I'm in the process of trying to find a new (more local) sharpener. I've found someone who can sharpen the matrix blades but looking at their website they seem to be focused on hockey sharpening and advertise a Blademaster Flat Bottomed sharpening. Does anyone have any experience of this sharpening on figure blades please?
http://howtohockey.com/flat-bottom-v
Ask specifically if they can sharpen figure skates and specify that you don't mean the crappy ones from a sports store. And you don't want the flat bottom v on your figure skates. Be specific. I'd say just to not go to a hockey skate guy, but some can be useful.
Don't get a flat bottomed sharpening on your figure skates.
1. Figure skate rockers are different that hockey rockers, so it may ruin your entire rocker
2. Even elite hockey players don't use it. (http://blogs.thescore.com/nhl/2014/01/09/the-hockey-players-guide-to-skate-sharpening-the-info-you-need-to-know/)
3. Ask if they do real figure skates not pond skates. They want your money, so they'll say 'sure'. That's not a good answer. Ask how many a week. ... a month...
Quote from: AgnesNitt on November 20, 2014, 05:51:27 AM
Don't get a flat bottomed sharpening on your figure skates.
1. Figure skate rockers are different that hockey rockers, so it may ruin your entire rocker
...
3. Ask if they do real figure skates not pond skates. They want your money, so they'll say 'sure'. That's not a good answer. Ask how many a week. ... a month...
Just to add to this- several years after I quit skating I had my skates sharpened by someone at the rink at college. BIG MISTAKE. He knew how to sharpen hockey skates and I guess rentals (do they ever sharpen those?), but wrecked my blades. Not a big deal given my situation at the time, but would be a big deal for you. It's worth it to vet these guys.
It's worth it to drive a couple hours if necessary to get to a reputable figure skate sharpener. A hockey guy *will* screw up your blade profile. I wouldn't bother talking to them - I would ask other skaters and especially coaches who they recommend.
The flat-bottomed sharpening is interesting from a physics perspective but no way would I try it on expensive figure blades. Plus they're equipment is probably only appropriate for thinner-profile hockey blades. How often do you skate on a flat when figure skating anyways?
I know that some of local figure skaters use this person however I don't know any of them personally or know who they are. I've been asking around but most of the skaters I know use a guy who can't sharpen the matrix blades.
Looks like another long trip to get my skates sharpened - good job the sharpening lasts >40 hours :)
The fact that a shop advertises hockey sharpening, does not imply they do or don't do a good job of figure skate sharpening. They advertise to hockey because that is most of the market. The obvious thing to do, as others have said, is to ask your coach and other good figure skaters where they go. Don't be surprised if they don't all agree - sharpening style is a matter of taste. Then ask the shop if they can deal with your Matrix blades.
Flat Bottom V is a trademarked name for a somewhat differently shaped hollow (width-wise concavity) produced by a particular company's patented device. In terms of what actually touches the ice, it isn't tremendously different from the cylindrical hollow used on most hockey and figure skates. But it is different enough that you decide you don't like the shape, and you want the sharpener to put your blade back to a cylindrical hollow, they will have to grind away enough metal that you will have lost at least 1 or 2 sharpening's worth (out of 30 or so) from the blade's lifetime. So unless you have money to burn, or love to experiment, the safe thing is to stay with a normal cylindrical hollow - most commonly about 7/16" radius-of-hollow (ROH - again, a matter of taste).
AFAIK, Flat Bottom V has nothing to do with the rocker (lengthwise convex curvature), so I wouldn't worry about that. Though, yes, a very bad or misinformed sharpener might mess up your rocker, grind off the tail, or remove the toe pick :( . Much more likely, they may grind off more of the metal per sharpening than is appropriate for figure skating - roughly 0.003 inches is about right. Or they might create uneven or inconsistent edges - though most hockey players hate that too.
I've heard good things of "Mr. Edge" (http://www.askmredge.com), around Chicago, which is fairly near Canada. But Canada is a BIG country, so maybe that is too far. If you aren't pickey, you may not need the best - someone who doesn't make any major mistakes will do. If you are pickey, you may eventually decide to do it yourself. :)
QuoteI've heard good things of "Mr. Edge", around Chicago, which is fairly near Canada.
