Using a blade angle tester and home sharpening

[Leif]

I have a blade angle tester (well, I actually have two for reasons I won't go into, and they disagree  ) and the reading differs depending on how I hold the skate. The instructions on the ProsSharp BAT say to hold the skate with the heel facing you, and place the BAT on the blade. Does anyone know if this is standard practice and why? I have always assume that blades are flat with the two faces parallel. Incidentally, I have hockey skates, but there is overlap here.

Secondly, does anyone have a home sharpening machine (not a handheld device, one with a high speed grinding wheel) and if so, is it hard to learn to get a correct edge? I am sick of travelling many miles to the one good sharpener I know.

[Bill_S]

It's too bad that Rusty Blades doesn't frequent this board anymore. She was a Canadian who built her own power sharpener.

I always enjoyed her posts - her topics ranged from welding steel, to shooting a bear that started hanging around her house. I think she even bulldozed space for an outdoor rink next to her house too.

[Query]

Here is a picture of one in use, I think:

https://www.google.com/search?q=%2BProsSharp+Blade+Angle+Tester&tbm=isch&imgil=1hDuMlCzxqKvMM%253A%253BVGkmiB_ssH7ccM%253Bhttp%25253A%25252F%25252Fwww.hockeystore.ch%25252Fen%25252Fprosharp%25252Fzubehor%25252Fprosharp-blade-angle-tester&source=iu&pf=m&fir=1hDuMlCzxqKvMM%253A%252CVGkmiB_ssH7ccM%252C_&usg=__FlhRmdGmHetKKsGHtAArYBfsrWc%3D&biw=1536&bih=793&dpr=1.25&ved=0ahUKEwiD28XknpjUAhUSfiYKHfsdA64QyjcITA&ei=B7ktWcO7GZL8mQH7u4zwCg#imgrc=1hDuMlCzxqKvMM:

BTW, "edge angle" most often refers to the angle between the two surfaces that create a single edge. You are talking about another angle - the angle between a line across the inside and outside edges, and another such line measured at a different point along the length of the blade.

Lots of people just use two long magnets for what you are talking about, the longer the better. I got a pair from a hardware store for $2 or $3, though they are only a couple inches long - I think 3-4" would be better. Also, my magnets are a little strong, which might mean they could dull the edge slightly. The idea is that you want the two magnets to line up when they are placed on different places on the blade. You sight the two magnets visually against each other. That shows that the two edges are even - or at least that they are uneven to the same extent - along the entire length of the blade. To some extent a skater can compensate for uneven edges if they are uniformly uneven, but you have to work harder to compensate when the angles change along the length of the blade.

Some of the fancier instruments have scales that show how many thousandths of an inch the alignment of the two edges are variant from one place to another. That is useful to some people, because they may actually want them to vary. For example, many hockey goalies dull the outside edge, in a small area near the back, to be .0005 to .002 inches shorter than the inside edge, so they can slide side to side easier. Some figure skaters who are learning to do "skidded double jumps" likewise want such an area near the front of the blade that they jump off of. Different people want the outside edge dulled to a different extent. Some hockey referees want the outside edge longer, because they constantly jump out of the way to the side when they drop the puck - and they keep wearing out the outside edge. But I think most skaters want the inside and outside edges to be of the same length, uniformly down the blade. They don't want to have to adjust their technique for inconsistent angles every time they get their blades sharpened.

http://www.iceskateology.com sells a $420 (plus shipping, I assume) home power sharpener called the Little Edger - but I've never used it. I've been reasonably happy with that company's hand sharpeners. They also sell a "precision square", which shows whether the line across the edges is perpendicular to one of the sides - which is a measure of whether the edges are even. That isn't ideal everywhere, because most blades are slightly twist warped - which is why you also want to sight visually for a uniform line across the edges, using the magnets.

Edges that are not uniformly even by accident, by the way, generally occur because the blade has a warp, that most powered sharpening machines can not follow, so that the grinding wheel lowers one edge near the ends, and the other edge near the center. The hand tools squeeze around the blade to follow it and therefore create less of a problem, but visual sighting using two magnets, at many different points lets you get it still more uniform.

