- Joined
- Aug 2, 2014
- Messages
- 746
A while back I had a discussion with another commenter at Axe Connected about the concept of the high centerline. I've thought about that a lot and the discussion got me thinking more about axe geometry. I also noticed a lot of people here agree with this writing on axe geometry and the concept of the high centerline comes up a fair bit.
I respect the thought, experience, and research that went into that piece, so I thought I'd share my own thoughts on it here, and maybe clear a few things up. One thing with the theory of the high centerline (which I'll call an arched bevel, I'll explain that further on) is that the example of the Gransfors forest axe is used to differentiate between flat European axes and American felling axes, and this suggests that the Gransfors felling axe is also flat (whether other Euro felling axes are flat is a whole other topic, but some American axes are flat beveled as well). I think this is an important mistake to consider because the axe Mr. Vido describes is a limbing axe - it should be flat because its purpose is to slice limbs and not pop chips.
A big problem here is that people then go on to say that Gransfors are poorly designed because they do not have an arched bevel (high centerline). This is simply untrue. My forest axe has some arch to it, but a fair comparison would be the Gransfors American Felling axe. Here are four different axes and their respective arches:
Emerson & Stevens (Not my profiling, one side looks as though it was taken down to match the other.)
Gransfors (factory profile, only ever used 2000 grit on it for light touch-ups)
Spiller (Edge arrived like this.)
Campbell's (Edge shows wear from storage in axe head crate, was an unused axe from 1926, never sharpened but obviously had minor dings from banging against other axes. Very hard steel so I'm just cleaning it up slowly as I use it.)
The Campbell's clearly has the greatest arched bevel, while the difference between the Gransfors, Spiller, and the E&S might be called insignificant. In Dudley Cook's book he says that most axes came from the factory with too much material, and that the material should be removed to almost flat. It seems that arching material in the bevel is up to personal preference, what trees one primarily works with, and what tradeoffs people are trying to balance. Some would say there is no significant difference in sticking between the axes that are flat and those that have an arched bevel.
But what about the theory itself? Is it even correct? I don't know that Mr. Vido references anything in his writing to suggest that this really was the purpose of the 'high centerline'. And Mr. Cook doesn't go on in detail about it in his book, so it would seem that it is not as significant a factor as bevel angles, length to axis, balance, etc.. Professionally skilled axemen like Mors Kochanski will tell you that if an axe sticks too much then dull it slightly. And that may be a big problem, few people can, or do, sharpen an axe to the level that a Gransfors is. The razor sharpness of an axe can certainly cause it to become stuck.
There is one important reference, however, in Woodcraft by EH Kreps:
"One of these rules, and the most important, is to have the blade or bit thinnest on the "inside corner," which is the end of the blade nearest to the user. The hasty conclusion would be that if this corner were thinnest, the opposite side of the blade should be thickest. This is wrong. The thickest part of the blade should be two-thirds of the way across from the inside corner..."
This is what the high centreline really is, it is primarily for balance. As far as I can remember Kreps doesn't go into detail about why this is so (I will check when I get a chance), so we have to wonder why most of the material should be two-thirds of the way to the outside corner. The most likely reason is for balance. When an axe is swung it is rounding, the force will not be in the centre, it will be close to two-thirds of the way to the outside corner. Think of racing cars, if a car must turn both left and right then the forces on that car will tend towards the centre, but if a car only ever turns left then the forces will always tend towards the right. The high centreline makes the axe balance towards its outside, preventing wobble.
Here I think there is another reason why some axes have higher arched bits than others. While some of this may come down to having to compete with cheap foreign imports (there seems to be a correlation between large makers and an increase in overdetermined centrelines), it may also be compensation for a widening of the poll. One aspect of Rockaway patterns and Hudson's Bay patters, bearded axes, is that there is less material behind the inside corner; the design inherently already has most of the mass behind the high centreline, the top two-thirds of the axe. But in dropping the poll this natural characteristic was lost, and so adding material in other areas compensated for the loss and mass. This meant a bulge in the bit, and a higher arch to maintain balance, not so much to prevent sticking (although that may be an accidental benefit).
If you look at the pictures used in the Axe Geometry writing the ruler is way back on the bit, in an area that would have no impact on an axe getting wedged in a tree. For the purpose of keeping the wood/chip from compressing and adding force to the edge it would not matter if the bit is flat or arched. That leads me to conclude that much of the idea of the 'high-centreline' is confused with the real purpose of the high centreline, which is balance. Axes can benefit from micro dips of convexity in the middle bit, an increased concavity here, and a ground edge there, but at that point we're getting into nuances which probably only benefit those with perfect swings anyway, or the racers. Other aspects of geometry are more significant for general use.