Not really close at all. :-\ The nearest point from Chicago is Windsor which is about 300 miles.
oops :nvm:
Quote from: Query on November 20, 2014, 04:25:28 PM
But it is different enough that you decide you don't like the shape, and you want the sharpener to put your blade back to a cylindrical hollow, they will have to grind away enough metal that you will have lost at least 1 or 2 sharpening's worth (out of 30 or so) from the blade's lifetime. So unless you have money to burn, or love to experiment, the safe thing is to stay with a normal cylindrical hollow - most commonly about 7/16" radius-of-hollow (ROH - again, a matter of taste).
I'd wager it would take a lot more metal than that, judging by the difference.
Quote from: Casey on November 20, 2014, 05:50:01 PM
I'd wager it would take a lot more metal than that, judging by the difference.
I said "at least". But the thing is, the difference at the bottom of the blade, where it counts, is actually very small, assuming you pick parameters to obtain the same edge angle (i.e., the angle between the side of the blade and the hollow). A sharpener does not have to grind it down until the part that doesn't touch the ice matches. Basically the first order shape (at the tip) is the same - there is only a second order difference there between having a circular hollow cross section and a triangular hollow cross section, because most of that cross section doesn't normally touch the ice. That edge angle is very likely the only thing in that cross section that matters much - why should it matter whether what doesn't touch the ice is curved or straight? I bet other factors in sharpening matter a lot more than FBV vs cylindrical hollow.
Structurally, the Flat Bottom V looks like it just makes the edge a little less resistant to being knocked down by a hard outside edge stop (because a little bit more material is removed in the part that opposes that), and a very tiny bit more or less drag (because the blade should sink a tiny bit more into the ice, but that what sinks in is a little thinner in places), but that otherwise there should be little or no effect. Of course I could be wrong about the effects, but that is what it looks like.
I suppose it is possible that on a very strong jump take-off or landing, the center of the blade (the hollow) touches the ice for a few milliseconds. The question is, is a triangular cross-section hollow more or less stable than a circular arc cross-section hollow? I don't know. I assume if Blackstone had any data to support the idea that Flat Bottom V is good for figure skating, they would present it. They don't.
Look at Blackstone's web site (https://blackstonesport.com). They provide no figure skater's endorsements of FBV. They provide one second tier NHL hockey player's endorsement, and an endorsement by an equipment manager on a second tier NHL hockey team. If FBV was really better for hockey, you would see endorsements by major players, especially if Blackstone (a major sharpening machine manufacturer) paid those players. And if it was better for figure skating, they would say something about that.
I can see that there is some interest to discuss about FBV sharpenings on figure skates so was waking up this old thread.
First at all, has anyone tried FBV sharpening for figure skates?
Secondly...if I have understood correctly, Blackstone offers FBV spinners with three different hollow depths. 0.001", 0,00075" and 0,00050". https://blackstonesport.com/technology/
Its true that hollows are not so deep as in traditional ROH sharpening, but I wonder what is the point to make three different depths so close to each others?
Lets assume they have lathe which is capable machine designed shape with mentioned accuracy. I believe next step in the manufacturing process is coat the spinner with diamond powder. I am a bit skeptic how this process is able to reach 0,00025" accuracy. Final step is I guess add the bearing inside the spinner. There is negative clearance between the spinner and ball bearing, which should mean that adding bearing should affect also to shape of the machined / coated hollow.
I have never measured FBV spinners or sharpening s which are made with FBV spinner. However I have measured blade which was sharpened with their traditional 1/2" spinner which equals 12.7mm. Actual measured radius in the blade was 13.2mm. Did this deviation come from my sharpening machine or spinner, that I cannot proof. However I have been chasing micrometers whole of my working career and with my experience I keep it impossible that spinners with diamond powder coating could provide 0,00025" accuracy. Even they could, it the ice absolute flat?
There is however one theory what I agree with them. Edges unevenness should not have so big negative affect as in traditional ROH shapening.
Kaitsu,
I don't have all the measuring tools that you do but one thing you wrote about made me recall something. Too Sharp skate tech told me that the Blackstone 7/16ths seemed to have a deeper actual hollow than the 7/16ths of his machine. (I forget what brand he uses, sorry.) He told me I may want to switch to 1/2" if I'm using the Blackstone, but I ended up loving the grip so far.
Anyway, I am curious about the flat bottom v and plan to try it. I remembered that my old Jackson Softecs could use a sharpening and could use those for some experimenting.
