Figure skate blade hardness

[Kaitsu]

Could you help me to find sources where blades hardness's are mentioned. Here is few examples...

Blade is tempered to a Rockwell C hardness of about 30 or 40, and the edge is re-hardened to about 60, according to some sources.

Mike Cunningham (a skate tech) had Rockwell hardness - he didn't say which one) measured professionally at a steel heat treatment plant for high end MK (and Wilson?) blades (high carbon steel) - the result was around Rockwell 60, at least when they do things "right".

https://precisionblade.com/index.php/blade-comparison/#collapse3710
Blade Hardness is measured by Rockwell C (HRC). High Carbon Steel used in making good quality figure skating blades should be around HRC 60.

https://iceskatingpassion.com/figure-skate-blades/
High Carbon Steel (runner and chassis)
The hardness should be around 60 HRC

https://edeaskates.com/en/ice/accessories/blades/mk-gold-star/
https://edeaskates.com/en/ice/accessories/blades/john-wilson-coronation-ace/
High quality carbon steel HRC 58 heat treated blade to keep the edges sharp. Chrome finish

https://www.ilpattinoriccione.com/edea-ice-fly-wilson-cor-ace
Advanced level freestyle blade. HRC 52 steel with polished chrome finish

https://www.shopsk8gear.com/product-page/x-pro-ice-figure-skating-blades
• Japanese high-quality carbon steel HRC 52 +/- 2

[tstop4me]

You can find some hardness information on one of the Paramount videos:  https://www.paramountskates.com/videos.  Click on the one with the title "Figure Skate Metals and Manufacturing".  Metals are discussed at ~3:19 to ~6:02. Shown are several data sheets for blade metals that include the typical maximum hardness; however, the video does not give any actual measured values.

[tstop4me]

Here is information I got via e-mail from Riedell/Eclipse in 2016:

"The hardness of the Aurora stainless steel blade is 55 – 57 Rockwell C hardness.
Carbon steel blades can range from 51 – 53 body hardness and 52 – 56 edge hardness, depending in the brand."

[Query]

Rockwell C involves hitting the steel with a diamond point, and measuring how deep the indentation is. That might be substantially different from the effects of skating on ice. So the real question is, why should you care?

I do not think companies like HD Sports (MK+JW) are likely to give you details, because they might be proprietary - plus they may not want to commit to meeting any particular spec.

A quick Internet search gives more pages:

https://www.promisesport.com/fox-brand-brand-hrc-track-blades-ice-skate-blades
https://www.slidingtiger.eu/en/Home/accessories/PS902277
https://patents.google.com/patent/US20050139290
https://skatenow.us/index.php/tutorial-blogs/item/38-ice-speedskating-overview (speed skates)
https://www.outsideonline.com/outdoor-gear/snow-sports-gear/what-are-best-recreational-speed-skates/
https://www.t-blade.de/usa/hockey-skates

https://www.bladesmithsforum.com/index.php?/topic/36617-testing-hardness/ mentions Rockwell files as a cheap but imperfect method of estimating Rockwell hardness testing.

[Query]

Perhaps skate blade edge wear involves at least two somewhat distinct mechanisms - abrupt deformation and abrasion - and the amount to which each occurs depends on what types of skating you are doing. E.g., whether you are gliding, doing high jumps, the running sprint starts that occur in hockey and speed, or the sudden stops and direction changes that also occur in hockey.

I guess Rockwell C measures abrupt deformation, but files measure abrasion. And there are several other steel hardness scales. I wonder what is best for various types of ice skating wear.

Perhaps deformation is easier to measure consistently and in a well calibrated way, and that's why Rockwell hardness is so often cited?

Could it be cheaper to pay someone to do a few measurements than to buy your own good quality tool?

[Kaitsu]

Thanx to tstop4me for good Riedell information!

I can see that I failed in my first post when I did mention figure skates only in thread subject field. In the text I just talked about the blades and things went a bit out of tracks.

