edge jointing and the mysterious vanishing camber

[tnimble]

Swap the blade, altough sharpening a a few more times may still sort it out (during heat treatment the outer most part of the metal will be softer, but this softer metal should have been removed after a few sharpening sessions)

 

[bugbear]

There was a glint visible on the back of the blade along the center of the edge indicating some sort of edge failure, I assume. (And this glint was pretty hard to remove at the stones.)

I would recommend a 10x loupe as part of everyone's sharpening kit. A plastic lensed one is quite good enough, and rather cheap.

BugBear

 

[Paul Chapman]

There was a glint visible on the back of the blade along the center of the edge indicating some sort of edge failure, I assume. (And this glint was pretty hard to remove at the stones.)

When a blade gets blunt, the previously sharp edge becomes rounded, so when honing it is necessary to remove this roundness, which will be on both sides of the blade. The more blunt the blade (ie the more you carry on using the blunt blade and delay honing) the more pronounced this roundness will become and the more honing you will need to do to remove it.

What I now tend to do when honing my blades is to hone them with a 30 degree bevel, using a Veritas honing guide, then use the feature which enables you to alter the roller to give a 1 or 2 degree micro bevel. I find this the fastest way to remove the roundness and achieve a perfectly sharp edge. Another way of doing it is to use the David Charlesworth 'ruler trick', although I don't favour that. Alternatively, you can just carry on honing at a single angle, but that will take longer.

The glint you are seeing on your blades is, I suspect, bluntness caused by not ensuring that the roundness is completely removed - a blunt blade will always show a glint whereas a sharp one won't.

The reason you are seeing this glint along the centre of the edge is, I suspect, because you have cambered the blade, so most of the cutting is taking place at the centre of the blade. The edges of a cambered blade won't be doing much, if any, cutting unless you have the blade projecting a fair amount and are taking thick shavings. That might also explain why you appear to be getting much more wear at the centre of the blade.

Hope this helps.

Cheers :wink:

Paul

PS Another way to see where the wear is taking place on the blade is to keep the end of the cap iron (chip breaker) polished. When you've been planing for a while and remove the blade and cap iron, you will see that resin and general gunge from the wood has collected on the cap iron. This is caused as the shavings pass through the mouth of the plane and over the cap iron. If your blade is cambered, you will no doubt find that this gunge covers only the central portion of the cap iron, because that's where all the cutting is taking place. Wherever the gunge has collected will show the portion of the blade where the wear has taken place.

 

[adrian]

When a blade gets blunt, the previously sharp edge becomes rounded, so when honing it is necessary to remove this roundness, which will be on both sides of the blade. The more blunt the blade (ie the more you carry on using the blunt blade and delay honing) the more pronounced this roundness will become and the more honing you will need to do to remove it.

I did inspect the edge with my Bellomo Triplet 10x loupe, and it appeared that the glint was due to rounding, but I find it remarkably hard to be sure of what I'm looking at. I think I need a microscope. In any case, it was more damage than I have observed in the past when I have been sharpening.

What I now tend to do when honing my blades is to hone them with a 30 degree bevel, using a Veritas honing guide, then use the feature which enables you to alter the roller to give a 1 or 2 degree micro bevel. I find this the fastest way to remove the roundness and achieve a perfectly sharp edge. Another way of doing it is to use the David Charlesworth 'ruler trick', although I don't favour that. Alternatively, you can just carry on honing at a single angle, but that will take longer.

The ruler trick and the secondary bevel are two completely different things. I use a secondary bevel. However, it tends to grow bigger and bigger and then the advantage is not so big until I grind back the primary bevel. At the moment, my secondary bevel on the clifton is about half of the bevel. On the other plane I think it's about the same. With only a degree or two difference (I use the Veritas as well) the secondary bevel grows pretty quickly. Charlesworth advocates the use of a tertiary bevel for rapid polishing. This bevel would be ground away completely each time you hone. I haven't been doing this.