AlbaNY,
Thanx for your post. I just realized that I did forget to think about that blade thickness affects to depth of hollow also on FBV sharpening. Blackstone web page does not mention what is the blade thickness in their sketches. I need to make my own sketch in some day.
One problem what skaters will face is the fact that even they would ask 1/2" ROH for their skates, in the reality they may get something else. In machines which are using spinners, deviation can come example from the earlier mentioned manufacturing uncertainties + possible parallelism errors between the spinner and wheel. In the machines which are using traditional diamond quill, scale is typically in the quill. Diamond tip in the end of quill is replaceable because it wears. Imagine that diamond quill would be wooden pencil which would has scale which is indicating distance to tip of your pencil when it is new. When you use the pencil, its obvious that tip of the pencil will wear and your pencil is getting shorter and shorter. However the scale remains in same position all the time. Pencil you can sharpen, but diamond tip needs to be replaced. What happens when you buy new diamond tip. Are you sure its length is same as in previous...how many skate techs will calibrate their diamond dresser from time to time or when they replace diamond tip?
In SSM-2 ROH is measured from the end diamond quill with ruler. In my opinion this most ridiculous way to measure ROH.
https://ssmhockey.ru/documents/ssm-2-pro-english-CE.pdf
Personally I will measure always the ROH setting from the tip of the diamond. This will ensure that ROH remains as close same as possible even diamond would wear or if I replace it with a new one. On top of this, I have calibrated my "scale" using H.D.I gauge and with another method to convince my selves that I have measured correctly. Shortly speaking I use method where I know that certain distance measured from certain datum with my digital caliper matches to wanted ROH. Sid Broadbent Super Groover is basically using same diamond quill calibration principle. You can see photo of Super Groove in here => http://www.trusted-edge.com/Equipment.html and earlier linked Youtube video.
So ROH is always less or more skate tech specific. Even two skate techs would make exact 1/2" ROH, the way how they do deburring, what wheel they use, how big tolerance they have for edges evenness, they has own impact how the skates feels after the sharpening. Due this its not recommend to sharpen your skates here and there.
PS. I am very interested to hear if someone has experiences of FBV in figure skates.
Quote from: Kaitsu on December 11, 2022, 12:30:33 PM
In SSM-2 ROH is measured from the end diamond quill with ruler. In my opinion this most ridiculous way to measure ROH.
https://ssmhockey.ru/documents/ssm-2-pro-english-CE.pdf
Personally I will measure always the ROH setting from the tip of the diamond. This will ensure that ROH remains as close same as possible even diamond would wear or if I replace it with a new one.
Hi Kaitsu,
I'm using a Wissota as well as a SSM sharpening machine.
For both machines the RoH is set by adjusting the shank of the diamond dresser.
You are right that the wear of the diamond tip will cause a small deviation of the RoH.
I've tried already measuring the distance from the diamond tip to a line between the 2 hinges of the pivot device.
Another way would be to measure the total length of the diamond dresser and make the adjustments accordingly.
But how much would the difference be ?
A diamond dresser has a very small single diamond mounted on a tip or shank by a sintering process.
Do you know how much diamond is actually sticking out ?
And how much can be worn off before the diamond should be replaced, considering that the dresser has been frequently turned to maintain a sharp conical tip ?
I made my own sketch like promised and now I am very confused. Maybe I am not just good enough with the inches when I got so strange conclusions.
If I have understood correctly, Blackstone sketch tries to tell that that their 100/1 spinner is comparable to traditional 3/8" ROH. They didn't tell the blade thickness, but they told ROH is 3/8" and depth of the hollow is 8 thou, which is 0,2032mm. Based on those values we can calculate that blade thickness in their sketch should be 3.915mm and bite angle 11.87°. In my sketch I used 3,92mm blade thickness which explains why depth of the hollow is 0,2038mm. I believe goalies blades are about 3.9mm thick and I can imagine that they also use 3/8" ROH unlikely the players. Hockey players skates blades are about 1mm thinner (2,8mm). Nothing strange so far. Blackstone wanted use thicker goalie blade and goalie ROH to demonstrate maximum hollow depth difference.
Now comes the part what I do not understand in my sketch. They explain that flat area in the hollow would be 100 thou which is I guess 2.540 mm and depth of the hollow is 1 thou, which is I guess 0,0254mm. If I use these three values, 3.92mm / 2.54 and 0.0254, it looks like the bite angle would be just 2.11°.
