This little handheld sharpening device was patented in 1920 by George H. Berghman of Chicago, IL. You squeeze the handles together at the top to open it. When you release the pressure, it clamps onto the sides of the blade. Then you slide it back and forth and the grinding stone inside does its work. The stone’s diameter is one inch, which means it puts a 1/2″ radius of hollow on your blades.
There are loads of these available on eBay and other internet sites for pretty low prices (though not as low as the original—$2.50 according to the price tag on mine, but only $1.25 according to advertisements in Boys’ Life. I guess girls are not supposed to use it.
The device seems a bit unwieldy. When I squeeze mine, it feels pretty wobbly—You have to be careful to keep the blade opening even along its entire length. And in mine, the stone is stuck to one side. I think this is a defect in my particular one rather than part of the design because the back of the box says to rotate the stone frequently by “turning the stone with thumb and forefinger.” Mine won’t budge.
The stuckness of my stone means that only one side of the holder opens with respect to it, so the stone will never be centered on the blade. This would cause uneven edges and really mess up my skating if I relied on it! But if it weren’t stuck, I suspect alignment would be rather difficult because there would be one more moving part.
To conclude, here’s an advertisement directed at hardware stores that promises the sharpeners “do a good sharpening job… and give you a good profit.”
It also features a sharpening machine: a bench grinder with an 8″ wheel and a skate-holding jig. The 8″ wheel implies a 4″ radius of hollow since it is set up to cross-grind.