BTW, it takes a lot of practice to use typical power tools accurately and consistently, because you can make a mistake that removes a lot of metal in a very short period of time. I tried a little without much success, briefly, using an old Blademaster sharpener, though I only had an hour or two on it to learn, my sharpening instructor wasn't very expert, and the blade holding jig was old and very hard to adjust. But if you are good at precision machine shop work, maybe you will do better.

[tstop4me]

Lots of people just use two long magnets for what you are talking about, the longer the better. I got a pair from a hardware store for $2 or $3, though they are only a couple inches long - I think 3-4" would be better. Also, my magnets are a little strong, which might mean they could dull the edge slightly. The idea is that you want the two magnets to line up when they are placed on different places on the blade. You sight the two magnets visually against each other. That shows that the two edges are even - or at least that they are uneven to the same extent - along the entire length of the blade. To some extent a skater can compensate for uneven edges if they are uniformly uneven, but you have to work harder to compensate when the angles change along the length of the blade.

The simple two magnet system you describe, in which both magnets are placed across the inside and outside edges of the blade at different positions along the blade, does in fact check for edge height uniformity along the blade, but it does not check for edge height evenness at all:  e.g., if one edge is uniformly .004" higher than the other, there will be no indication that your edges are uniformly messed up.  I'd much rather have a blade with edge height variations of +/- .001" (or even +/-.002") than a uniform +.004".

The better edge checkers have two separate pieces.  One piece sets a reference horizon line orthogonal to the side of the blade.  This piece is held by a clamp or a magnet attached to the side of the blade.  The second piece is a measurement straight edge held (by a magnet) across the inside and outside edges of the blade.  You sight the orientation of the measurement straight edge with respect to the reference horizon line.  If the edges are even, the measurement straight edge will be parallel to the reference horizon line.  If the edges are not even, the measurement straight edge will be skew to the reference horizon line.

http://www.iceskateology.com sells a $420 (plus shipping, I assume) home power sharpener called the Little Edger - but I've never used it. I've been reasonably happy with that company's hand sharpeners. They also sell a "precision square", which shows whether the line across the edges is perpendicular to one of the sides - which is a measure of whether the edges are even. That isn't ideal everywhere, because most blades are slightly twist warped - which is why you also want to sight visually for a uniform line across the edges, using the magnets.

(a) The Little Edger is not a stand-alone home power sharpener.  It is an attachment to the Incredible Edger, which as of the 2014 price list on the website, retails for $3400.

(b) The Incredible Edger is sold by Sidney Broadbent's company; the hand sharpener that you use (Pro-Filer) is sold by Brad Anderson's company.  They are not the same company, as far as I know.

(c) I have precision squares (including a diemaker's square) for shop work.  They are not very useful for checking edge evenness within required tolerances because it's difficult to resolve small differences with respect to the reference edge of the square.  The purpose of the "bat" edge checkers is to use an extended lever arm to magnify the effect of a small difference in edge height to a more easily resolved difference in angle.

[tstop4me]

An alternative to bats is the Hollow Depth Indicator (HDI) gauge.  It measures the edge height difference directly (instead of estimate via angular deviation); as well as the depth of hollow.  The dial indicator has .001" tick marks; you can estimate to the nearest .0005".  The disadvantage is it's a bit pricey (~$250).  Easy to use.  I've used one for ~2 yrs now, and have been happy with it.

http://www.pro-filer.com/hdi/

[Leif]

Thanks all. The HDI looks a bit pricey. My gauge is as described by tstop4me i.e. two piece of aluminium/aluminum right angle, a couple of small magnets, and a scale. It checks that the edges are at the same height. Clearly it does not check the depth of the hollow.

I contacted Wissota a day or two ago and as they have no UK dealers they are preparing a quote for the 911. It'll be expensive, especially with shipping, but I'm tired of travelling out of my way to get to the good sharpeners.