It seems that to get 11.87° bite angle FBV spinner should be 145/1 or 100/6 or blade thickness should be 2,8mm. Have I made some mistake or what?
I think they are wrong about the depth being a thousandth. Or wrong about something else. I also get an angle of 2.11 degrees with the geometry they describe.
R45,
I believe the deviation which comes when diamond wears is relatively small. Most likely biggest deviations comes from the "zero point set" and when diamonds are replaced with a new one. In Wissota you should have that screw what you can adjust to calibrate the scale zero point. Most likely Wissota is not providing any calibration piece together with the machine, but you can produce that also by your selves if you or some of your friend does have access to lathe. You should machine shaft which fits between you diamond dresser hinges. Drill center holes in to the both ends of the shaft. Then use tail stock (cones) at both ends to machine shafts so that you have example 1" diameter (1/2" radius) in the area where your diamond tip would hit. Rest of the shaft can be thinner to reduce weight.
Remove the the diamond mechanism from your Wissota and put in on to your calibration shaft. Let the diamond tip contact gently to 1" area in your calibration piece and adjust your scale zero point screw if needed. Be careful not to crack your diamond tip.
Is the radius 13 or 12.7mm does not matter so much as long skater uses same skate tech all the time. Problems may appear if skater uses several skate techs and they all have different kind of deviations in their scales and methods how they do the job.
I do not understand where to use information how much diamond sticks out, but you should be able to measure it example with caliper. Diamond is worn out already long time ago before it wont stick out anymore. When its too worn out, for that I believe no-one has clear answer to you. You need to listen your machine while dressing the wheel. When spindle bearing are in good condition and diamond is sharp, dressing process is silky smooth. Something is wrong if your diamond quill starts to vibrate and you can hear how dressing is loading the electric motor. Ones you see / hear these, you will know what I mean.
Attached picture from one of the diamonds which I have rejected as a worn out. I did include 0.7mm mechanical pencil to give you some idea about the scale.
Kaitsu,
Thanks for the replies.
QuoteI believe the deviation which comes when diamond wears is relatively small
Which is also my conclusion, my guess is that it will be less than 0.5mm before the diamond has to be replaced.
I'll make sure to turn the shaft of the diamond dresser regulary, in order to keep the point of the diamond conical and sharp as long as possible.
Quote from: Kaitsu on December 12, 2022, 01:08:06 PM
I made my own sketch like promised and now I am very confused. Maybe I am not just good enough with the inches when I got so strange conclusions.
If I have understood correctly, Blackstone sketch tries to tell that that their 100/1 spinner is comparable to traditional 3/8" ROH. They didn't tell the blade thickness, but they told ROH is 3/8" and depth of the hollow is 8 thou, which is 0,2032mm. Based on those values we can calculate that blade thickness in their sketch should be 3.915mm and bite angle 11.87°. In my sketch I used 3,92mm blade thickness which explains why depth of the hollow is 0,2038mm. I believe goalies blades are about 3.9mm thick and I can imagine that they also use 3/8" ROH unlikely the players. Hockey players skates blades are about 1mm thinner (2,8mm). Nothing strange so far. Blackstone wanted use thicker goalie blade and goalie ROH to demonstrate maximum hollow depth difference.
Now comes the part what I do not understand in my sketch. They explain that flat area in the hollow would be 100 thou which is I guess 2.540 mm and depth of the hollow is 1 thou, which is I guess 0,0254mm. If I use these three values, 3.92mm / 2.54 and 0.0254, it looks like the bite angle would be just 2.11°.
It seems that to get 11.87° bite angle FBV spinner should be 145/1 or 100/6 or blade thickness should be 2,8mm. Have I made some mistake or what?
I've rechecked the math. My results are in close agreement with yours.
For a conventional cylindrical hollow, with a radius of hollow (ROH) = 3/8" = 0.375" and a depth of hollow (DOH) of 0.008", I calculate a blade thickness of 0.154" and a bite angle of 11.9 deg.
For a flat-bottom V, with a blade thickness of 0.154", a V depth of 0.001", and a flat bottom channel width of 0.100", I calculate a bite angle of 2.1 deg.
I'm really surprised at such shallow V depths (0.0005 to 0.001"). I've never measured the depth of a blade tracing of ice, but I would have guessed that, if you were gliding on a flat, with this shallow a bottom, the entire bottom would contact the ice. And I'm surprised you can hold such high tolerances: transferring spinner geometry to sharpening wheel geometry and transferring sharpening wheel geometry to blade geometry, taking into account runout, and vibration.
