sharpening problem with a camber

OK, so I am trying to get a camber on my no 4 1/2. I've been having this problem where I am getting more cutting from the edges of the blade when I try to add a camber, rather than the middle. In other words, the exact opposite of the camber I want. I just sharpened my blade and it is doing it again. I put the blade back in the plane, and using a scrap of pine to set it up, I can get wispy flakes from the edges, but the middle isn't contacting, and when I advance until the middle hits, naturally I'm getting heavier cuts from the edges. I can't figure out what I'm doing wrong.

I am using Norton stones: 220, 1000, 4000, 8000. I am using a DMT Dia-Flat 8" lapping plate, which I purchased new from sharpening supplies 2-3 years ago. The lapping plate and Norton stones are all about 8"x3".

I'm using the Lie-Nielsen instructions: blade in honing guide, hitting a secondary bevel of about 27 degrees. Pulling back with finger pressure 6x on the right edge/corner, 6x on the left edge/corner, 4x between the edge and middle on the left and right, 2x with finger pressure on the middle. when I just did this I made sure I could feel a burr on the back all along the edge, and I could. The instructions are to do with with 1000 grit first, then 8000. I finish up with a few back and forth using the ruler trick.

I mean, logic tells me that if I'm cutting heavier on the edges than the center, I must be creating a mound on the stone. That would result in the middle of the blade being ground away more than the edges (despite the fact that I'm doing more passes on the edges?!). When lapping, I'm going back and forth on the stone, directly over it along the long axis, then finishing up with a little swirl.

Suggestions? This is driving me batty.

I’m sure smarter folks will comment but here’s my humble offering…

It sounds like you’ve made sure that the stones (especially the coarser stones) are flat and have no high spot in the center. if not, start there.
Have you held the side of the blade to a square and spotted it to a light to check your suspicions of a ‘reverse’ camber?
If the stones are square and you have managed to sharpen a dip on the center, I’d hold the blade perpendicular and flatten the end again.

With a flat edge (or until you get the camber you desire), I’d increase the differential between the 5 pressure points. Start with getting a small burr across the edge. Then I generally do 15 more to the outside, 10 to the midpoints. With A2, it’s tough stuff. The Norton stones are the water stones they sell right? Keep going back to the back lit square and rest timber until it’s how you want it.

Also, 27* is fairly low for A2. I use 35* on A2 LN.

Thanks. I just checked with the light and my little machinist's square. I forgot to do that. Reverse camber is present. I'm going to try as you suggest tomorrow and reflatten the edge on the secondary bevel, then try to camber it again with more strokes and a steeper secondary bevel. I'm also going to reflatten the stones, which I do a lot while sharpening to clear away swarf. I'll check to see if the blade is flat across after reflattening the stones. Maybe the lapping plate has gone bad. Maybe the diamonds are worn out more in the middle than the sides and so it is leaving a mound.

Well, I suppose first I'll check the reflattening of the stones by just trying to do a straight edge on the blade. If the stones are not getting flattened, then I suppose I'll have to get a new lapping plate. I hope it's not that. I thought the DMT would last longer than a couple years.

Swarf isn’t too bad, use the lapping just when you suspect the stone is out of flat. Are you drawing the lines/matrix to see what’s being removed when you flatten? The reverse camber is strange (at least to my mind). I suspect one or more of your stones has a bump in the middle.

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I finish up with a few back and forth using the ruler trick.

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Something tells me there is more trick taking place at the center of the blade than at the edges.

This is one of my reasons for suggesting people not try every trick there is.

Step one: Get a good bevel

Step two: Do a couple passes for a camber. It really doesn't take much to keep the edges from cutting.

After you get that working, then try adding a trick if you like.

Here is an old post with thoughts about cambering > https://sawmillcreek.org/showthread.php?158373

jtk

Abrasion is favouring the edges/perimeter.
That could be because your plane was lapped on a larger surface than the plane is, with lots of elbow grease involved
i.e a heck of a lot more effort than some who just knock off the rust might consider,
causing the plane to have a gutter profile...
The toe and heel if abraded excessively will cause that, as the plane won't have those points to be registering properly on the plate.

