Skate Sharpening Advice - when there's no one local

[amy1984]

The long time figure skate sharpener in my area has closed up shop.  There are a couple of options around but nothing on the level he was.  I'm going to try a couple of others out but I just wanted to ask... What do those of you who don't have someone close by to sharpen your skates do?  Have any of you found a home option that actually works?  Do any of you mail out your skates?  I have a couple people within a hours drive who are by appointment but I have such a wonky schedule that this almost never works out for me.  There are a couple store front locations (with regular hours, which is great for me) that other skaters say are 'okay', which I will try, but I'm already trying to think of what other options there are when you're SOL in terms of someone local.  The closest really good sharpener I can think of is a two and a half hour drive away.

Have any of you successfully told a non-figure skate person 'how' you like your skates sharpened and been successful?  There are several really reputable hockey sharpeners in my area and they all say 'yah, we sharpen figure skates' until they see that they're not cheap skates from Canadian Tire and then they sort of balk at doing them because they know enough to know that they don't know how to sharpen an ACTUAL figure skate and they probably also know the cost of replacing the blade if they screw up   I feel that these sharpeners could do a good job but I just don't know enough myself to tell them what I want and I don't want to come across as telling someone how to do their job.  I found one hockey guy who did a great job on the edges but he, over time, left a lump right behind the toe picks because he just wasn't familiar with what to do with figure skates.  I'd go back but how do you bring this up in a way that isn't going to make someone defensive?  Also, a lot of hockey guys in my area seem to use flat bottom v and I'm not sure about mixing this with figure skates.

If it matters, I'm in central Canada.  Anything that ships to the US, I can get here.  Sorry, this is a bit of a ramble.

[Query]

DIY!

A good, consciencious person who is good with their hands, and who is willing to take the time and money, can learn. Since he already knows how to use the machine, it shouldn't take him too much time, with proper instruction from a suitable expert, to do the basics, especially if the sides of your blade are flat and parallel. (I.E., if you don't have parabolic, or thinner at the front or rear, or vertically side honed blades: I'm told that learning to handle those things well on a powered machine takes a lot of time.) "Mr. Edge" will train him to sharpen for $3500 in 3 days, and will teach him all the basics for $15000.

But if you can't DIY (Do It Yourself), I think you might have trouble teaching a good hockey skate tech what to do yourself.

If the hockey tech left a lump next to your toe pick, maybe he was being cautious, and not letting the grinding wheel anywhere near the toe pick. That's a lot better than rounding off the toe pick, or rounding off the back of the blade, as some hockey-only skate techs have done. If someone does either of those, you pretty much might as well throw away the blades.

But eventually the lump will interfere too much with figure skating. What he should do now is to compare the shape to a new blade of the same type, and match that profile. What you should have done was to trace the rocker profile of your new blades, and checked it yourself repeatedly.

How many sharpenings did it take to create a lump, and how large is it? A good figure skate tech, using a powered machine sharpener, only takes off about 0.003" (0.0118 mm) per sharpening. So if, for example, that lump is 0.1" high, and he never took off any metal next to the toepick, that should have taken about 0.1 / .003 = 33 sharpenings. If it took significantly fewer sharpenings than that, he is taking off too much metal, and you will need new blades much sooner than you should, costing you more money. That's acceptable for hockey blades, because hockey play puts deep gouges in blade edges, and hockey blades cost less to replace.

Have you talked to other good figure skaters about what to do? How far are you from the nearest good figure skate tech? Can you carpool there with other figure skaters, or ask a good tech to drive to your area once in a while to sharpen all of your skates at the same time?

[tstop4me]

The answer will partly depend on what blades you have, in particular whether they are parallel, tapered, parabolic, dovetailed, sidehoned.  What make and model blades do you have?  I'll look up their geometry.

[tstop4me]

With sufficient sharpenings with a standard longitudinal wheel, a "lump" next to the bottom pick will eventually develop because the wheel can't access the region immediately adjacent to the bottom pick.  Properly trained and equipped figure skate sharpeners touch up the region near the toepick (when needed) with a cross-grinder, which can get right up to the toepick.  Not all shops have this capability.

[amy1984]

The answer will partly depend on what blades you have, in particular whether they are parallel, tapered, parabolic, dovetailed, sidehoned.  What make and model blades do you have?  I'll look up their geometry.

I have Ultima Legacy blades.  Nothing special about them - not tapered or anything.

