Originally Posted by
ian maybury
Think there's cross purposes involved here David, and it'd be a pity to end up arguing. I can assure you that a WorkSharp can do an excellent job of flattening chisel backs when correctly used. Anything that gives good control, removes material fast enough to be reasonable (multiples of the rate of removal by a 120grit waterstone), puts in minimum heat and creates a surface flat enough to subsequently clean up all over in a minute or two on a 1,000 grit waterstone can't be doing a bad job. It requires a fair degree of finesse in use, but if you too found yourself with little option but to work through a full set of chisels (bought some years previously, left untouched as a result of illness/other priorities and past being returned) with unexpectedly badly humped backs one after another you would likely find yourself quickly looking for a power assisted back flattening method too...
You're a better man than me though if you can get a WorkSharp to remove the large amounts of metal needed to reset the bevel angle on a thick BU plane iron within a reasonable period of time, and without requiring a second mortgage for consumables. Especially at UK £ to dollar prices. I wouldn't think of trying to use it to flatten the back of a plane iron unless it was very close already, it's just not big enough. Luckily the issue hasn't arisen given the excellent flatness and surface finish of Lee Valley BU plane blade backs.
For sure it's also possible to correctly grind a small tool on a high speed high heat inducing grinder - it's only a matter of reducing the pressure and contact time enough, and of achieving accurate alignment from first touch. It's clearly not the preferred option though, because it all becomes a very touchy operation - you wouldn't be using pink low heat low heat stones on your own grinder if it was.
It seems clear that what you describe is a proven high speed/low heat solution, but it's hollow grind.
You may well be correct that a hollow bevel is OK on japanese chisels (and it's clearly very convenient), but there's an awful lot of people out there that would (rightly or wrongly) beg to argue that it's not a good idea. I don't have a firm view on the matter. The decision to sharpen my set of chisels single bevel was entirely pragmatic. i.e. it was made on the basis that (as a person new to Japanese chisels) I wasn't if I could help it going to risk finding out the hard way that there is good reason for the caution about hollow grinding them.
I'm not keen on using all sorts of different bits of equipment if I can avoid it, hence this thread in the hope of flushing out some one stop flat bevel grinding solutions (a variable speed belt sounding very promising because it should be able to handle the more delicate tasks done by the WorkSharp, and also the faster metal removal with low heat build up that's useful for working heavy blades) - but don't mistake my floating a question based on a line of thought for dogmatism or some sort of fascination.
It may or may not prove a good option in practice, but it seems worth a look before discarding the possibility. One option should it prove impractical would be to trial a few chisels with a hollow grind and see how that goes...