Low-Cost Basic Even Edge Checker

[tstop4me]

BACKGROUND


We have had several discussions on tools for checking the evenness of edges.  These tools range from crude (e.g., a quarter or a popsicle stick used as a level indicator) to intermediate (e.g., a machinist’s square or a magnetic level indicator) to sophisticated (e.g., a Hollow Depth Indicator), with prices ranging from a few cents to about $260. As with most tools, there are compromises with respect to price, ease of use, accuracy, amount of information provided, and range of applicability [all tools will work on traditional blades with flat, parallel sides; but some tools will not work on blades with more complex geometries (e.g., tapered thickness, concave side hone, or chassis plus a small-width runner)].  In particular, note that neither a quarter nor a popsicle stick are machined flat; a quarter has fairly small dimensions and does not provide a long lever arm to magnify small differences in edge height; and both a quarter and a popsicle stick must either be carefully balanced across the inside and outside edges, or be carefully held in place with a fingertip.

A popular tool in the intermediate range is a magnetic level indicator; several manufacturers refer to them as a blade angle tester (BAT).  The better units comprise two components:  (1) a reference piece and (2) a test piece.  One typical example is the Wissota “Elite” Even Edge Checker ($129.99) (https://wissota.com/product/elite-edge-checker/).  On some units (including the Wissota Elite), the reference piece attaches with a magnet to the side of the blade and provides a reference horizon line for level edges; on some other units, the reference piece attaches to the blade with a clamp.  The test piece sits transversely across the inside and outside edges, and is held in place by a magnet.  The test piece provides a long lever arm to magnify small differences in edge height.  If the edges are level, the test piece will be oriented parallel to the reference horizon line.  If the edges are not level, the test piece will be oriented skew to the reference horizon line.  On some units (including the Wissota Elite), the reference piece has graduation marks to indicate how uneven the edges are; on some other units, the reference piece has no graduation marks.

With the Wissota Elite, and most similar units, the reference piece is designed to attach to traditional blades with flat, parallel sides; they typically do not work (well or at all) on blades with more complex geometries.  Paramount provides three different edge checkers; each with a specific reference piece designed to attach to a blade with a specific geometry.  The Paramount reference pieces have no graduations. [For more details, see the Paramount video “Sharpening & Leveling” at https://www.paramountskates.com/videos (3:15 onward).]

As a generic compromise that works with any blade (but provides less information), Wissota provides the one-piece “Basic” Even Edge Checker ($49.99) (https://wissota.com/product/universal-hockey-and-figure-skate-even-edge-checker/).  This tool is merely the magnetic test piece included in the Elite unit; there is no reference piece.  The user needs to visualize (eyeball) an appropriate reference horizon (depending on the particular geometry of the blade) and check the orientation of the test piece against the visualized reference horizon.  Essentially, the basic checker is a more accurate and easier-to-use version of a popsicle stick:  the test piece is machined flat; and the magnetic attachment provides for easier, more reliable, and hands-free positioning of the test piece across the edges.  But for that limited capability, the price tag is still about $50.


LOW-COST BASIC EVEN EDGE CHECKER


I will describe a basic even edge checker that’s just as good as (and, in some respects, superior to) the Wissota basic unit; and it costs only about $3 to $4, instead of $50.  It requires only two readily available piece-parts, no machining, and practically no assembly.  Due to the low cost, a skater can make multiple units to check uniformity of edge evenness along the length of a blade.

*  PIX 1. shows photos of common machinist's rules with a length of 6”/150 mm.  These rules are typically fabricated from magnetic stainless steel or magnetic chromed steel. 

*  PIX. 1(a) shows an example of a high-grade tool listed as a “flexible, spring-tempered” rule. The width is about .45” to .50”; the thickness is about .016” to .020”; and the weight is about 5 g to 7 g.  High-end units from major tool makers such as Mitutoyo and Starrett currently sell for about $10 to $30.  These will work for our purposes.  If you have one stashed in your tool chest, you can use it.  But since we will not be using the graduations, an expensive, high-end unit with precise graduations is not needed.

