Powered skate sharpener alternatives - brainstorming

[Bill_S]

Query wrote in another thread

Huh - found a few posts in other forums and on youtube for home-made skate sharpening machines. They all look more challenging than I hoped.

Here is something along the lines of what I had in mind, to create a simple cross grind sharpening machine:

1. I believe some drill stands and drill presses have a way to precisely adjust height with a screw or knob, and that they have tables beneath the drill that you can clamp things to - yes? One very high end skate holder I've seen lets you adjust the height of the blade in discrete 1/2000 inch increments - do these drill stands or presses let you adjust the drill to that level of accuracy?
 
2. Some drills are said to be reversible. Do they have enough power and speed in both directions to power a grinding disk? That is highly desirable in a cross grind sharpener, because, otherwise, they create edges with uneven height and shape.

If so, place one in the stand, and put a sanding or grinding disk on a shaft in the drill, whose radius matches the desired ROH.

3. Securely clamp a square or rectangular bar or board to the table of the press or stand, to create a horizontal ledge that you can slide the blade along, a little in front of the outside of the disk. It is very important that the right angles be exact, so that the ledge is EXACTLY horizontal. The ledge must also be very smooth.

4. As with a purpose-built powered skate sharpener, you should ideally oil that ledge and/or the sides of your blade, so the sides of the blade don't get scratched. While you are at it, oil the bottom of the blade, so you create clean edges.

5. Similar to a purpose-built powered skate sharpener, precisely adjust the height of the disk, so that the disk scratches a the center height of a skate blade slide along that ledge.

6. Use it the way you use any skate sharpening machine. In the final passes, reverse drill directions to even-out the edges.

Does that sound do-able?

P.S.  Some additions to above.

7. The drill and stand need to hold the sanding or grind disk very steadily. Any vibration could mess up the edges. So, everything needs to be fairly solidly built.

8. You need a sanding disk or grinding disk with a strong shaft. Otherwise it could break, fly off, and hurt you.

9. Regardless, as with any powered sharpening machine, you need first class eye protection. Even if nothing breaks, the steel filings that would fly off are dangerous. I can't think of a good way to protect the hands - I think protective gloves around fast moving machinery might be more dangerous then safe - they could get caught in a moving part and draw the hand in.

P.P.S. I just realized that would only work if the drill press or stand holds the tool horizontal, because the disk needs to be vertical, and it cuts the hollow on a horizontal skate blade. I have seen stands that can do that, but am not sure they have all the things I required.

Also, I hope no one tries this with a Dremel tool or an even cheaper made equivalent - I don't think they are sturdy and solid enough to be safe.

I looked at my drill press and it doesn't look good as a substitute for an sort of sharpener. First, for cross grinding, you've got the chuck in the way. See picture...



If you get a long enough shaft to avoid the chuck, you'll have so much runout that you couldn't do much. Chucks for drill presses aren't that accurate. I sometimes have to tighten a drill, turn it on to watch for rounout, then loosen and retighten several times to reduce it. It's somewhat hit or miss, even with the quality Jacobs chuck that I used to replace the original.

If I get a dressed grinding wheel (not cross grinding), I'd have better luck but I'd still have runout unless I can dress the wheel while it's running. Each time that I'd remount the wheel, I'd have to do significant dressing.

I'm not quite sure what you are asking in some of the other points, but my drill press has a table that can rotate to the side, or to any in-between position. It can be raised or lowered, but its crude with nothing like 0.001" accuracy. When I loosen the clamp to raise or lower the table, it also rotates a bit on its own, so things have to be set up for each new height.

I have a quill travel adjustment to limit the depth of drilling, but it has only about 6" of travel. The accuracy for depth is better than table height, but probably not good enough for super-precise travel.

[Query]

OK, so no good.

Is there something similar you could do with another machine? A router, a milling machine, etc.?

Or would they end up costing more than the real thing?