The ruler trick is a method of applying a tiny back bevel so that you can polish the back of the blade up next to the edge without having to work a large area to a high polish. I don't think it would help much for removing a rounded over area at the edge--one doesn't generally try to reshape the blade by working the back. The ruler trick is an attractive idea to me because trying to get a decent polish up at the edge on a flat blade is very difficult, at least for me. The plane sticks to the stone, and it's very hard to get a decent polish. I've never gotten the back of my blade to look as good as the bevel. The problem with the ruler trick is that you have to take the blade out of the honing guide to use it, so you can't go back to the bevel side afterwords unless you go to a higher angle.

I've been reluctant to use it because of this limitation, but I keep looking at those not-very-polished backs, and think that maybe things could be better, so I actually tried to sharpen a blade the Charlesworth way (with tertiary bevel and the ruler trick). The Veritas guide actually damaged the edge when I reinserted the blade for the final polish. (The damage is where the cambered blade pressed up against the stop that determines the extension. It may be necessary to avoid using the stop and just estimate the projection for the final step. Or to do like Charlesworth and switch guides, I suppose.)

The glint you are seeing on your blades is, I suspect, bluntness caused by not ensuring that the roundness is completely removed - a blunt blade will always show a glint whereas a sharp one won't.

Well, assuming that I did a decent job, that glint wasn't there after I had sharpened.

PS Another way to see where the wear is taking place on the blade is to keep the end of the cap iron (chip breaker) polished. When you've been planing for a while and remove the blade and cap iron, you will see that resin and general gunge from the wood has collected on the cap iron.

I'll have to check the cap iron and see if I notice anything. There is a deposit of gunge on the blade right in front of where the cap iron was, and indeed it is heaviest in the center where, presumably, the most cutting took place. (It's recalcitrant gunge...I've had difficulty cleaning it off, actually.)

 

[Paul Chapman]

I use a secondary bevel. However, it tends to grow bigger and bigger and then the advantage is not so big until I grind back the primary bevel.

What I do is hone the blade at 30 degrees on my coarse and fine diamond stones and this quickly removes the old, very small, micro bevel, then put on a new micro bevel each time. I then finish on a leather strop with jewellers rouge.

If you keep on honing the secondary bevel so that it gets bigger each time, your honing is going to take longer and it will take a lot of honing to get rid of the rounded over edge. If you do it my way, it's very quick and you don't have to bother with grinding.

Don't bother with microscopes :shock: If you hold the blade up to the light and the light catches the edge, the blade isn't sharp. A really sharp edge won't reflect the light.

Cheers :wink:

Paul

 

[tnimble]

The Veritas guide actually damaged the edge when I reinserted the blade for the final polish. (The damage is where the cambered blade pressed up against the stop that determines the extension. It may be necessary to avoid using the stop and just estimate the projection for the final step. Or to do like Charlesworth and switch guides, I suppose.)

The stop is of soft aluminium the blade is high carbon tool steel ground around 30 degrees. It should not be able to damage the edge inless slammed / pressed pretty hard into the stop. With HCTS ground at this angle it's even possible to plane some length of aluminium (yes I have done that, last week I planes a dado in some poly carbonate with my LN shoulder plane)

 

[Jake]

This saga gets more and more strange. Are you sure you haven't put a slice of cheese in the plane by mistake? :lol:

Got any pictures to share, or did I miss them?

 

[woodbloke]

Paul Chapman wrote:

What I do is hone the blade at 30 degrees on my coarse and fine diamond stones and this quickly removes the old, very small, micro bevel, then put on a new micro bevel each time. I then finish on a leather strop with jewellers rouge.

If you keep on honing the secondary bevel so that it gets bigger each time, your honing is going to take longer and it will take a lot of honing to get rid of the rounded over edge.

...which is basically what I do. Grind at 23deg, honed bevel at 30deg, micro-bevel at 32deg. Eventually the 30deg bevel will get too wide and then it's time to regrind again. I also use the 'ruler-trick' to polish the back of the blade - Rob

 

[adrian]

I use a secondary bevel. However, it tends to grow bigger and bigger and then the advantage is not so big until I grind back the primary bevel.

