my blades (Ultima Synchro).

[Rusty Blades]

I stand corrected on the "factory sharpening".

[Zac911]

Three different sharpeners told me that 5/8" is the factory standard. Is that true, Zac?

Also, just for the record, do all skate sets come pre-sharpened?

(I understand if you can only speak for Riedell/John Wilson.)

while blades come with a factory hollow i strongly suggest getting them sharpened. all blades are different as to what ROH comes on them. most come with a 7/16, but Freestyle and Dance are generally deeper 3/8 to 5/16.

[Isk8NYC]

Someone once told me (about 20 years ago) that the bit of sharpness good blades come with result from the finishing process and it's good enough to use in checking blade mounting for a few turns. *Shrug* while blades come with a factory hollow i strongly suggest getting them sharpened.What about the skate sets such as the Riedell Ribbon and Medallion series? I've always wanted to ask a manufacturer rep this question: Do the skate sets come pre-sharpened? I know of several places that sell skates (not pro shops, sporting goods stores) that claim the skates are already sharpened. Yet, they don't feel very sharp to me - is it a " lasts 2 hours" sharpening? lol

ETA: I had a beginner student skate today on brand-new skates with their "Factory Sharpening." They were Reidell's with leather heels, so I think they're probably Medallions. The kid really struggled with gliding from the moment she stepped on the ice. The blades just stopped as soon as she stopped pushing or marching. The girl said they felt "sticky."

I felt the blade edges and they were dull - didn't even need to do the fingernail scrape test. I gave them a few strokes with my sharpening stone - they felt rough and unfinished. Maybe I removed some junk, but she was able to glide by herself almost immediately and by the end of the session, she was pushing one foot at a time and really skating much faster than she should have been, lol. I suggested that the mom have the skates sharpened.

[Skittl1321]

It took me FOREVER to find this page, but I had just read it before this conversation came up, so I thought it was worth tracking down.

Here it seems like people are saying the competitive sharpenings are deeper than the recreational ones (or maybe I've got the numbers backwards?)

This site, lists the opposite
The theory is that the degree of hollow put on a blade is inversely proportional to the skater's fundamental skating qualities.

http://fredsskatesharpening.com/qa_blades.html

What do you all think of that? (The link to this guy is from Detroit Skating Club's website)

[dbny]

C'mon - tackle 1-1/2" (mainly because I don't quite get it myself, lol)

Oh wait, I can still do math. 1-1/2" = 3/2 = 12/8"

Nope, still don't get it. To me, that says the RoH would result in a blade with the edges higher than the center.

Remember that the RoH describes the Radius of a circle. But it is an arc of the circumference of that circle that fits the curvature of the hollow of your blade. Bigger radius = bigger (and flatter) circumference.

[doubletoe]

It took me FOREVER to find this page, but I had just read it before this conversation came up, so I thought it was worth tracking down.

Here it seems like people are saying the competitive sharpenings are deeper than the recreational ones (or maybe I've got the numbers backwards?)

This site, lists the opposite


http://fredsskatesharpening.com/qa_blades.html

What do you all think of that? (The link to this guy is from Detroit Skating Club's website)

You know, I actually have to agree with that. Daisies passed all 8 figure tests and prefers blades that would probably have me slipping all over the place. Her form is perfect and her skating always looks effortless, so it's consistent with that argument.
What I like about freshly sharpened blades is that I can get away with poor alignment on my edges and my blade will still hold the ice. When my blades are dull, I need to make sure I'm aligned perfectly over my hips whenever I do a deep edge like a spin entry, salchow takeoff or landing edge. Otherwise, I will slip off of it. I use a 1/2" ROH but my blades are side honed so I think that increases the bite on deep edges.

[dbny]

You know, I actually have to agree with that. Daisies passed all 8 figure tests and prefers blades that would probably have me slipping all over the place. Her form is perfect and her skating always looks effortless, so it's consistent with that argument.

I don't know if Daisies uses patch blades, but if so, they use a very, very shallow hollow and the tracings show only one edge when the figures are skated properly.

[Rusty Blades]

I don't want to derail the thread but would like to make a couple of comments on RoH.

Radius is only half of the equation for 'grippy-ness' - the other factor is blade width. RoH together with width create what is called "bite angle" and it is actually Bite Angle that we feel when we are skating. A wider blade with a shallower RoH will have the same 'bite' as a narrower blade with a deeper (smaller) RoH.

In terms of performance and/or skill, a blade with a smaller RoH has less tendency to slide sideways and will be less forgiving of mistakes or inaccuracies in landing, footwork, etc.

I had heard (and believed) that the deeper the RoH, the less efficient (and more work) was required in skating. When I switched from 3/8" RoH to 5/16" (a 12% change) my perception was the opposite - it was like being on ball bearings! Not only were my edges more secure (being able to hold an edge right down to the point where the boot touches the ice) but my glides were longer - seemed like much more than 12%! On the other hand, when you put your foot down, you had better be prepared to go in the direction the blade is pointing because you have no choice! (Ask my coach who watched me do a laughable splits coming down out of a spiral!)

[doubletoe]

I don't know if Daisies uses patch blades, but if so, they use a very, very shallow hollow and the tracings show only one edge when the figures are skated properly.

