Cliff Stamp
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- Joined
- Oct 5, 1998
- Messages
- 17,562
First off, pretty much the obvious question I wanted to answer was which one would out chop the other, and would it be to a significant degree. As soon as I chopped through a couple of pieces of wood the answer was obvious - the khukuri was the clear winner. I started off on small wood, about three inches or so in diameter and the Ang Khola would consistently give greater penetration than the hatchet. In fact, even though the khukuri is more than two inches wide, I had no difficulty sinking the whole blade profile into the wood. Due to the primary double hollow grinds and the convex edge profile the khukuri also did not bind in the wood and powerfully wedged it apart.
For those who want some raw numbers, the ratio of number of chops (hatchet vs khukuri) was 1.20 +/- 0.03. Thus the performance of the khukuri ranged from about 14 to 26% in excess of the hatchet. I later on did some chopping on larger wood, and even on wood more than six and a half inches thick, the khukuri could still match the performance of the hatchet. The hatchet was however starting to gain ground rapidly on the khukuri as the wood grew larger, on wood any bigger than this, the khukuri started to fall behind because of the lower impact pressure given the larger contact area. For more detail here is a histogram :
http://www.physics.mun.ca/~sstamp/images/ak_18_hatchet_hist.jpg
You can see that very rarely was the hatchet able to outperform the khukuri, but the knife was able to out chop the hatchet often, and some times by as much as 2:1. A lot of variance is to be expected in such work because the nature of the wood can vary tremendously, even clear wood can season differently and cause a large difference in the penetration a given blade will achieve. Thus it takes a decent amount of comparison chops to get a stable result. For this run ninety nine pieces of wood were cut through ranging in size from three to just under seven inches. A total of 1609 chops were made by the hatchet and 1374 by the khukuri.
Ok beyond the raw chopping ability are there any other significant difference in the performance. Yes, many things. For example the penetration of the hatchet is independent of the size of the wood, as long as the wood is larger than the face of the hatchet. Now the shock that you feel after a chop is directly related to the penetration, the greater the penetration the lower the shock. Since the penetration of the axe is high, this means the shock is pretty much always low. However as the size of the wood increases the khukuri will get lower penetration and thus a higher impact shock is felt. Therefore on really large and or hard wood, the hatchet is more comfortable to use.
It is critical to note that you will only feel any feedback if you use a tight grip and a lot of heavy wrist action which is what I was doing. The hatchet would be snapped from the shoulder, and the khukuri would involve even more wrist action as the blade was torqued into the wood after impact. The greater wrist drive on the khukuri also accounted for its increase in shock on the larger wood. You can avoid much of the feedback if you use a looser grip and a "whippy" motion for the chopping. However if you do this you will see the khukuri loses a large part of its chopping advantage over the hatchet, as its ability to be torqued into the wood accounts for a significant amount of its chopping ability.
In general, the khukuri is more functional as for example the greater blade length allows more reach doing sweeping cuts through small branches and other light vegetation. As well in general the longer edge length allows more versatility. The tip can be used very roughly for digging or cutting very hard material without effecting the chopping performance as it is done in a different area. It is the same thing in regards to slicing, after a hard days chopping there were still be lots of parts of the edge that were untouched and thus still just as sharp as when you set out. As well the khukuri has a more pronounced point and thus has penetration advantages. It also makes a much greater pry bar, and doesn't have the durability concerns of breaking a handle or the problem common with hatchets which is the head / handle bond.
Does the hatchet offer any advantages over the khukuri? Yes. Besides the above mentioned ease of working on larger wood, the hatchet is also lighter. It is 600 g to the khukuris 920. The hatchet is also significantly cheaper, less than half the price of the blade. The hatchet also makes a much better hammer, and is far safer for the inexperienced user. The handle on the hatchet is optomized for chopping (surprise), and does account for a significant part of its performance. I have planned to replace the grip on one of my Ang Kholas with a hatchet-like handle and see how much of an improvement it makes.
