Pro-Filer maintenance

[Bill_S]

There has been some recent discussion about the Pro-Filer handheld blade sharpening tool. I'm one of the people here who uses it exclusively to sharpen my blades.

Over time, the fine stone looses its ability to hone because of steel swarf that builds up on the stone. All power grinding wheels are similarly impacted, but they are frequently refreshed with a dressing tool. I have several power grinders for tending to household and woodshop needs, and I have some diamond grit dressing tools for maintaining the grinder wheels. These cost around $10. I decided to try one of them for the Pro-Filer fine stone.

Here is a shot of a brand-new Pro-Filer fine stone unit for 3/8" ROH...



Anyway, it was taking longer to fine-hone my blade after the coarse diamond unit had rough-sharpened it. There was definitely a build up of "stuff" on the surface. I took apart the fine-stone Pro-Filer unit by driving out a pin that holds the stone in place. I used a long stem punch for doing that.

I took a diamond dressing tool meant for dressing rotary grinding wheels, and placed it flat on the workbench surface. With the stone removed, I rolled it toward the dressing tool while my right hand (not shown, it was taking the picture!) grasped the dressing tool. I slid the dressing tool back and forth across the stone's surface as it rolled toward the tool. I held a modest amount of pressure against the stone's motion with the diamond dressing tool.



Here's the gunk that came off of the stone's surface after a few revolutions...



I didn't remove much stone material, and the stone fit the Pro Filer handle about the same as before. In use, I couldn't detect that it was any smaller in diameter because the fit is loose in the holder anyway.

When reinstalled and used, I could tell that it cut better by the sound of the stone over the blade, and the reduced time needed to polish out the grooves left by the coarse stone.

The coarse stone doesn't appear to collect steel swarf like the fine stone. The space between diamond grits is large enough that it doesn't build up. It will get dull after years of use though.

Alternative methods: It's likely that some really coarse sandpaper would work too. Maybe a 60 or 80 grit would be appropriate. When it loads (clogs) with swarf, move to a new spot on the sandpaper. I was able to clean the diamond wheel dresser using a paper towel and some water.

Work to do: Measure the before-and-after diameter of the fine honing stone. I didn't do it this time, but I am curious how much the diameter changes. My feeling is that it isn't much but I'd like numbers. Because this procedure was performed after 6 years of usage, it probably won't be measured anytime soon.

Edit: I might also mention that I have a web page showing its usage, and some measurements of how much material is removed from the blade when sharpening. The address is http://www.afterness.com/skating/profiler.html
This url has been changed in October from the old ohio.edu domain where I initially posted it.

[tstop4me]

When I was using the Pro-Filer, I cleaned both stones (the diamond and the finishing) after each use.  I also removed a roll pin from each handle to remove the stones.  To make assembly and disassembly easier, I did not reinstall the roll pins.  I simply inserted an Allen wrench of the right size to hold the stone in the handle during use (the Allen wrench is gripped during use, so it doesn't fall out), and pulled out the Allen wrench when I needed to remove the stone.

To clean the stones, I soaked them in mineral oil, and scrubbed them with a toothbrush (or similar brush with plastic, not metal, bristles); no chance of damage to the stones this way.  I found more swarf coming off the diamond than the finishing stone.  You can then wipe off the stones with a towel.  I also cleaned out the insides of the handles after each use.  I found that cleaning after each use kept the sharpening more consistent.  If you clean after each use, you won't get the heavy build-up that requires more drastic dressing to remove.

[Bill_S]

I found more swarf coming off the diamond than the finishing stone.  You can then wipe off the stones with a towel.

I should mention that I use a paper towel to turn both stones between strokes, and that picks up a lot of swarf from the exposed center.

That's an ambitious cleaning schedule that you have outlined above, and I'm sure it would even further extend the effectiveness of a Pro-Filer set.

[Query]

Fabulous! I should dig up the one I stopped using when it clogged. Hope I didn't throw it away.