Oh no, not for freestyle, LOL! But she only sharpens her blades a few times a year and may even dull them down a little right after sharpening.

[Bill_S]

I had heard (and believed) that the deeper the RoH, the less efficient (and more work) was required in skating. When I switched from 3/8" RoH to 5/16" (a 12% change) my perception was the opposite - it was like being on ball bearings!



I remember your post about that. It WAS surprising. I wanted to ask some questions about that, but never did at the time.

I have felt a fresh sharpening to be faster than an old sharpening. Are you sure it wasn't just a shiny new edge that made the blade faster, and not the ROH change?

I'm sure you felt the extra speed, but I'm trying to narrow down the other variables that might have been at work.

Plus, a flatter rocker will be faster too (I felt that BIG TIME when I had a pair of blades ruined by a rink sharpening). When you went to the smaller ROH, I'm sure that you had to remove more metal than a touch-up sharpening. Could that have contributed?

Oh, to have rink time and research dollars available! Right now, I'd settle for just the rink time. :twisted:

[Rusty Blades]

Oh, to have rink time and research dollars available! Right now, I'd settle for just the rink time. :twisted:

Yes, you, me, and Sid Broadbent (an engineer who has studied the skate/ice interface for years)!

I have felt a fresh sharpening to be faster than an old sharpening.

Then you have had the same experience! A fresh sharpening creates a sharper bite angle where before there was a radius (worn edge) created a more obtuse angle.

Since I have my own sharpening machine, I tend to touch up my blades frequently (10 to 12 hours) so I don't have that dull-to-sharp shock. When I switched radius, it DID take a lot of grinding but they weren't anywhere near dull.

So who is going to fund our Radius of Hollow research project? ;)

[dbny]

Yes, you, me, and Sid Broadbent (an engineer who has studied the skate/ice interface for years)!


I have his book, which I picked up at Klingbeils with Don's approval to permanently remove it. DH copied it, but I have yet to remember to return it.

[daisies]

Oh no, not for freestyle, LOL! But she only sharpens her blades a few times a year and may even dull them down a little right after sharpening.

Hey party people! Thank you, doubletoe, for the compliment. :)

Yes, I did pass my 8th figure test on patch blades, sharpened at 1-1/2. But my freestyle blades are 5/8, and I only get them done maybe three times a year ... and that's pushing it. LOL. Twice a year is more like it. And when I do have them sharpened, I have the person sharpening them use a stone to "take the bite out of them" too!

I don't know if there is any correlation between skating quality and degree of hollow, I just know I hate sharp blades. Even as a kid I rarely got them sharpened. I must say, the biggest advantage is that my current blades are almost seven years old and they still have a lot of sharpenings left in them! (Unfortunately, the boots are also seven years old and are on their last legs!)

[Virtualsk8r]

The pie analogy got me thinking (and hungry)....

Figure sharpening - basically dull & flat = nibble out of a cookie
5/8 or 10/16 Recreational sharpening- sometimes called combination= bigger nibble
1/2" or 8/16 = freeskate sharpening = small bite
7/16 = sharper freeskate = bigger bite
3/8 or 6/16 = dance sharpening = biggest bite

The bigger the bite out of the flat blade - the deeper the hollow on the sharpening and the higher the edges are on the inside of the blade, which means deeper edges. The shallower the bite out of the blade - the lower the hollow is to the ice and the smaller the edge, which means you will slip more without a great deal of lean etc.

[Skating Jessica]

I don't know if there is any correlation between skating quality and degree of hollow, I just know I hate sharp blades.

Perhaps it varies from skater to skater. Personally, I find that when my blades are getting too dull, I have trouble spinning (especially camel spins and flying camels), the take-offs of jumps like my double sal get worse, and I have trouble really holding on to my edges or taking deep edges to begin with on my [Gold] dances.

[Skate@Delaware]

Funny but (sadly) true!

1/2" = 4/8" -- does that help when comparing?

5/8" = Shallow ROH
4/8" = Deeper ROH
3/8" = Deepest ROH (of my examples, lol)

Now, let's throw in a metric monkey wrench. My patch blades are 1-1/2" ROH. I'm confused?!?!?
Maybe your patch blades are flatter...and that will make a big difference with the hollow.

Everyone likes a different "bite" to their blade, and it also depends on the weight of the skater and their style. My husband, who is just above a beginner, has the same roh as I do. My daughter, who was working on a double loop and such before she left home, has been skating on a 1/2" roh.

go figure ;)

[singerskates]

You had my attention when you started talking about pie, then you had to go getting all technical and stuff...;) :lol:

If my sharpener offered me pie instead of fractions, I'd be there every week!

My dd's typical ROH is 7/16, that is her Freestyle edge. I have read/heard/been told that most children will like a sharper blade (deeper hollow) because they don't have the weight to force the edges to grab the ice on a shallower edge...I guess that makes sense

The reason I used the "pie" analogy was to simplify things at first. But being that most who are online here are 12 and older, I moved on without the pie for the rest of the fractions. I knew somehow that those who were a bit confused with the differences of 5/8 and 7/16 would catch on once they were reminded that all they had to do was to get a common denominator for whatever ROHs they were comparing.