A sharpening machine is in theory such a simple idea. It seems like it ought to be possible.

If you had a dressed wheel you could maybe figure out a way to mount it on an ordinary cheap tool sharpening machine, like they use to sharpen planers and chisels and lathe tools - though I'm not sure any have horizontal ledges. On the ones I have seen, the ledge on which you rest the tool is tilted.

However, purpose-built dressing machines are fairly expensive too. So requiring that you be able to produce dressed wheels adds a lot to the cost.

[Bill_S]

Continuing on - there is one advantage that a slow-turning device like a drill press has. It would have much less tendency to remove the temper in hardened skate steel. If hardened steel gets red hot, it anneals - gets soft. The soft metal edge won't last as long.

I have three different bench grinders, although one is technically a rotary sharpener. The most common grinder turns at 3450 rpm, and will quickly destroy temper unless used very gingerly.

Here's a photo of that grinder...



This is the most common kind of grinder found in garages. It makes quick work of removing regular steel (angle iron, bolts, lawn mower blade sharpening, etc.) but is a disaster for heat-treated metals.

Here's the label, and you can see that it spins at a fast 3450 RPM unloaded. It's fast, but a brute with fine steel.



Moving to a grinder that is better suited for heat treated steels, you'll find a slow speed grinder turning about half of the speed of the one above.



And the label advertises it to be a slow speed grinder at 1750 RPM.



For the finest edges on woodworking tools and knives, I have a Tormek water-cooled grinder turning at 100 RPM. It's the most expensive by far, and the bottom of the wheel rotates in a water bath. The grit is very fine, and it can make things razor sharp.





One could contemplate using it to cross grind, but you'd have a 5" ROH.

When I was checking into the Wissota, it spins at the speed of my fastest grinder. It would take a gentle touch to prevent annealing the steel, and even then I'm not sure how the thin edges fare. Maybe they do lose temper and that's a reason that power sharpened skates may need more frequent sharpenings.

[Query]

Am I right that on the bench grinders you show, the sharpening surface is either tilted or is off-center, so the edges would be uneven?

Would the right oil cool the metal enough to eliminate the tempering problem? Or could you squirt water on it, so it stays below its boiling point? I vaguely recall from high school shop that people chose the drilling oil for metal shop drills by boiling point - I'm not sure if that was the reason.

...

So many little details. Maybe I should go back to the idea of making a hand-held sharpener like the Pro-Filer and the old Berghman tools

All they really need is a hole just large enough to hold an abrasive cylinder (such cylinders are available many places, in varyious grits and compositions, with various diameters). And a gap into which to slide the blade, the width of a blade, possibly cut with a saw, centered on the cylinder.

At least I understand that, though I'm not sue how to center the gap so precisely.

[Bill_S]

The tool rest can be adjusted for tilt to produce even edges. It would take a dedicated unit for that unless you want to experiment getting things aligned each time you sharpen.

The wheel is water cooled - no oil. It takes tap water in the black tray under the wheel. Here's another photo of it when it was new getting ready to sharpen a plane blade. The blade holder slides on the round bar left and right to even out the wear on the wheel. The front tool rest isn't mounted in this photo.



Remember that you'd have a HUGE ROH because of how big the wheel, motor, and frame are. The wheel arbor shaft is probably as large as most ROHs.

[Query]

O.K. I shouldn't modify a post while you are posting!

For me, it's indeed back to the idea of hand-held tools. I've been trying to figure out how to make one with other ROH's that imitates the Berghman tools (which were all 1/2" ROH), because I like the idea of an adjustable gap.

If I figure out how to do that, I'll start another thread for it.

[Bill_S]

At least I understand that, though I'm not sue how to center the gap so precisely.

And THAT is precisely the challenge. Unless you have a mill, that's not straightforward. Using wood and common woodworking tools, one could approach it with trial and error to find one good unit, but that's time consuming.

[Bill_S]

Just one more thought.