What is my interest is...
* What kind of hardness's different blade manufacturers promises to their FIGURE skate blades. This could be also beneficial to inform in the blade specifications, if they can promise (and also keep the promise) that their blade is harder than competitor blade. This even it would not have any real benefits to the skaters. In the other hand, if you know that your blades are softer than competitor blades, you may not want to promote that.
* How far or deep the hardening is made in the chromed FIGURE skate blades. This is something what manufacturers will not definitely want to tell us. This interest relates to the common "sharpenable region" myth. Does the blade become so soft, that they have to be rejected due that. Most likely "sharpenable region" is causing concerns only in chromed blades where its more visual.

What comes to the hardness measurements, isn't it obvious that no-one is not so keen to know their blades hardness that they would invest tens of thousands for equipment to find out that. Its always cheaper to buy that service. I would say that even the bigger problem is that you have to sacrifice some blade(s), if you want to know in detail their hardness and hardening depth.

[Query]

How far or deep the hardening is made in the chromed FIGURE skate blades. This is something what manufacturers will not definitely want to tell us. This interest relates to the common "sharpenable region" myth.

Shortly before Riedell started selling their own blades, I spoke to a person at Riedell who sharpened the blades that they mounted on Riedell boots that were ordered with blades. I asked him what the hardened depth was on MK and JW blades. He didn't know, but guessed it was substantially greater than the chrome relief zone depth.

[Kaitsu]

Making this study required quite a lot of efforts, but now one task from my dream list has been completed. I dreamed about this so many years. Unfortunately limited budget has been main reason why it took so long time. In the same reason I could not make tests with several blades or even with the brand new blade.

Even though this is very limited study, I would say that its unique in the means that no-ones has published similar study before. Or at least I haven't found any other study and it seems people from the forum either has not found. Now we have some numbers which has been taken from the real blade. This time numbers are not based to the general steel specifications, manufacturers specification´s, myths or rumors. Measurements has been done in the laboratory by the professional metallurgist.

https://youtu.be/qVccidxgd5g

[Bill_S]

Nice work.

I used a Rockwell hardness testing machine back in engineering school. After I getting my engineering degree, I never had to do it again. Because I'm still in the town where I went to college, I had weighed the option of taking a blade to the engineering department for testing. However, all of my former instructors and contacts there are gone (most of them deceased by now).

I'm glad that you tracked down a source for this information.

[supersharp]

Wow! Thanks for sharing this.

Excellent study, Kaitsu. +GOE for the third-part verification so we don't have to just listen to marketing hype. 

This makes me feel more confident about re-profiling blades and removing a bit of height from the drag pick to restore the initial heel lift. From a skater's perspective, it is definitely better to reset that profile regularly so you don't ever have to make a big adjustment (for example, when getting new blades...if your blade profile has deteriorated, a new set of blades if the same model will feel unfamiliar.

I've also been considering re-profiling older blades for people who might actually have chosen an unfavorable blade model for their natural balance point.  I have one skater that struggles with too much tipping forward on a new MK Pro, and used to like them better as they aged...until I got a cross-grinder and started resetting the profile. The worn blades were more the shape of the Coronation Ace. Now she has less trouble adapting to new blades (because the profile feels familiar) but she still has the tipping problem.  I'm thinking about setting up an old pair of her blades with the CoroAce profile for her to try next time she is ready for new blades. I know I have made a few blade changes that instantly fixed some of the things I was struggling with, and this seems like a safe way to get at least some idea about whether you would prefer a different profile. It's (of course) more complicated than that because you would also need to account for stanchion heights varying with blade models, but that could be tested with some shimming under the sole plates.

[Kaitsu]

Supersharp,
If the skater does have tipping problems, perhaps Ultima blades would better for her?

It would be shame not to share study which probably answers to the question which many of us has been thinking for years. Sharing one "secret" is one step further. There are still many secrets, myths and open questions relate to the figure skates what to puzzle. As long as we are keen and motivated, we can learn new things and help each others.

Bill,
You have also made several nice studies which you have shared with us. Your knowledge and experiences are highly appreciated!

[Query]

Great tests! And not something most of us could afford to do, especially not with blades we wanted to continue using.