The alternative is the Sparx machine, but that needs a grinding wheel for each hollow, and as yet it is not available outside of North America although they do plan to make it available to Europeans. 

[Query]

Oops. And oops. And oops.

Actually, I'm not sure that hockey goalies always want the skid point on the outside back edges either -- e.g., if they want to get into full split position, to cover the ice between their feet, it would be virtually impossible to be on their outside edges. I'm not sure if they ever try to skid sideways in that position, but they would need a skid on the back inside edges too. It seems pretty common for hockey goalies to do their own sharpening, or at least to modify what is done by the pro shop, because not many pro shops are good at goalie skate sharpening.

In fact, hockey skaters in general seem to to handle their own sharpening much more often than figure skaters. I guess that is because Perhaps that is because

1. Some of the tools are only designed for hockey skates. Both hand tools, and some of the fancy pro tools, like CAG machines that re-do the profile.
2. Hockey skaters mess up their edges a lot more often. It really impresses me how fast a good defensive hockey skater can accelerate and stop. And how often hockey skaters smash up each other's blades. They often need to do emergency repairs, during the game, and can't wait to take it to some guy with a machine. Less common in figure skating, though Mike C. did give a short lecture on doing them at a PSA conference a few years ago.
3. Figure skaters have been historically more willing to spend money on expensive professional sharpening. Most highly competitive figure skaters come from wealthy backgrounds, whereas hockey is a bit more of a mix, and includes more people who's parents who work in the trades, and have more confidence working with tools.
4. Some combination of above.

Which means that a hockey skating board might be the best place for a hockey skater to get info on sharpening their own blades, as well as simply restraightening edges. I'm not saying looking here is bad. I'm just saying they might know some of the details better. For example, all my info on hockey skating, and how their blade shape should look, is second hand. I've skated in hockey skates, but I've never played hockey. Plus, the expert pro figure skate tech, I talked to most is one of the best in the world, whereas the hockey skate techs who have been willing to share their secrets with me, are more typical.

Hmmm... I'm trying to think if I can improvise something cheap to create the orthogonal horizon line. I've occaisionally tried to use a cheap lightweight plastic square, but I don't have much confidence in my ability to hold it precisely and steadily across the 2 edges. Heavier big metal ones I definitely can't hold still that way - it's sort of like trying to hold still balanced on one skate on the ice, without gliding on the ice.

I use a symmetric sharpening technique (changing skate orientation every few strokes) which creates approximately even edges, so I don't need to worry about that too much. But if you really had a .004" edge height difference, I think it would be pretty obvious, not just on the ice, but because a line across the edges would obviously not be at right angles to the sides, even to the naked eye, because the angles at the two sides wouldn't look the same.

I would love to find a cheap equivalent to the HDI indicator. Unfortunately, the heads of my micrometer and the depth indicator on my calipers aren't really thin enough for me to trust them to accurately measure the center-of-hollow point. $250 is a lot for one skater, especially if your goal is to save money.

In any event, it is possible that if you intermix your own sharpening with simple tools with an occaisional visit to a really expert pro shop to fix whatever you do wrong, you can get away with slightly imperfect sharpening technique. Of course they will give you nasty comments about how you must have taken it to a second rate pro - which you can learn from, to correct your technique.

[tstop4me]

I contacted Wissota a day or two ago and as they have no UK dealers they are preparing a quote for the 911. It'll be expensive, especially with shipping, but I'm tired of travelling out of my way to get to the good sharpeners.

Be sure they supply a quote with a motor compatible with UK mains; otherwise, you'll end up shelling out even more money for a mains converter.

[Query]

Be sure they supply a quote with a motor compatible with UK mains; otherwise, you'll end up shelling out even more money for a mains converter.