For a tool with an adjustable gap, Precision Blade Honing sells this unit. They advertise it as a hollow polishing tool. Note the adjusting screws in each side. The screws can be brought in for narrow blades, or out for wider freestyle blades.

The honing cylinders are wrapped with adhesive sandpaper, which should cut steel just fine. And sandpaper is cheap.

[Query]

I'll look into that tool.

But back to the idea of making a hand-held sharpening tool, even though this is out of my league - though some community centers have wood shops available:

Would it be easier to cut the gap first, as deep as the center of the piece of wood you are going to use, then center the drill on part of that gap, with a good quality drill press? You could center it while the drill is off, and turn it by hand to verify that the drill  bit is mounted so as not to wobble.

I think it would work best to start with a pilot-hole sized drill bit, that was the width of the gap you have cut, because then you can easily see or feel that it is in the right position.

However, trying to get sub- .001" level precision has got to be challenging in wood.

Maybe it would be easier in metal - but can a wood-shop metal drill press drill in metal?

I don't know anywhere I can cheaply rent the use of metal-shop level tools - and they are remarkably expensive.

[Query]

I can't find the hollow polishing tool at http://precisionblade.com - can you, or is there a different link?

BTW I've sometimes used sandpaper glued to dowel rods. It sort of works, if you are very, very careful. For example, if I wanted to change hollow or a rocker profile, I would do that, rather than wear done the expensive Pro-FIler stones, because I, like you, already wore one out that way. I've also used short ones as emergency pocket tools.

P.S. Oh, now I see it. Didn't realize I had to advance pages. A bit pricey, but not more so than Pro-Filer.

[Bill_S]

However, trying to get sub- .001" level precision has got to be challenging in wood.

Maybe it would be easier in metal - but can a wood-shop metal drill press drill in metal?

Yes, getting 0.001" in wood is very difficult with ordinary woodworking tools.

A drill press will work for either wood or metal. Same machine, no difference. Mine is a 15" swing, belt-drive, floor-stander.

[Bill_S]

I've had some thought about adapting the Pro-Filer to work with thinner blades. It would require guiding on the OUTSIDE of the body instead of on the slot. Here's a terribly out-of-proportion, not-to-scale concept sketch for something like that...



There are other problems to be worked out with that concept, such as adapting to the rocker curve along the blade.

[Query]

I'm really impressed by what Precision Blade Honing has to offer. I spent a dozen years figuring out some of what they sell pre-packaged, and some of what they have appears to be better, like you would expect from people with access to a precision machine shop, and the tool-using knowledge that goes with it. Of course, it's all priced for professional skate shops, a bit high for home users. But what a great resource!

Have you tried the hollow sharpening tool that you mentioned? In particular, you once mentioned looking for a hand-tool to create 7/16" hollow. BTW, I'm not sure if ordinary sandpaper would fit their tool. Maybe the sandpaper needs to be a particular thickness.

I've had some thought about adapting the Pro-Filer to work with thinner blades.

Wouldn't your scheme bring you back again to the difficult problem of centering of stuff exactly?

I've dealt with thinner blades by taping the blade, along the edge, with a carefully selected tape. Requires a lot of care to be even, but it can work.

I've tried to tape the Pro-Filer gap itself - but can't figure out a way to apply enough pressure to make it stick well, while keeping the tape in the right position.

I also once widened a Pro-Filer gap with a file to handle an extra thick blade, and made the blade-end surface thinner to handle what Precision Blade Honing calls "carrier-held" blades (Matrix, though it looks like Paramount blades are like that too, as are many hockey blades), in which the available sides of the blade aren't long enough for the standard Pro-Filer tool, especially after they've been through a few sharpenings. I hated doing that. Such an expensive tool to potentially mess up, but it worked.

If you are super-super picky about centering, because your Pro-Filer is very slightly off center, you can use slightly different tapes on each side, or sand one piece of tape. But most recently, I mostly just turn the skate around every few strokes, instead. Especially if I'm not trying to create an ultrasharp foil edge, which requires that one be super-uniform and super-careful.