Since you used a .5" hollow Pro-filer in your test, have you tried the very cheap old used Berghman tools? If you want a finer or more modern stone, just use the ones from your 1/2" Pro-Filer. I think you will find the Berghman handles somewhat superior, in that they have an adjustable gap width, and are easier to control, especially near the toe pick, in that there is no pin or screw to get in the way, so you can use the stone right up to the edge. Though the Pro-Filer handles look much nicer.

On your web page you cite Brad's statement that 3/8" and 7/16" ROH have only about .001" difference of hollow depth.

Based on the math at http://www.skateny.com/sharpening/s_hollowmath.jpg, which I believe to be correct, the hollow depth difference is about .068", for .16" thick blades. So Brad is only off by a factor of 68. I think. But go ahead and check our math.

I haven't measured the thickness of the chrome relief facet (Sid Broadbent's term) for Ice Dance blades - which is where people most often choose 3/8" ROH, because ice dance blade facets are often machined thinner. You can measure your effective thickness and run your own calculations for your particular blades.

I worked out the edge angle geometry some time ago. If I remember right, the edge angle difference sounded significant between 3/8" and 7/16" ROH too. In practice, I am certain I can tell the difference in feel between 3/8" and 7/16" hollow blades. However, if you are happy with 3/8" hollow, and Brad doesn't really make 7/16" kits, but merely markets 3/8" kits as 7/16" kits, which is what I understood to be true from an old phone conversation, maybe you could just stay with the 3/8" ROH that you are now used to.

[tstop4me]

Fabulous! I should dig up the one I stopped using when it clogged. Hope I didn't throw it away.

Since you used a .5" hollow Pro-filer in your test, have you tried the very cheap old used Berghman tools? If you want a finer or more modern stone, just use the ones from your 1/2" Pro-Filer. I think you will find the Berghman handles somewhat superior, in that they have an adjustable gap width, and are easier to control, especially near the toe pick, in that there is no pin or screw to get in the way, so you can use the stone right up to the edge. Though the Pro-Filer handles look much nicer.

On your web page you cite Brad's statement that 3/8" and 7/16" ROH have only about .001" difference of hollow depth.

Based on the math at http://www.skateny.com/sharpening/s_hollowmath.jpg, which I believe to be correct, the hollow depth difference is about .068", for .16" thick blades. So Brad is only off by a factor of 68. I think. But go ahead and check our math.

I haven't measured the thickness of the chrome relief facet (Sid Broadbent's term) for Ice Dance blades - which is where people most often choose 3/8" ROH, because ice dance blade facets are often machined thinner. You can measure your effective thickness and run your own calculations for your particular blades.

I worked out the edge angle geometry some time ago. If I remember right, the edge angle difference sounded significant between 3/8" and 7/16" ROH too. In practice, I am certain I can tell the difference in feel between 3/8" and 7/16" hollow blades. However, if you are happy with 3/8" hollow, and Brad doesn't really make 7/16" kits, but merely markets 3/8" kits as 7/16" kits, which is what I understood to be true from an old phone conversation, maybe you could just stay with the 3/8" ROH that you are now used to.

As for difference in depth of hollow for 3/8" vs 7/16" ROH, Brad is correct.  Your calculation (.068 in) doesn't pass a basic sanity check.  I posted calculations for depth of hollow and blade edge angles previously:

http://skatingforums.com/index.php?topic=7547.msg90418#msg90418

Regardless of the small differences in geometrical parameters, there is surprisingly a noticeable difference in actual skating.

I had occasion once to measure the thickness of an Eclipse Dance blade; it was .12 - .13 inch in the chrome relief region (difficult to measure accurately). 

[Query]

Actually, Bill said he used both ROH's for his tests.

But you are right - I forgot to divide t by 2, and ignored the subtraction from R.

For t=.15", the depth difference is about .001405"...

So why is there a noticeable difference in feel? I'm certain I feel it. A lot of other people have said so too. Including tstop4me.

I've noticed other inexplicable factors before. When I measured or calculated rocker profiles and side honing shapes, of different figure skate blades, they are literally close to identical within thousandths of an inch, sometimes less, except for toe picks, within the same brand line. Yet people express extremely strong preferences for one model blade over another. Exactly what can possibly cause a few thousandth's of an inch in rocker profile or side honing to affect skating? I have come up with no physical model that can explain this. I'm reluctant to claim it is all psychological.