*  PIX. 1(b) shows an example of a generic pocket rule with the same nominal specs as above. These often have a removable pocket clip, as shown on the right; for our purposes, we will remove the pocket clip. Amazon and Home Depot carry some for less than $3 (at time of this post). E.g.,

Amazon:

https://www.amazon.com/Johnson-Level-Tool-7202-Contractor/dp/B00004T7ZU/ref=pd_bxgy_2/132-9064740-5922516?pd_rd_w=4Cl4T&pf_rd_p=6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_r=12E9NYPNSDRFR4R4XAYT&pd_rd_r=1fb4868b-56ae-4cc7-91a6-fa7fb68fea8b&pd_rd_wg=XsbIU&pd_rd_i=B00004T7ZU&psc=1

https://www.amazon.com/General-Tools-305ME-Precision-Stainless/dp/B00004T7T1/ref=sr_1_20?crid=3V8DGALWPWCUT&keywords=6%22+pocket+ruler&qid=1643572600&sprefix=6+pocket+ruler%2Caps%2C122&sr=8-20

Home Depot:

https://www.homedepot.com/p/Johnson-6-in-Stainless-Steel-Pocket-Clip-Rule-7202/204513472

https://www.homedepot.com/p/Empire-6-in-Pocket-Ruler-2730/202035324

I have several from brands such as Craftsman, Jensen, and General; I do not know what the original costs were, since I got them as freebies at trade shows over past years.  They are all flat when placed on a quartz reference plate.

* As a word of caution, do not purchase a rule as shown in PIX. 1(c). These are listed as “rigid”, rather than “flexible”.  The width is about .75”; the thickness is about .040”; and the weight is about 24 g. 

*  PIX 2. shows the other piece-part needed:  a small button magnet, which is attached over the center of the rule.  For our purposes, we do not want a supermagnet (which could strongly whack against sharp edges and damage them).  We want a fairly moderate magnet.  PIX. 2(a) shows an old Alnico shop pickup magnet (.69” diam X .63” high).  PIX 2(b) shows an el-cheapo ceramic bulletin-board magnet (.75” diam X .25” high).  Instead of the small cylindrical magnets shown, small rectangular magnets can be used.  If you don’t have a suitable magnet lying about, you’ll probably need to buy a pack; but the unit cost will be well under $1.  Note:  For a convenient, dedicated unit, the magnet can be permanently attached to the rule with a dab of glue; but, in practice, if you want to continue to use the rule for general measurements, the glue is not necessary.

*  PIX. 3 shows a top view of two units attached to a blade.  With a thin rule, the magnetic field penetrates the rule.  And with a lightweight rule, the magnetic field is sufficient to hold the rule firmly and reliably across the inside and outside edges.  No fingertip pressure is needed:  (a) proper alignment of the rule across the inside and outside edges is automatically maintained; (b) both of your hands are free to pickup the skate to orient the rule and blade for optimal viewing; and (c) multiple units can be attached along the length of the blade to check for variations in edge evenness. 

*  PIX. 4 shows a more frontal view of two units attached to the blade.

*  PIX. 5(a) and PIX. 5(b) show frontal views of the individual units.  In this instance, the blade is a Coronation Ace.  You would visualize a reference horizon orthogonal to the sides of the blade. In other instances, e.g., you would visualize a reference horizon orthogonal to a suitable reference surface, such as the side of a stanchion.


[Click on Photos to Enlarge]

[Bill_S]

Nicely done!

For a quick reference, I used just the "basic" part of the Wissota edge checker and sight just as you have described. This is the DIY version of that with a substantial savings.

[Query]

Also, am I wrong to assume the thin edge is more straight than the bendable flat sides are flat? So putting a metal rule on the side might be better.

So: use the first steel rule with the right angle sliding part
 
  https://www.amazon.com/Johnson-Level-Tool-7202-Contractor/dp/B00004T7ZU/ref=pd_bxgy_2/132-9064740-5922516?pd_rd_w=4Cl4T&pf_rd_p=6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_r=12E9NYPNSDRFR4R4XAYT&pd_rd_r=1fb4868b-56ae-4cc7-91a6-fa7fb68fea8b&pd_rd_wg=XsbIU&pd_rd_i=B00004T7ZU&psc=1

(or the 3rd or 4th one) but you put it on its side, instead of horizontal. Then you can use the sliding piece to check how square it is relative to the sides. You have to hold it, rather than use a magnet, to check, but you don't have to eyeball the right angle.

Maybe you could buy two, and bracket the blade with the sliding pieces from each, mounted on one rule.

(Note: I'm not sure if the sliding piece fits loosely. If it is loose, my idea won't work, because it will wobble.

If the blade is side honed, so the sides are not parallel and flat, the idea is to look to make the two side relationships symmetrical. Or you could just flip the tool around, and apply it to the other side, to try to make the relationship the same on both sides.

Of course, if the blade has twist warp, that won't help. But I think twist warp is less common than sideways warp.