I've also used pie to teach note values. For example a whole note (circle) would be a whole pie or 1/1 or in music 4/4. A quarter note (filled in circle with a stem attached) would be a quarter of a pie or ¼.

By the way, what flavour is your pie? I love cherry, strawberry, apple, apple & rhubarb and blueberry pies. But I have to be careful that they aren't made with artificial colour, artificial flavours or sweeteners that aren't sugar because of my alergies.

[sk8lady]

I think a lot of other variables must go into what sharpening works best for each skater, including the skater's ability; what the ice is like; and what kind of sharpening the skater learned with.

I find that I can spin better on duller blades, but that I can jump and ice dance better with sharper blades. Our rinks are all bitterly cold with very hard ice. I much prefer the sharper blades; however, most of the other adult skaters here tell me that it's harder for them to skate on newly-sharpened blades.

(And I can just barely do a two-foot spin in my hockey skates--sharpening is probably about the same, but a much narrower blade and different rocker.)

[Isk8NYC]

Yes, you, me, and Sid Broadbent There's a country song in there somewhere...

That would make a great research paper. I wonder if the University of Delaware has done anything like this in their Sports Science program?

[BuggieMom]

The reason I used the "pie" analogy was to simplify things at first. But being that most who are online here are 12 and older, I moved on without the pie for the rest of the fractions. I knew somehow that those who were a bit confused with the differences of 5/8 and 7/16 would catch on once they were reminded that all they had to do was to get a common denominator for whatever ROHs they were comparing.
By the way, what flavour is your pie?
I get the "pie" analogy...I am a home school mom/teacher as well, and am well versed in the "pie" analogy thingie! I am also getting really good at learning (read: re-learning) math along with my dd! I was making a joke about just "pie" in general...of which I LOVE raisin pie..mmmmmm!...after that, I guess any berry will do...*licks lips just thinking about it...*

It definitely does help to reduce all fractions to the common denominator to decide which it the largest/smallest.

There's a country song in there somewhere...
LMAO!!!!

[Bill_S]

Originally Posted by Rusty Blades

"Yes, you, me, and Sid Broadbent..."

and from Isk8NY, "There's a country song in there somewhere..."



...and the name of the group would be "Rusty Blades and the Professors"


One thing no one has mentioned yet is to use decimal equivalents for the fractions. In other words,

3/8" ROH = .375"
7/16 = .4375
1/2 = .5
5/8 = .625

Or would that be confusing too?

I know I'd prefer it though.

[Rusty Blades]

...and the name of the group would be "Rusty Blades and the Professors"

Or Engineers on the Edge ;)

Personally I usually work in decimals for mechanical stuff. Fractions get WAY too confusing when working to tight tolerances. Quickly, in your head, solve:

1" + 3/128 + 5/64 - 3/32 = ?

See what I mean :roll:

And if that's not confusing enough, try reading a Vernier caliper that is calibrated in fractions!!! :giveup:

[sk8lady]

Or Engineers on the Edge ;)

And if that's not confusing enough, try reading a Vernier caliper that is calibrated in fractions!!! :giveup:

Or you could just spend the extra $2 and get one with a digital readout... ;)

[Rusty Blades]

Or you could just spend the extra $2 and get one with a digital readout... ;)

That's what I have Hon, all dial instruments now! :mrgreen:

[Bill_S]

I saved the $2 and still use vernier calipers - decimal inches and millimeters. Trouble is that my eyes aren't what they used to be.

At least with the $2 I saved, I can put that toward a skate sharpening. :D

[Rusty Blades]

At least with the $2 I saved, I can put that toward a skate sharpening. :D

Or reading glasses! ;)

[Bill_S]

Or reading glasses! ;)

:D :D Wish you were around at some of my college parties! We could have used some wit like that in engineering school. :D

Since you are an engineer and prefer numbers over vague and various descriptions, but are also sensitive to the non-engineers, why not create a series of sharpenings that use decimal inches in 0.05 increments? That's roughly a 1/16th.

The series could be:

.5 - average to light freestyle or recreational grind (exactly = 1/2")
.45 - general freestyle (roughly equivalent to 7/16")
.40 - for experienced skaters who love a deep bite (roughly = 3/8")
.35 - for semi-lunatic skaters who drag their boot edges in turns or for thinner dance blades, etc. (sharper than 3/8")

You might even pick and choose from these to avoid so many different grindstone dressings.

This avoids the messy four-digit decimals, and customers can remember it easier. It provides precision in discussion about edges that any engineer could appreciate.

[Rusty Blades]

Since you are an engineer and prefer numbers over vague and various descriptions... why not create a series of sharpenings that use decimal inches in 0.05 increments?

Better than that ..... I'll flip all my skaters out and go METRIC - I'll tell them it is the ISU standard:

13 mm - recreational
11 mm - freestyle
9 mm - elite freestyle
7 mm - super skaters (like me! LOL!)

[Skittl1321]

Better than that ..... I'll flip all my skaters out and go METRIC - I'll tell them it is the ISU standard:

13 mm - recreational
11 mm - freestyle
9 mm - elite freestyle
7 mm - super skaters (like me! LOL!)