Its nice to see that others are getting in to the same conclusions with me. If the numbers (thou) what Blackstone is sharing are true, my opinion is that they are just theoretical. However I believe they may not share their real depth values and now I am referring to their theoretical values. They have interesting theory, but is it just theory like many other inventions.
If the maximum depth of the hollow is just one thou, I believe you can get FBV sharpening also by girding blade groove-less and using Sweet-Stick or some other stick sharpener. They are not removing material from your blades. They just roll the edges by creating foiled edges which looks then like a FBV sharpening. Most likely idea to FBV shape is taken from there.
There are several comparison tables available where FBV is compared to ROH values. Based on our bite angle calculations I can see some mismatch between them. Or maybe there is just something what I do not understand in FBV.
You folks have been discussing the Blackstone FPV. But the original poster asked about the Blademaster flat bottom sharpening, not Blackstone. Blademaster provides a form dressing system for ordinary sharpening wheels (presumably for multiple brand sharpening machines, including their own) so those wheels will create a FPV.
See page 10 of https://blademaster.com/web/img/cms/2018%20BMCatalogue%20Email.pdf
This includes Blademaster's estimates of equivalent ROH for various flat bottom specifications. The confusing thing is that they do not adjust that estimate for blade width - which makes no sense.
However, note that Blademaster here, as on page 17 of their catalog, has somewhat unusual recommendations for ROH for figure skaters.
In particular, my understanding is that, while there is a fair range of personal choice, the most common ROH among figure skaters is 7/16" (but many ice dancers choose 3/8" on MK Dance blades, because MK Dance is ground "thinline" - i.e., it is narrower at the working surface). But Blademaster seems to be implying that figure skaters usually choose larger ROH.
Blademaster does imply that some figure skaters want flat bottom sharpenings. (Blademaster seems happy to provide whatever anyone might ask for, - for a price. If you bought everything in their catalog, you would spend a lot of money. :))
Quote from: Query on December 18, 2022, 06:52:16 PM
You folks have been discussing the Blackstone FPV. But the original poster asked about the Blademaster flat bottom sharpening, not Blackstone.
Could you kindly tell us more clearly how this was explaining why Blackstone claims 2 degrees FBV bite angle to be equivalent with 12 degree bite angle in ROH?
Quote from: Query on December 18, 2022, 06:52:16 PM
You folks have been discussing the Blackstone FPV. But the original poster asked about the Blademaster flat bottom sharpening, not Blackstone. Blademaster provides a form dressing system for ordinary sharpening wheels (presumably for multiple brand sharpening machines, including their own) so those wheels will create a FPV.
See page 10 of https://blademaster.com/web/img/cms/2018%20BMCatalogue%20Email.pdf
This includes Blademaster's estimates of equivalent ROH for various flat bottom specifications. The confusing thing is that they do not adjust that estimate for blade width - which makes no sense.
However, note that Blademaster here, as on page 17 of their catalog, has somewhat unusual recommendations for ROH for figure skaters.
In particular, my understanding is that, while there is a fair range of personal choice, the most common ROH among figure skaters is 7/16" (but many ice dancers choose 3/8" on MK Dance blades, because MK Dance is ground "thinline" - i.e., it is narrower at the working surface). But Blademaster seems to be implying that figure skaters usually choose larger ROH.
Blademaster does imply that some figure skaters want flat bottom sharpenings. (Blademaster seems happy to provide whatever anyone might ask for, - for a price. If you bought everything in their catalog, you would spend a lot of money. :))
Blackstone discloses technical details of their flat-bottom V; hence, there is a basis for rational discussion. If you look through the Blademaster documentation you cited, you will note that they disclose no technical details of their flat-bottom architecture (what is X5 through X9, and what is GX6 through GX8?); hence, there is no basis for rational discussion. I did a quick (by no means thorough) search for Blademaster details outside the documentation you cited, and came up empty. If you've found relevant technical details, please provide them.
If you're merely arguing that the original thread launched in 2014 asked about Blademaster and should be limited to Blademaster, and that Kaitsu should have launched a separate thread on Blackstone, that's a mere formality our moderator can readily address by splitting the thread if they deem appropriate.