If you use a squish-able foam tape, the gap size doesn't need to be exact - elastic compression will do a good job of centering the blade, though you have to slow down your sharpening technique.

I think foam tape could also handle a side-honed blade (sides not exactly straight and parallel, e.g., dovetail cut, tapered, parabolic, etc.) - but I haven't tried it, because I've never had one. I'm not even sure that side honed blades are side-honed on the part of the blade the gap centers on - maybe only very close to the working surface, or whether that varies from brand to brand.

(I've thought of imposing side honing on an old pair of blades, just to see if it improves things - but I think that would be hard without a milling machine. Mike C. pointed out to me that even professional blade makers like HD Sports sometimes manage to add their side honing off center, which creates an interesting sharpening problem. Then again, he also pointed out to me that they don't always center the countersink on their screw holes right - maybe they don't use countersink drills? Ane everyone knows about their factory sharpening issues.), so maybe they just aren't as careful as they should be. Besides, I'm probably not good enough to tell the difference side honing makes. I'm not even sure what that difference is supposed to be - people have been debating the benefits of side honing skate blades in the same various ways at least as far back as the late 1800's. But I am drifting more off-topic.)

[Bill_S]

Wouldn't your scheme bring you back again to the difficult problem of centering of stuff exactly?

Yes, centering is still going to be a problem. It is a rough idea, but those tracks holding the sharpener could be adjustable. Find center, set and forget - until you buy new blades.

I've thought of imposing side honing on an old pair of blades, just to see if it improves things - but I think that would be hard without a milling machine.

You wouldn't use a mill on hardened steel like a skate blade. You could use one before heat treating, but not afterward. Instead, you'd use a surface grinder with a liquid coolant system. The work would be held with a magnetic chuck.

Here's one similar to the unit that we used at Battelle...


(Photo from WikiMedia Commons, Photograph taken by Glenn McKechnie, September 2005. )

You can see that it's not going to be found in a home workshop, but you can sometimes find grinding services in major metro areas. For example, there was a fellow who specialized in grinding hand-planes to restore worn, un-flat surfaces, and to make the sides perfectly square with the bottom. (Sometimes planes are used laying on their side to plane a vertical edge.)

This Stanley #5 plane was probably made in the 1950s, and the grinding to flatten it made it look new again, and with square sides. It's probably better now than when it was new.





Surface grinding is a very precise operation, and it can hold tight tolerances.

BTW, holding 0.001" tolerance in manufacturing is difficult. It's even hard to measure reliably. A more common "good" tolerance for metalworking is 0.005", and that's still considered tight.

[Bill_S]

In an earlier post you mentioned using a woodworker's router. At first I thought that this might work, especially one mounted in a cast iron router table.

I quickly realized that the spindle speed for a typical router is 8,000 - 20,000 RPM. That would instantly frag most grinding wheels, even fairly small ones.

There are other problems too for a typical router in a table. Generally the router doesn't sit above the surface of the table. Only the bit does, and the height of any grinding wheel would be too low. It might be possible to raise the motor above by rigging some external support, but it still doesn't solve the problem of super-high RPM.

It would be easier to start with a 1/2 or 1/3 H.P.  motor turning at a more reasonable RPM, then adapt it to a cast iron router table. Motor - $150. Table - $450, but uh-oh, the table has holes and tracks milled into the top surface where you'd want to slide the skate holder. You are approaching the cost of a bare-bones Wissota unit, it has problems, and still have to buy the skate holder, grinding wheel, and fab up a wheel dresser.

It might be possible to find an old, non-working table saw and scavenge a cast iron surface, but you'd still have to work around the miter slots and blade opening.

[Bill_S]

You mentioned the difficulty of sticking adhesive tapes in the blade gap to shim the Pro-Filer for thinner blades. I've been thinking about that problem too, but haven't had any luck.