[amy1984]

How many sharpenings did it take to create a lump, and how large is it? A good figure skate tech, using a powered machine sharpener, only takes off about 0.003" (0.0118 mm) per sharpening. So if, for example, that lump is 0.1" high, and he never took off any metal next to the toepick, that should have taken about 0.1 / .003 = 33 sharpenings. If it took significantly fewer sharpenings than that, he is taking off too much metal, and you will need new blades much sooner than you should, costing you more money. That's acceptable for hockey blades, because hockey play puts deep gouges in blade edges, and hockey blades cost less to replace.

Have you talked to other good figure skaters about what to do? How far are you from the nearest good figure skate tech? Can you carpool there with other figure skaters, or ask a good tech to drive to your area once in a while to sharpen all of your skates at the same time?

I don't think me getting equipment and learning how to sharpen is going to happen anytime soon, especially considering the cost.

I can't quite remember how long it took for the lump to form.  A handful of times, I would guess.  It was fixed pretty easily by my now retired sharpener.  I don't use these blades anymore for other reasons, so it's no longer an issue.

I have talked to some other skaters.  One of the main clubs in my area has someone who gets sent skates by a coach and does them, and then sends them back to the rink with the coach.  The only problem I have is that I am only at the same rink as this coach once a week so I run into times where I don't have my skates - ie: send my skates with her one day, then have a skating day or two where she's not there (so no skates) and then I see her again the next week.  There's another person who takes appointments and is out of town but only by about 1/2 a hour.  Unfortunately, I have a difficult time fitting my schedule in with when he's available.  There's a good sharpener/tech about a 2 hour drive away.  There's one other local option, but it's a business that seems to have been bought by someone new... the original guy is no longer there.  I'm going to try that one out and see how it goes.  The original owner did figure skates.

[amy1984]

With sufficient sharpenings with a standard longitudinal wheel, a "lump" next to the bottom pick will eventually develop because the wheel can't access the region immediately adjacent to the bottom pick.  Properly trained and equipped figure skate sharpeners touch up the region near the toepick (when needed) with a cross-grinder, which can get right up to the toepick.  Not all shops have this capability.

This is exactly what happened.

[Query]

I don't think me getting equipment and learning how to sharpen is going to happen anytime soon, especially considering the cost.

The cost of the most common current hand tool is $90, with shipping - and there is an old used tool you can get for much less if you can stand 1/2" ROH. You would need to spend $10 - $100 on other tools. Considering the cost of driving, and the savings from probably grinding away less metal, it probably saves you money in the long run. But there is a substantial learning curve, which mostly occurs by learning from your mistakes. At least that is how I learned.

1/2 hour to 2 hours is well within what a lot of people drive to get skates sharpened well.

There are even skaters who ship their blades or their entire skates to their preferred skate tech. (They either have a spare pair, or they use overnight express mail, both ways, to complete the process in one day.) I spent a few months watching an expert skate tech one day a week, who had a lot of such clients. They spent substantially more on shipping than on sharpening. I think there are other experts who specialize in doing that. (BTW, you have to know what you are doing to unmount and remount blades without damaging the screw holes.)

Oh, and some expert skate techs don't cross grind next to the toepick; they just carefully grind as close as they can to the toepick. Because of toepick geometry, that part of the blade never touches the ice, except perhaps during high jumps. But it requires time, care and fine motor control to come that close. It's easier to handle that area with hand tools.

It's basically up to you what you want to do.

[Ethereal Ice]

1/2 hour to 2 hours is well within what a lot of people drive to get skates sharpened well.

My sharpener is two hours from my home. I would do two and a half, even three if we had to. I am a newer skater and got very frustrated with the first few sharpenings I had at our pro shop as I was literally unable to skate after each one, I won't get too specific but something was quite off about them even after I got used to then and they dulled a bit but I thought it was me being a bad skater. I also stated to discover that nobody I met that skated there regularly seemed to get their skates sharpened there, but they were very vague about where they actually went. On my own I found my sharpener at a far away rink I had skated at as a kid, and lo and behold, after he sharpened my skates not only could I skate on them right away but I was able to do some really basic moves that I had been struggling with for ages. I later found out that the whole thing at my rink was basically political, and I did get the name of the mystery sharpener, but frankly, I was so irritated by the whole thing and so pleased by my sharpener's work that I have stayed loyal. We plan to make the trip down every 1.5-2 months usually 30-40 hours on my blades for me, 30 is where I get when I start noticing a need and we start planning the drive. Some things are worth the effort and right now I am very comfortable with my sharpener.