What I do is hone the blade at 30 degrees on my coarse and fine diamond stones and this quickly removes the old, very small, micro bevel, then put on a new micro bevel each time. I then finish on a leather strop with jewellers rouge.

If you keep on honing the secondary bevel so that it gets bigger each time, your honing is going to take longer and it will take a lot of honing to get rid of the rounded over edge. If you do it my way, it's very quick and you don't have to bother with grinding.

Er, maybe I'm misunderstanding, but this means you're grinding the primary bevel every time you sharpen. If the microbevel is so very small, then chances are I'd need to grind the primary bevel anyway to get rid of the type of rounding I was observing. This would mean that instead of my honing taking longer and longer each time it would just always take an eternity as I'd always be grinding away at the entire primary bevel instead of working on a secondary bevel that was gradually getting bigger. Even if I didn't have a problem to grind away, I still have the issue of having to grind away the microbevel each time by working the entire primary bevel. That doesn't sound fast.

The point of grinding is that you use a fast very coarse abrasive. I have two ways of grinding, a 120 micron diamond stone and a WorkSharp fitted with 40 grit sandpaper. Both leave big nasty gouges in the metal that you wouldn't want up near your edge. If I were to use these methods to grind back a 30 degree bevel and then I went to put on a microbevel...by the time the microbevel was fully established and the scratches from the previous step were gone, it wouldn't be a very tiny microbevel any more. So if I wanted to make this system work I'd have to grind back the 30 degree primary bevel with something finer...which would take a long time. It doesn't sound very quick...

 

[adrian]

This saga gets more and more strange. Are you sure you haven't put a slice of cheese in the plane by mistake? :lol:

I've got some old Parmesan in the back of the refrigerator. Maybe I should try fitting it into the plane and seeing if the performance improves.

Got any pictures to share, or did I miss them?

Hmmm. It hadn't occurred to me to try to photograph this. It just didn't seem like something that would work...but as I think about it now it seems like I ought to be able to put a bright light behind the blade and get some kind of image showing the concavity.

The next time this happens I'll give it a try. At the moment I have only 3 more joints to match up, then I have to glue everything. And then I'll have to work the resulting panels to their final dimension. I don't know if it's enough more work to cause the problem again. On the other hand, I'll need to work the dreaded end grain somehow.

 

[Paul Chapman]

Er, maybe I'm misunderstanding

Possibly. You also seem reluctant to try anything anyone suggests. Maybe the best thing would be to find someone who lives near you and who knows how to sharpen blades, to show you how to do it.

Cheers :wink:

Paul

 

[woodbloke]

Adrian wrote:

but this means you're grinding the primary bevel every time you sharpen

No...the primary bevel (in my case 23deg, the big wide one) is re-ground only when the secondary bevel (the one at 30deg) has been honed so much that it becomes difficult to establish an edge (and ultimately remove the micro-bevel). The grinding process shortens the effective length of the steel (which is why old, well used blades are always short) but at the same time it also narrows the 30deg bevel from being fairly wide (say 2mm) to the width of a hair :wink: so that it then becomes much easier to make the micro-bevel at 32deg...this is achieved with about six strokes on a very fine stone, I use a Spyderco 10000g ceramic - Rob

 

[ivan]

You mention trouble with the lateral position - is this shifting in use? One of my Clifton frogs required a bit of flattening as did the blade face that meets the frog. When rectified the lateral adjustment was much stiffer with a similar lever cap setting, and it stopped drifting in use. Flat the 'working' underside of the lever cap. Don't assume anything is actually flat! A cheap Chinese granite surface plate has definite rigidity, I think Harbor freight do one, was in FW?. Mine is big enough for a #8.

If the blade has a lot of camber with a fine cut set, on flat work, the plane will cut initially in the blade centre, and then will stop cutting when the edges of the sole touch the work. (unless you then increase the cut).

You should still be able to get a full width shaving with a cambered blade, so the camber must be a shaving thickness or less. If you plane watching the mouth, till you get a continuous shaving (on an edge), the shaving should be in the centre of the mouth or the lateral lever needs adjsuting.