Similarly, hollows seem like they shouldn't matter much. No hollow (like a speed skate) means the bottom of the blade meets at 90 degrees to the ice. By your own measurements, hollow only changes this by a small number of degrees. How can that significantly affect how effectively a blade cuts into the ice? I have an unconfirmed theory for that: I think that blades more or less hydroplane across the surface on a thin layer of fluid, much like a tire in heavy rain. But a blade with hollow pushes some of that water out of the way, like a tire with deep tread.

There are physical models, and some static x-ray diffraction measurements, that say the top 40 or so nm of ice at rink temperatures act like a liquid rather than a solid, because the water molecules near the surface are only chemically bound on one side. I theorize that the slight difference in blade angles due to hollow, combined with the weight of the blade, pushes the water layer into the center, much like the tire push rain water into the deep treads. The difference in angle from 90 degrees strongly creates a sideways component to the force from the blade, which is missing without hollow. So, in my model, a speed skate simply hydroplanes, while a blade with hollow pushes some of the water out of the way, into the center, before the top ice molecules can lose cohesion with the rest of the ice, and liquefy as well. Hence a speed skate glides with less resistance, but a figure or hockey blade pushes more strongly. But I have way whatsoever to confirm this theory. One needs a confirmed physical model to explain why such tiny differences matter. Besides, my model falls apart when you edge the blade. A tilted blade should push the water to the side, even without hollow.

(Note, however, that it is fairly common for speed skaters to deliberately create foil edges at the sides of the blade, extending down into the surface, by re-pointing the sharpening burr. Some figure and hockey sharpeners sometimes do this too - but many simply deburr, as do some figure and hockey sharpeners. A foil edge allows a speed skater to push strongly, and accelerate strongly, at the start of the race, while the foil is still intact. Likewise, they edge the blades strongly at the start of a race.)

But, like I said, even if my hydroplane/center-water-push model is right, it doesn't explain anything about how such tiny rocker profile changes or side honing changes can make a difference. Take, for example, parabolic cut blades. There is a huge difference in turning effectiveness with skis, on curved hills, because the parabolic cut can fit the side of the hill, increasing the length of ski that interacts with the surface, and because skis bend to conform to the surface. But most figure and hockey skating is done on flat surfaces, and the blade is not very flexible. So how can .001 or .002" of parabolic cut (fairly typical) make a significant difference? In fact, does it?

Likewise, if the water layer is only 40 nm thick (there is some variation with temperature), it doesn't take much curved length to take the blade out of that water layer, so, yes, rocker curvature should matter. But one should have a physical model of why that matters. Sure, the more curvature, the less length is within that layer. If one does hydroplane, that should push a bulge of water ahead of the point of contact, so the relationship between rocker radius and hydroplaning should be very complex. Should rocker curvature still matter much?

So why does all this matter to Pro-Filer use? Because I believe Pro-Filer creates a slightly different edge shape than typical powered sharpening machines. In particular, hand sharpening speeds give you a longer sharpening burr, which can be reshaped into a longer foil edge, unless you make a point of removing it. This creates a sharper initial edge. So it is very important how you deburr, or polish and repoint the burr into a foil edge, or somewhere in between. It is an interesting question how the suggested maintenance of the Pro-Filer affects the length and shape of the burr...

And how that burr is produced and repointed. If I understand correctly, hardened steel shouldn't be able to deform or bend that much. There have been claims that sharpening burrs must not contain much of the carbon-related crystal structure that hardens steel, because hardened steel breaks if you bend it more than a few degrees, and that the burrs must somehow be closer to iron than fully hardened steel. Huh? How could that happen? Where does the carbon go? Does the effectiveness of the abrasive affect this in some way? To what extent does the same thing happen at the faster machine sharpening speeds?

[tstop4me]

There have been claims that sharpening burrs must not contain much of the carbon-related crystal structure that hardens steel, because hardened steel breaks if you bend it more than a few degrees, and that the burrs must somehow be closer to iron than fully hardened steel. Huh? How could that happen? Where does the carbon go?

