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convex sharpening method?

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Forum topic by 12strings posted 04-20-2013 11:43 PM 968 views 0 times favorited 18 replies Add to Favorites Watch
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12strings

405 posts in 1036 days


04-20-2013 11:43 PM

Are there any disadvantages to sharpening freehand in the method that has you rocking the iron back and forth as you grind and hone, so that you end up with a convex bevel (the opposite of hollow grind)?

I have tried it and really like it, as opposed to trying to keep my bevel constant freehand (I don’t use a honing guide).

Thanks for any input.

-- I'm strictly hand-tool only...unless the power tool is faster and easier!


18 replies so far

View USMCSergeant's profile

USMCSergeant

28 posts in 606 days


#1 posted 04-21-2013 12:22 AM

I convex most of my knives, ones that have a thick enough blade to really take to a convex edge. The smoothness of the cut, and how sharp the edge becomes is the definition of scary sharp.

My method is using a phone book, topped with a mouse pad. I tape the sandpaper to the mouse pad and pull-stroke the blade across. I usually sharpen to 2000, and on 800 and above use a little water. Then I strop on leather. The soft backing gives just enough to creat a convex curve which the blade takes it shape.

I’ve never sharpened a hand plane or chisel with this method, but I have thought about it a few times. I think the reason I haven’t is that a plane and chisel have single bevels – a chisel cut edge. I’m not sure how strong the tip would be with one side convexed and the other flat.

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Loren

7543 posts in 2299 days


#2 posted 04-21-2013 01:23 AM

If you can make it work for you, go for it.

-- http://lawoodworking.com

View BTimmons's profile

BTimmons

2123 posts in 1136 days


#3 posted 04-21-2013 01:30 AM

USMCSergaent, here’s Paul Sellers’ method of sharpening plane irons freehand with a convex bevel. Looks surprisingly easy and foolproof. Kinda want to try it myself.

http://lumberjocks.com/PaulSellers/blog/27886

-- Brian Timmons - http://www.BigTWoodworks.com

View lwllms's profile

lwllms

544 posts in 1933 days


#4 posted 04-21-2013 03:01 AM

You mean disadvantages that go beyond wasting time, effort, and stone life? Honing the bevel shouldn’t take more than a few strokes. The bevel is the easy part. The harder part is keeping your tool’s flat face and your stones repeatably flat. Harder but still relatively easy and quick if you’re even half-way diligent about it.

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USMCSergeant

28 posts in 606 days


#5 posted 04-21-2013 04:20 AM

Thanks BTimmons. I use the same green material on my strop that he does. I may just convex everything now, but I still like my sandpaper route!

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12strings

405 posts in 1036 days


#6 posted 04-21-2013 07:25 PM

It is Paul Sellers method I’m asking about…I used it recently for a few plane Irons and chisels.

Lwllms…Once the chisel/Iron has that shape, O don’t see how it will waste any more time than another method. To re-hone, I still don’t take very many strokes, and to re-grind once that convex bevel gets too steep, is something you have to do anyway occasionally with any method, right?

I don’t seem to have too much trouble KEEPING the back of my tools flat, once the initial work is done…and my waterstones flatten up super fast on my big chunk of granite with sandpaper on it…That might mean I have cheap waterstones that won’t last too long…we’ll see.

-- I'm strictly hand-tool only...unless the power tool is faster and easier!

View Don W's profile

Don W

15019 posts in 1219 days


#7 posted 04-21-2013 10:21 PM

I would think you’d still need to keep the bevel constant, but now your rocking the iron. I suppose if you like it and don’t like hollow grinding, then its an advantage, but I can’t see how its really any easier.

-- Master hand plane hoarder. - http://timetestedtools.com

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12strings

405 posts in 1036 days


#8 posted 04-21-2013 11:17 PM

The advantage for me is that, freehanding, It’s easier to come to the same angle at the backstroke of my rocking than it is to slide the iron around while trying to keep the same angle the whole time.

-- I'm strictly hand-tool only...unless the power tool is faster and easier!

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lwllms

544 posts in 1933 days


#9 posted 04-22-2013 12:15 AM

12strings,
You’re going to end up honing away metal that has no impact on your cutting edge. Traditionally, you grind at 25° and hone at about 30°. After the initial setting up of a new tool, all you’re doing when grinding is maintaining a very small bevel to hone. When honing the bevel it should literally take only a pass or two to raise the wire edge on each grit of stone you use. That wire edge being raised across the whole cutting edge is your indicator that you’ve done all you need to.

Paul Sellers’ method ignores the wear bevel that forms on the flat face. Both surfaces that make up a cutting edge suffer dulling wear as the tool is used. If you don’t remove the wear on the flat face, you’re only addressing half of the cutting edge. Sellers strops, I can’t remember, maybe something like 30 strokes on each surface of the cutting edge. He’s actually spending more time and creating a future problem. Stropping dubs the edge just like dulling wear dubs the edge. Pretty quickly you’ll lose control of the whole process. If you try to strop to a sharp edge you’ll soon give up because success will become elusive and time consuming.