BTW, I briefly tried something much cruder. I took a cheap dollar store square, and cut it down to size, to use like a precision square. Once again, since I don't trust the right angle on a tool so cheap, I applied it to both sides, and made sure any gaps were symmetric. I ended up with sharp edges where I cut it, but maybe I could have sanded the edges smooth.

The point of cutting it down was to reduce the weight. A big heavy square won't lay flat across the two edges. Otherwise I would have just used my calipers - the jaws are at right angles.

I suppose you could do the same thing with a somewhat more expensive square, whose right angle you trust better, as long as it is thin and light.

[tstop4me]

Also, am I wrong to assume the thin edge is more straight than the bendable flat sides are flat? So putting a metal rule on the side might be better.

Flatness is not an issue with the rules I’ve described when they are used as I’ve described.  The rules are lightweight, flexible, and spring-tempered.  If you flex them within the elastic limit, they will spring back to a flat shape.  The light weight means there is no significant sag when mounted as described.  Sure, if you abuse them, you can permanently deform them; but they will then be obviously bent.

So: use the first steel rule with the right angle sliding part
 
  https://www.amazon.com/Johnson-Level-Tool-7202-Contractor/dp/B00004T7ZU/ref=pd_bxgy_2/132-9064740-5922516?pd_rd_w=4Cl4T&pf_rd_p=6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_r=12E9NYPNSDRFR4R4XAYT&pd_rd_r=1fb4868b-56ae-4cc7-91a6-fa7fb68fea8b&pd_rd_wg=XsbIU&pd_rd_i=B00004T7ZU&psc=1

(or the 3rd or 4th one) but you put it on its side, instead of horizontal. Then you can use the sliding piece to check how square it is relative to the sides. You have to hold it, rather than use a magnet, to check, but you don't have to eyeball the right angle.

Maybe you could buy two, and bracket the blade with the sliding pieces from each, mounted on one rule.

(Note: I'm not sure if the sliding piece fits loosely. If it is loose, my idea won't work, because it will wobble.

The crossbar (opposite the actual clip) is provided so you can use the rule as a depth gauge.  But there is some play in the clip assembly; and the unit isn’t a good enough square for an edge checker.  If you use two clip assemblies as a clamp, the unit won’t be stable, because of the small contact surfaces:  too easy for the unit to flop over and fall off when you’re handling the skate.  But what’s the point?  Even if the clamps were more precise and secure, the rule would no longer automatically sit across the inside and outside edges; the alignment would be set by the clamps and the surfaces they clamp onto (and would primarily be limited to flat, parallel surfaces).

The unit I’ve described is intended only as a low-cost alternative to the Wissota basic even edge checker.  It’s not intended to be a low-cost alternative to a precision square.  If you prefer a square for your measurements, I would recommend that you buy a precision square.  As I've mentioned previously, every tool has its pluses and minuses.

If the blade is side honed, so the sides are not parallel and flat, the idea is to look to make the two side relationships symmetrical. Or you could just flip the tool around, and apply it to the other side, to try to make the relationship the same on both sides.

Not necessarily.  One rough approach is to visualize a flat side superimposed over the concave side.  Another approach is to follow Paramount’s lead:  assume the stanchions provide suitable reference surfaces (I have not personally checked out the validity of this assumption).  You can use a precision square at the stanchions to check that the edges are level at those spots.  If so, then you can place a magnetic level checker at one or more stanchions to serve as reference horizons.  You can then place another magnetic level checker at other positions along the blade and sight it against a reference horizon on the closest stanchion.  As I mentioned above, the cost of the unit I’ve described is so low that you can easily make multiple units (whereas the Wissota basic checker will set you back $100 for just two units).

[Kaitsu]

Good that you raised this topic. Often skates are selected with logic that blades and boots are skaters most important tools and therefore you can use quite a lot of money for them, even it hurts. When they have been purchased, people don´t often understand how important it is that they are also maintained and sharpened properly. Even the world best blades wont help you, if they are sharpened poorly. I would not trust to any skate tech, no matter if the skate tech would be 10 times world champion in the skating. As I have said several times, most of skate techs start to use shortcuts when they need to choose if the want to earn some money or do sharpening just for fun.

Method what tstop4me introduced is already so low cost that money should not be excuse for skaters to skip this inspection after every sharpening. You don´t necessary need to even buy steel rules and magnets. Just a regular plastic ruler used on the schools or even credit card can do the job. Note that your credit card magnet strip may not like strong magnet fields (if that strip is even used anymore anywhere). Steel rulers with magnets helps quite a lot to keep them on place. Its not so easy to balance rulers when blade is on the boot.

tstop4me already told one reason to avoid extreme strong neodymium magnet. Another reason to avoid these super strong magnets is that they leave residual magnet to the blades. When you sharpen blades, there is no doubt if they are magnetic. After grinding blades does have "punk style hair look". If magnets are too strong they may start to also warp your steel rulers. It happened at least to me even I used regular whiteboard magnets on rulers which were just 0.02" thick. 0.03" thick rulers worked better with the magnets I used. Diameter and flatness of the magnet may also affect.

