Low-Cost Basic Even Edge Checker

[Query]

I guess I somehow imagined that it rested entirely on the hollow, and worked off measuring pins that sought to rest the center of the hollow, and the edges.

The way I imagined the tool to work couldn't possibly work. As long as the hollow has a circular arc cross section, the center won't be of a different shape, so there is no way to have the pin "feel" for the center. And the perpendicular bisector of the line across the edges will always also be the perpendicular bisector of the circular arc (that is the circular cross section) between them.

I.E., a tool to measure the levelness of the edges (i.e., symmetry) with respect to the shapes of the sides must reference the sides of the blade.

Oh, well.

[Kaitsu]

Here is short introduction of Hollow Depth Indicator – H.D.I.
https://youtu.be/QNsBftemCNA

It is useful measuring tool if you want to calibrate scale of your skates sharpening machine diamond quill, but for edge checking there are cheaper and more user friendly tools available.

[Query]

Thanks Kaitsu! Very clear

The gauge you have is labelled Sylvac, where as the Wissota (older name: Edge Specialties) tool is not. Did you replace the dial gauge, or is this a different tool altogether?

Is there space to try adding compressible foam tape to the jaws, so it could be maybe used on blades with side honing?

An HDI measurement will not correctly determine the ROH if the edges are significantly worn down (because they were skated on) - because the measured hollow depth will be less than on a freshly sharpened blade, right? For that you would probably use a radius gauge that touches appropriately curved surfaces against the center of the hollow...

The Wissota web page says it can also measure rocker radius.

The H.D.I. is the only measuring tool that indicates the precise depth
of hollow, the edge balance and rocker radius.

But tstop4me said it can't.

Does it in fact have a way to do so? Or did Wissota confuse estimated ROH with rocker radius?

[tstop4me]

The Wissota web page says it can also measure rocker radius.
But tstop4me said it can't.

Does it in fact have a way to do so? Or did Wissota confuse estimated ROH with rocker radius?

Comparing the Edge Specialties/Wissota H.D.I. gauge with the Skateology Rocker Radius gauge (http://www.iceskateology.com/Skateology/Rocker_Radius_Gauge.html), I now realize that the H.D.I. gauge can be configured to measure rocker radius [this is not presented in the instruction manual].  But you would need to first zero the gauge on a reference straight edge; use the gauge to measure a three-point arc height of the blade on the dial indicator; and then separately calculate a rocker radius from the appropriate trigonometric formula (you also need to measure the spacing between the guide pins and the tip of the dial indicator).  For this operation, the guide pins of the H.D.I. would need to rest on the edges (my photo in Reply #40 of https://skatingforums.com/index.php?topic=8632.25 shows the guide pins).  You would not get a direct reading of the rocker radius on the dial indicator of the H.D.I. gauge, however.  The Skateology site does mention that their original version of the rocker radius gauge also did not read the rocker radius directly on the dial indicator (which their current version does):  you took a reading on the dial indicator and then used a supplied graph to convert the reading to a rocker radius.  [Note:  With the H.D.I. gauge, you also do not get a direct reading of the radius of hollow (ROH).  You get a direct reading of the depth of hollow (DOH); measure the blade thickness separately with a micrometer or caliper; and then use the appropriate trigonometric formula to calculate the ROH.]

ETA:

* I'll have to do further calculations to determine whether the supplied dial indicator would work over the wide range of rocker radius common in figure skates (from ~8 feet in the main rocker to ~12 inch in the spin rocker). The supplied dial indicator has a full-stroke range of 0.125 inch, and the dial has a one-revolution (of the indicator hand) range of 0.040 inch (configured as 20-0-20 readings).  So the full stroke would correspond to 3+ revolutions.  Some dial indicators have a revolution counter, so you can read the absolute distance the dial indicator tip is depressed.  But the supplied dial indicator does not.  An electronic gauge with a zero button (as Kaitsu showed in one of his videos) would be a much better choice.

* Also, from taking a closer look at the H.D.I. gauge configuration right now, it's not clear to me how useful it would be for characterizing the spin rocker. 

[Kaitsu]

The gauge you have is labelled Sylvac, where as the Wissota (older name: Edge Specialties) tool is not. Did you replace the dial gauge, or is this a different tool altogether?

I did buy my H.D.I gauge without dial gauge as I didn't want to use inches as a unit in scale

Is there space to try adding compressible foam tape to the jaws, so it could be maybe used on blades with side honing?

