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View Full Version : Putting a curved/convex edge on a bevel up plane iron etc?



ian maybury
09-22-2012, 4:48 AM
Having been getting by on a couple of diamond plates, I'm now just getting into 'properly' sharpening hand tools - mostly Lee Valley bevel up planes, and some fairly decent white steel Japanese chisels. There's an as yet unused Work Sharp 3000 (bought to put on flat primary bevels), and a set of Shapton Professional waterstones to hand. (bought for their reportedly low wear and low water use)

There's lots of sharpening information about, but the one issue that's a little more awkward is that of putting a convex bevel on a fairly thick bevel up plane blade. The problem being that the geometry means the curve needs to be rather more pronounced than on a bevel down iron.

I've seen Derek Cohen's write up on the topic that suggests using a curved wooden template on a belt grinder, and another somewhere about mounting the iron in a holder that pivots around a fixed pin at the required radius.

Are there any other takes on getting this job done, including specific set ups for use with a Work Sharp? (it has the bolt on top surface)

Some extra sharpening and honing strokes out to the sides of the blade on a waterstone seem to be enough to put a curve on with a bevel down blade, but a bevel up may be a bit more complicated. What's the experience of sharpening and honing these on waterstones given that it starts with a curved primary bevel?

I have Clifton number 5 (?) and Lee Valley jacks, but an undecided which to curve, and which to keep sharpened straight for use on a shooting board. Any thoughts on this?

Thank you

ian

Jim Belair
09-22-2012, 8:47 AM
I would keep the LV jack (if its the popular LAJ and not the 5 1/4 "junior" jack) straight for use on the shooting board. The lower angle performs better on end grain I think (although this is debatable).

For final smoothing, the amount of curve is very small, like a few thou (or a bit more to account for the geometry). If you're taking shavings of .001 thickness you just want enough curve that the shaving tapers down to nothing at the edge of the blade. I usually just freehand it.

Don Dorn
09-22-2012, 9:24 AM
Everyone does things a bit differently, my method is that I don't try and get a cambered blade, but with just a little extra push on each side at the end of honing, they come out that way - at least enough for my use.

As to the convex edge - when I saw Paul Sellers do it, I thought I'd give it a try. After about four months of doing it now, I've discovered that the blades are just as sharp, (probably not sharper) as other methods, but I have discovered that the edge lasts longer and that it takes less time to get it done. The theory of an ax making it's initial cut into wood using the edge, then the convex angle after that "splitting" the wood makes sense to me and am wondering aloud if that is what makes the edge last longer. In any event, I don't really see changing this method because it works very well for me.

ian maybury
09-22-2012, 11:00 AM
Thanks guys.

It's an LA Jack Jim. I bought the Clifton years ago not long after they came out, and as my only quality plane have used it for all sorts of stuff. I got the opportunity to kit up last year and hope to go at least semi professional, and also added the Lee Valley planes. All low angle/bevel up. A smoother (the wider one), a jack and a jointer.

It makes perfect sense to use the LA J on the shooting board now that you mention it, as well as low angle being better cross grain it would avoid needing to curve it too.

My instinct would be that it should be possible to add enough curve even on the low angle/bevel up blades with a few extra strokes or some extra pressure on the waterstone - but Derek's piece seemed to imply that it might not be enough. No reason not to do this on the Work Sharp if needed too.

A scrub plane would be different, in that the blade is much more highly curved, but doesn't need a lot of precision. A smoother or a jointer clearly doesn't need much curve anyway. The jack is probably in between..

ian

jason thigpen
09-22-2012, 11:10 AM
if you have a simple honing guide, the WS3000 will put a nice camber on the blade. when sharpening, just put even pressure on the center of the blade for a few seconds, then put pressure on each respective corner for a few seconds. the longer you press on the corners, the more pronounce the camber will be. if you are using the blade for smoothing purposes, the camber only has to be enough so that the blades corners won't dig into the wood and leave tracks. i just keep checking the blade with a square, looking for just a little light to peek through the corners. when you think it's enough, install the blade and try it out. if it leaves a smooth surface, you're good to go. if not, put it back in the honing guide and try again until you reach your desired result. i have one blade for my LAJ that is perfectly square for use on the shooting board. i have one with an aggressive camber that i sharpened in a similar fashion to derek. this one is used for quick stock removal. and i have two other blades with different angles that have just the slightest camber to help eliminate blade tracks. these are used for smoothing purposes.

ian maybury
09-22-2012, 11:27 AM
Thanks Jason. I have a Veritas honing guide with the barrel shaped roller, and also one of the stock Eclipse models - not to mention it's easy enough to buy another if needed.

Sounds like i've got the basis of a decent set up with what I have, which is great.

I've just started building a proper Roubo bench which will have a Benchcrafted-like DIY wagon vise at the end, and proper dog holes etc. I've not before had the means to properly hold workpieces for planing.

It's interesting the way that all this stuff hangs together as an integrated solution - how the bench opens up the possibility of working to a good standard, which opens up the needs for a more specialised approach on planes (see the other thread), which opens up the question of more sophisticated sharpening technique. And vice versa. It's been slowly coming together for the last few years. Finishing the bench is the last big step.

The primary reason for buying the Worksharp was for putting flat bevels on Japanese chisels, but it seems like it helps with convex bevels too.

I recently concluded that the set of Shaptons was worthwhile in the interests of especially sharpening and fine honing too.

ian

jason thigpen
09-22-2012, 11:38 AM
that roller on the Veritas guide is exactly the tool you need to accomplish the camber. i utilize that and my WS3000 for 80% of my sharpening needs. and you are gonna love that bench! i just finished my bench about two months ago. not a day goes by that i haven't come into the house and told my wife, "how did i ever build anything without this bench!" it will open up a whole new world to you!