I'm simply saying that Blademaster's system (BFD=Blademaster Flat Bottom) may be significantly different than Blackstone.
As a first cut, you could take a common hockey blade thickness, and estimate the angle from Blademaster's table of equivalents.
I suppose one could call Blademaster and ask for details.
Other websites have tried to address Blademaster's shapes:
At https://sharpskates.files.wordpress.com/2012/10/bfd-flyer.png and https://sharpskates.files.wordpress.com/2012/07/bfdflatbottom1.pdf Blademaster implies that their flat bottom shape actually retains a bit of an arched radius, to improve strength - but is not specific. But as you have pointed out, Blackstone isn't specific either - or rather, the dimensions they give are contradictory.
BTW, Blackstone's number do identify the flat width and edge height - if https://salemskates.com/flat_bottom_form_dressing.html is correct. Unfortunately, without a specific blade width, there is still no way to identify the angle those two dimensions create. That guy also claims that Blackstone offers a dressing system for other brand sharpening machines too. But he also implies flat bottom shapes give the inexpert skate tech more potential to mess up.
At least with conventional ROH systems, the hollow shape is fairly clear. But, as this discussion points out, neither Blackstone nor Blademaster give enough details to determine the exact cross section shape.
In fact Blackstone's image https://blackstonesport.com/technology makes it clear that they are assuming a (hockey) blade width of .070 - .100 inches - and they aren't specific as to which the equivalents were determined.
I don't understand Blackstone's argument - why does putting the top of the hollow closer to the ice make it better and faster? I guess you could say that, since the physics of ice skating remains under debate (e.g., does the boundary layer behave as a 3 dimensional liquid, or as something much more complex, as some recent studies have suggested), they determined that empirically - and that would be fine if everyone agreed it was true. (Which they don't. Many hockey players have stated online that they notice no difference between standard arched constant radius hollow, and flat bottom sharpenings. I haven't found anywhere where figure skaters have made similar comparisons. It might be amusing if a good figure skater here would - but there are costs to doing so.)
First FBV sharpening test to Coronation Ace blade is now completed by using Blackstone 100/75 spinner. Unfortunately I did forget to take my precision square with me, so we used Blackstone Z-02 BAT gauge to check edges evenness. As you can see from the picture, we didn't succeed so well at first trial. There is 0.25mm error in skate carriage height adjustment, which caused 0.035mm height difference to the edges height. I used H.D.I gauge to measure edges height difference.
As we failed to get hollow into the middle of the blade, I cannot measure all features what I am interested. Or I can measure, but they are not giving us the correct information. I need to make new attempt to grind hollow in to the middle of the blade.
I could conclude already from the existing measurement that width of the hollow is not 100 THOU (2,54mm) like stated on the spinner. Measured width seems to more close to 75 THOU (1.91mm) than 100 THOU. We can also conclude that if the bottom of the hollow is kept as a datum, there is 1 degree bite angle difference between the outer and inner edge. This should not change even we adjust skate carriage height. Even the bottom of the hollow is a bit wrong datum when we try to evaluate bite angle, in my opinion it is indicating exactly those problems what explained in earlier post. Before making any final conclusions, I need to make new test.
I can confirm that it is possible to make FBV sharpening also to figure skate blades. Will I ever start to make FBV sharpening's to figure skates, most likely not.
ps. actual measurement data cloud points are visible under the red lines.
Interesting results. What was the depth of the channel (hollow)? Obviously considerably more than the target range of 0.0005" to 0.001" (0.0127 mm to 0.0254 mm) stated by Blackstone. I can see how a spinner controls the width of the channel (hollow) and the edge angles. But I don't understand how the depth of the channel (hollow) is controlled to the extreme accuracy stated by Blackstone.
The thickness of the grinding wheel is 8mm. Hollow in the spinner has to be wider than wheel, otherways you cannot dress the wheel. So in theory wheel thickness defines the maximum blade thickness on both sharpening methods (ROH & FBV).
Depth of the hollow what you get is blade thickness specific. Also this is valid to both sharpening methods (ROH & FBV). Wider the blade is, deeper the hollow you get. Deeper the hollow is, more bite you will get. This is something people dont usually realize when they ask same ROH than in previous skates. I can do the same ROH as in previous skates, but bite angle can be then different. Such can happen easily example if you change from Coronation Ace to Ace Lite. If we would like to be accurate, we should talk about bite angles instead of hollow radius. Then you would get always same kind of sharpening even blade thickness varies...at least in theory.