The rounded shape of the Pro-Filer makes things difficult for adjustment screws like that used in the Precision Blade Honing product. I though once about attaching thin brass shim stock through the slot and fastening it to the Pro-Filer ends, which are flat. I'd drill and tap for small screws to hold them onto all four ends.

I made a quick-n-dirty paper mock-up (for one side), and instantly realized that it put the shim into the stone's access area. It would be hard to turn the abrasive stone with shims in the way.



The shim stock wouldn't be perfectly flat either, so I'd probably have to start the Pro-Filer at the end of the blade, instead of placing it in the center of it.

Even this is fussy work, but I thought that I'd toss the concept into your ball park.

[tstop4me]

You mentioned the difficulty of sticking adhesive tapes in the blade gap to shim the Pro-Filer for thinner blades. I've been thinking about that problem too, but haven't had any luck.

The rounded shape of the Pro-Filer makes things difficult for adjustment screws like that used in the Precision Blade Honing product. I though once about attaching thin brass shim stock through the slot and fastening it to the Pro-Filer ends, which are flat. I'd drill and tap for small screws to hold them onto all four ends.

I made a quick-n-dirty paper mock-up (for one side), and instantly realized that it put the shim into the stone's access area. It would be hard to turn the abrasive stone with shims in the way.



The shim stock wouldn't be perfectly flat either, so I'd probably have to start the Pro-Filer at the end of the blade, instead of placing it in the center of it.

Even this is fussy work, but I thought that I'd toss the concept into your ball park.

I've also played around with tape and brass shims on the Pro-Filer.  Also another idea that requires a good drill press (which you have, but I don't).  I'll spin off a separate thread on brainstorming modifications to the Pro-Filer.

[tstop4me]

It would be easier to start with a 1/2 or 1/3 H.P.  motor turning at a more reasonable RPM, then adapt it to a cast iron router table. Motor - $150. Table - $450, but uh-oh, the table has holes and tracks milled into the top surface where you'd want to slide the skate holder. You are approaching the cost of a bare-bones Wissota unit, it has problems, and still have to buy the skate holder, grinding wheel, and fab up a wheel dresser.

Yeah, the Wissota figure skate holder by itself costs $375.  So when you add up just the price of the components, the Wissota package ain't bad.  The other approach with some home units [OK for hockey, but iffy for figure] such as Sparx and the home Pro-Sharp is to forgo the dressing system and use interchangeable wheels with different fixed ROH [diamond coated mandrels, precision centered and balanced].

[Bill_S]

If I'm dreaming pie-in-the-sky, I'd forego diamond abrasives for modern CBN. Cubic Boron Nitride. Here's why:

"Although diamond wheels were once the preferred superabrasive for industrial grinding, the diamond’s carbon content would dissolve iron at high temperatures. This made diamond wheels ineffective at grinding steel tools.

Today, CBN wheels grind hard ferrous metals, nickel- and cobalt-based superalloys, and cast iron. And because the Borazon crystal can withstand temperatures greater than that of a diamond, CBN wheels are great for grinding hardened steel tools, cutting glass and diamonds, and jewelry making."

(from https://www.eaglesuperabrasives.com/cbn-wheels)

So if you are thinking pre-profiled, interchangeable wheels, that would be my choice.

I was thinking about how to get a cast iron surface for sliding the skate holder, and thought to substitute 3/4" (or thicker) MDF for light, non-production duties. It's very flat, although it is soft. Also felt skate holder feet won't slide on it without a finish (it's like Velcro with felt in its native state), but even some penetrating shellac + paste wax could work to harden it a bit and to reduce the "snag" that felt would experience.

Mounting to it must be engineered carefully to not stress and bend it. It's very cheap, so some experiments could prove it's worth.  FWIW, my entire router table is MDF. I bought the laminated MDF top with hardware from Rockler, and built a cabinet stand for it with 3/4" MDF.