In my case any tape tricks are out of the question. However I have special version of H.D.I gauge. I am not sure how many of these special models Edge Specialities were actually selling and is it anymore available when they sold it to Wissota. This special version does have spring loaded pins which should center the tool if blade sides are not be parallel. You can see in my video how well those pins work.

An HDI measurement will not correctly determine the ROH if the edges are significantly worn down (because they were skated on) - because the measured hollow depth will be less than on a freshly sharpened blade, right?

Correct

For that you would probably use a radius gauge that touches appropriately curved surfaces against the center of the hollow...

Correct

The Wissota web page says it can also measure rocker radius.
But tstop4me said it can't.

Does it in fact have a way to do so? Or did Wissota confuse estimated ROH with rocker radius?

It seems you have not read what has been replied to you earlier or you need to refresh your memory. Try to read following thread again.
http://skatingforums.com/index.php?topic=8573.25

Comparing the Edge Specialties/Wissota H.D.I. gauge with the Skateology Rocker Radius gauge (http://www.iceskateology.com/Skateology/Rocker_Radius_Gauge.html), I now realize that the H.D.I. gauge can be configured to measure rocker radius [this is not presented in the instruction manual].  But you would need to first zero the gauge on a reference straight edge; use the gauge to measure a three-point arc height of the blade on the dial indicator; and then separately calculate a rocker radius from the appropriate trigonometric formula (you also need to measure the spacing between the guide pins and the tip of the dial indicator).

Note that in H.D.I gauge dial gauge is not positioned symmetrically in the middle of the pins like in Sid gauge. In my opinion you will need a bit more complex calculations to get rocker radius even you would have described straight calibration piece. You need to ensure also that dial gauge is in the highest point of the edge and not either side of edge highest point. Dial gauge tip and pins has to have same contact line.

[Query]

So, an HDI gauge is also useful for something else: If there the HDI measurement yields a ROH that is larger than the true ROH at the center of the hollow, that would indicate the edge is worn down.


Edge evenness often creates edges of unequal sharpness.

In the real world, skaters measure "sharpness" in various ways that are harder to quantify. E.g.,

1. They feel the edge with their finger. Even if you don't create a foil edge, you can do that. In fact, I think it applies to almost any edged tool.

2. They skate. If they skid, or they otherwise have trouble holding an edge, it's not sharp enough.


Skating is also the ultimate way skaters use to measure edge evenness itself. E.g.,

If you skid on one edge, but not another, that may indicate edge unevenness - though that isn't the only possible cause.

If a properly aligned body weight creates skids, but an improperly aligned body does not, the edge might not be be sufficiently even. Unfortunately, that effect can also be created by nicks an edge which isn't aligned in the right direction (at the original sharpening, or by something that happened later, like a collision, or very strong stops).

BTW, some skaters adapt fairly quickly to uniformly slightly uneven edges, and may not be conscious of them. Perhaps it doesn't even matter much for those skaters, as long as they have sufficient time to adapt.

If as you roll down the blade while skating, the edge seems to push your body one way or another, that indicates a rather extreme form of varying edge unevenness. I've had that happen. Though, probably, unevenly aligned edges could do that too.

Again, if the blade skids near the center or near the ends, but not elsewhere, that might indicate the type of edge unevenness that a warped blade creates, if it was sharpened while warped. Though again, there are other possible cases.


I'm not sure if a blade could feel uneven if some parts of the blade were more sharp than others, but it is conceivable. It could certainly feel inconsistently even if the edge was aligned in one direction on one part of the blade, and another direction in another, or if our skating wore down one edge more than another.


Many of you love the idea of measuring sharpness and evenness using repeatable technical measurement methods, that can be performed in the shop, but the skater's world may be a bit different. Consistency and feel are often far more important than absolute criteria.


An edge checker is something a skater who is dissatisfied with the job a pro shop has done can bring to the pro shop to help explain why they are dissatisfied. Though, if the skater needs to do that, they should probably stay away from the pro shop altogether, or make sure they only use the best skate tech at the shop. A bad skate tech who makes uneven edges, or creates inconsistent sharpness, might do other bad things. If you need technical measurements to figure out what the skate tech is doing wrong, it is probably just best to avoid that skate tech, and maybe to assume that the whole pro shop is badly managed, and may deliver bad results in the future.