Why I say in theory? (sorry...a bit out of topic). How many of us has wondered what happens when blade thickness is someting than 4mm and why hockey player can manage so shallow hollows compared to figure skaters even the balde is so narrow? It is for sure that blade thickness has some impacts for the skating, but what is totally missing from the hockeys? It is the chrome removal grinding. It is not just ROH which defines the angles of the edges you use for skating. Each edge you use for skating has also two edges. One of those you can define by choosing certain ROH, but the other side of the edge comes from the factory. If they roll that another side of your skating edge, like Wilson usually do, angle of the edge changes. This is why I hate so much blades where chrome is removed. Each blade is unique, even left and right foot.
Depth what balckstone gives for their FBV is valid to the certain blade thickness what they do not tell. This is what I tried to explain earlier. I am not sure if they try to a bit fool people in their sketch by comparing Hockey player FBV sharpening (3mm) to goalie ROH sharpening (4mm). This would at least give maximum hollow depth difference. Even at the ROH sharpening 3mm blade thickness would give shallower hollow than 4mm blade, even ROH would be same in both blades.
I didnt give the depth for the hollow and "real bite angles" for two reasons...
1. Edges were not even, which means that one edge was 0.035mm higher that the other. However the calculated depth of the hollow was following (0.035/2)+0.150= 0.1675mm. This I measured with H.D.I gauge from the one location.
2. Edges height values what I did get by another method didnt match with my H.D.I gauge measurements. As the edges were not even I didnt start to investigate why two different measuring methods didnt give same results.
We will get more detailed data when I manage to do better gringing for the blade. That I try to do in next week.
When "real bite angles" are measured, I should use the edges (line between the highest points) as a datum. Now I used bottom of the hollow as I didnt have any other realiable datums. In my opinion bottom is the hollow or channel does not need to be parallel to the edges. Most important it that edges are in square to the side surfaces of the blade. That I will try to improve on next grinding attemtp. I hope you can understand what I mean.
Thanks for the response. I'll wait for your further measurements. Blackstone's presentation is very confusing to me still.
ETA: I've gone over the Blackstone material again, and I've identified the major source of my confusion. In standard radius of hollow (ROH) sharpening, we are explicitly concerned only with the edge angles. For a given blade thickness, the edge angles are controlled by controlling the ROH. The depth of hollow (DOH) per se is not explicitly a parameter of concern: the DOH results incidentally from the blade thickness and the ROH.
But in FBV sharpening, as presented by Blackstone, we are explicitly concerned with both the edge angles and the depth of the channel (hollow). And according to Blackstone, the depth should be much shallower than is found in standard ROH sharpening and much more accurately controlled. E.g., Blackstone offers three different depths, with the difference in depths between adjacent values being only 0.00025" (0.00635 mm = ~6 microns!). To avoid significant overlap between adjacent values, that would mean that each depth would have to be maintained to a tolerance of ~ +/- 0.00005" (0.00127 mm = ~1 micron!). I worked with such tight tolerances in semiconductor wafer polishing. I don't see how that can be attained with spinners, grinding wheels, and skate sharpeners.
I think good hockey players get by with longer ROH - i.e., wider edge angles, even though they have narrow blades and often skate on cold, hard ice, because Hockey players are told to skate very "aggressively". They push very hard against the ice. They helps them do the sudden stops and direction reversals that help them confuse their opponents by being less predictable. It may not create the aesthetically beautiful skating that is expected in figure skating, but that doesn't matter.
Hockey skaters have a huge advantage. I was told by a hockey coach that a typical hockey skater only stays on the ice for about 45 seconds at a time. That means they indeed can push very, very hard, during those short times, giving deeper penetration into the ice.
I'm not exactly sure how the difference in rocker radius affects the differences. Hockey blades have a longer rocker radius (more flat) in the center than figure skates. As best I understand it, they spend a lot of their time gliding on that. (But they have shorter rocker radius at the ends, for fast turns.)
I think hockey skaters typically push and stop off the center of the blade too. The longer central rocker radius gives them more length to push off of, or stop on. And that lets them accelerate very fast. Of course they need to push very hard against the ice to take advantage of that - but, as mentioned above, they do.
Another aesthetic factor is that figure skaters are not supposed to have much (if any) side slip. That requires sharp edges, which are achieved in part by shorter ROH. There is of course no such aesthetic standard in hockey.