[tstop4me]

(1) Yeah, getting proper sharpening for figure skates is a real pain.  Even in major metro areas in the States, the demand for good sharpeners often far outstrips the supply.  Costs mount up quickly if you skate frequently, or if you have two or more skaters in the family.  Even if cost is not an issue, inconvenience and timely scheduling often are.  In the shops I've done business with, there's usually only one guy that does decent work on figure skates.  If he's out for whatever reason, you're out of luck until he returns.  Even if you have access to another decent sharpener in the area, the results will probably feel different, due to differences in machines and operator technique.

(2) For hand sharpening, there is the Pro-Filer, which I, and several other forum members here, use.  Info can be found on their website:  http://www.pro-filer.com/profiler/.  Bill_S has a good write-up on his website:  http://www.afterness.com/skating/profiler.html.   The unit works well on parallel blades (although the instructions state they can be used on parabolic blades).  The price is US$79.95.  You'll need to contact the company for shipping charges to Canada; I believe you could be hit with customs as well; so get a good estimate of the total cost.  I once saw an ad for a Canadian distributor, but I can't find it now.

A few considerations:

(a) The stock guide block has a throat opening of 0.170 in.  You then need to allow for a layer of tape on each side of the blade plus clearance for sliding the guide block.  That effectively means that the maximum permissable thickness of the blade is 0.164 in. The unit uses the sides of the blade as guides.  For good results, the thickness of the blade should be uniform within 0.003 in (that is, the difference between the maximum and minimum values should be 0.003 or less) along the full length of the blade (pick to heel).  So if you consider this option, first check your blades with an accurate micrometer or caliper.

(b) Unlike standard shop power sharpeners, Pro-Filers do not have the capability for varying the radius of hollow (ROH) with a single unit.  Each kit has a fixed ROH.  For figure skates, you can get kits with the following ROH values:  1/2", 7/16", 3/8", 5/16".  Note:  As discussed in a recent post (http://skatingforums.com/index.php?topic=7339.0), however, the kits for 3/8" and 7/16" are in fact identical except for the label.  Further note that the actual ROH will depend on the blade geometry and the operator skill.  With the 3/8"|7/16" kit, my actual ROH varies from 7/16" to 1/2".

(c) If you decide to go the Pro-Filer route, there are several of us here that can provide you with helpful hints on how to get good results.  It's best to practice on old blades first.  But, since the removal rate is slow, it's not likely that you will damage blades beyond repair by a decent skate tech (if you can find one, that is).  Just be warned that there is a learning curve; not a simple matter of unboxing the kit and going at it.

(3)  Here's a recent post concerning home power sharpeners in the US$1000 – 2000 range:  http://skatingforums.com/index.php?topic=7239.0.  In my area, the cost for sharpening figure skates runs US$20-30.  If you sharpen monthly (and especially with two or more skaters in the family or group pool), the price is reasonable.  But, requires space, power, and operator skill.  And, if you goof, you can destroy your blades in one shot.

[Query]

There is a huge learning curve to use the powered sharpening machines. I haven't mastered them myself, though I tried for a few hours.

[riley876]

Luckily flogged out figure blades (to practice on) are essentially free.

[amy1984]

(1) Yeah, getting proper sharpening for figure skates is a real pain.  Even in major metro areas in the States, the demand for good sharpeners often far outstrips the supply.  Costs mount up quickly if you skate frequently, or if you have two or more skaters in the family.  Even if cost is not an issue, inconvenience and timely scheduling often are.  In the shops I've done business with, there's usually only one guy that does decent work on figure skates.  If he's out for whatever reason, you're out of luck until he returns.  Even if you have access to another decent sharpener in the area, the results will probably feel different, due to differences in machines and operator technique.

(2) For hand sharpening, there is the Pro-Filer, which I, and several other forum members here, use.  Info can be found on their website:  http://www.pro-filer.com/profiler/.  Bill_S has a good write-up on his website:  http://www.afterness.com/skating/profiler.html.   The unit works well on parallel blades (although the instructions state they can be used on parabolic blades).  The price is US$79.95.  You'll need to contact the company for shipping charges to Canada; I believe you could be hit with customs as well; so get a good estimate of the total cost.  I once saw an ad for a Canadian distributor, but I can't find it now.

A few considerations:

(a) The stock guide block has a throat opening of 0.170 in.  You then need to allow for a layer of tape on each side of the blade plus clearance for sliding the guide block.  That effectively means that the maximum permissable thickness of the blade is 0.164 in. The unit uses the sides of the blade as guides.  For good results, the thickness of the blade should be uniform within 0.003 in (that is, the difference between the maximum and minimum values should be 0.003 or less) along the full length of the blade (pick to heel).  So if you consider this option, first check your blades with an accurate micrometer or caliper.