I take it you are talking about electrical issues - things like voltage, AC frequency, supply and overload breaker amperage rating, capacitive phase compensation, and, for a small motor like that that isn't directly wired into the circuit, plug type... Maybe a few things I don't know about. I knew an electrician who told me a professor at the university he worked for tried to save money and get high quality by using a big surplus motor from Japan instead of the U.S., where the university is. Fortunately, the electrician specialized in motors, and knew a shop with the equipment and expertise to rebuild the motor (different wire gauge and length wire) for U.S. electricity to make the adjustment, without shortening the motor lifetime, and the electrician was a master electrician who knew how to figure out amperage and overloads, and had access to building engineers who understood phase compensation. The cost of rewinding the motor, etc.,  was more than the cost of a new motor, but he didn't have to tell the professor that the professor had made a bad choice. He believed most electricians and motor shops, including most master electricians, couldn't have handled it right. Though it occurs to me that if the professor ever had to replace the motor, there could have been problems.

[Leif]

Be sure they supply a quote with a motor compatible with UK mains; otherwise, you'll end up shelling out even more money for a mains converter.

Thanks. Yes I will check that, we are nominally 240V here. The quote was quite reasonable, the shipping cost was high, but that is not surprising given the weight, and a reliable shipper is essential. Unfortunately I have found out that it cannot be kept in my cold garage, and I am sure it is a fire hazard in a spare room with hot metal filings flying around, and the potential to burn small holes in curtains, carpets etc.  I might be able to store it inside, and move it out to the garage when needed, during the cold months.

Or I wait for the Sparx. The Wissota is £1350 with P&P and tax, the Prosharp Home is £1750 with P&P, no extra tax, the Sparx is unavailable as yet but likely priced as per the Wissota.

The nice thing about the Wissota is the ability to change the RoH at will. Prosharp charge £100+ per grinding wheel.

[tstop4me]

Good series of video reviews from Hockey Tutorial:

Comparing Prosharp Home vs Sparx:  https://www.youtube.com/watch?v=qQ1vWEzcUX0


Sparx review:  http://www.hockeytutorial.com/latest-news/sparx-hockey-home-skate-sharpener-review/

Prosharp Home review:  https://www.youtube.com/watch?v=U1gij1zdJUA

Being able to dress a wheel to a desired ROH is very handy for commercial sharpeners because different customers request different ROHs; changing wheels with a fixed ROH is time consuming.  For personal use, though, you won't need to change the ROH on the fly.  The Prosharp wheels are pricey, but the manufacturer claims that one wheel will sharpen 500 pairs:  the wheels are coated with diamond abrasive.  I don't know about specials in the UK, but in the US there was a X-Mas special, I believe they knocked ~$200 off.   For hockey skates, looks like the Sparx might be worth waiting for. 

[Leif]

Good series of video reviews from Hockey Tutorial:

Comparing Prosharp Home vs Sparx:  https://www.youtube.com/watch?v=qQ1vWEzcUX0


Sparx review:  http://www.hockeytutorial.com/latest-news/sparx-hockey-home-skate-sharpener-review/

Prosharp Home review:  https://www.youtube.com/watch?v=U1gij1zdJUA

Being able to dress a wheel to a desired ROH is very handy for commercial sharpeners because different customers request different ROHs; changing wheels with a fixed ROH is time consuming.  For personal use, though, you won't need to change the ROH on the fly.  The Prosharp wheels are pricey, but the manufacturer claims that one wheel will sharpen 500 pairs:  the wheels are coated with diamond abrasive.  I don't know about specials in the UK, but in the US there was a X-Mas special, I believe they knocked ~$200 off.   For hockey skates, looks like the Sparx might be worth waiting for.

Thanks. Yes I've seen those videos, they are very good. Clearly the ProSharp is a nice unit, well made, durable, but it is expensive. In UK money the Sparx is £700. Throw in an estimated £200 for distributor profit, and £200 for tax, and that comes to £1,100, which is still very affordable, and much less than the ProSharp. Maybe if I get a set of spare blades, I can get two sets sharpened at once, to reduce travelling times while I wait for the Sparx to be available to us Europeans. I guess you figure skaters don't have the luxury of spare blades.

[Query]

Based on what it looks like in those videos, these machines are taking off a fair amount of metal - probably too much for expensive figure skate blades, IMO.