For longer boards, if you plane 2 together, you can invert one on the other and test the joint in the straightedge way - pivot from both ends - then joint is hollow, eye shows how much.

Whilst testing out your planing and the plane itself, by practicing, you could revert to a straight edge which removes one variable, and then introduce it later. As you can see, camber can give rise to odd effects if you keep planing over exactly the same ground.I was taught to correct an edge to 90 deg (with a straight ground blade, camber was only for rough stuff) by tweaking the lateral lever to correct, but find the cambered blade method easier.

 

[adrian]

Possibly. You also seem reluctant to try anything anyone suggests. Maybe the best thing would be to find someone who lives near you and who knows how to sharpen blades, to show you how to do it.

Paul

In the case of sharpening, there is a huge diversity in recommendations for how to go about it. I have been sharpening (or at least trying to sharpen) for almost ten years now and while I don't claim to be an expert at it by any means, I do have some modest amount of experience and hence some idea what will happen if I try a particular approach.

And I'm pretty darn sure that if I try an approach where I grind the full bevel each time that it will take me longer---probably quite a bit longer. I can't try everything, so I have to consider what seems reasonable and this just doesn't pass the test. (Another consideration is how long does it take to try something and how easily is it reversible. One reason I was reluctant to try the ruler trick is that it appears very difficult to reverse if I don't like it.)

Now putting a tiny tertiary bevel on the edge seems reasonable (as suggested by Charlesworth and as woodbloke does). I was a bit nervous about how long it takes to remove the microbevel each time, though it couldn't possibly be any worse than the time required to remove the rounding I observed recently....or re-establish the camber. I did just go ahead and try this on one of my blades. This is like what you're doing without the painful grinding of the entire primary bevel each time.

Here's a question that arose with the microbeveling. So I raised my bevel angle from 30 to 35 as Charlesworth suggests and went to the polishing stone and started to create the microbevel. How can I tell when the microbevel is done, when the polish is sufficient and the scratches from the coarser stone removed? I'm not sure I did enough polishing on the blade that I converted to this approach.

 

[adrian]

Adrian wrote:

but this means you're grinding the primary bevel every time you sharpen

No...the primary bevel (in my case 23deg, the big wide one) is re-ground only when the secondary bevel (the one at 30deg) has been honed so much that it becomes difficult to establish an edge (and ultimately remove the micro-bevel).

According to Paul Chapman (the "you" in my quote above), he doesn't have a 23 deg bevel. He just has a primary bevel at 30 degrees which he works every time with "coarse and fine diamond stones". He says that one advantage of his way is "you don't have to bother with grinding". You're doing something different than him, I think.

The grinding process shortens the effective length of the steel (which is why old, well used blades are always short)

I don't think the grinding process should have any effect on the effective length of the steel. When you grind you won't go all the way to the edge, so the blade length will not change. The reason old blades are short is that the honing removes material at the edge and gradually makes the blade shorter. Even if you don't grind, you'll still lose length---it'll just be more work.

 

[adrian]

You mention trouble with the lateral position - is this shifting in use?

I don't think so. I was paying attention to where I had to position the plane to achieve a full width shaving and it was staying in the same spot.

One of my Clifton frogs required a bit of flattening as did the blade face that meets the frog. When rectified the lateral adjustment was much stiffer with a similar lever cap setting, and it stopped drifting in use. Flat the 'working' underside of the lever cap. Don't assume anything is actually flat! A cheap Chinese granite surface plate has definite rigidity, I think Harbor freight do one, was in FW?. Mine is big enough for a #8.

However, I have not done any adjustments to the frog or lever cap. I worked the chip breaker to get a good fit, but that's about it, I think.

If the blade has a lot of camber with a fine cut set, on flat work, the plane will cut initially in the blade centre, and then will stop cutting when the edges of the sole touch the work. (unless you then increase the cut).

Wouldn't this require a very extreme camber to occur on the edge of a board? The shaving would have to be less than the edge width. On a face you could easily get this behavior.