One thing that is rarely mentioned about the arched bit is that it is also a tradeoff. More material means that you cannot cut as deep, and that extra few millimetres will cause your axe to have an increased potential for glanced blows. The high arch is a tradeoff, not a necessary benefit of the axe. It is also one of the less important aspects of axe geometry, so flat cheeks should not used as an excuse to say Gransfors have poor geometry. Gransfors have a significantly shorter length than the vast majority of vintage axes, a correct profile (specialised for softwood, so hardwood shortcomings aren't really a downfall), shorter axis to edge (accuracy), correct negative edge angle (helps with hitting squarely rather than on the heel), relatively flat edge curvature, and excellent balance. That's how the axe should be judged, how it compares to others and approaches the ideal, and not that it misses in one arguably insignificant area (which is a myth anyway).
This is not to say it is the best axe, as I think it comes up short in some areas when compared to a Spiller, E&S, or any top quality double-bit. But its geometry is actually far better than some give it credit for, and better than at least 99% of old axes that were made. The truth is that these ideal axes are extremely hard to come by. How many axes do you see that even come close to what Cook described? I will assume that most have seen none, since it took me a lot of searching to find any examples at all (then I found two in one place). Hopefully that is not too forthright, as I am aware that Cook's 'Efficient Ax' may not be the ideal for some, and some changes might have to be made for different forests and types of wood. But I am not willing to accept that one area of geometry is more important than several others.
I hope this makes sense. It is not intended as a final word or anything like that. I could very well be wrong and Mr. Vido quite correct (he's more experienced than I am, surely). I'm just trying to work this out myself and figure out a few things about axes. I will be doing some testing in the coming weeks and months since I haven't used my Gransfors a lot since getting other axes, so I will let you all know what I think after some side by side testing.
Here are a few more pictures of the axes I'll be using:
You can see how poor my handle skills are compared to the others here, but I did it with only an axe and knife and it was my first try hafting as well. If anyone has thoughts on the age of the Spiller, or how much material you think it has lost let me know. I'm guessing around 1/4" or a little less, but I'm not as experienced with Maine axes as some here.
Some trail/road clearing.
This one was rotten in the middle and made quite a mess. Pictured with the knife I carved the handle with and a nice drink (deserved I think after a rotten tree hangup).
I respect the thought, experience, and research that went into that piece, so I thought I'd share my own thoughts on it here, and maybe clear a few things up. One thing with the theory of the high centerline (which I'll call an arched bevel, I'll explain that further on) is that the example of the Gransfors forest axe is used to differentiate between flat European axes and American felling axes, and this suggests that the Gransfors felling axe is also flat (whether other Euro felling axes are flat is a whole other topic, but some American axes are flat beveled as well). I think this is an important mistake to consider because the axe Mr. Vido describes is a limbing axe - it should be flat because its purpose is to slice limbs and not pop chips.
A big problem here is that people then go on to say that Gransfors are poorly designed because they do not have an arched bevel (high centerline). This is simply untrue. My forest axe has some arch to it, but a fair comparison would be the Gransfors American Felling axe. Here are four different axes and their respective arches:
Emerson & Stevens (Not my profiling, one side looks as though it was taken down to match the other.)
Gransfors (factory profile, only ever used 2000 grit on it for light touch-ups)
Spiller (Edge arrived like this.)
Campbell's (Edge shows wear from storage in axe head crate, was an unused axe from 1926, never sharpened but obviously had minor dings from banging against other axes. Very hard steel so I'm just cleaning it up slowly as I use it.)
The Campbell's clearly has the greatest arched bevel, while the difference between the Gransfors, Spiller, and the E&S might be called insignificant. In Dudley Cook's book he says that most axes came from the factory with too much material, and that the material should be removed to almost flat. It seems that arching material in the bevel is up to personal preference, what trees one primarily works with, and what tradeoffs people are trying to balance. Some would say there is no significant difference in sticking between the axes that are flat and those that have an arched bevel.
But what about the theory itself? Is it even correct? I don't know that Mr. Vido references anything in his writing to suggest that this really was the purpose of the 'high centerline'. And Mr. Cook doesn't go on in detail about it in his book, so it would seem that it is not as significant a factor as bevel angles, length to axis, balance, etc.. Professionally skilled axemen like Mors Kochanski will tell you that if an axe sticks too much then dull it slightly. And that may be a big problem, few people can, or do, sharpen an axe to the level that a Gransfors is. The razor sharpness of an axe can certainly cause it to become stuck.