(b) Unlike standard shop power sharpeners, Pro-Filers do not have the capability for varying the radius of hollow (ROH) with a single unit.  Each kit has a fixed ROH.  For figure skates, you can get kits with the following ROH values:  1/2", 7/16", 3/8", 5/16".  Note:  As discussed in a recent post (http://skatingforums.com/index.php?topic=7339.0), however, the kits for 3/8" and 7/16" are in fact identical except for the label.  Further note that the actual ROH will depend on the blade geometry and the operator skill.  With the 3/8"|7/16" kit, my actual ROH varies from 7/16" to 1/2".

(c) If you decide to go the Pro-Filer route, there are several of us here that can provide you with helpful hints on how to get good results.  It's best to practice on old blades first.  But, since the removal rate is slow, it's not likely that you will damage blades beyond repair by a decent skate tech (if you can find one, that is).  Just be warned that there is a learning curve; not a simple matter of unboxing the kit and going at it.

(3)  Here's a recent post concerning home power sharpeners in the US$1000 – 2000 range:  http://skatingforums.com/index.php?topic=7239.0.  In my area, the cost for sharpening figure skates runs US$20-30.  If you sharpen monthly (and especially with two or more skaters in the family or group pool), the price is reasonable.  But, requires space, power, and operator skill.  And, if you goof, you can destroy your blades in one shot.

Thanks very much for all the info!  I think I'm going to look into the pro filer to buy myself some time between sharpenings and then probably find another person in the general vicinity of the city I live in to either ship to or drive to less often than I visited my regular sharpener.  It's funny how something so small can really throw you off.  When I saw he'd retired I almost had a heart attack!

[mamabear]

You may also be able to send your skates with someone else visiting the sharpener that is a few hours away.  I know that recently more people in our club have been posting or texting other club members when they are making the drive (most of us drive to one of the skate shops that is 3 hours away) so they can take additional pairs of skates if needed. 

[fsk8r]

My preferred skate sharpener is about 90min each way and he offers that if you take 5 pairs of skates, the drivers skates are free. I've always offered to take other people's skates this me as it makes sense to have a car load.
At one point I tried to start a facebook group to get a rota going, but I've discovered that people generally don't manage to plan these trips  in advance, or if they do they very rarely give notice so you can get your skates to them.
These days as I'm getting fed up that I'm so often taking other people's skates and no one ever takes mine, I go out of my way to get my skates to anyone who happens to say they're going to just try to encourage them to take a few extra pairs.

[tstop4me]

Thanks very much for all the info!  I think I'm going to look into the pro filer to buy myself some time between sharpenings and then probably find another person in the general vicinity of the city I live in to either ship to or drive to less often than I visited my regular sharpener.  It's funny how something so small can really throw you off.  When I saw he'd retired I almost had a heart attack!

If you plan on ordering the Pro-Filer directly from Edge Specialties (the manufacturer), then I would recommend that you order their Hollow Depth Indicator (HDI) at the same time (http://www.pro-filer.com/hdi/).  This is a handy tool for quantitatively measuring evenness of edges and radius of hollow (ROH).  Note:  This tool actually measures the depth of hollow (DOH) [vertical distance between edges and bottom of hollow].  You need a separate micrometer or caliper to measure the thickness of the blade.  From the two measurements, you can calculate the ROH.  Yeah, it's pricey (US$249.95 + shipping).  But if you're hand sharpening and going to one or more pros, it's worth it to find out what the end results are.  Well built and very easy to use.

[Bill_S]

Even though I own a Pro-Filer (actually, a number of them) and have access to a lot of measurement tools, I wouldn't go as far to recommend a purchase of something like their expensive gauge. Someone can use a Pro-Filer all by itself and get good edges if they just pay attention  to technique and are patient. They certainly won't wreck a blade by using a Pro Filer per instructions.

As far as measuring precise ROH, there are times that I believe it's a bit over rated. Pick something middle-of-the-road like the 1/2" unit and get used to how it feels. Sharpen for 15 minutes per blade once per month, and you should be just fine.

[Query]

The depth guage is a bit expensive.

A cheaper tool would be a set of "radius gages", "fillet gages" or "feeler gages" - all of which are just curved lengths of metal that you fit against the hollow. (You want an "inside" radius or fillet gage" set.

I have seen a single piece of metal that has little pieces that match each of the common skate ROH, but I don't know where to find it.