Don't know the specifics of the particular instances you are discussing.  But, in general, steel has a complicated microstructure, which depends not only on the chemical composition, but also on the mechanical and thermal treatment.  If you start with hardened and tempered steel [fully hardened steel is typically too brittle to be serviceable, so it's typically tempered to soften it a bit], it has a particular microstructure.   If you overheat it, it can change to a different microstructure that is softer.  You could say that the carbon (and other elements) go to different atomic positions.  When you see metal being ground by a power grinder, you see a "shower of sparks", which are bits of really hot metal; so you know that power grinding can locally create high temperatures.

[Query]

To say nothing of mechanical stress - e.g., blacksmiths sometimes "beat" steel to bring impurities to the surface, and it may also be possible to break up the embedded microcrystals that supposively block the "plastic" deformation of hardened steel.

I don't really believe that it is economically practical to determine the microscopic structure of exactly how ice skates interact with the ice. I suspect that is just as hard a problem as modeling how ships interact with the water, a problem that still has not been completely solved after an astonishing amount of time and resources have gone into it - even when it comes to completely practical simple questions, like how to design a ship for optimal speed, tracking, stability and/or power expenditure.

But for those of us who sharpen for our selves, it can still be a very interesting to determine how to optimize sharpening for minimum drag, maximum resistance to sideways skid, edge longevity, and other factors that influence skating. For example, if you look at a newly sharpened blade under a microscope, you will see ragged teeth that are much larger in scale (say, for example, .0001 - .001 inch) than the hypothetical 40 nm layer thickness I mentioned. Does the size and raggedness of those teeth have as much or more impact on skating as hollow depth, edge angle, steel composition, sharpening grit composition and size, how much gunk is embedded in the stone (before the maintenance discussed in the o.p.'s post),  etc.? Is the way in which those teeth change in size, raggedness and shape one of the principle effects of hollow depth, edge angle, etc., and if so, are there ways to improve sharpening technique for optimal (figure) skating, involving the shaping of those teeth?

Or does it make more sense to just practice skating, and ignore such technical issues?

[Bill_S]

I appreciated the way that tstop4me used a quick-release method for holding the sharpening stones in place. It made me think about alternate ways to do it. I spent a couple hours in the shop this morning and came up with this...



With this modification completed, I timed the removal of a stone and it took 10 seconds to unscrew and drop out the stone. Now I have no further excuse not to keep the stones in great condition.

Doing this was very simple using a drill press. With care, you could probably do it using a hand drill too, but use techniques to ensure drilling steps are made square.

Because I used common 8-32 threads, I first drilled the existing holes through with a #29 drill. That's what's required for tapping 8-32 threads.



I then used an 11/64 drill on one side to provide a loose-fit clearance for the screw. I cut the threads on the far side only. This picture shows another reason you want a larger hole on one side. The un-threaded part of the tap is larger than the threads...



I then followed that up with a countersink step so that the flat-head screws are flush with the surface...



I used screws that were originally 1-1/2 inch long and trimmed their length to fit the Pro-Filer without protruding.

It took about 2 hours to do, and makes removal of the stones for cleaning dead simple and very fast.

[Query]

One of my Pro-Filers had screws. Maybe that was the hockey model. I think the instructions said you could tighten them to reduce the gap size, but am not sure anymore.

Bill, maybe you could suggest to Brad that screws would be a good idea. I needed help to learn how to remove pins, and had to buy a pin punch.

For someone like you with access to and skills to use a metal shop, would it be hard to make your own Pro-Filer equivalent? (I'm not suggesting you go into business doing so. Brad sued Blade Doctor for patent violation. I don't know who won.)

[Bill_S]

Query: Because the Pro-Filer already exists and works, I would be foolhardy to attempt to make something similar. Most engineering changes would be to avoid patent claims, and that's not a great way to innovate - especially for such a small market.

Brad paid a considerable tooling expense to get the first one from a production line. The bodies are aluminum extrusions, and tooling charges would be high to make something similar. I'm sure that the stones are custom fabricated by another vendor for the sharpener, and they would want their tooling money. The price to get in the door for production would be high.