Do Canadians freak out over metric? I thought that was a US thing.

[fsk8r]

Do Canadians freak out over metric? I thought that was a US thing.

I think all poor skaters would flip out over metric. We might all be taught metric at school, but when you have someone tell you that your blades take a 4/8 or 8/16 or 1/2" sharpening that's what you remember. To be told you want something different will freak anyone out, Canadian or European.

[Zac911]

Someone once told me (about 20 years ago) that the bit of sharpness good blades come with result from the finishing process and it's good enough to use in checking blade mounting for a few turns. *Shrug* What about the skate sets such as the Riedell Ribbon and Medallion series? I've always wanted to ask a manufacturer rep this question: Do the skate sets come pre-sharpened? I know of several places that sell skates (not pro shops, sporting goods stores) that claim the skates are already sharpened. Yet, they don't feel very sharp to me - is it a " lasts 2 hours" sharpening? lol

ETA: I had a beginner student skate today on brand-new skates with their "Factory Sharpening." They were Reidell's with leather heels, so I think they're probably Medallions. The kid really struggled with gliding from the moment she stepped on the ice. The blades just stopped as soon as she stopped pushing or marching. The girl said they felt "sticky."

I felt the blade edges and they were dull - didn't even need to do the fingernail scrape test. I gave them a few strokes with my sharpening stone - they felt rough and unfinished. Maybe I removed some junk, but she was able to glide by herself almost immediately and by the end of the session, she was pushing one foot at a time and really skating much faster than she should have been, lol. I suggested that the mom have the skates sharpened.

all blades come with a factory hollow, but again i strongly suggest getting them sharpened. most sporting goods stores don't have a sharpener and will tell you that they do not need to be sharpened. a real pro shop will sharpen the skates for free first time when you purchase the skates from them. when your student says they are sticky... generally i associate sticky with a deep hollow.... hard to say.

[Zac911]

I don't want to derail the thread but would like to make a couple of comments on RoH.

Radius is only half of the equation for 'grippy-ness' - the other factor is blade width. RoH together with width create what is called "bite angle" and it is actually Bite Angle that we feel when we are skating. A wider blade with a shallower RoH will have the same 'bite' as a narrower blade with a deeper (smaller) RoH.

In terms of performance and/or skill, a blade with a smaller RoH has less tendency to slide sideways and will be less forgiving of mistakes or inaccuracies in landing, footwork, etc.

I had heard (and believed) that the deeper the RoH, the less efficient (and more work) was required in skating. When I switched from 3/8" RoH to 5/16" (a 12% change) my perception was the opposite - it was like being on ball bearings! Not only were my edges more secure (being able to hold an edge right down to the point where the boot touches the ice) but my glides were longer - seemed like much more than 12%! On the other hand, when you put your foot down, you had better be prepared to go in the direction the blade is pointing because you have no choice! (Ask my coach who watched me do a laughable splits coming down out of a spiral!)

a deeper hollow digs in considerably more and is most definitely slower/takes much more work and fatigue sets in faster. i see way too many skaters in a hollow that is too deep for them. they tire easily and wreck... sometimes getting hurt..... the most frustrating part is that they will blame the sharpener thus ruining the sharpeners reputation ( a reputation is not something that is easily built.... it takes YEARS and someone with reckless comments based on perceived knowledge rather than ACTUAL knowledge can ruin all those years of hard work ). i would have to respectfully disagree with your last statement. perhaps you are much stronger than the average skater, but the laws of psychics are fact not perception. a Freestyle blade that is side honed offers a better bite angle to the ice, so a super deep hollow is not always necessary. same principal also applies to a dovetail ( Phantom Special ). throw in a Parabolic for even better cornering and faster take offs and there is no need to go with a deep hollow..... let the technology work in your favor.

[Zac911]

I think a lot of other variables must go into what sharpening works best for each skater, including the skater's ability; what the ice is like; and what kind of sharpening the skater learned with.

I find that I can spin better on duller blades, but that I can jump and ice dance better with sharper blades. Our rinks are all bitterly cold with very hard ice. I much prefer the sharper blades; however, most of the other adult skaters here tell me that it's harder for them to skate on newly-sharpened blades.

(And I can just barely do a two-foot spin in my hockey skates--sharpening is probably about the same, but a much narrower blade and different rocker.)

ice conditions/temperature play a factor without a doubt.

[dbny]

the laws of psychics are fact not perception.

Er, methinks you mean physics, not psychics http://www.cosgan.de/images/smilie/figuren/c040.gif.

Sorry, had a rough day and just couldn't resist :lol:.

[Rusty Blades]

The physics of ice skating are far more complex than most people would realize, which is why some very analytical people have spent years studying it.

The only reason we can 'skate' on ice is because it liquefies under pressure. When subjected to a given force applied on an acute edge it is distinctly possible that it liquefies faster due to the greater concentration of force, though this would have to be verified experimentally. It would be a reasonable assumption that regardless of the angle of bite, for a given temperature of ice and a given weight of the skater, that the area of ice liquefied at any instant will be the same (same pressure PSI required to cause melting and a film of water) so the real question is if there IS any difference caused by the SHAPE of the water film (i.e. the blade).