But with the rough treatment hockey skates get, it's probably fine for hockey people. A bit expensive to be sure, and it really makes the most sense for someone maintaining a lot of skates - e.g., the skates for a whole team. If it saves you 3 - 4 minutes per pair over the time required to use the hand tools, but you are sharpening 10 or 20 pairs at a time, that could be a big deal. Especially if you are doing sharpening during a game, and the players can't get back into the game until their skates are sharpened. (Note though, that an increasing number of hockey players are using rapidly interchangeable blade systems...) Maybe worth the 1 - 2 orders of  magnitude of price difference, and the reduction in portability, relative to hand tools.

It also looks like there is less of a learning curve than with hand tools, and much, much less of a learning curve than with the high end pro machine tools. So you could assign someone on the team to do it, without much training.

I doubt someone super-picky about their edges and profile shapes is going to be completely satisfied with these tools. You need individual attention to give yourself exactly the edge shapes that YOU personally want.  But there probably is a pretty big potential market for these tools.

[Query]

Thanks. Yes I will check that, we are nominally 240V here.

Maybe you also need to make sure they use the right AC frequency - e.g., 50 Hz vs 60 Hz.

[tstop4me]

I would love to find a cheap equivalent to the HDI indicator. Unfortunately, the heads of my micrometer and the depth indicator on my calipers aren't really thin enough for me to trust them to accurately measure the center-of-hollow point. $250 is a lot for one skater, especially if your goal is to save money.

You can use a ball-end attachment to fit over the spindle or the anvil of a standard flat-face micrometer.  One common diameter for the ball is .200", so it'll reach to the bottom of a skate hollow.  The ball is mounted on a sleeve of various diameters to fit the spindles and anvils of common micrometers.  Here's a reference to the Starrett line of ball-end attachments: 

http://www.starrett.com/metrology/product-detail/Micrometer-Accessories/Micrometers/Precision-Hand-Tools/Precision-Measuring-Tools/247D

; but other toolmakers such as Mitutoyo also make them.

[tstop4me]

Based on what it looks like in those videos, these machines are taking off a fair amount of metal - probably too much for expensive figure skate blades, IMO.

But with the rough treatment hockey skates get, it's probably fine for hockey people. A bit expensive to be sure, and it really makes the most sense for someone maintaining a lot of skates - e.g., the skates for a whole team. If it saves you 3 - 4 minutes per pair over the time required to use the hand tools, but you are sharpening 10 or 20 pairs at a time, that could be a big deal. Especially if you are doing sharpening during a game, and the players can't get back into the game until their skates are sharpened. (Note though, that an increasing number of hockey players are using rapidly interchangeable blade systems...) Maybe worth the 1 - 2 orders of  magnitude of price difference, and the reduction in portability, relative to hand tools.

It also looks like there is less of a learning curve than with hand tools, and much, much less of a learning curve than with the high end pro machine tools. So you could assign someone on the team to do it, without much training.

I doubt someone super-picky about their edges and profile shapes is going to be completely satisfied with these tools. You need individual attention to give yourself exactly the edge shapes that YOU personally want.  But there probably is a pretty big potential market for these tools.

As emphasized in one of the videos (and comments from various posters, including me and the OP, on this forum), it's not the cost of sharpening that's often the primary consideration ... it's often a matter of (a) finding a decent sharpener at all, (b) time and hassle driving to and from the sharpener (unless you luck out and find one close by), and (c) time and hassle waiting in queue when he's available ... and often he might not be available when you need him.  And even decent sharpeners have off moments.  So I'm glad to see product offerings such as the Sparx.  Will need to wait and see how well it handles figure skates.  As for the amount of metal removed ... we need measurements, hard data, before making any judgements.  As I posted in another thread, ~$1000 is a good price point (even for a single user) for a unit that does not require a skillful and artful touch (assuming it works, of course).

