Sharpening a scrub plane iron?

What's the best way to sharpen a scrub plane iron w/ a fair bit of camber to it? I've seen a picture of some sort of jig that mounted the iron on a pivot and the arc traveled by the edge of the plane iron created the camber when using a bench grinder.
So far I've not had a lot of luck doing much w/ the grinder besides really messing things up, so I have some reservations about the above. Normally I've been using Scary Sharp for my sharpening so far, w/ decent results as long as I use a jig. This scrub plane iron doesn't look like it'd lend itself to a regular jig very well.
How sharp does a scrub plane iron have to be to be effective? I guess sharper would be better, but w/o a jig, I'm not all that good at sharpening free hand. I can probably make it sharp enough to be dangerous, but thats about it. Is the whole deal w/ secondary or tertiary bevels out the window for this application?
Sorry if some of these questions seem silly, but I figured I was better off asking than guessing...
Thanks,
nuk
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If your iron is dangerous, it is sharp enough;-)
A scrub plane iron is easy to sharpen freehand, because it does not have to be perfect like in a smoothing plane. Lie Nielsen has instructions online: http://www.lie-nielsen.com/faq.html?cart 6370438462#12
Wolfgang
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Well, thanks guys for the input. I guess I'll quit sweating it so much!!
Thanks again,
nuk
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and not nearly enough to do very many useful things.
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Like Wolfgang said, it doesn't have to be perfect. If you think about what portion of the iron is going to be in contact with the wood, you see that you can concentrate your efforts on a fairly small area of the iron. I've always gotten by pretty well with just using SS paper and rotating the iron as I pull it towards me. The bevel doesn't look perfect, but that's OK; the edge is all I care about anyway.
The technique mentioned on the L-N site is probably worth a try. (For some reason I never thought of bringing the stone to the tool for a scrub plane iron, even though I use that technique for various larger carving tools.) But obviously you need to be really careful. I would even recommend using gloves. For example, I use batting gloves when I'm sharpening a drawknife by bringing the stone to the blade. They could be cut through if you're careless, but they give you just a bit of extra "insurance".
Chuck Vance
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