In regards to materials and heat treatment. The hatchet is forged by a single smith out of most likely something similar to L6 or 5160. The same is true of the khukuri. The hatchet is spec'ed at 57 RC, it is just at the point where is can be worked with a file. The khukuri I would guess is very similar as they react almost identically to a file. Both blades have a differential hardening, the edges are much harder than the spine/poll. This both reduces shock (not sure as to how much of an effect this makes), and more importantly allows the spine/poll to be hammered on without harm. This is with moderate force of course, if you hit the hatchet hard enough you will deform the eye, this takes sledge hammer class hits.
How do the steels behave? In regards to corrosion resistance, both will rust very easily if you leave them wet. Some of the above chopping was done in the rain, and at times I had stopped chopping for 10-15 minutes while I felled, limbed out and brought out a few trees (done with other blades / saws). During this time both hatchet and khukuri would develop visible rust. However while they were being used no rust would develop as it was just getting burnished away. Both react very similar to honing in the speed of metal removal and the edge finish.
Edge retention? During the above chopping the blades were not sharpened, not even given a light stropping. After a days work they would be oiled and put away until next time. After the chopping was done both blades had lost the blazing sharp feel that they had just after they were first honed (4000 grit waterstone, light stropping on CrO loaded leather), but they were still easy sharp enough to do any manner of wood work. They were also sharp enough to bite into some 3/8 inch poly on a slice and were were still aggressive enough to allow me to cut through bundles of light dry grass for tinder. No edge damage was visible or could be felt by my finger pad, the edges had just worn down smoothly.
Both blades were sharpened in a short period of time starting with a 1000 grit waterstone, then switching to a 4000 and finishing on CrO loaded leather. This took less than five minutes for the hatchet, and about 15 for the khukuri as it has a much longer edge and I was using small one by four inch hones. Both blades were no restored to the same level of sharpness as before the chopping. They wold push shave easily and could for example easily lop off a dry piece of free standing grass.
Finally, the khukuri comes with a more functional sheath, and both have very solid warranties.
The edge profiles for those that are curious :
http://www.physics.mun.ca/~sstamp/images/ak_18_edge.gif
http://www.physics.mun.ca/~sstamp/images/gb_hatchet_edge.gif
-Cliff
For those who want some raw numbers, the ratio of number of chops (hatchet vs khukuri) was 1.20 +/- 0.03. Thus the performance of the khukuri ranged from about 14 to 26% in excess of the hatchet. I later on did some chopping on larger wood, and even on wood more than six and a half inches thick, the khukuri could still match the performance of the hatchet. The hatchet was however starting to gain ground rapidly on the khukuri as the wood grew larger, on wood any bigger than this, the khukuri started to fall behind because of the lower impact pressure given the larger contact area. For more detail here is a histogram :
http://www.physics.mun.ca/~sstamp/images/ak_18_hatchet_hist.jpg
You can see that very rarely was the hatchet able to outperform the khukuri, but the knife was able to out chop the hatchet often, and some times by as much as 2:1. A lot of variance is to be expected in such work because the nature of the wood can vary tremendously, even clear wood can season differently and cause a large difference in the penetration a given blade will achieve. Thus it takes a decent amount of comparison chops to get a stable result. For this run ninety nine pieces of wood were cut through ranging in size from three to just under seven inches. A total of 1609 chops were made by the hatchet and 1374 by the khukuri.
Ok beyond the raw chopping ability are there any other significant difference in the performance. Yes, many things. For example the penetration of the hatchet is independent of the size of the wood, as long as the wood is larger than the face of the hatchet. Now the shock that you feel after a chop is directly related to the penetration, the greater the penetration the lower the shock. Since the penetration of the axe is high, this means the shock is pretty much always low. However as the size of the wood increases the khukuri will get lower penetration and thus a higher impact shock is felt. Therefore on really large and or hard wood, the hatchet is more comfortable to use.
