Bending Diamond Stones to Produce Camber on Irons?

[Steve H Graham]

I had a nutty idea, so I thought I would run it up the flagpole and see who salutes, as Joseph Heller put it.

One of the annoying things about sharpening plane irons is that they work best with curved edges, but stones are flat, so they produce straight edges. To get around this, we rock irons while we sharpen them, or we use other tricks.

What if someone put a diamond stone (steel plate with diamonds in it) in a hydraulic press and squooshed it so it developed a slight concavity, turning it into a trough shape? If you could lower the middle by five thousandths, you would have an automatic camber when you sharpened an iron.

Genius or heresy?

[Robert Hazelwood]

Interesting idea, but it's trivial to make a camber on a flat stone so I don't think it's worthwhile. That stone would lose its utility for anything besides sharpening an iron of a specific camber. Maybe in some special case where you needed an exact shape and had to replicate it over and over through repeated sharpening. But for that I would probably carve a block of wood to the shape I needed and stick sandpaper to it.

[Barney Markunas]

I'm not sure if they are still available but they were a few years ago. Search for something along the lines of "Odate crowning plate". I was curious but too cheap to pony up the $$ at the time.

[Steve H Graham]

I think it would work for irons within a fairly big width range. The radius would not be critical. If you ended up with 4 thousandths of relief on one iron and 5 thousandths on a wider iron, it wouldn't matter.

It's an interesting subject, because "experts" contradict each other. One will tell you to just round the corners, and another will tell you that just gives you rounded plane marks, so you have to put a radius across the entire edge. Rounded corners and a radius are totally different things.

It must not be necessary to put a radius across the whole edge, because there are successful woodworkers who don't do it. If rounded corners didn't work, these guys would be making furniture with ruts in it.

[Lasse Hilbrandt]

Usually one need more than one Grit to sharpen a plane iron. That Means you need to bend more than one plates to the exact same camber. That could be difficult.

[Tom M King]

Just off the top of my head, I thought of nine planes that I use which all have different cambers. That would require a lot of diamond plates, which I don't like that much anyway.

[mike holden]

I had the chance to use the odate crowning plate at a sharpening class given by Chris Schwarz a few years back. I really liked it and the results for my number 7. Did not buy the plate though.
I use the cambered roller on my veritas to get the crown, works just as well.
Mike

[Jim Koepke]

It must not be necessary to put a radius across the whole edge, because there are successful woodworkers who don't do it. If rounded corners didn't work, these guys would be making furniture with ruts in it.

On the final smoothing passes on a piece if the blade is sharp and taking shavings in the sub-thou range the tracks will be next to unnoticeable. A slight over lap of passes should remove any tracks.

I usually know it is time to work on flattening my water stones when unintentional camber shows up on my blades when sharpening.

Why mess up a good diamond stone to do what people are always trying to correct on a water stone?

Here is an off the wall method of achieving a camber on a blade:

http://www.sawmillcreek.org/showthread.php?158373

It is possible with a cambered blade to leave taller tracks than with a straight blade. It is all in how they are used.

jtk

[Mark AJ Allen]

Bending a steel plate with the stones already on them is a little nutty.

Bending a steel sheet, then applying a diamond paste to it ... much less nutty.

[george wilson]

Just learn how to sharpen. A bent plate is totally un necessary. It never would have occurred to me,even as a young man,to have a dished stone to produce a cambered plane iron.

It is exceedingly simple to just tilt the iron a bit each way while honing. Besides,a rounded cutting vs a flat cutting surface with slightly rounded corners can have different uses. A dished stone would allow only one shape.

[Patrick Chase]

OK, you're going to mock me for this (esp George) but there's one case where I've found a curved diamond plate to be useful: Concave spokeshaves.

In particular I made a concave diamond-surfaced dressing tool out of wood and the cheap iWood diamond tape that Stu sells. I use it to dress the surface of a large slip-waterstone (reclaimed chunk of an old worn-out and broken stone) to the right radius for grinding the primary bevel. Note that the primary bevel radius is significantly different from the cut radius of the spokeshave due to the impact of bed angle, so the usual advice to "cut the profile you hone with" is far from ideal.

IMO it works a lot better than a dowell and PSA sandpaper or the aforementioned "use the spokeshave to create its hone" approach.