Just to give you an idea, here's a quote from a stamping shop to make some photographic filter-gel holders. Note the date (1986), and double any costs you see...



Note that the engineering service charge is $1740 regardless of volume. That's for tooling to form the part. The other costs going across left-to-right are the costs per each starting in quantities of 500 ($1.18 each), 1000 ($0.79 each), on on up. That was for a simple set of sheet-metal stampings for the item shown on the right in the following picture...



(In the end, this didn't make it to market because someone beat me to it by two months. There went my dreams of being a photo accessory mogul!)

The bottom line is that it would cost too much to make a competing product, and the stakes are low. The Pro-Filer works well now, so there's really no need to attempt making something similar, whether for personal use or for production.

[tstop4me]

One of my Pro-Filers had screws. Maybe that was the hockey model. I think the instructions said you could tighten them to reduce the gap size, but am not sure anymore.

Bill, maybe you could suggest to Brad that screws would be a good idea. I needed help to learn how to remove pins, and had to buy a pin punch.

For someone like you with access to and skills to use a metal shop, would it be hard to make your own Pro-Filer equivalent? (I'm not suggesting you go into business doing so. Brad sued Blade Doctor for patent violation. I don't know who won.)

The Pro-Filer Plus handle, which is used in the current hockey models, is made from two pieces held together by two screws [no gap adjustment that I know of].  Last I spoke to Brad (earlier this year), he told me he was planning to switch the figure units over to the new handle.  Don't know his current plans.

[Query]

Getting back to the extremely practical, I desire a dresser tool that is substantially cheaper than buying a new grinding cylinder.

I get, BTW, that you haven't seen these items. If you work in a metal shop, you are used to spending serious money for high quality tools. Perhaps you wouldn't trust a cheap tool to be safe held against a powered spinning grinding wheel, because it might break and cause serious injury. I'm just asking for rough guesses as to what will likely work for this more limited purpose at a reasonable cost.

Would a cheap ($2.63, USD, including shipping to U.S.) dresser tool like this probably work?

https://www.ebay.com/itm/Diamond-Coated-Dressing-Bench-Grinder-Grinding-Wheel-Stone-Dresser-Tool-Metal/112333340173?hash=item1a2796be0d:g:iIUAAOSw4A5Yxg73

The ad doesn't mention the grit size, but it looks about the same as this $10.51 36 grit item:

https://www.ebay.com/itm/POWERTEC-71003-Diamond-Grinding-Wheel-Dresser-4-5-8-36-grit-BRAND-NEW/391927569822?epid=2254340376&hash=item5b40b41d9e:g:9sUAAOSwUn9aDRKq

Is that probably too big a grit size?

Here is one for $4.33 + $0.49 shipping that at least looks like a smaller grit:

  https://www.ebay.com/itm/Sintered-Diamond-Grinding-Disc-Wheel-Stone-Dresser-Tool-Dressing-Bench-Grinder/112197762606?epid=1066086976&hash=item1a1f81fe2e:g:FxgAAOSwLsBZQLV3

Does that seem more like what I should be looking for?

[Bill_S]

The first two items are similar to what I have. I have no experience with the third item in your message.

About grit - I grabbed what I had on hand. There's nothing special about the 36 grit that I used. Something a little finer than my coarse 36 grit would work too.

Just don't use these diamond tools on the diamond sharpening stone. The toothbrush method mentioned by tstop4me using either mineral oil or water w/ drop of detergent would work for that. I recall that you used water as a honing fluid (very common). If so, use water and detergent on the diamond stone to clean it, then dry thoroughly.

Remember, you could get some coarse sandpaper and try that too. Lay out a generous strip, and wipe the cylinder along it like you wipe your feet. All that's necessary is to remove the compacted swarf from the stone's surface to renew its effectiveness.

FYI,  when sharpening hand-plane blades with water stones, I use flooded wet-or-dry sandpaper stuck onto a granite block to refresh them. It works very well.

[Bill_S]

Query - you sent a PM to me. I tried to reply, but your mailbox is full.

[Query]

My inbox is almost empty. I can't figure out how to get to the outbox - I'd like to copy it to a file on my machine, and empty it.

I'll send you my email address.