After recording the video I noted that these thicker rulers had quite bad burrs on the edges. Check that before use so that they do not cause false results. Rulers has to be also quite close to 90 degrees angle on blade. You will see on video what happens if they are not. One purpose of my video is demonstrate how just eyeballing the blade cannot be accurate. Even you "extend" your 4mm thick blade with 200mm (8") ruler, its not so easy to judge by eye if ruler is in 90 degrees angle compared to the side surfaces. If skate is in skate holder, your skate holder may do this even more difficult. Some skate techs uses skate holder a kind of datum or kind of "second ruler". I have seen even instructions to use bubble level while skate is on skate holder. I tried that ones and never since that.

In the video you can also see some kind of accuracy comparison between the ruler and precision square. Even-though tstop4me instructions were very clear, this video may help someone to understand the idea of this inspection even more clearly. https://youtu.be/Mpmxw4-84ug

[Query]

I think the sightings along the blade - hopefully done in multiple places - is I think even more important than that the edges be level. You can adapt to a small amount of edge evenness. But if the edges sway back and forth, as you roll down the blade, that is harder to adapt to. Someone once sharpened blades for me that way.

Kaitsu, I know that isn't the point, but the topicks in the video you just provided are in terrible shape. Hard to believe that jumping can do that much damage. I guess I'm just not a strong enough jumper to do that!

Can you also come up with a method to align the blade with the leg, not the arbitrary bottom of the boot? Obviously, you might shim the blade mount to do that - but how do you know you have done it as correctly as possible? In other words, I want to align the force so the main bones are only compressed, not torqued, because bone (being made of materials like Calcium and Calcium carbonate) is less likely to fracture under compression (from jump take-offs and landings) than bending. (I assume of course that the skater approximately aligns their legs with gravity+centrifugal force.)

[supersharp]

Aligning the blade with the leg should be part of the mounting process.  Your tech needs to look at how you stand on and off the ice and shim inside the boot (under the insole) or under the blade (if there is not room inside the boot) until you can stand in a neutral position and be standing on both edges evenly (assuming your tech has sharpened your skates with level edges).  This can actually be quite complex and requires looking at how the skater stands on two feet and on one foot, and then seeing what works best in actual skating practice. If the blade isn't set up in a neutral position, you won't have equal access to tipping motions laterally and medially.  This is also why you want to be careful not to just attach the blade to the boot when there is a gap between the unmounted sole plates and the sole--most traditional blades are not torsionally stiff enough to resist twisting when the sole plates are screwed down.  The thinner the blade, the more likely they are to twist or pull into a curve.  Parabolic and side-honed blades have areas of thinner cross-section and I find them more likely to tweak out of alignment than parallel blades. 

Blades like Paramount and Matrix are wider above the blade insert, so they are less likely to experience twisting.  I have only sharpened Paramount blades for one skater, and I was able to use a square to check for levelness at the stanchions.  No one around here has Matrix blades, so I haven't sharpened any of those.

I use a precision square to check edge levelness, worth every penny I paid for it.  I actually have three--one that is getting a bit old but is still usable, one that is not adjustable and is oversized for some blade uses, but can be very handy for certain uses, and a newer adjustable one that I use all the time. 

[Kaitsu]

Another reason to avoid these super strong magnets is that they leave residual magnet to the blades. When you sharpen blades, there is no doubt if they are magnetic. After grinding blades does have "punk style hair look"

This is what I did mean. I used regular whiteboard magnets, but still its easy to detect where magnets has been. Not an issue from skating point of view but if you use Pro-Filer, this might not be wanted feature. In some circumstances it may cause small issues also for skate techs using power grinder / bat gauges.

[Kaitsu]

Kaitsu, I know that isn't the point, but the topicks in the video you just provided are in terrible shape. Hard to believe that jumping can do that much damage. I guess I'm just not a strong enough jumper to do that!

To me they look quite normal cross cut toe picks with small dents.

[supersharp]

They also look normal to me. I’m not sure where the perceived damage is.

[Query]

I'm looking at these images from individual frames of that video. It at least looks to me like the sharp edges on the toe picks have been rounded off, and roughed up.