Physics is only 'simple and straight forward' when viewed from a distance!

[Bill_S]

Ice may not liquify under pressure as previous believed. There was a story in either Scientific American or a physics journal several years ago that examined the physics of ice skating and found that the pressures produced were insufficient to cause liquification.

Wish I could remember more, but like my old eyes, my memory sometimes fails me. It might be a good read if you can get to a library though.

[Rusty Blades]

Ice may not liquify under pressure as previous believed.

REALLY??!! How do they explain the low coefficient of friction?

I found mention of the new findings here http://www.exploratorium.edu/hockey/skating1.html

Now I have to track down the research and see how the current theory works.

[fsk8r]

REALLY??!! How do they explain the low coefficient of friction?

I found mention of the new findings here http://www.exploratorium.edu/hockey/skating1.html

Now I have to track down the research and see how the current theory works.

From what I remember reading in the newspaper a few years ago, it's got something to do with dangly molecules waving about in the wind. Can't remember how they got around the friction issue or the full details. (Yes I'm an engineer and really should remember this sort of stuff).
I'm glad that they've proved it's not the pressure of the blade melting the water. I never liked that explanation and was turned down from Cambridge as a teenager because I didn't agree with the professor at the interview on this point. Just shows, that because someone says it's right, it doesn't mean it always is right.

[Madame Sk8Ball]

...but the laws of psychics are fact not perception. Er, methinks you mean physics, not psychics My humble apologies. I was "reading" him at the time...

(just kidding!)

[BuggieMom]

Ummmm...Physics?!?!

Liquification?!?!

Can we go back to talking about PIE? :yum: :yum: :yum:

And I must protest...there should be no talk of "dangly molecules waving about in the wind"...this is a Family Friendly place. Put your molecules away...

:lol: :twisted: :lol: 8O

[dbny]

Ummmm...Physics?!?!

Liquification?!?!

Can we go back to talking about PIE? :yum: :yum: :yum:

And I must protest...there should be no talk of "dangly molecules waving about in the wind"...this is a Family Friendly place. Put your molecules away...

:lol: :twisted: :lol: 8O

Don't you mean Pi? :lol: :lol: :lol:

[Zac911]

Er, methinks you mean physics, not psychics http://www.cosgan.de/images/smilie/figuren/c040.gif.

Sorry, had a rough day and just couldn't resist :lol:.

much appreciated! i am on the road..... 18 hour days are the norm.

[Zac911]

The physics of ice skating are far more complex than most people would realize, which is why some very analytical people have spent years studying it.

The only reason we can 'skate' on ice is because it liquefies under pressure. When subjected to a given force applied on an acute edge it is distinctly possible that it liquefies faster due to the greater concentration of force, though this would have to be verified experimentally. It would be a reasonable assumption that regardless of the angle of bite, for a given temperature of ice and a given weight of the skater, that the area of ice liquefied at any instant will be the same (same pressure PSI required to cause melting and a film of water) so the real question is if there IS any difference caused by the SHAPE of the water film (i.e. the blade).

Physics is only 'simple and straight forward' when viewed from a distance!

i have spent hours talking with the gentleman at HD Sports about blades. i wish i could have you all there when these conversations occur. there are many factors that are not always taken into account and certainly if we were able to isolate every individual factor it would make sense. in a scientific experiment they change one variable at a time and run tests. it is through this isolation they are able to come to accurate conclusions. the problem here is that all sorts of people are throwing there personal experiences out there and the reality is that in each instance there are far more than one variable in play. i would like to be able to test on the same skater on the same ice conditions every time-- and then try different RoH as well as different blade models- Tapered Side Honed, Dovetail, Standard, 7ft Radius, 8 ft radius and then for $hits and giggles throw in a Parabolic on each one of those. the problem i fear though is that through all these different possible combinations there is skater fatigue to deal with which will also contribute to the consistency of the testing. i am not trying to start an argument here, but the problem i encounter in the field is that i come into contact with many people in the skating industry and it is surprising how little is known about blades, and some of these people are Professional Instructors. to be the best Professional Instructor possible it is not acceptable to tell a student to use XX blade/boot because, that is what they used when they were competing. THE BEST INSTRUCTORS will understand the differences in the blades/boots and how to best use the technology available to make the student the best they can possibly be. i would love to talk about this more, but i have already spent more time than i have today.... sorry i gotta get back out on the road. Cheers!

[Rusty Blades]

i would like to be able to test on the same skater on the same ice conditions every time-....

To remove as many variables as possible (including the human element) would be to use a simple mechanical machine with proper instrumentation - it isn't hard - it just takes MONEY! All factors can be controlled and results obtained in quantitatively.

[Zac911]

To remove as many variables as possible (including the human element) would be to use a simple mechanical machine with proper instrumentation - it isn't hard - it just takes MONEY! All factors can be controlled and results obtained in quantitatively.

i will take your word for how easy it is and look forward to your donation to my testing. :P

[Isk8NYC]

i will take your word for how easy it is and look forward to your donation to my testing. :P
Hey, I've got a matched set of preteens who would *love* to help you out there Zac, if Riedell's paying! :mrgreen:

[black]

ice conditions/temperature play a factor

Exactly! I'm glad somebody pointed that out, every rink is different and unless they take their ice seriously it will vary. I have thought about getting an infrared thermometer to measure the ice before skating. That sure edge you've calibrated through practice one morning could be all over the place the next.