As a cheap approximation, you can use coins, e.g., according to Wikipedia,

1. A U.S. quarter has a .4775" radius, a little less than 1/2"

2. A U.S. nickel has a .4175" radius, between 3/8" and 7/16"

3. A U.S. penny has a .375" radius, exactly 3/8"

4. A U.S. dime has a .3525" radius, between 5/16" and 3/8"

So,

1.  If your blade has a ROH over 1/2", a U.S. quarter will fit inside the hollow (across the blade), with a little space between the quarter and the center of the hollow width.

2  If your blade has a 1/2" ROH, a U.S. quarter should fit inside the hollow (across the blade), with a little space between the quarter and the sides of the hollow width.

3. If your blade has a 7/16" ROH, a U.S> quarter would fit with a little space between the quarter and the center of the hollow width, but a U.S. nickel would fit with a little space between the nickel and the sides of the hollow width.

4. If your blade has a 3/8" ROH, a U.S. penny will fit precisely against the hollow.

5. If your blade has a 5/16" ROH, a U.S. nickel would fit with a little space between the nickel and the center of the hollow width, but a U.S. dime would fit with a little space between the dime and the sides of the hollow width.

Hope I did that all right...

[tstop4me]

A cheaper tool would be a set of "radius gages", "fillet gages" or "feeler gages" - all of which are just curved lengths of metal that you fit against the hollow. (You want an "inside" radius or fillet gage" set.

Have you actually used a set of radius gauges against a skate blade?  I have a set of precision radius gauges as part of my overall toolkit (not specifically for skates).  For freestyle blades, the blade thickness typically falls in the range of .150 to .170 in.  Visually distinguishing differences in arcs with different ROHs ranging from 3/8" to 7/16" to 1/2", when the arcs are constrained to a chord length of .150 to .170 in, is extremely difficult because the differences are inherently small to begin with.  Furthermore, radius gauges are typically made from thin plate (mine are 1/32" thick hardened and ground steel plate), so properly aligning a gauge against a blade is also difficult. 

You need to check the ROH at multiple sites along the length of the blade.  If you simply hold the boot in one hand and the radius gauge in the other hand, very tricky.  I clamped the boot down in a jig, and mounted the radius gauge on an adjustable arm to steady the measurement setup, and backlighted the radius gauge and the section of the blade it was resting on with a small flashlight.  Better results this way, but not a convenient setup, and still not satisfactory.

Also, radius gauges won't measure how uneven the edges are (differences in height between the inside and outside edges).  The HID gauge will (.001 in increments, estimates to nearest .0005 in).  The usual squares and wobble sticks will give you quick visual indication that the edges are way out of whack, but not quantitative measurements, and not such small differences.  AgnesNitt recently posted that she dumped one sharpener because her edges were uneven by .001 in.  I'm not that demanding.  The guys at Wissota say that a difference of .001 in is acceptable, but a difference of .003 in is not [they didn't say how they arrived at that conclusion; but, for now, I'll accept it]; .003 in is difficult to measure without proper instrumentation.

[Query]

Have you actually used a set of radius gauges against a skate blade?

Yes.

Visually distinguishing differences in arcs with different ROHs ranging from 3/8" to 7/16" to 1/2", when the arcs are constrained to a chord length of .150 to .170 in, is extremely difficult

It isn't just visual You physically touch one curve against the other. You can look for gaps, against a light. But it also feels different for radii that are bigger or smaller than the gage size, if you roll the gage against the blade. In particular, in one case, there are two clicks, as you move from side to side, whereas in the other case, it rolls continuously.

As best I understand, feeler gages (occaisionally spelled "guages") of various types have a long history in precision metal shop work. For example, though I don't know the details, auto mechanics do something inside brakes using these tools, and I think they also use them to measure rebuilt combustion cylinder diameters.

Likewise, "rocker bars", which are cut to specific radii, are a type of feeler gage used to check rocker radii on skate blades. Companies like Edge Specialties sell them. They are used along the blade in much the same way as radius gages are used across the blade. You can detect fairly small curvature deviations. Similar devices play a roll for checking the curvature of real and model train tracks.

You need to check the ROH at multiple sites along the length of the blade.

You could. Can you think of an easy way for even an inexperienced skate tech to accidentally vary ROH along the blade? There are a few very badly designed hand tools that don't lock in ROH, but other than that, unless a skate tech was deliberately varying ROH - not very common at all - I don't see how it could happen. Oh wait. You could use a new ROH, and only sharpen half the blade. Not a common error.

Also, radius gauges won't measure how uneven the edges are (differences in height between the inside and outside edges).

True.