BTW I assume you have an image viewer (like PaintShop Pro) that lets you zoom in to the image, almost to the point that individual pixels are visible.

Of course you can only see the roughness and rounding this because Kaitsu has done an incredibly good job of close up photography.

Do those look like normal toe picks to you?

[supersharp]

Yes, they look normal to me. Brands and models within brands vary, but the cross-cut toe picks are often a little amorphous.  The chrome plating seems to be less smooth than on blades with straight-cut teeth. Fortunately, the toe pick doesn’t need to be extremely smooth or sharp to do it’s job.

[tstop4me]

I'm looking at these images from individual frames of that video. It at least looks to me like the sharp edges on the toe picks have been rounded off, and roughed up.

BTW I assume you have an image viewer (like PaintShop Pro) that lets you zoom in to the image, almost to the point that individual pixels are visible.

Of course you can only see the roughness and rounding this because Kaitsu has done an incredibly good job of close up photography.

Do those look like normal toe picks to you?

* I know you're obsessed with high magnification.  But you should look up the terms "empty magnification"/"empty resolution".  At some point, merely blowing up an image will cause you to lose, not gain, information.

* When it comes to resolving features, particularly boundaries of 3D features, magnification by itself is not dispositive.  Particularly when it comes to resolving boundaries, excessive magnification can be deleterious.  There's the old adage, "You can't see the forest for the trees."  If you want to delineate the boundary of a forest on a surveillance map, you don't zoom in on a tree; or worse yet, on a leaf.

* You really need to be careful about other factors; e.g., angle of view, angle of lighting, depth of field, and contrast.  The video that Kaitsu cited in Reply #4 was intended to display the operation of a magnetic level checker.  For that purpose, which he accomplished very well, he optimized the imaging conditions. 

* You then zoomed in on details of the picks, for which the imaging conditions were not optimized.  Your enlarged frames show somewhat of a blurry, low-contrast mess; and you drew some conclusions from that.  In Reply #8, Kaitsu optimized the imaging conditions for details of the picks, and a far different story (picture) emerges.

[tstop4me]

This is what I did mean. I used regular whiteboard magnets, but still its easy to detect where magnets has been. Not an issue from skating point of view but if you use Pro-Filer, this might not be wanted feature. In some circumstances it may cause small issues also for skate techs using power grinder / bat gauges.

That's a really interesting result.  I should get some iron powder and see if my blades have any residual magnetism when used with my magnetic level checkers.  Somewhere in my basement, I have one or two degaussing coils stashed away.  I haven't needed them in ages, but I guess I should go find them.

[Query]

This is what I did mean. I used regular whiteboard magnets, but still its easy to detect where magnets has been. Not an issue from skating point of view but if you use Pro-Filer

Actually I'm not sure what you meant.

Why would magnetism be bad on the Pro-Filer. Do you think magnetism would interact with the tool? The Pro-Filer handle is aluminum - essentially non-magnetic. The stone - i.e., abrasive cylinder is probably a plastic resin, impregnated with diamond dust in the coarse case, and maybe something like Aluminum Oxide in the other (they don't say). In neither case would magnetism matter much.

Maybe a strong magnetic field could make iron/steel filings stick around, rather than fall off. I doubt that matters, but could be wrong. But I doubt the residual magnetic field from your whiteboard magnets have a strong enough field to significantly magnetize the blade or the filings.

If you instead mean that the force of the magnet creates little dents in the edge - that's obviously true. But that isn't going to affect the Pro-Filer tool.

OTOH, I like to create foil edges. I.E., I take the sharpening burr (which is typically bent sideways), and polish and re-align it to create my edge - a thin sheet of metal. Maybe  your magnets - or, for that matter, the force from a micrometer - might disrupt the structure of the foil edges a little, and make them more fragile. However, if the level checks and measurements are done BEFORE the burr is polished and re-aligned, I THINK the foil edge won't be much affected by the pressure, because the pressure is spread out over a larger area.

But some people create foil edges using powered sharpening machines too. Again, a few people use Blackstone flat bottom V edges, which are almost as fragile - and which are ground to shape in proper alignment. I suppose very strong magnets, or perhaps a micrometer, might make a slight indentation in those edges, though I'm not certain of that. But FBV edges are not very commonly asked for.

*You then zoomed in on details of the picks, for which the imaging conditions were not optimized.  Your enlarged frames show somewhat of a blurry, low-contrast mess; and you drew some conclusions from that.

I wasn't interested in the blurriness or low contrast. I was interested in the shapes of the picks - especially the boundaries between the nominally flat surfaces of the picks, which are supposed to dig into the ice. The look like the have been rounded off.