Big plates are only for a mere lick when flat is achieved, and it's impossible to get there, unless the plane is concave very slightly to begin with.
Once the perimeters registration on the lap has been wiped out, tis a personal thing regarding how flat you wish to keep it.


Or, the very same thing is happening with the flattening of the hone.

Spot working is the solution, without removing material from the perimeter.
i.e retaining the pencil markings all around, should you wish to do so.
You'll see many, i.e Cosman with the older videos, no DMT hone, but 1000g waterstones to flatten each other,
focusing in the centre by skewing the held hone, greatly but not totally removing the convex profile.
Probably much faster with his current setup, so you might have missed that.

All the best
Tom

Step 1: make sure your stones are flat to slightly dished. It sounds like your stones have a slight belly. This is easy to do if you are lapping with grit on a backing or if using a Norton Flattening Stone that's not been lapped itself. It is also very easy to do with diamond plates if you're not careful to check actual progress.

Every Norton stone I've bought recently came in with a belly, but when I dug out my old Norton flattening stone, it had a pretty uniform dish.

What worked for me personally. I clamp a sheet of sandpaper to my surface plate, and only work away from the clamps. I start at 60 grit to fix the geometry and then smooth the scratch marks with finer papers - usually no more than 220, but some go to 4000+.

Some people get excellent results from lapping compound. I have not. Stones I lapped with loose compound tended to belly. Others get good results, so there's that too.

On a flat stone it's very difficult to make a reverse camber even if you try. So I would check that your stones is not convex.

Another thing to look at is the plane sole. The only time I've ever experienced what you are describing is with my old No 8. I thought I had somehow sharpened the blade into a reverse camber. But actually the sole was convex across its width - actually it was flat across the center 2/3 and very slightly fell off towards the edges - like 2 or 3 thou. But that was enough to cause the corners to cut first.

This happened to me once. It was because my flattening stone had become worn out of flat. So I had to reflatten it. Mine's not a diamond lapping plate, however, so it's more prone to getting out of flat. One thing I learned from that is you can't just lay the flattening stone over your whetstone and rub back and forth. You have to turn the lapping plate sideways and all different angles, so you're not just wearing your lapping stone and whetstones in the same spot by always using them in the same direction. By attacking it from different angles, you're increasing the odds that anything that's not true will even out.

And secondly, make sure you're applying pressure to the corners of your plane irons when you sharpen them, not the middle. Even a thick plane iron will flex some. So if you're putting your pressure down the middle, it'll flex the middle downward and wear the middle unevenly. If anything, you want the opposite, where the edges wear faster than the middle. So when I sharpen, I put both of my index fingers on the two corners to hold the iron down.

Other techniques you can try that work better if you're working with a non-flat whetstone are, you can turn the iron 90° and sharpen it that way. It's harder to do it that way, but you eliminate most issues that come from an uneven whetstone. Sharpening in circles also helps, so long as you move your circles around the whetstone. You could also try taking short strokes across width of the whetstones, instead of across the length. And just work your way front to back.

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Originally Posted by Matt Hunstiger

OK, so I am trying to get a camber on my no 4 1/2. I've been having this problem where I am getting more cutting from the edges of the blade when I try to add a camber, rather than the middle.

I'm using the Lie-Nielsen instructions: …

I finish up with a few back and forth using the ruler trick.

Suggestions? This is driving me batty.

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It is interesting sometimes to go back to the beginning of a thread to see how things started. What was missed by me in the original post was the part about "using the Lie-Nielsen instructions."

The thought from Robert's post this morning came to mind. For some reason it was not brought up. Perhaps it was seeing "Lie-Nielsen and dismissing the thought.

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Originally Posted by Robert Hazelwood

On a flat stone it's very difficult to make a reverse camber even if you try. So I would check that your stones is not convex.