[Rusty Blades]

I have thought about getting an infrared thermometer to measure the ice before skating .... could be all over the place the next.

It will be. Ice temperature can rise as much as 10F after a flood. How fast it returns to the preset temperature depends on the capacity of the refrigeration plant, the thickness of the ice, and the temperature in the rink. Ice is a fairly good insulator so if the ice is thick and the rink warm, the surface may be just barely freezing.

[Query]

1. Does anyone know how hollow affects ease of turns and twizzles?

2. As indicated by others, various sources claim that desirable hollow will differ by the blade width, side honing angle, ice hardness, and most of all, individual preference.

All other things being equal, smaller radius of hollow makes blades slow, bites into ice more, slides sideways less, requires more precise blade placement.

This page lists some factory hollows:

http://www.pro-filer.com/html/education.htm

This lists some more, in 3 pages, if you click on blades:

http://www.icepalace.com.hk/shop_index/catalogue/blade_index/bladeinfo/bladeinfo.html

And some more:

http://www.faqs.org/faqs/sports/skating/ice/rec-skate/appendix1

E.G., factory sharpening on MK dance is 5/16" (small), because the blade is so narrow (which makes it fast). Hockey skates have narrower blades, and speed skates still narrower, so the hollow must be smaller to give the same "bite".

I am annoyed that Pro-Filer doesn't have hand sharpeners for 7/16", the factory width of my Ultima Dance and Supreme blades. I could go with 3/8" or 1/2", but either is a big difference. Does anyone know another brand hand sharpener that gives precise hollows too, that offers more radii?

3. Maybe this will help people compare things, increasing by 1/16" (" means inch) on each line:

4/16" = 1/4"
5/16"
6/16" = 3/8"
7/16"
8/16" = 1/2"
...
16/16" = 1"
...
24/16" = 1-1/2" (might as well be flat :) )


3. I doubt there is consensus in the physics and engineering communities on why ice is slippery under skates. The idea that ice fully melts to liquid due to ice skate pressure still appears in many introductory physics books (this generation's textbooks are written by people who read the last generation textbook, so errors continue forever, especially if they seem interesting), even though the pressure of skating isn't high enough to shift the melting point much, by conventional theory - Geology textbooks now say that many glaciers don't liquify either.

There isn't a lot of money put into this type of research - not critical to national security.

In the end, why should we care, as long as it is slippery?

[icestalker]

Sorry to dredge up this old thread! But I think it's such an interesting discussion. The theory of skating on liquefied ice is what my coaches told me, but they said not from pressure, but from body heat. Our body heat slightly heats the metal and causes the ice to melt in a little river beneath our blade. Then it quickly freezes, leaving the tracks on the ice. Anyone been given that theory before? I'm not joining in the physics side of it, all of it just goes over my head. But if the blade condensates after skating on it, how can body heat have warmed it up?

I don't want to derail the thread but would like to make a couple of comments on RoH.

Radius is only half of the equation for 'grippy-ness' - the other factor is blade width. RoH together with width create what is called "bite angle" and it is actually Bite Angle that we feel when we are skating. A wider blade with a shallower RoH will have the same 'bite' as a narrower blade with a deeper (smaller) RoH.

In terms of performance and/or skill, a blade with a smaller RoH has less tendency to slide sideways and will be less forgiving of mistakes or inaccuracies in landing, footwork, etc.

I have the same ROH on my old and new blades. But I noticed that my new blades look like they are a bit wider than my old blades. I measured them and they are wider by about one little mark on the measuring tape. So that would mean that my new blades have more bite?
(Info- 1/2" ROH, new blades are Aces)

So when I did my patch class today, I pushed off into a forward outside eight and the blade.. well, don't know how to describe it, but it grabbed the ice and took me for a ride 'round the circle. I had zero control and was leaning at a 45 degree angle to the ice like a speed skater. After a few more circles I learned how to control the blade by angling it closer or farther away from the ice, thus making a deeper or shallower edge. I could never do that on my old blades. I also managed a few shaky serpentines- the only change of edge I had learned before was power pulls. Come to think of it, I haven't tried to do power fulls on these blades yet. Might I get another 45 degree edge?

It's also forced me to have real crossovers. Instead of stepping wide over my foot, I have to tuck the crossing foot close to the skating foot to avoid faceplanting. Don't know why.

There's a chart here with bite angle (if you scroll down to "What is the correct ROH for me?"). It says that a 7º bite angle is shallow, while a 10º would be pretty deep. How does that work with Parabolic blades? According to this bite angle thing, it'd be deep on the front and back of the blade, but as the blade thins out in the center, it becomes shallower. So how does that help our edges?

http://gourmetskates.com/sharpening.php

[Query]

I completely disagree with the "Is it wise to put new blades on old boots?" and "How should I tighten the screws on my blades?" sections of the link Skittl1321's provided:

http://fredsskatesharpening.com/qa_blades.html

Take a look at the bottom of that boot. The sole is completely rotted out, indicating they were not waterproofed. And the screw holes have been completely enlarged and stripped. IMO this person has no idea whatsoever how to take care of boots or to mount blades.