Since I don't jump much, perhaps I just don't appreciate how much wear and tear jumping places on the picks. Maybe that is normal. But it doesn't seem so to me.

If the edges on a toe pick are rounded off, it may be much less effective. That's why people sometimes re-sharpen toe picks too. Of course, that's a non-trivial thing to do. If your average level skate tech tried to do it, using a tyipcal powered sharpening machine, they might just make it even less effective.

If you want to delineate the boundary of a forest on a surveillance map, you don't zoom in on a tree; or worse yet, on a leaf.

I'm not completely going to agree with you there.

It might also depend what type of surveillance you are doing. E.g., do you want to estimate crop yield or crop health? That can have a huge affect on civilian government policy. Do you want to know where people or their machines can hide? Do you want to plot the best route for an invasion from the sea? Do you want to know what areas were flooded by a storm, and use that to plan relief efforts?

I used to do image processing and statistics work on radar (SAR) images, for the U.S. Navy. With the instruments we used, we couldn't see and weren't interested in individual leaves, but the statistical scattering characteristics that result from their presence and shapes can help you identify tree species, or other crop cover, as well as estimate tree or vegetation height. (Now there are published articles on super-resolution SAR. I wouldn't be surprised if some of them can see large leaves. For that matter, I never tried to look at palm trees, which have large leaves. Maybe they can be resolved.)

Again, if you want to create an elevation map, through interferometry (i.e., by looking at the relative wave phases from different viewing angles) the individual leave and tree features may not be relevant - but they help you identify corresponding areas in the two images. In particular, you might look at how to warp two images together to optimize larger area correlation coefficients. Elevation maps have a lot of applications in both the military and civilian world.

At one point I was asked to create a program which could do image segmentation (identified areas with similar statistical characteristics) on aircraft or satellite images, and generated maps, which could be used for various purposes. I don't know that anyone cared about the individual trees or other plants that might conceivably show up in such images, if the resolution was fine enough. But again, the statistical characteristics that result from such details to some extent underlie what is being done.

In the same ways, the very small details of shape on a toe pick, underlie how well it can punch into the ice surface.

[tstop4me]

I wasn't interested in the blurriness or low contrast. I was interested in the shapes of the picks - especially the boundaries between the nominally flat surfaces of the picks, which are supposed to dig into the ice. The look like the have been rounded off.

Since I don't jump much, perhaps I just don't appreciate how much wear and tear jumping places on the picks. Maybe that is normal. But it doesn't seem so to me.

If the edges on a toe pick are rounded off, it may be much less effective. That's why people sometimes re-sharpen toe picks too. Of course, that's a non-trivial thing to do. If your average level skate tech tried to do it, using a tyipcal powered sharpening machine, they might just make it even less effective.

Precisely.  If you're interested in the shapes of the toepicks, you need to delineate their boundaries, correct?  And you can't properly delineate their boundaries from a blurry, low-contrast image, correct?  Again, compare your blowups of video frames with Kaitsu's photo in Reply #8, specifically configured to reveal details of the toepicks.

[tstop4me]

Actually I'm not sure what you meant.

Why would magnetism be bad on the Pro-Filer. Do you think magnetism would interact with the tool? The Pro-Filer handle is aluminum - essentially non-magnetic. The stone - i.e., abrasive cylinder is probably a plastic resin, impregnated with diamond dust in the coarse case, and maybe something like Aluminum Oxide in the other (they don't say). In neither case would magnetism matter much.

Maybe a strong magnetic field could make iron/steel filings stick around, rather than fall off. I doubt that matters, but could be wrong. But I doubt the residual magnetic field from your whiteboard magnets have a strong enough field to significantly magnetize the blade or the filings.

If you instead mean that the force of the magnet creates little dents in the edge - that's obviously true. But that isn't going to affect the Pro-Filer tool.

* I bought my Pro-Filer ~2015/2016.  The diamond abrasive tool on my unit has a steel mandrel.  I just checked; a magnet sticks to it.  But that's not the point ...

* In Reply #7, Kaitsu concludes that, in his scenario, portions of the blade, when exposed to a magnetic level checker, can become sufficiently magnetized to retain metal particles ("swarf") generated during sharpening.  The question then is whether these retained metal particles clump sufficiently to interfere with attainment of a fine edge.  This issue could conceivably apply to a hand sharpener, such as the Pro-Filer, as well as a power sharpener.