[Leif]

Quite right, it is the convenience. As to the amount of metal removed, I suspect they remove less than a skilled sharpener given that you can select the number of passes, so if you just want to refine the edge, two passes might do, but if you want to remove nicks, then 6 or more might be required. According to Sparx, these can get edges level to within 1/1000", better than most skilled manual sharpeners can achieve. And I believe the pressure is uniform, so there is no danger of overheating the blade and changing its hardness/brittleness, and there is less (or even no) danger of changing the profile.

Really for me the purpose of this is to avoid travelling to the sharpner, and the ability to get a first rate sharpen out of the box. Honestly it really is shocking how dreadful most sharpening shops are in my experience and by all accounts the US is no better.

[Query]

As to the amount of metal removed, I suspect they remove less than a skilled sharpener given that you can select the number of passes, so if you just want to refine the edge, two passes might do, but if you want to remove nicks, then 6 or more might be required. According to Sparx, these can get edges level to within 1/1000", better than most skilled manual sharpeners can achieve....

Well... A typical hockey sharpening removes an order of magnitude or more more metal than a good figure sharpening, so the fact that it requires several passes doesn't mean it is ideal for figure blades...

When I do it very carefully by hand, I can't feel anything uneven when I skate. But it is still sometimes the case that I don't get it sharp enough at first - probably because I try to remove as little metal as possible, and I try to straighten first before actually sharpening, for the purpose of minimizing metal loss. That is easy to correct, with hand tools, at the rink, in a few minutes, so I prefer to try minimal sharpening first.

It is unlikely a rink that has sold a pro shop concession would let you bring your big home sharpening machine to a public or freestyle session, to make adjustments. Hand tools are much less obvious, but I still try to be inconspicuous. But many pro and college hockey teams do bring their own sharpening equipment to games - I think they sometimes use it right in the hockey boxes. It's possible they need permission to do that at some rinks.

With hockey skates, there is another option. Many high end hockey (and speed) skates come with rapidly removable interchangeable blade runners. You can have a pro shop sharpen a bunch of them at once. Then you don't need to visit the pro shop so often. A lot of people would love it if figure skate blades were available again like that. Having a lot of extra pairs of blade runners might be expensive - though hockey blade runners cost somewhat less than high end figure blades.

[AgnesNitt]

I feel really lucky: we have 3 figure skating sharpeners at my rink. One mom of a coach, one coach, and one skater. All are very good. $10.

[Leif]

Well... A typical hockey sharpening removes an order of magnitude or more more metal than a good figure sharpening, so the fact that it requires several passes doesn't mean it is ideal for figure blades...

Hockey skates have ten times as much metal removed? I don't believe that. Where I get my hockey skates sharpened, they also do figures, using the same machine, and I know from figure skaters they do a good job.

[accordion]

The lover (aka husband) recently bought a powered grinding wheel. Every knife in the house is now sharp. Every pair of scissors and every chisel - now sharp.

Miss 17 clutched her skates and ran screaming away. She has new blades and is rather protective 

The lover comments that he needs another attachment to do skating blades. I smile sweetly and ask him about what other tools he wants.

[tstop4me]

The lover (aka husband) recently bought a powered grinding wheel. Every knife in the house is now sharp. Every pair of scissors and every chisel - now sharp.

Miss 17 clutched her skates and ran screaming away. She has new blades and is rather protective 

The lover comments that he needs another attachment to do skating blades. I smile sweetly and ask him about what other tools he wants.

Sounds like a promising script for a Halloween horror flick.

[Bill_S]

The lover comments that he needs another attachment to do skating blades. I smile sweetly and ask him about what other tools he wants.

Be careful. Not every sharpening device can do skate blades. If he purchased something like a Tormek to do knives, scissors, chisels, and plane blades, it will not be suitable for skate blades unless you want a nearly-flat ROH.

[tstop4me]

Be careful. Not every sharpening device can do skate blades. If he purchased something like a Tormek to do knives, scissors, chisels, and plane blades, it will not be suitable for skate blades unless you want a nearly-flat ROH.