I think one of the most important things from skaters' point of view is to be able to talk to the skate tech who sharpens their blades before during and after sharpening, and to be able to give and get feedback, and understand what can and can't be done. I hated shops that kept the skater away from the skate tech, just like I hate auto repair shops where you talk to a customer rep instead of the mechanic, or you can't see what the mechanic is actually doing.

Honesty is also very important. If the skate tech pretends the blade was sharpened well, or pretends that the job done by a competitor was bad when it wasn't (extremely common - though sometimes occurs they just disagree on sharpening technique), or doesn't know the answer to a question but pretends to, that is very bad too.

It is a very good idea for a skate tech, especially one who is still perfecting their technique, to use an edge checker, or to analyze a problem a skater has told them about. It can also help a skate tech verify that their technique remains good, and some skate techs never reach the point of being able to produce good results without such tools.

It might be a good idea for a bad for a skater to use who wants to figure out why they are dissatisfied with a sharpening to use an edge checker. But edge checking isn't the whole story.

But I think skaters mostly need to pay attention to the way we feel the blade and our bodies interacting with the ice. And to treat the technical tools more as analysis teechniques than as the prime determinant. Of course, skaters who don't sharpen their blades, need to learn to be able to describe to the skate tech, things they want changed. And the shop needs to let them do that.

My conclusion: Sure, skaters should get and use simple measuring tools to check out their blades. Especially tools like this that don't cost much, are easy to carry with you, and can be applied quickly.

While you are at it, get a cheap radius gauge that lets you see if the skate tech has altered the ROH without being asked to. And trace and check the rocker profiles to see if they are changing over time - though if we don't feel a problem, maybe there isn't an important one. It would also be quite easy to use a ruler to measure the distance from the back toe pick to the point it touches on the rockered part of the blade, to feel whether the relationship of the toe pick to the rest of the blade has changed too much, making it too difficult to stay off the toe pick (there are special purpose tools for that, , but that's silly) - though that is a thing where the feel matters more than the technical measurement too.

[tstop4me]

Note that in H.D.I gauge dial gauge is not positioned symmetrically in the middle of the pins like in Sid gauge. In my opinion you will need a bit more complex calculations to get rocker radius even you would have described straight calibration piece. You need to ensure also that dial gauge is in the highest point of the edge and not either side of edge highest point. Dial gauge tip and pins has to have same contact line.

I have started a new thread to address this issue:  https://skatingforums.com/index.php?topic=8723.msg104512#msg104512

[tstop4me]

The HDI gauge clamps onto the sides of the blade.  The clamp is designed to clamp onto flat, parallel surfaces.  So it doesn't seat reliably on blades that (a) are tapered in thickness, (b) have a parabolic thickness profile, or (c) have a concave side-honed profile.  I'm not sure whether it will work with slimline blades or dovetailed edges.

Also, as I previously explained in https://skatingforums.com/index.php?topic=8632.25 Reply #40, it will not work with a blade having a chassis + runner construction (even if the runner has flat, parallel sides) if the depth/width of the runner is too small.  Note:  To avoid previous confusion, I'm not talking about the thickness of the blade (distance between inside and outside edges).  I'm talking about the distance measured along the side of the blade from the chassis-runner interface to the edge.

<<Emphasis added.>>  Update.  I just mounted a pair of MK Dance blades for a friend.  I took the opportunity to try my HDI gauge on the blades.  The slimline geometry of the blades does not allow the gauge to seat and clamp reliably.  So the stock HDI gauge does not work on MK Dance blades.

[Query]

So the stock HDI gauge does not work on MK Dance blades.

And I once thought it looked like a cool tool. Someday, if I can allow myself to waste the money I spent buying up Matrix I runners, I may go back to MK Dance, which I loved.

Actually it still looks like a cool tool. Just not as universally useful as one might hope.

[Kaitsu]

Example photo of poor sharpening. Your skates should NOT look like this when you use Low-Cost Basic Even Edge Checker.
99% of figure skates what this skate tech has sharpened are looking like this. Radius of hollow was also 11/16", so I believe they are terrible to skate.

[supersharp]

Example photo of poor sharpening. Your skates should NOT look like this when you use Low-Cost Basic Even Edge Checker.
99% of figure skates what this skate tech has sharpened are looking like this. Radius of hollow was also 11/16", so I believe they are terrible to skate.

Terrible!  The back is so far off that it should be easily visible upon inspection...if the person doing the sharpening bothered to check.  I've seen this when they just matched what was there, usually because they matched the factory "sharpening" which is generally done without any attempt to create level edges.

Skating on these blades would be torture.