* There are a lot of variables at play; e.g., the particular magnetic level checker (in particular, the magnetic field strength that penetrates the blade), the particular blade (in particular, the steel composition and how it's processed), how long the magnetic level checker is left in contact with the blade, and how the magnetic level checker is moved with respect to the blade.

* I have an HDI gauge, so I normally don't use a magnetic level checker on my own blades.  But I do keep a magnetic level checker in my kit bag to check out other skaters' blades.  Fortunately, as I previously discussed, I deliberately use a weak magnet to avoid whacking the edges.  I never thought about unintentionally magnetizing the blade and possible deleterious consequences.  But now that Kaitsu has raised the issue, I'll definitely check it out ... before offering to check any more blades.

[Query]

* I bought my Pro-Filer ~2015/2016.  The diamond abrasive tool on my unit has a steel mandrel.  I just checked; a magnet sticks to it.  But that's not the point ...

I just checked mine. It does interact weakly with a refrigerator magnet. (Because of what you said, I didn't let the magnet touch what you call a mandrel and I have called the abrasive cylinder. Maybe it would have interacted strongly if I did.) I was totally wrong to assume non-magnetic construction.

I also just checked an old Berghman sharpener. Both the cylinder holder and the springs look like ordinary steel. Not surprisingly it interacts strongly with a magnet.

Do powered sharpening wheels have iron cores?

A lot of powered sharpening machines them have what look like steel tables, which I suppose might become magnetized too, but I'm not sure. Has anyone here ever seen swarf clinging to a wheel or to a table?

* In Reply #7, Kaitsu concludes that, in his scenario, portions of the blade, when exposed to a magnetic level checker, can become sufficiently magnetized to retain metal particles ("swarf") generated during sharpening.  The question then is whether these retained metal particles clump sufficiently to interfere with attainment of a fine edge.  This issue could conceivably apply to a hand sharpener, such as the Pro-Filer, as well as a power sharpener.

He didn't mention swarf. He talked about a "punk style hair look", which you interpret that way. You might be right. But I thought he might mean indentations in the edge.

Do you believe that refrigerator strength magnets are strong enough to impose a significant magnetic field, in a few seconds, that would remain in the blade after the magnet is removed? I've seen a lot of skate techs, including very good ones, use magnetized level checking devices. It never occurred to me it could be a problem.

https://askinglot.com/is-440c-stainless-steel-magnetic says that 440 series stainless steels, like my blades are made of, can be magnetized. So maybe I should keep magnets away? I'm not sure.

I've only used non-magnetized level checkers, including Popsicle sticks, and plastic and steel straight edges and rulers - but without magnets. It is harder to balance them without magnets, and I've thought of adding some magnets - but if you think it is an issue, maybe not. The way I sharpen, reversing the orientations of the tool and the skates every few strokes, pretty much guarantees even edges, so I don't normally use level checkers anymore. But the way most powered sharpening tools that I've seen work, you would have to re-clamp the blade to reverse it, so that wouldn't be efficient.

It is obvious that Pro-Filer and Berghman tools might have a problem if a magnetic field caused steel filings remained in the space between the cylinder and the blade - because the filings could scratch the entire length of the blade.

Perhaps is less of a potential problem on powered sharpening machines with a rapidly rotating wheel, because the wheel would push the filings off, maybe even get the blade hot enough to destroy the field?

The HDI tool looks very cool. I wish I could figure out a cheap way to make something like it. Why don't you carry it with you in your skate bag, instead of metal rules and magnets? Are you worried it might get stolen, because it is a bit expensive?

[tstop4me]

He didn't mention swarf. He talked about a "punk style hair look", which you interpret that way. You might be right. But I thought he might mean indentations in the edge.

Do you believe that refrigerator strength magnets are strong enough to impose a significant magnetic field, in a few seconds, that would remain in the blade after the magnet is removed? I've seen a lot of skate techs, including very good ones, use magnetized level checking devices. It never occurred to me it could be a problem.

* We'll wait for Kaitsu to confirm, but ...

* He specifically mentioned issues with residual magnetization in the blade.  If he were concerned with indentations in the edges caused by a strong magnet whacking into the edges, the concern would not be residual magnetization in the blade. 

* Look at his photo in Reply #7.  Looks to me like swarf clinging to portions of the blade, not indentations in the edges.

* I would not be surprised by a supermagnet causing residual magnetization.  I am surprised by a bulletin board magnet.  However, the only way to find out whether I have a problem with my gear is to run a test.  I plan to order some iron powder.

The HDI tool looks very cool. I wish I could figure out a cheap way to make something like it. Why don't you carry it with you in your skate bag, instead of metal rules and magnets? Are you worried it might get stolen, because it is a bit expensive?