BTW, I've known figure skaters who use 3/4" - 1" ROH, perhaps because it creates less friction, giving a longer glide. So it isn't universal that figure skaters tend to use shorter ROH. Especially for School Figures. Possibly for Moves in the Field, though I'm not sure. (Some people advocate even longer ROH for School Figures.) For both of those skating disciplines, glide length is very important, AFAICT, because you are often expected to go fairly long distances off of a single push. (Also, if what I've seen is typical, the speeds over the ice in those disciplines is fairly slow, so maybe they don't need very sharp edges??) If Blackstone is right, and FBV really does create less friction, maybe it would be good for School Figures and Moves in the Field??
Kaitsu - once you fix the uneven FBV edges, hopefully you can find good figure skaters willing to try out your FBV sharpened blades. It would be interesting to know what they think. Ideally, you would want them to at least try to use objective measures - e.g., how long a glide they can create, how fast they can go, how fast they can accelerate, how much unintentionally sideways skid they have, how much they travel when they spin, how stable their jump landings are, etc. If you don't use objective measures, they might be inclined to believe they feel what they expect to feel.
Unfortunately I have difficulties to get good datum's from the chromed side surfaces. This will increase bite angles measuring uncertainly. Form errors are also causing similar issues. Best fitted (red) lines positions will change depending which all measuring points are taken in account. Even H.D.I gauge did give 0.01mm edge height difference when it was rotated 180 degrees. This I did test several times to see that its repeatable issue.
This is the best report what I can provide with reasonable efforts. Please enjoy!
Link to report: https://www.dropbox.com/s/4oga3rl86wi3x6t/FBV%20100_75_reduced%20size.pdf?dl=0
My own conclusions:
* Flat bottom width is not definitely promised 100 thou (2.54mm). Perhaps it is width before diamond grit coating?
* Even there is some measuring uncertainly in the bite angles measurement, it's quite clear to me that there is about 0.5° degrees difference between inner and outer edge
* The edges of the blades have strange gaps. Whether they are caused by a worn spinner or some other reason, I don't know. In any case, various measurement errors were to be expected. Diamond grain coating is not a micrometer precision job with such a grain size
* Measuring results were confirming my thoughts that personally I am not going to jump from ROH sharpening's to FBV´s.
* 1/2" inch ROH would provide 9.4° bite angles. This study didn't help at any level to understand why 100/75 would be comparable with 3/8" ROH.
How does the grit size of Blackstone spinners compare to the grit size of coarse and fine grain grinding wheels used in skate sharpeners?
Do you think Blackstone ROH shaped spinners would also give relatively poor results, or did you not test that enough to tell?
Is there anything at all that you like about Blackstone sharpening machines, compared to other machines?
I was using couple years Blackstone ROH spinners in my previous power grinder. In that means I do have much more experience about their ROH spinner than the FBV spinners. Also, on the ROH spinners the actual radius in the blade wasn't same as what they state at spinner. Did the error come from the spinner or perhaps the spinner was not exactly parallel to my wheel? That I didn't ever investigate.
Even there was +0.5mm deviation in the radius, I was able to repeat the radius more accurately than with the original diamond quill system, which was real disaster in that machine. In some reason 1mm adjustment of diamond didn't mean that radius in the blade would change 1mm. With my experience most of the traditional diamond quill machines can have even bigger radius deviations than 0.5mm. People are trusting a bit too blindly to the machine's scales.
During the years I ordered couple new spinners to replace existing ones. Just by judging by eye ball, it seems that Blackstone has made changes to the diamond coating grit size or it is some normal process variation. Check the attached pictures and you can judge by your selves if those two 1/2" spinners do have same grit size. In another picture you can see spinner and Blademaster Ruby wheel side by side.
For the discussions about the Blackstone machines we can perhaps open new thread?
We don't need a new thread. You answered my questions about Blackstone sharpeners sufficiently.
Excellent study of the FBV, Kaitsu. I still would like to skate on it to see how it feels, but seeing this confirms my satisfaction with the ROH approach to sharpening.
I have a pair of old boots that I could use for interesting experiments if I replaced the tongues (current tongue does not protect my ankles enough so all I can really notice is the discomfort). I can re-profile some used blades and then start looking around for someone with FBV machine... now that I can't get new SkateScience blades, I can't afford to experiment much on them.