There is one important reference, however, in Woodcraft by EH Kreps:
"One of these rules, and the most important, is to have the blade or bit thinnest on the "inside corner," which is the end of the blade nearest to the user. The hasty conclusion would be that if this corner were thinnest, the opposite side of the blade should be thickest. This is wrong. The thickest part of the blade should be two-thirds of the way across from the inside corner..."
This is what the high centreline really is, it is primarily for balance. As far as I can remember Kreps doesn't go into detail about why this is so (I will check when I get a chance), so we have to wonder why most of the material should be two-thirds of the way to the outside corner. The most likely reason is for balance. When an axe is swung it is rounding, the force will not be in the centre, it will be close to two-thirds of the way to the outside corner. Think of racing cars, if a car must turn both left and right then the forces on that car will tend towards the centre, but if a car only ever turns left then the forces will always tend towards the right. The high centreline makes the axe balance towards its outside, preventing wobble.
Here I think there is another reason why some axes have higher arched bits than others. While some of this may come down to having to compete with cheap foreign imports (there seems to be a correlation between large makers and an increase in overdetermined centrelines), it may also be compensation for a widening of the poll. One aspect of Rockaway patterns and Hudson's Bay patters, bearded axes, is that there is less material behind the inside corner; the design inherently already has most of the mass behind the high centreline, the top two-thirds of the axe. But in dropping the poll this natural characteristic was lost, and so adding material in other areas compensated for the loss and mass. This meant a bulge in the bit, and a higher arch to maintain balance, not so much to prevent sticking (although that may be an accidental benefit).
If you look at the pictures used in the Axe Geometry writing the ruler is way back on the bit, in an area that would have no impact on an axe getting wedged in a tree. For the purpose of keeping the wood/chip from compressing and adding force to the edge it would not matter if the bit is flat or arched. That leads me to conclude that much of the idea of the 'high-centreline' is confused with the real purpose of the high centreline, which is balance. Axes can benefit from micro dips of convexity in the middle bit, an increased concavity here, and a ground edge there, but at that point we're getting into nuances which probably only benefit those with perfect swings anyway, or the racers. Other aspects of geometry are more significant for general use.
One thing that is rarely mentioned about the arched bit is that it is also a tradeoff. More material means that you cannot cut as deep, and that extra few millimetres will cause your axe to have an increased potential for glanced blows. The high arch is a tradeoff, not a necessary benefit of the axe. It is also one of the less important aspects of axe geometry, so flat cheeks should not used as an excuse to say Gransfors have poor geometry. Gransfors have a significantly shorter length than the vast majority of vintage axes, a correct profile (specialised for softwood, so hardwood shortcomings aren't really a downfall), shorter axis to edge (accuracy), correct negative edge angle (helps with hitting squarely rather than on the heel), relatively flat edge curvature, and excellent balance. That's how the axe should be judged, how it compares to others and approaches the ideal, and not that it misses in one arguably insignificant area (which is a myth anyway).
This is not to say it is the best axe, as I think it comes up short in some areas when compared to a Spiller, E&S, or any top quality double-bit. But its geometry is actually far better than some give it credit for, and better than at least 99% of old axes that were made. The truth is that these ideal axes are extremely hard to come by. How many axes do you see that even come close to what Cook described? I will assume that most have seen none, since it took me a lot of searching to find any examples at all (then I found two in one place). Hopefully that is not too forthright, as I am aware that Cook's 'Efficient Ax' may not be the ideal for some, and some changes might have to be made for different forests and types of wood. But I am not willing to accept that one area of geometry is more important than several others.
I hope this makes sense. It is not intended as a final word or anything like that. I could very well be wrong and Mr. Vido quite correct (he's more experienced than I am, surely). I'm just trying to work this out myself and figure out a few things about axes. I will be doing some testing in the coming weeks and months since I haven't used my Gransfors a lot since getting other axes, so I will let you all know what I think after some side by side testing.
Here are a few more pictures of the axes I'll be using:
You can see how poor my handle skills are compared to the others here, but I did it with only an axe and knife and it was my first try hafting as well. If anyone has thoughts on the age of the Spiller, or how much material you think it has lost let me know. I'm guessing around 1/4" or a little less, but I'm not as experienced with Maine axes as some here.
Some trail/road clearing.
This one was rotten in the middle and made quite a mess. Pictured with the knife I carved the handle with and a nice drink (deserved I think after a rotten tree hangup).