Is there a practical way for an HDI gage to do so? (I haven't used one.) If you just use the HDI gage as a micrometer, to measure the distance from each edge to the top of the blade, you are trusting the top of the blade to be uniform across and square to the sides. You could try to use a precision square to check that the edges are the same height relative to a right angle from one of the sides - but that's not quite right either, because blade are often warped. You really need to sight flat pieces across different parts of the blade to do it right. I like popsicle sticks , though magnetized flat metal strips are easier to balance. Some fancier sighting tools help you measure the edge height difference. But that is getting into a price ranges more appropriate to a professional skate tech than a single skater.

[tstop4me]

Even though I own a Pro-Filer (actually, a number of them) and have access to a lot of measurement tools, I wouldn't go as far to recommend a purchase of something like their expensive gauge. Someone can use a Pro-Filer all by itself and get good edges if they just pay attention  to technique and are patient. They certainly won't wreck a blade by using a Pro Filer per instructions.

As far as measuring precise ROH, there are times that I believe it's a bit over rated. Pick something middle-of-the-road like the 1/2" unit and get used to how it feels. Sharpen for 15 minutes per blade once per month, and you should be just fine.

Bill, in your circumstance, you use only the Pro-Filer, and you are proficient with tools (that is, you have a good feel for what you are doing), so you can get by without a specialized gauge such as the Hollow Depth Indicator (HDI).  In fact, most of the sharpening pros I've dealt with don't use much of any instrumentation to check their results (only one was really fastidious about measurements).  But here are two instances in which purchase of the HDI is justified.

(1) When I first started practicing with the Pro-Filer on old blades, I found that I was consistently getting uneven edges.  As measured with the HDI, one edge was consistently .002 - .003 in higher.  Based on this result, I realized that I had to more frequently flip the blade to even things out.  I now get edges within .001 in or better.  AgnesNitt recently posted that her skate sharpener told her that she was killing her inside edges with her Pro-Filer.  Not exactly sure what that means.  But measurements would confirm improper sharpening technique and provide a diagnosis for remedial action.

(2) Some people use a Pro-Filer for touch-ups in between major sharpenings by a skate pro (sometimes by different pros), so an HDI is very useful for checking consistency. 

I got more involved with measurements, because (like several others here) I'm trying hard to execute a decent scratch spin.  I noticed that when my blades were freshly sharpened by a pro, I'd be able to hook the spin.  But after about two weeks (~15 hrs skating time), I'd start to have problems getting a good hook.  I'd then hand hone the blades with a honing steel to get a sharp edge again, and the hook would be better, but not quite as good as with freshly sharpened blades.  I then noticed that with my last couple of sharpenings, the hook wasn't as good and didn't last as long.  Same sharpener; same specified ROH (7/16").  I suspected something wrong with the ROH.  I bought the HDI.  I had an old pair of blades that had been freshly sharpened and used only a couple of times before I bought a whole new set of boots and blades.  The measured ROH was close to the target 7/16".  I measured the ROH (on my new blades) right after sharpening; the ROH was nearly 9/16".  So, either the calibration on the machine had slipped, or the sharpener was not dressing the wheel frequently enough.  I dropped that sharpener, and found a different guy.  Close to target ROH, and hook returned.  Meanwhile, I find that my Pro-Filer (nominally a 7/16" kit, really a 3/8" kit) is actually giving me something closer to 1/2" ROH, and hook is not as good.

And to put the price in perspective, I see lots of little girls running around with Zuca bags and Kiss 'n Cry totes.  That's ~$200 worth of gear right there.

[tstop4me]

I'll refrain from an extended general discussion of gauges.  Not of interest to most readers here.  Though I do have a couple of key comments that I'll defer to a later post.  Here, I'll focus on two issues of direct relevance to skate blades.


(1)

You could. Can you think of an easy way for even an inexperienced skate tech to accidentally vary ROH along the blade? There are a few very badly designed hand tools that don't lock in ROH, but other than that, unless a skate tech was deliberately varying ROH - not very common at all - I don't see how it could happen. Oh wait. You could use a new ROH, and only sharpen half the blade. Not a common error.

You're assuming that the ROH of the blade is entirely set by the radius of the tool (where the tool refers to, e.g., the grinding wheel for a power sharpener or the stone for a Pro-Filer).  Under ideal conditions, there is deliberate movement of the tool along the longitudinal axis (direction of pick to heel) of the blade and along the normal axis (direction of the depth of the hollow) of the blade, but no deliberate movement of the tool along the transverse axis (direction of inside edge to outside edge) of the blade.  Under these ideal conditions, the assumption is valid:  if the radius of the tool is fixed throughout the sharpening operation, the ROH of the blade should not vary with position along the blade.