I'm a bit unclear what you mean by the "chrome relief end" test. Where were those tests done?

Incidentally, it seems the Riedell factory skate tech I spoke too wasn't too far off when he said the height of the hardened area was about 3/8".

Supersharp: As a non-destructive initial test, instead of trimming your student's drag toe picks to improve balance and the tendency to catch her pick on the ice, could you reshim the mount, so as to add more height to the forward part of the blade, including the toe pick. (If that puts the student too high off the ice, you could also sand away part of the heels - but that would be a somewhat difficult to reverse test too.)

My feeling is that my own similar problems stem in part from heels that are too high. I should really do something about that. It doesn't help that an ice dance coach taught me to lean forwards while stroking forwards - though in fairness, he also wanted me to bend my knees further than I am now strong enough to do - he wanted me to assume a sitting pose at the lowest point in the stroke, and sometimes to go even lower.

[Kaitsu]

My understanding has been that terms of sharpenable region, sharpenable zone, sharpenable area, chrome relief zone and chrome removal area, they all have the same meaning. Means width or height, depending on how you see it, where the chrome has been ground away at the factory. In the other words, chrome removal ends at some point / depth and that can be measured example using caliper.

As the blade which was used on measurements was used, side surfaces has been honed several times when they have been sharpened and deburred. Deburring honing has hit also to the chromed area. It was not 100% clear where the edge where the factory chrome removal ends / chrome starts, so I took photo where you can see blade and slide caliper with 3mm reading next to each others. From that photo everyone can judge by them selves, if chrome removal ends at 3mm like I was defined, or somewhere else.

I also thought that it could be also helpful, if I add line to graphs to show where chrome removal ends. It visualizes that hardening goes deeper than where the chrome removal ends. Chrome removal ends somewhere at 3mm and blade is getting softer somewhere at 7mm depth. I hope this clarifies things to Query.

[Query]

Oh. I misinterpreted your diagram. You are saying that on the cross section, the region where the chrome (and the nickle plating that is applied before chrome plating) plating was ground away is 3 mm above the inside or outside edge. In which case disregard my comment about 3/8" - and in fact, since it is a used blade, it is hard to guess how much height was ground away by sharpening.

But what your diagram does then show is that there are about 4mm of fairly hard steel above the chrome relief zone, that one could use, though many people think that isn't true.

But maybe one should first ground off the chrome (and nickle), because the chrome and nickle are less hard, and won't hold an edge long.

I wouldn't be surprised if companies like HD Sports (which makes MK and JW blades), and other blade makers actually do similar studies of hardness when they do quality control. But they might not publish those results, because it might make it easier for other companies to produce similar blades. In other words, they would treat those studies as proprietary information. And the other current blade makers might have tried to approximately copy the tempered and edge hardened hardness values from studies of MK and JW blades, on the theory that MK and JW did it right.

[Kaitsu]

But what your diagram does then show is that there are about 4mm of fairly hard steel above the chrome relief zone, that one could use, though many people think that isn't true.

Did you read the diagrams axis titles at all?

If you look slide number 6, you can see cross section specimen and three dotted lines. They are hardening dept measurement points. Hardening depth was measured in 0.5mm steps from the outer and inner edges and from the middle of 4 mm thick blade. These three measurement location witness if blade has same hardness all the way though the material thickness. Since measurements has been made from the cross section specimen, chrome layer in not included in the measurement results.

As said, measurement points were taken in 0.5 mm steps all the way to the 10 mm depth. See diagrams from the slides 7 and 8 and axis titles.

[Query]

I read everything.

I take "Distance from the sharpening edge" to be a vertical distance, from the edges at the bottom of the blade.

And I therefore finally took the dotted vertical line to represent the height where the chrome relief starts - i.e., 3 mm above the current edge bottoms - which roughly matches the caliper measurement you show.

That's correct?

In which case, all three solid measurement lines (inner edge, outer edge, and middle) appear to drop fairly abruptly around 7 mm above the bottom of the edges - which is 4 mm above the top of the chrome relief zone. Correct?