There is no reason you shouldn't be able to remount blades many times on typical figure skating boots, if you press down hard with the screwdriver when you re-tighten screws, and don't tighten so far that you strip the holes. Even if you do strip the holes, plugging holes is quite easy, and there is little reason to send the boot back to the maker for something so trivial.

---

The depth of hollow should depend a lot on the width of the blade, and to some extant whether it is side honed, because those things alter the ankle of the edge created by the intersection of the hollow curve with the side of the blade, a major component to the effective sharpness. In addition, the sharpness you want will likely depend on how cold, and thus how hard, the ice is. A very sharp edge may sink too far into soft ice.

Since you (O.P. = Rusty Blades) like Sid Broadbent's theories, that may be clear if you look at the his diagram (http://www.iceskateology.com/Skateology/Blade_Geometry.html).

(He doesn't show a side-honed blade, but it should still be obvious to someone with your background that the angle would change if the side of the blade is slanted with respect to vertical.)

I happen to disagree completely with the physics he applies - after all, figure skaters use outside edges too (so do most good hockey skaters), and I prefer a different edge shape, one in which the lip or burr is straightened vertically into a thin sheet that cuts into the ice, producing an edge that has a lot more bite. That also lets me create a higher effective degree of sharpness while using a fairly large diameter ROH, increasing blade life. But very few sharpeners choose to create such an edge, and it is probably easier to create with hand sharpening tools.

I think it takes a lot more skill to skate on dull blades, or large ROH blades, because you will skid unless your balance is exactly right. But I prefer very sharp blades. :oops: They let me push more strongly, and I feel more in control. Once in a while I let them get dull, to better refine my balance.

---

All my blades - my old Coronation Ace, as well as my old MK Dance and my new Ultima Dance, Supreme, Synchro blade runners all came factory-sharpened, and were sharpened reasonably well, though the Coronation Ace blades were laterally curved, and should have been returned as defective to the manufacturer.

---

AFAIK, skate/ice physics remains controversial. It was once widely believed that pressure altered the melting point sufficiently to induce melting, but a variety of published studies indicate that the amount of pressure in the blade/ice interface is insufficient to significantly alter the melting point from a static pressure point of view. My Coronation Ace blades got very hot, so I think maybe they partly melted the ice by raising its temperature. Other alternatives include poorly understood surface physics effects. I love the idea that the water molecules are be sheered from the ice, then internal fluid motion prevents it from re-freezing, just like flowing water in a lead between ice sheets, or in whitewater rapids, but I'm not an expert in ice physics. The Wikipedia article (http://en.wikipedia.org/wiki/Ice) and this one (http://en.wikipedia.org/wiki/Ice_skating) prefere a different explanations, based on the idea that the top of any ice surface with air at normal temperatures is actually water. An interesting fact is that my blades are wet after skating, which suggests that some thermal melting has occurred. Another interesting fact is that the blade tracing is partially filled with and surrounded by snow, instead of reverting to ice. I don't buy the body heat theory - surely friction generates heat more quickly at the ice surface than is conducted from the body. Anyway, why does it matter?

[icestalker]

Agree with you, Query, on that 'expert,' after reading the link. In the Boots FAQ he talked about beauty and symmetry. *crickets chirp* Beauty? Have you seen a serious figure skater's boot? Completely nicked, scuffed, and with Sk8Tape holding together the toe after ripping it one too many times on jumps/spins. But it still supports the skater while landing a double axel, doesn't it?

If only we had a book on blade width vs. ROH vs. special features that explains exactly how to match the bite angle on a wider blade vs. with that of a narrower blade, and all of the other little mysteries.

IMO, skill has nothing to do with skating on dull blades. You're going to slip on that spin entrance with dull blades no matter what your skill level. And you could be perfectly balanced on a landing and still wobble from dull blades. Dull blades are an equipment malfunction and sign of negligence, not a skill challenge.

The human race has to know everything about everything, that's why it matters. :lol:
I always thought that the blades collected ice and then melted after getting off and sitting in the warm-ish lobby. I'll have to check that out next time I skate.
That's one thing I want to know- why snow is made instead of the ice just re-freezing in its new position.
And why spin circles are forever put into the ice by a zamboni? There's two spin places that have always been in the ice at one corner of my rink. If you skate over it, it's bumpy. I have yet to solve that mystery.

[renatele]

IMO, skill has nothing to do with skating on dull blades. You're going to slip on that spin entrance with dull blades no matter what your skill level. And you could be perfectly balanced on a landing and still wobble from dull blades.

Can't fully agree with this ... coach sharpens his blades at most once a year (he only coaches, however full time) and never even wipes them, yet still can demonstrate just about any moves/dance turn or element absolutely beautifully. Me? I'd probably fall over in a nanosecond if I was to try his blades. In this case, it is his skill that allows him to skate on such neglected blades - weight placed in just the right place, with the kneebend and anklebend that allow even super-dull blades to cut into the ice, etc.