* It's expensive to carry around.

* It's bulky to cart around in a kit bag.

* It's sensitive to shock.  I don't want to have it in a place where it might easily get knocked to the floor.

* It doesn't work on all blades.

[Kaitsu]

Here are some new information...

The blade what I used to make edger checker video is same blade as I used in metal removal rate video. When I started to make metal removal rate test, I noted already in very first passes that steel dust was sticking into the points on the blades where the magnets had been a bit little longer. After every passes, steel dust was concentrated to the same spots. This didn't occur before edge checker test. Residual magnet is pretty familiar topic to me as I have made small investigation report at my work how much you need to have residual magnet so that steel particles starts to stick in to the parts. Based on this study we decided acceptance levels for parts residual magnetism. What I know, there is no any standard which would define acceptance criterion's. There are just some general recommendations which are very hard to reach even on raw materials.

Highers residual magnet levels concentrates typically in to the sharp edges / corners and from those you can probably find residual magnet even you would use demagnetize function.

As this forum does have quite limited file size limits, I uploaded higher resolution pictures to Dropbox

Residual magnet 2 picture is presenting the same blade which was used edge checker test and it has been taken when I started to make metal removal rate test. I have posted picture from the same blade also earlier in this thread. https://www.dropbox.com/s/jyzhniqnfl8fqob/Residual%20magnet%202.jpg?dl=0

Magnetism picture I did take from the cheap stainless steel blades which had very coarse "chrome removal" grinding. I tried to hone it manually more smoother. I have never touched with magnet to these blades. Here you can see the "punk style" concentration of steel dust. Higher the magnetism revels are, more punk hair style you can probably see.
https://www.dropbox.com/s/omfgdnu2tjm6mbg/Magnetism.jpg?dl=0

Answer to question why this would be problem for Pro-Filer users. Imagine that you should sand down some wooden block. You are doing the sanding and I will cover your wooden block with wheat flour powder after every stroke. How much you actually remove metal or are you just milling steel dust to smaller particles?

[Query]

* I would not be surprised by a supermagnet causing residual magnetization.  I am surprised by a bulletin board magnet.  However, the only way to find out whether I have a problem with my gear is to run a test.  I plan to order some iron powder.

I assume hope you won't run the test on your blades! Or on a blade holder used for sharpening. Or on your shop vice. Or anything that might matter to you if it collects swarf, or might induce a field on anything that might.

What types of blade does the HDI tool not work well with, and why?

It never occurred to me to worry about residual magnetization. I'm not an engineer, or a technician. I'm only a retired "scientific programmer", with a B.A. in physics from a liberal arts college, and I was never good at lab or shop stuff. I've written and used data acquisition and control system software, and software to analyze the results, but I didn't design, fully understand, or maintain the hardware. I've had to try to figure out a lot of things for myself, don't know everything, nor always think of what I should.

In this case, it sounds like some engineers don't think of everything either. A LOT of people use magnetized level checkers. And magnetized screwdriver tips. And power tools that generate magnetic fields. How far should we take this idea? Should we try to demagnetize all our iron and steel tools that don't rely on permanent magnets (like the motors in some power tools do)? Or the vehicle we carry our skates in. This could get ridiculously extreme.

I have seen people sharpen skates on sharpening machines without cleaning off the metal filings on the table the skate holders are pushed. I thought that was a bad idea, because the filings might scratch the blade, or cause the edges to be ground unevenly, and in an unpredictable manner. Plus, as Kaitsu says, it might make it harder to sharpen the blade is the first place, though that didn't occur to me. In retrospect, it might also be a bad idea to have a magnetized skate blade, or skate blade holder, or sharpening device, or vice... or anything.

Somewhere I have an old (audio) tape demagnetizer. Not sure that is strong enough for blades and tools.

[tstop4me]

What types of blade does the HDI tool not work well with, and why?

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.

[tstop4me]

I assume hope you won't run the test on your blades!

Of course not.  I plan to purchase a brand new pair of John Wilson Gold Seal Parabolic Revolution Blades (Custom Black Finish) as a test piece.

[Kaitsu]

You can see actual residual magnet levels from here https://youtu.be/jJcNrhtiIEI

[Query]

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.

Oh. Now I got it. 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.

Such a nuisance side honing and low clearance mounts make.

Wissota's pictures help me understand how the HDI tool is applied. Maybe(??) you could attach compressible foam tape to each side of the clamp, to overcome side honing problem, but if there isn't room for low clearance mounts, all you could do would be to risk modifying the tool, by shaving off the bottom of the clamps.