It is critical to note that you will only feel any feedback if you use a tight grip and a lot of heavy wrist action which is what I was doing. The hatchet would be snapped from the shoulder, and the khukuri would involve even more wrist action as the blade was torqued into the wood after impact. The greater wrist drive on the khukuri also accounted for its increase in shock on the larger wood. You can avoid much of the feedback if you use a looser grip and a "whippy" motion for the chopping. However if you do this you will see the khukuri loses a large part of its chopping advantage over the hatchet, as its ability to be torqued into the wood accounts for a significant amount of its chopping ability.
In general, the khukuri is more functional as for example the greater blade length allows more reach doing sweeping cuts through small branches and other light vegetation. As well in general the longer edge length allows more versatility. The tip can be used very roughly for digging or cutting very hard material without effecting the chopping performance as it is done in a different area. It is the same thing in regards to slicing, after a hard days chopping there were still be lots of parts of the edge that were untouched and thus still just as sharp as when you set out. As well the khukuri has a more pronounced point and thus has penetration advantages. It also makes a much greater pry bar, and doesn't have the durability concerns of breaking a handle or the problem common with hatchets which is the head / handle bond.
Does the hatchet offer any advantages over the khukuri? Yes. Besides the above mentioned ease of working on larger wood, the hatchet is also lighter. It is 600 g to the khukuris 920. The hatchet is also significantly cheaper, less than half the price of the blade. The hatchet also makes a much better hammer, and is far safer for the inexperienced user. The handle on the hatchet is optomized for chopping (surprise), and does account for a significant part of its performance. I have planned to replace the grip on one of my Ang Kholas with a hatchet-like handle and see how much of an improvement it makes.
In regards to materials and heat treatment. The hatchet is forged by a single smith out of most likely something similar to L6 or 5160. The same is true of the khukuri. The hatchet is spec'ed at 57 RC, it is just at the point where is can be worked with a file. The khukuri I would guess is very similar as they react almost identically to a file. Both blades have a differential hardening, the edges are much harder than the spine/poll. This both reduces shock (not sure as to how much of an effect this makes), and more importantly allows the spine/poll to be hammered on without harm. This is with moderate force of course, if you hit the hatchet hard enough you will deform the eye, this takes sledge hammer class hits.
How do the steels behave? In regards to corrosion resistance, both will rust very easily if you leave them wet. Some of the above chopping was done in the rain, and at times I had stopped chopping for 10-15 minutes while I felled, limbed out and brought out a few trees (done with other blades / saws). During this time both hatchet and khukuri would develop visible rust. However while they were being used no rust would develop as it was just getting burnished away. Both react very similar to honing in the speed of metal removal and the edge finish.
Edge retention? During the above chopping the blades were not sharpened, not even given a light stropping. After a days work they would be oiled and put away until next time. After the chopping was done both blades had lost the blazing sharp feel that they had just after they were first honed (4000 grit waterstone, light stropping on CrO loaded leather), but they were still easy sharp enough to do any manner of wood work. They were also sharp enough to bite into some 3/8 inch poly on a slice and were were still aggressive enough to allow me to cut through bundles of light dry grass for tinder. No edge damage was visible or could be felt by my finger pad, the edges had just worn down smoothly.
Both blades were sharpened in a short period of time starting with a 1000 grit waterstone, then switching to a 4000 and finishing on CrO loaded leather. This took less than five minutes for the hatchet, and about 15 for the khukuri as it has a much longer edge and I was using small one by four inch hones. Both blades were no restored to the same level of sharpness as before the chopping. They wold push shave easily and could for example easily lop off a dry piece of free standing grass.
Finally, the khukuri comes with a more functional sheath, and both have very solid warranties.
The edge profiles for those that are curious :
http://www.physics.mun.ca/~sstamp/images/ak_18_edge.gif
http://www.physics.mun.ca/~sstamp/images/gb_hatchet_edge.gif
-Cliff
