Reply To: New vs old hand plane lineup
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Presumably, hollow grinding is not an option for those who follow Paul’s method of using diamond stones? Only ask as I don’t know.
Hollow grinding has nothing to do with which method of sharpening you prefer. It’s done on a grinding wheel before the sharpening process. Hollow grinding your bevel saves tons of time when it comes to sharpening, and since you’re on your stones far less time, it thus also has the side benefit of greatly reducing wear on your stones. It also makes it much easier to keep the correct orientation when sharpening by hand, as you have two bearing surfaces on which you can balance, as opposed to only one with a flat bevel.
Works on your plane irons, chisels (don’t think I would recommend it for mortise chisels), router plane irons. Night and day difference in time to a perfect edge over any other approach, obviously. I’m sharpening about half a mm of steel compared to … well even the thin old Stanley irons were over 2mm, so sharpening an old Stanley iron represents 4 times the surface area.
I have a CBN grinding wheel on a high-speed grinder — it takes no time to hollow grind an edge. Here’s the entire process in real time:
And that will cut your sharpening surface area by 3/4 on a Stanley plane iron (with a far greater reduction on other tools) for months and months. Think about how much faster you’d be sharp if you had at least 75% less steel to deal with. You don’t need a CBN wheel or even an electric grinder — hand-cranked grinders with inexpensive wheels work just fine and get results just as good, it just takes a bit longer as you need to cool the steel when grinding.
However, a CBN wheel such as I’d recommend (https://www.amazon.com/gp/product/B01GG5GIGC/ref=oh_aui_search_asin_title?ie=UTF8&psc=1) has another nice advantage — the CBN wraps around onto the flat machined surface on the side of the wheel. This is done intentionally so you can use that perfectly flat surface for grinding. It wraps about 3/4 of an inch. So if you buy, e.g. an old chisel, and you need to grind down past the pitting and flatten the back of the iron before sharpening, well you can do that in about a minute. That saves a ridiculous amount of time, not to mention wear and tear on your stones. I went through a phase where I avoided vintage tools because of the time involved in the restoration process. Now I jump at them. This is especially pertinent if you’re considering a set of vintage planes.
I only wish I had known about CBN wheels sooner, between flattening backs and hollow-grinding to a wire edge they are complete game-changers when it comes to getting a perfect edge.