My interpretation of that is that the concern that many people have, that they cannot sharpen past the chrome relief zone, because they think the steel is only hard at the heights where the chrome is removed, is wrong; they have another 4 mm or so of hardened steel - as long as they do their own chrome relief.

Of course, doing your own chrome relief well would be pretty hard - you'd want to remove similar amounts of metal on both sides of the blade in a uniform fashion, along the whole length of the blade, or you wind up with a weird blade shape. I'm not sure anyone without a high precision machine shop could do that in a uniform fashion. I probably couldn't - unless there is a way to file away the plating without removing some of the steel.

BTW, Mike Cunningham once told me that according to his measurements, MK didn't always plate symmetrically - i.e., the thickness of the nickel/chrome plating wasn't always the same on both sides. I'm not sure that matters, unless you use the sides of the blade in the plated zone to center the grinding wheel.

[supersharp]

Great tests!

Supersharp: As a non-destructive initial test, instead of trimming your student's drag toe picks to improve balance and the tendency to catch her pick on the ice, could you reshim the mount, so as to add more height to the forward part of the blade, including the toe pick. (If that puts the student too high off the ice, you could also sand away part of the heels - but that would be a somewhat difficult to reverse test too.)

Query:  Trimming the drag pick is done to improve the heel lift on a blade as part of the reprofiling process.  It is not something I would ever do to improve balance or correct a tendency to catch a toe pick on the ice. 

My point in that discussion was that each skater can have a more or less favorable experience on various blade profiles.  Since Kaitsu has verified that the edges are hardened to above the chrome relief, I was commenting that I'm now more comfortable reprofiling old blades further than I used to be, and that I might take an old pair of this same skater's blades (MK Pro) and shape them to match the Coronation Ace profile so she can try this profile without having to invest in new blades.  It would just be an interesting experiment. 

[supersharp]

Continued...

Kaitsu's suggestion of the flatter Ultima blades is another good experiment, or (as you propose), shimming the toe plate to reduce the overall ramp angle. The skater wears lightweight custom Harlick boots that have a carbon fiber layer on the soles, so I would not want to do any grinding on the soles (and I agree that I would prefer to use reversible techniques).  In my experience, even a mm shim under the front sole plate changes the ramp angle enough that you can feel it. This is the approach I would take if someone asked me to help them avoid catching their toe picks on the ice. The skater in question isn't catching her toe pick, but she complains that she feels like she is on a bucking bronco when she rocks forward.  My guess is she would prefer a profile with a flatter spin rocker, but she doesn't want to try anything different because it's a big investment and she may like something different even less. I have suggested shimming the toe plates but it was a struggle getting the blades aligned...so neither of us want to move them until she needs to replace them.  At that point, it would be interesting to experiment with creating a couple of different profiles for her to try.

I ordered neoprene sheeting in a couple of different thicknesses (probably from Grainger) for shimming sole plates. It is flexible but dense enough that it doesn't compress. You may want to experiment with a 1 mm or 2 mm shim under your front sole plate to see if you like it better. You can do a preview of the feel by standing with the ball of your foot on the shim material and the heel on the floor, either in stiff shoes or in your skates (probably best with hard guards on).

[Query]

Query:  Trimming the drag pick is done to improve the heel lift on a blade as part of the reprofiling process.  It is not something I would ever do to improve balance or correct a tendency to catch a toe pick on the ice. 

For me personally, it IS all about toe pick catches.

Why do you care so much about heel lift? Does it have something to do with jump mechanics?

[tstop4me]

For me personally, it IS all about toe pick catches.

Why do you care so much about heel lift? Does it have something to do with jump mechanics?

There are several factors that contribute to how easily a skater can catch a toe pick.  One contributing factor is low heel lift:  as you rock forward on a blade, the lower the heel lift, the sooner the drag pick will contact the ice.

The heel lift also has an influence on spins.  Since, in past threads, we never came to an agreement on definitions for basic terms such as "sweet spot" and "cusp", however, I won't pursue this.

I'll leave it to others to comment on whether or not heel lift has an influence on jumps.