Another thing to look at is the plane sole. The only time I've ever experienced what you are describing is with my old No 8. I thought I had somehow sharpened the blade into a reverse camber. But actually the sole was convex across its width - actually it was flat across the center 2/3 and very slightly fell off towards the edges - like 2 or 3 thou. But that was enough to cause the corners to cut first.

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This can happen to any plane for any number of reasons. One of my planes suffered this problem and was mentioned in this old post > https://sawmillcreek.org/showthread.php?132457 < It starts out as a quick fix for stripped threads for the tote bolt. The convex base was discovered after the thread fix. Since the pull out the bolt has been JB Welded into place and the plane is still useable but most likely will end up being a parts plane. A pair of type 11 #4s have since been purchased.

When a problem like Matt's comes up, it might be a good first step to put a square or straight edge up to everything in the loop.

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Originally Posted by Jimmy Harris

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One thing I learned from that is you can't just lay the flattening stone over your whetstone and rub back and forth. You have to turn the lapping plate sideways and all different angles, so you're not just wearing your lapping stone and whetstones in the same spot by always using them in the same direction. By attacking it from different angles, you're increasing the odds that anything that's not true will even out.

And secondly, make sure you're applying pressure to the corners of your plane irons when you sharpen them, not the middle. Even a thick plane iron will flex some. So if you're putting your pressure down the middle, it'll flex the middle downward and wear the middle unevenly. If anything, you want the opposite, where the edges wear faster than the middle. So when I sharpen, I put both of my index fingers on the two corners to hold the iron down.

Other techniques you can try that work better if you're working with a non-flat whetstone are, you can turn the iron 90° and sharpen it that way. It's harder to do it that way, but you eliminate most issues that come from an uneven whetstone. Sharpening in circles also helps, so long as you move your circles around the whetstone. You could also try taking short strokes across width of the whetstones, instead of across the length. And just work your way front to back.

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Technique is important in getting anything accomplished when hand guided mechanical motion is involved.

I haven't used my water stones in a while. Cold weather usually has them setting dry. When they are used they do not get a regular flattening. When they get worn, they may camber a blade without any effort. The effort is to hone a blade without getting a camber. If they are far out, being careful with another water stone can flatten them or they can be run over an abrasive sheet on a flat surface. This should be done wet or while wearing a dust mask.

A link posted earlier > https://sawmillcreek.org/showthread.php?158373 < indicates very few strokes are needed on the back of a blade to affect the penetration of the blade's edges. This is what led me to believe it might be the "ruler trick" back bevel causing a problem.

jtk

Warren Mickley has posted a number of times about intentionally letting a stone slightly dish so that you can sharpen the desired camber into irons. He explains it better than I can, but the oversimplification is to sharpen in the middle and just let the stone dish until it makes the "Right" amount of camber for your plane, and then manage the stone wear to keep it approximately at that level.

OK, so thank you all for your comments. I think the problem is with lapping plate which is affecting my stones. I reflattened my 1000 stone using the lapping plate and drawing the pencil grid. That flattened out quickly and evenly. When I took the iron out of the guide and checked it it was perfectly flat across after using the 1000 stone. Then I went back and did the cambering, using 15 strokes on the two outsides, then 10 in the two middles, then 5 in the center. I did this on the 1000 and then the 8000. Then I checked the cutting edge against the machinist square. It wasn't square anymore, but I couldn't really see much of a camber either, which leads me to the next thought...

The thing that got me concerned was the flattening of the 8000 stone. When I did that with pencil lines, 3 along the length, and a bunch along the width, I could really see how the middle was not being hit like the 1000, where the whole surface was clearing away at the same time. It took noticeably longer to remove all the pencil marks on the 8000 stone. Now, the 8000 is harder, so my thought is that the dishing that is present on the lapping plate is only really showing up when I flatten the 8000 stone and is not noticeable when I do the 1000 stone.

In any event, I was able to resharpen my no 4 1/2, block plane, jointer, and low angle jack blades. I was able to achieve the desired feathering out on both sides with a solid shaving in the middle on my scrap piece once I got all the blades centered.