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12strings

405 posts in 1036 days


#10 posted 04-22-2013 04:32 PM

1. I understand what you are saying about not needing to hone the entire convex bevel, just the very edge, since the rest doesn’t touch the wood…but as long as i’m not really trying to get more than the very tip honed…I guess I don’t see how it is going to take any significantly more time. Re-grinding on low grits, or a wheel is going to be necessary occasionally no matter what method you use, as your micro-bevel gets bigger and bigger, right?

2. Are you saying He doesn’t hone the back at all? I guess I didn’t get that. I assumed even using the convex method, you would still take off the wire edge by honing the back. How can doing something different tot he bevel side have a different affect on the flat face?

(I’m not trying to argue…but you seem to know what you are talking about…I don’t understand why what your saying means this method is bad.)

-- I'm strictly hand-tool only...unless the power tool is faster and easier!

View Loren's profile (online now)

Loren

7543 posts in 2299 days


#11 posted 04-22-2013 06:10 PM

I just looked at the Sellers video. A few comments.

1. He has control on the stones. He is not rocking the bevel
on the stones. He is grinding it flat.

2. The convexity is introduced in stropping. The leather
gives under the pressure and rounds the bevel.

3. Sharp enough to tear a piece of paper is probably
fine for a chisel, but for a plane iron for fine finishing, I
am skeptical.

I don’t have a problem with stropping. There is a knack
to it and if the bevel is rounded too much stropping or
buffing at the edge, it seems to lose the acuteness
that is essential to getting the finest finish cuts with
hand planes.

-- http://lawoodworking.com

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12strings

405 posts in 1036 days


#12 posted 04-22-2013 06:27 PM

Update: I just watched the Paul Sellers sharpening video, and I don’t think that’s what I am thinking of, or describing what I do…I can’t find the video I saw (here’s an example…watch from the 1:50-2:10 mark to see the motion…http://www.youtube.com/watch?v=F9DzOtsYxIA),

The difference was not in the stropping (I don’t own a strop, and don’t strop anything)...I stop at a 6000 grit waterstone.

It was that, starting at the grinding stage all the way up to honing, I eye-ball the angle I want (25 or 30 deg.) and start the iron at that angle closest to me, rock it back as I go forward, then bring it back to that angle each time. This doesn’t give you precise angles, but on a bevel-down plane, it doesn’t matter.

Do the disadvantages some have described apply to this method as well?

-- I'm strictly hand-tool only...unless the power tool is faster and easier!

View Dan's profile

Dan

3543 posts in 1532 days


#13 posted 04-22-2013 06:39 PM

If you are able to get the edge sharp enough for your liking by using your method then there is no disadvantage. If you feel like your not getting a truly sharp edge then I would say you might want to try something else.

-- Dan - "Collector of Hand Planes"

View Loren's profile (online now)

Loren

7543 posts in 2299 days


#14 posted 04-22-2013 07:19 PM

As long as you manage to hone to the acute edge with all
the stones without gouging them, I don’t see a problem. Be
aware that it is possible to fool oneself into believing the
edge is being honed evenly when it isn’t. There’s an
area of play between honing to the edge evenly and
gouging the stone, 2 or 3 degrees maybe.

-- http://lawoodworking.com

View lwllms's profile

lwllms

544 posts in 1933 days


#15 posted 04-23-2013 12:55 AM

12string, you asked,

”1. I understand what you are saying about not needing to hone the entire convex bevel, just the very edge, since the rest doesn’t touch the wood…but as long as i’m not really trying to get more than the very tip honed…I guess I don’t see how it is going to take any significantly more time. Re-grinding on low grits, or a wheel is going to be necessary occasionally no matter what method you use, as your micro-bevel gets bigger and bigger, right?

2. Are you saying He doesn’t hone the back at all? I guess I didn’t get that. I assumed even using the convex method, you would still take off the wire edge by honing the back. How can doing something different tot he bevel side have a different affect on the flat face?”

Here’s the link:
http://www.youtube.com/watch?v=vvTcReENk9g

Watch the whole thing.

Sellers doesn’t grind. There’s no secondary bevel, just one rounded bevel. He doesn’t deal with the wear on the flat face. His method ignores the whole point of traditional honing—grind at a more acute angle than you hone at and keep the honed bevel small so it’s easy to deal with.

His method isn’t the traditional honing method. Get any woodworking book before about 1975 and they all describe the same honing method. About 1975 Japanese tools started making inroads into Western woodworking and a lot of sharpening gimmicks started showing up. Sharpening was a life skill for a long time so specific honing methods are often overlooked in early texts. Joseph Moxon alluded to the traditional method in his book published in the 1680’s, Peter Nicholson described it well in the 1830’s, and it was even printed on Stanley’s plane iron packages in the 1970’s. I can give you scans or screen shots if you’d like and there are more books I can scan.

There’s no effect of his rounded bevel on the flat face. Just like honing guides, his method causes people to focus on the bevel and ignore the flat face. Focus on the cutting edge, not irrelevant things like rounded bevels.

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