In actual practice, however, the ideal conditions are not satisfied, and the assumption is not valid.  Non-deliberate, unintentional transverse movement of the tool with respect to the blade will effectively cause an increase in the ROH of the blade.  Uniform transverse movement would cause a uniform increase.  Nonuniform transverse movement would cause a nonuniform increase.  [This is a simplified discussion, nonuniform movement along other axes will also cause problems.]

So what are sources of transverse movement?  For the Pro-Filer, the primary source of transverse movement is wobble.  The Pro-Filer centers the tool transversely via a guide block that slides along the sides of the blade (typically covered with tape to control the clearance between the guide block and the sides of the blade and to protect the sides of the blade from scratches).  The degree of wobble depends on the clearance [decreasing the clearance decreases the wobble, but too small a clearance will cause the guide block to snag; also, the clearance can vary along the length of the blade because the thickness of the (taped) blade can vary].  The degree of wobble will also depend on the skill of the operator (i.e, maintaining a steady stroke and even pressure along the contour of the blade).

For a grinding wheel, the primary source of transverse movement is chatter.  Chatter is caused by vibrations from the motor and by rebound when the grinding wheel contacts the blade.  The degree of chatter depends on the equipment (including, but not limited to, the motor, frame, guide bed, grinding wheel, bearings, and skate holder).  The degree of chatter will also depend on the skill of the operator (i.e, maintaining a steady stroke and even pressure along the contour of the blade); variations are likely to be the highest where the contour changes the most (near the pick and near the heel).  With the HDI gauge, I checked the ROH of blades freshly sharpened by a local tech (target ROH:  7/16"; measured ROH:  7/16" to 9/16").

By the way, another reason to check the blade at different spots is because the unevenness of the edges can vary with location.  For a power sharpener, this will easily happen if the skate holder is not properly aligned with the grinding wheel.


(2)

Is there a practical way for an HDI gage to do so? (I haven't used one.) If you just use the HDI gage as a micrometer, to measure the distance from each edge to the top of the blade, you are trusting the top of the blade to be uniform across and square to the sides. You could try to use a precision square to check that the edges are the same height relative to a right angle from one of the sides - but that's not quite right either, because blade are often warped. You really need to sight flat pieces across different parts of the blade to do it right. I like popsicle sticks , though magnetized flat metal strips are easier to balance. Some fancier sighting tools help you measure the edge height difference. But that is getting into a price ranges more appropriate to a professional skate tech than a single skater.

The HDI gauge measures the difference in height of the edges directly.  It is essentially a miniaturized version of the setup that Bill_S used to measure rocker radius (can't find his post right now).  In Bill's setup, the dial indicator is fixed, and the blade moves longitudinally.  In the HDI gauge, the blade is fixed, and the dial indicator moves transversely.  The HDI gauge is basically a dial indicator (.001 in graduations, estimates to nearest .0005 in) mounted on a precision sliding stage.  The HDI gauge is designed to clamp onto the sides of the blades such that the stage slides along the transverse axis.  You first slide the gauge such the contact point of the dial indicator rests on the first edge (inside or outside); zero the reading by rotating the dial; and then slowly slide the dial indicator across the hollow to the second edge.  The lowest negative reading encountered along the travel is the depth of hollow (DOH).  The reading at the end of the travel tells you the difference in height [high (positive) or low (negative)] of the second edge relative to the first edge.  I haven't tested the accuracy of the dial indicator itself.  But I have attached the HDI to a precision rectangular gauge block (simulates a blade with a precision flat grind):  barely perceptible movement of the needle as I slid the contact point across the reference surface.

[tstop4me]

This post has no info specific to skate blades.

As best I understand, feeler gages (occaisionally spelled "guages") of various types have a long history in precision metal shop work. For example, though I don't know the details, auto mechanics do something inside brakes using these tools, and I think they also use them to measure rebuilt combustion cylinder diameters.

Likewise, "rocker bars", which are cut to specific radii, are a type of feeler gage used to check rocker radii on skate blades. Companies like Edge Specialties sell them. They are used along the blade in much the same way as radius gages are used across the blade. You can detect fairly small curvature deviations. Similar devices play a roll for checking the curvature of real and model train tracks.

(1) You use the term "feeler gauges" to refer to a class of gauges, including radius gauges and rocker bars.  I don't believe this is correct.  I've checked several major tool catalogs and done a Google search on "feeler gauge".  I find no support for this usage.

