Flat bottomed sharpening?

[Christy]

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?

[Casey]

http://howtohockey.com/flat-bottom-v

[amy1984]

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.

[AgnesNitt]

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.
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...

[Loops]

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.

[Casey]

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?

[Christy]

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

[Query]

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", 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. 

[rachelplotkin]

I'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.

[Query]

oops 

[Casey]

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.

[Query]

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. 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.

[Kaitsu]

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. 

[AlbaNY]

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. 

[Kaitsu]

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.

[Kaitsu]

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.

[R45]

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 ?

[Kaitsu]

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?

[supersharp]

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.

[Kaitsu]

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.

[Kaitsu]

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.

[Kaitsu]

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.

[R45]

Kaitsu,
Thanks for the replies.

I 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.

[tstop4me]

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.

[Kaitsu]

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.