[tstop4me]

Making this study required quite a lot of efforts, but now one task from my dream list has been completed. I dreamed about this so many years. Unfortunately limited budget has been main reason why it took so long time. In the same reason I could not make tests with several blades or even with the brand new blade.

Even though this is very limited study, I would say that its unique in the means that no-ones has published similar study before. Or at least I haven't found any other study and it seems people from the forum either has not found. Now we have some numbers which has been taken from the real blade. This time numbers are not based to the general steel specifications, manufacturers specification´s, myths or rumors. Measurements has been done in the laboratory by the professional metallurgist.

https://youtu.be/qVccidxgd5g

Good test results, Kaitsu.  At the very least, the results indicate that worn-down figure skate blades are still useful as recreational blades for casual skating round rinks and ponds.

I have a separate question for you.  Do you have an estimate of the plating thickness?  I've often wondered whether the chrome relief is needed.  Or is that another myth?

[Kaitsu]

Unfortunately, the thickness of the chrome layer was not measured. It would probably require cross-sectional specimen etching and SEM imaging. To be honest, the thickness of the chrome layer is not so interesting to me (at the moment) that I would look into it further.

The reasons are as follows:

1. I'm not sure how the chroming process behaves. Does it accumulate in sharp corners more than flat surfaces or vice versa. So I would need to measure several blades, or at least in several different places, to get some idea of the magnitude of the variations. Perhaps even new blades where chrome has not been ground away. It is anyhow 100% sure that the thickness of the chrome layer varies. See an example picture where you can see sagging on the chrome layer.

2. From what I have seen of the chrome chipping blades, visually I would say that the thickness of the chrome layer is very close to the aluminum foil used in the kitchen. See the attached picture.

3. Even if I know how thick the chrome layer is, how can we judge how thick a layer would actually matter for skating?

4. From what I've heard, the chrome plating is removed because would start chipping easily when the blades are sharpened. That would lead to customer complaints. I can easily believe this reason.

5. If we look at the other edges of the blades, we can see how they are rounded. I assume that the rounding is caused by the polishing process. Presumably, the edges, which are more important for skating, will also be rounded in same polishing process. It would be possible to remove the rounding of the edges by chrome removal grinding, if the rounding has not been ground off in an earlier stage of the process. As I have witnessed in several videos, JW either "hides" the rounding of the edges from the chrome removal grinding, or their grinding fails miserably. I do see that this is bigger issue than the chrome layer thickness.

[tstop4me]

4. From what I've heard, the chrome plating is removed because would start chipping easily when the blades are sharpened. That would lead to customer complaints. I can easily believe this reason.

Thanks.  This makes more sense than the usual reason I've read.  The argument for the chrome relief I've seen is that the chrome (plus nickel) layers as plated are relatively soft.  Therefore, they must be removed to expose a hard steel edge.  But if the plated layers are relatively thin (to be determined), they should not have a substantial effect, especially since a whetstone is used to debur the edges after sharpening.

[Query]

Not everyone uses a whetstone. If a skate tech uses a coarse wheel to sharpen, sometimes even a medium wheel, there often is no visible burr, even with a microscope.

Those pictures make me wonder whether a person could injure themselves on peeling chrome/nickel plate, if they touch it. Seems like a potential liability issue.

But if someone bought expensive blades, and they peeled like that, I think they would feel completely justified in believing that the manufacturer had done a bad job. Especially since one of the major selling points of MK and JW blades has been their beautiful chrome finish, which is much shinier than the stainless steel blades that I personally prefer for other reasons. In fact, it's hard to believe those companies would want to release a product like that. It's not like MK and JW are economy brands. At the luxury end of any market, appearance matters a lot - you don't need any technical expertise to see this problem. (In contrast, hardness is a lot less obvious to the inexpert consumer. Even uneven rocker profiles and such are a lot less obvious.

I wonder why HD sports doesn't pay more attention to these things. Maybe they would benefit from new management...

[Kaitsu]

From talking with my local skate tech, his sources told him the manufacturer was in the middle of replacing aging equipment. And that a lot of this was happening for that reason. Now whether these blades were coming from the old or new machinery, no one had any idea.