"Feeler gauges" is a well-established term used by machinists, mechanical engineers, mechanics, and others.  They refer specifically to thickness gauges.  I have several sets.  Typically they are strips of steel (or other metal) sheet or plate ground to precise thicknesses.  You use them to measure the width of a gap or slot by consecutively inserting feeler gauges of increasing thickness until you reach a gauge that's too thick to insert.  A common application, e.g., is measuring the gap of a spark plug.  So, e.g., if a .034 in thick feeler gauge slides into the gap, but a .035 in thick feeler gauge doesn't, you know that the width of the gap is greater than .034 in, but less than .035 in.  This assumes you don't force the gauge into the gap such that you deform the gauge, the workpiece, or both.

(2) You give the impression that I believe there is no useful purpose for radius gauges.  That is not the case ... otherwise I wouldn't have a set.  The issue really is selecting the right tool for the target application; the key parameters being required range and accuracy.  For linear measurements, e.g., there are times when I grab a ruler, times when I grab a digital caliper, and times when I head for a toolmaker's microscope.  There are applications in which radius gauges are both convenient and accurate.  For skate blades, though, the constraining factor is the narrow thickness of the blade.  This was covered by Bill_S here (http://skatingforums.com/index.php?topic=7339.msg87501#msg87501).  To rephrase:  when comparing arcs with different ROH and a fixed chord length, as the chord length decreases towards 0, all the arcs degenerate to the same line segment.

Similarly, if I need to measure the length of an object to within 0.005 in, I could grab my Starrett scale graduated in .01 in divisions, align it with the object carefully, adjust the lighting carefully, and view the scale and object under a 7X or so magnifier.  But, why would I, when I could use my Mitutoyo digital caliper more conveniently and reliably?  On the other hand, if I need to measure a length within 1/16", a ruler will do just fine.

[Query]

I carefully tape the gap so there is little or no motion across the hollow; hence ROH is reasonably fixed. I am careful to try several types of tape, of different thicknesses. I also try to make sure that when I flip the blade 180 degrees, there is as little change in centering as possible.

I'm doubtful that there is much difference to the skater between an ROH of, say .500" and .505". As long as you are consistent.

Consistency is a problem at commercial pro shops, using dressed wheels. In particular, if they do it a little different every time, that means they waste metal on your blade when they sharpen. This is conceivable a plausible reason for a skate tech to try to get everyone to use the same hollow. An alternative, used by some techs, is to use different wheels to grind different hollows.

It sounds like, on a twist-warped blade, the HDI gage does indeed measure the wrong thing. Right? Of course, that is a hard thing in any event: On powered machine sharpenners, in order to keep the centering of the wheel on the bblade consistent, the better grade figure blade holders temporally un-warp blades while they sharpen. Pro-Filer sort of does that too, by following along the blade, with a stone that is only about 3" long. But when the blade is taken out of the holder, you end up, for a twist-warped blade, with uneven edges.

Likewise, some blades are ground, by accident, with assymetric sides. It sounds like the HDI gage may get that wrong too.

I guess there might be specific reasons for deliberately changing the ROH along the blade: There is a portion of the blade next to the toe pick that normally can't touch, because of toe pick geometry. But it may touch when taking off and landing jumps, due to higher pressure. I can think of reasons why you might want that to have a different ROH from the rest of the blade, to help deal with under and over rotated jumps. Depending on your individual needs, you might want to get a stronger bite into the ice, to stop your skid. Or you might want a weaker bite so you don't fall over. Or you might want less snow, to make the under or over rotation less obvious to the judges. Likewise, I can imagine reasons why a skater might want a greater or lessor ROH at the back edge of the blade.

None of the skate techs I've discussed sharpening with have mentioned any form of deliberate ROH modulation, but that doesn't mean there aren't any who do so, for some customers. I do notice that Ultima creates a much sharper edge on their toe picks than MK and Wilson - I'm not sure what the consequences are.

No doubt a picky coach would claim that if small differences in sharpening affect the entry into your spins, you need to work on technique. I've noticed that some very good skaters can compensate for inconsistent sharpening.

[tstop4me]

No doubt a picky coach would claim that if small differences in sharpening affect the entry into your spins, you need to work on technique. I've noticed that some very good skaters can compensate for inconsistent sharpening.

Yes, very good skaters can compensate for deficiencies in gear and ice conditions.  During the summer, my rink is plagued by bad ice conditions (too soft, too wet, too many bumps, too many ruts, ....).  I've noticed that the adults (especially beginner adults) tend to carp about these conditions a lot ... meanwhile, several little girls are jumping and spinning like mad on the same surface.  Oh, well.

But since I'm not a very good skater, I approach skating the way I approached my physics experiments and engineering projects:  identify the variables that affect the outcome, and control them, if feasible; proper measurements, if feasible, are key to that approach.