You should still be able to get a full width shaving with a cambered blade, so the camber must be a shaving thickness or less. If you plane watching the mouth, till you get a continuous shaving (on an edge), the shaving should be in the centre of the mouth or the lateral lever needs adjsuting.

I thought you wouldn't want a full width (of the blade) shaving because then the plane would leave lines at the edges of the shavings when it cut. You want the shaving to taper off to nothing at the sides so that you can make a smooth surface. For edge planing it seems unlikely that you'd get such a large camber that you wouldn't get a full width shaving.

For longer boards, if you plane 2 together, you can invert one on the other and test the joint in the straightedge way - pivot from both ends - then joint is hollow, eye shows how much.

This would require a straight blade, right? (No camber.)

Whilst testing out your planing and the plane itself, by practicing, you could revert to a straight edge which removes one variable, and then introduce it later. As you can see, camber can give rise to odd effects if you keep planing over exactly the same ground.I was taught to correct an edge to 90 deg (with a straight ground blade, camber was only for rough stuff) by tweaking the lateral lever to correct, but find the cambered blade method easier.

What test would you propose that I perform with a straight edge? Given the difficulty I have with lateral adjustment, it seems like using a straight blade would be more difficult, though I suppose it could be an opportunity to practice lateral adjustment. (I noticed that Rob Cosmon shows this technique in his DVD, Rough to Ready.)

 

[adrian]

The stop is of soft aluminium the blade is high carbon tool steel ground around 30 degrees. It should not be able to damage the edge inless slammed / pressed pretty hard into the stop. With HCTS ground at this angle it's even possible to plane some length of aluminium (yes I have done that, last week I planes a dado in some poly carbonate with my LN shoulder plane)

Because the blade is cambered it meets the stop at a single point, so all the forces and stresses that I might apply as I try to get it properly positioned will be focused on one single point of the edge. Even so, you think the aluminum is too soft to damage the blade? (If so, I'll have to investigate further the source of the damage.)

 

[tnimble]

The stop is of soft aluminium the blade is high carbon tool steel ground around 30 degrees. It should not be able to damage the edge inless slammed / pressed pretty hard into the stop. With HCTS ground at this angle it's even possible to plane some length of aluminium (yes I have done that, last week I planes a dado in some poly carbonate with my LN shoulder plane)

Because the blade is cambered it meets the stop at a single point, so all the forces and stresses that I might apply as I try to get it properly positioned will be focused on one single point of the edge. Even so, you think the aluminum is too soft to damage the blade? (If so, I'll have to investigate further the source of the damage.)

Never noticed any damage to any of my blades. And I sometimes go back and forth between the bevel edge and the back while forming a blade to shape (I've made some moulding plane blades and odd sized straight blades) to prevent a larger bur to form.

I'll insert one of my Hock blades into the Veritas MKII not so gently for you. :shock: (got a box with a couple of unused and unfettled blades anyway)

 

[tnimble]

I did most of the flattening of the back of this new Hock 1 3/4" O1 chisel. It should be pretty comparable to the characteristics of a Clifton blade. Then I made the basic shape for a very light cambered edge suitable for a no 3 smoother. I used the Veritas using the no 2 setting on the roler posision, and the set the angle gauge to the position inbetween the 25 and 30 degrees.

I took the blade out and repolished the blade to remove the burr created by putting on the shape to the bevel edge. Then I reinserted the blade in the veritas MKII. With the blade not contacting the angle gauge i hit the back of the blade with my palm, I repeated this 3 times. Then whilst pushing the blade against the angle gauge I tightened the blade clmap. I tapped the end of the angle gauge ruler thingy a couple of times, loosed the screw and removed it. This is how the blade looked like after that treatment:

I switched to the Canon EF 100/2.8 usm macro lens to get a better look of the corner of the blade where it has forcefully met the angle gauge a couple of times. I can't see or feel any damage to the edge.

 

[Mr Ed]

I think Jakes 'slice of cheese' theory is looking like my favourite explanation.. :lol:

Cheers, Ed