What do you use as a grindstone?
The figure skating Pro-Filer kit. No longer available new.
See
https://www.afterness.com/skating/profiler.htmlHad 2 abrasive cylinders ("stones"), whose radius was the ROH. The coarse grain cylinder had diamond grit. The fine grain cylinder had something else.
It was available for 5/16", 3/8" and 7/16" and 1/2" - but the 7/16" was actually 3/8"
(where " = US standard inch = 2.54 cm)
Each cylinder fit into a handle, with a gap to fit the blade at right angles. I added scotch tape to each side to make it snug, and stop scratching, & folded the tape over the top, so the sides wouldn't scratch.
There was a flat stone, which could be used to shape or remove the sharpening burr. Mine was missing, so I used a 5000 grit flat stone.
Kaitsu 3D printed something similar.
The hockey version contained 1 cylinder and one handle. It was coarse grained; the gap was too small for figure blades. Some are for sale on eBay. I once carefully widened the gap so it could fit my figure skating blades.
Another good but very old hand tool was the Berghman skate sharpener, available used on eBay. I love the design, but the stone was a natural stone (??) - very coarse grained and crumbly. Probably should be replaced by a better finer grain diamond grit cylindrical stone. ROH=1/2"
I have tried some other hand skate sharpening tools, but none of those I tried were good enough quality to give consistent results. But I think they may be some good ones for hockey skates.
As with any sharpener sharpener, the tricky part is keeping the edges even (I reverse the blade every few strokes), making a smooth grind (I lubricate with water; some use oil), maintaining the profile (good idea to trace or photocopy the blade at the start), and eventually you may want to trim the drag pick (the pick nearest the main part of the blade), when too much metal has been sharpened away, and if you aren't careful you will smooth out the difference between the spin rocker and the main rocker, too much, or round off the back. (Some JW blades have two spin rocker zones.) And many skaters want the transition between the main rocker and spin rocker moved to be under the ball of their foot, or 1 or so mm ahead of it.