Another bit of advice I took was increasing my secondary bevel to 35. I don't know why I had them so low. Maybe I was sharpening my chisels too and got into a rhythm and forgot what I was doing. I don't know.

I'm leery of intentionally having my stones dish because of sharpening chisels and my straight blade on the low angle jack, which I use for shooting.

Another thing I'm thinking about is the comment about moving my lapping plate around more. I go back and forth along the long axis, and swirl at the end, but it would be a good idea it seems to also lapp with the stone and lapping plate perpendicular in their long axes.

So I think paying closer attention to my finger pressure, the higher number of strokes, and using the pencil grid helped me out a lot here. IF, and I mean IF, my lapping plate is the culprit here that's irritating, since I thought a DMT would last longer than a few years, but also maybe I'm just not mixing up my directions with it enough. Maybe when these stones wear out I'll get some diamond plates.

Remember the pencil grid does not ensure flat. It ensures wear all the way across the stone. If the substrate is not flat, or if the method results in uneven wear, then the pencil lines simply show where the most wear is occurring. For example, I was using coarse lapping grit on plexiglass clamped to a surface plate. The pencil marks were wiped away on the ends but not the center. It turned out that my lapping method tended to heavily wear the ends at the expense of the center - and thus actually install a belly on an otherwise flat or dished stone. I kept going backwards and it took me a while to figure out why.

Similarly, if I was lapping two stones against each other, I would regularly check both of them with a straight edge to verify progress was heading in the right direction on both, and one of the two was not undoing the progress on the other. So for example, check your 1000 stone after lapping the 8000 to verify you aren't putting a belly on it.

Yes. I will check them.

Too much gear by at least half. You're shaping and honing the iron, not all that stuff you've managed to collect. Buy a coarse oilstone and shape the iron freehand checking it frequently against a straightedge -- a ruler, piece of wood, whatever. Once it's shaped, then hone it. All of this could be done on the worst dished stones imaginable if you're willing to simply watch progress. It's better if they're not, but it's up to you to monitor what's going on at the business end of the cutter. Adding more gear and gewgaws won't help. You don't need to read a dissertation on metallurgy to shape a plane iron, nor do you need several hundred dollars' worth of stones. Simplify everything in your shop.

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Originally Posted by Jim Koepke

Something tells me there is more trick taking place at the center of the blade than at the edges.

This is one of my reasons for suggesting people not try every trick there is.

Step one: Get a good bevel

Step two: Do a couple passes for a camber. It really doesn't take much to keep the edges from cutting.

After you get that working, then try adding a trick if you like.

Here is an old post with thoughts about cambering > https://sawmillcreek.org/showthread.php?158373

jtk

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This!

In particular, this -

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Originally Posted by Jim Koepke

Something tells me there is more trick taking place at the center of the blade than at the edges.

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I struggled with this issue on and off for literal years. I spent untold hours and good money trying to sort out exactly the issue you are describing. I chewed through an entire LN blade trying to figure out what was causing "uneven" honing of *some* of my blades. I finally traced it back to haphazard application of the ruler trick, which was creating an inconsistent bevel on the back of my irons. I'm not against the ruler trick, and I continue to use it, but it absolutely has a dark side. This dark side seems to be relatively uncommon, as posts describing the issue you're describing are quite rare (i've seen them all), but when the issue pops up, it's a bear to diagnose.

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When I took the iron out of the guide and checked it it was perfectly flat across after using the 1000 stone. Then I went back and did the cambering, using 15 strokes on the two outsides, then 10 in the two middles, then 5 in the center. I did this on the 1000 and then the 8000. Then I checked the cutting edge against the machinist square. It wasn't square anymore, but I couldn't really see much of a camber either, which leads me to the next thought...

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It all comes down to how much camber you are trying to create. The amount of camber should be in relation to the thickness of shaving one wants to achieve.

If you want to take final smoother shavings of ~0.001", there is no need to have a total camber of 0.01" out to the edge. That would be more in line with a try/scrub plane taking a shaving in the 0.005 - 0.008" range.

jtk