Skate sharpeners (with exceptions such as Sparx and Prosharp and some oldies) are typically configured with the plane of the grinding wheel oriented horizontally to work with a horizontal guide bed and a horizontal skate holder.  Most shop bench grinders (including the Tormek) are configured with the plane of the grinding wheel oriented vertically.  Although hypothetically one could design a skate sharpening jig to work with a wheel in this orientation, it would be really awkward (even assuming you could get a wheel with the desired ROH).

[Query]

In theory a vertical wheel rotation is better, could lead to more symmetric results. But the main problem is being able to view the blade as it is being sharpened - which is probably better with horizontal rotation.

Sparx and Prosharp are designed for automated sharpening, so that doesn't matter.

As for the amount of metal removed - several good professional figure sharpeners quoted .003" removal per sharpening to me as about right. From what I have been able to tell, that's mostly a matter of the minimum removal amount a high speed grinding tool can do smoothly, and leave a reasonably clean edge - I don't really understand the reasons why that would be true. You can get away with less at hand-grinding speeds, provided you haven't let the blade go too long (if you have, you need to restore part of the hollow, which requires more metal be removed). (But part of the reason you can remove less with hand tools, is that at slower grinding speeds, you are working and reshaping the metal without needing too remove much.)

OTOH, hockey sharpeners want to remove large nicks, which are often deeper than .01 or .02" or even .03", though .03" would be pretty extreme.

If you assume that a figure blade needs to be discarded after about .1" has been removed (because the toe pick is beyond reasonable adjustment to keep the same relationship to the rest of the blade, because the angle of the tooth means that you can't just keep trimming it), that gives a lifetime of about 33 sharpenings of .003 each. If you skate about 40 hours / sharpening (that varies a lot, as you know), that means a blade lasts about 1320 hours of skating per blade. If you skate 10 - 20 hours/week (that varies a lot too), that is 66 - 132 weeks (1.27 - 2.54 years) blade lifetime. You might get about twice or three times that if the skate tech merely straightens the blade most of the time, though that depends a lot on other things, like the roughness of your ice, your skating style, what type of moves you do, and even your weight. Of course careful hand sharpening can extend that a good deal further - I sometimes try for about .001", if it is still reasonably sharp, and I do only straighten  when I can - but extremely few figure skaters or skate techs use hand tools to sharpen. You can also extend it a little further if the sharpener is expert enough to compensate a bit for toe pick trimming angle, by a number of techniques, though it mostly isn't considered worth it, perhaps because the pro shop earns extra money by replacing blades.

Some sharpeners don't even know how to trim the toe pick to compensate for relationship to the rest of the blade at all, so .1" is be more than figure skaters can have removed by them and still skate well. For that matter, I've met many parents whose kids outgrow their equipment before it can wear out - remarkably expensive, but it is what it is.

The reason many figure skaters don't complain is that they don't know better. The blade (hopefully) feels sharp, and they get a clean even edge. They blade just doesn't last as long. But they have nothing to compare it too, because everybody else who uses the same skate tech gets the same results. If everyone they know gets, say, 10 sharpenings per blade lifetime, they have no reason to assume that isn't normal. I met one skater who loved split jumps, but doesn't always do them perfectly, and sometimes broke her blades before they run out of metal.

It might seem that removing, say, .01 to .02" would mean that hockey skaters get many times less blade lifetime, especially since many of the good ones sharpen at least once / game. But it isn't quite as bad as it seems, because you can remove more metal from a hockey skate and have it remain useable - there is no toe pick. Besides, a lot of the ones who get sharpened once or more / game are pros, who get free blades, or are on school-sponsored teams that pay for the blades, so it doesn't matter much (to the players). Hockey blades are cheaper too.

It is possible the amount removed varies a lot even for good hockey sharpeners. It might be, for example, that crashing into each other's blades doesn't happen much at the lower hockey levels - so maybe they could get away with .003" too. It's also possible that the hockey sharpeners I have talked to aren't all that good, and that they remove too much. Most of the good figure sharpeners who will talk to me in detail about what they do are close to retirement, and don't worry much about trade secrets. Most of the hockey sharpeners who have talked to me in detail aren't very experienced or expert, and I wouldn't let them touch my blades.