[icedancer2]

Can't fully agree with this ... coach sharpens his blades at most once a year (he only coaches, however full time) and never even wipes them, yet still can demonstrate just about any moves/dance turn or element absolutely beautifully. Me? I'd probably fall over in a nanosecond if I was to try his blades. In this case, it is his skill that allows him to skate on such neglected blades - weight placed in just the right place, with the kneebend and anklebend that allow even super-dull blades to cut into the ice, etc.

This is absolutely true. IMHO of course.

[icestalker]

Can't fully agree with this ... coach sharpens his blades at most once a year (he only coaches, however full time) and never even wipes them, yet still can demonstrate just about any moves/dance turn or element absolutely beautifully. Me? I'd probably fall over in a nanosecond if I was to try his blades. In this case, it is his skill that allows him to skate on such neglected blades - weight placed in just the right place, with the kneebend and anklebend that allow even super-dull blades to cut into the ice, etc.

I still don't think it requires 'skill.' It's more likely just skating years under the belt, and superior balance. Not 'skill.' Skill makes it sound like there's an art to skating on dull blades. Do you think Olympians sharpen their blades once a year? They are most likely more skilled than your coach. (Not to say that your coach is a bad skater, just to say that not many skaters reach that level.) Not wiping his blades off certainly isn't a demonstration of skill, it's a demonstration of bad care habits.

[renatele]

I still don't think it requires 'skill.' It's more likely just skating years under the belt, and superior balance. Not 'skill.' Skill makes it sound like there's an art to skating on dull blades.

Superior balance on the blades - isn't that skill, or sign of skill?
And I was not talking of the skill of skating on dull blades, just great skating skills that make it possible.

Do you think Olympians sharpen their blades once a year? They are most likely more skilled than your coach. (Not to say that your coach is a bad skater, just to say that not many skaters reach that level.)

:lol: he is an Olympian! (or I guess I should say "was", back in 70s).

Not wiping his blades off certainly isn't a demonstration of skill, it's a demonstration of bad care habits.

:lol: completely agreed, but it is his skating skills that keep him upright and gliding on the said neglected blades.

[Skittl1321]

but it is his skating skills that keep him upright and gliding on the said neglected blades.

Must be a former elite skater thing. I asked one of the (young, former international competitor- though not the Olympian level) coaches at our rink who sharpens his blades. He admitted he hasn't had them done in a year and a half. And he doesn't just teach- I've seen him do double axels recently. And he demonstrates spins beautifully- no slipping in entrances.

[doubletoe]

Let me guess, they did figures, right? Nothing like practically flat figure blades to develop perfect edge control and technique! :bow:

[icedancer2]

Let me guess, they did figures, right? Nothing like practically flat figure blades to develop perfect edge control and technique! :bow:

OMG that is so true!

And I am not an Olympian or even close, but back when I did some freestyle, the only time I ever noticed my blades being dull is if I kind of skidded through a spin. Otherwise, I never understood why people needed their blades sharpened so often... must be just a thing I guess.

[Skittl1321]

Let me guess, they did figures, right? Nothing like practically flat figure blades to develop perfect edge control and technique! :bow:

Although I'm sure he played with them a bit (because at some point, doesn't everyone?), the person I was talking about is too young to have done figures as a requirement.

[Query]

Agree with you, Query, on that 'expert,' after reading the link. In the Boots FAQ he talked about beauty and symmetry...
That's one thing I want to know- why snow is made instead of the ice just re-freezing in its new position.
And why spin circles are forever put into the ice by a zamboni? There's two spin places that have always been in the ice at one corner of my rink. If you skate over it, it's bumpy. I have yet to solve that mystery.

I'm glad someone agrees with me about something!

Don't dismiss Sid Broadbent completely - he is an engineer, and he once received a grant from USFSA to study skate physics. He designs and sells sharpening machines too.

I think snow is large ice crystals with a lot of air around them, but don't assume my thoughts are correct. (I think when you crush snow into a snowball, you are squishing out the air to make more solid ice.) It may even be a different phase of ice, since ice has many phases. Snow often forms when water freezes in the air, as well as when you shave a layer from the ice. Either explanation could apply, to both skate tracings and Zamboni circles - or some other explanation altogether.

When you turn a Zamboni, it must be pushing sideways against the ice (sheer force) to make the turn possible. It's like driving a car or bike so fast around a turn that it skids. It's easy to see how you could affect something as fragile as an ice surface. Also, Zambonis are often set to cut (shave) off the top ice layer. Though the detailed physics might require study.

I confess the explanation for the slipperiness of ice cited by the Wikipedia articles makes some sense. After all, ice is slippery with surfaces like shoes even when you don't put much pressure on it, and don't try to sheer off anything. But I think the grooves (tracings) left by skates implies that sheer plays a role too, not just the surface water layers.

If you want to study these in depth, you might get a PhD in solid state physics, and convince someone to give you a few million dollars for research into these topics. Governments fund research that is important to their national security - i.e.,, that keeps incumbents in office. Companies fund research in hopes of huge future profits. I know this is hard to believe, but the proposed research may be a bit of a hard sell.

When merely inquiring minds like ours want to know, without a solid background in existing knowledge and expensive research to back it up, there is no real way for us to test that our speculations are correct. Let's just go skate.

Have fun.