A while back, I ordered a 24" Kobra blade only from Uncle Bill. It arrived yesterday.
Remarkable what a difference even a few thousandths of an inch can make. The blade only was (obviously) an inch shorter than my beloved 25" Kobra; also slightly thicker (0.395" at the elbow, as against 0.350") with rather less distal taper towards the point, and a tad wider from elbow to point. Theres also a more pronounced upsweep at the point, so that the fuller-profiled cutting edge at the point end more closely resembled a Japanese kissaki. Minor differences; but I could tell as soon as I opened the box that this was going to be a very different tool from the 25".
Heavier, stouter, more weight-forward; potentially even more slicing and shearing power, because although the blade is shorter, because of the extra width the cutting edge is actually longer. I was already beginning to see this khuk in terms of a heavier-duty application - maybe for felling, lopping, trimming and shaping lumber, rather than clearing brush. Of course, the 25" fells, lops, trims and shapes like a lightsaber already - but nothings so good it cant be improved, right?
First job was to clean it up. The blade as it came out of the box was beautifully and symmetrically shaped, coated all over with firescale and a little rust. For those of you who havent encountered firescale, its the baked-on residue of the forge fire, slate-gray in color and hard enough to turn a new, sharp file. Horrible stuff.
Getting rid of it can be a real problem. Hand-sanding or stoning it away is a heartbreaking job. The kamis grind it off with a bench-grinder, but unless you have a very light and sure touch (as they have) you risk scoring up the blade with deep, ugly grind marks thatll have to be ground out in turn, costing you precious blade thickness. Same goes for an angle-grinder with a grinding disk. A belt-grinder whisks off firescale fairly quickly, but the curves and bevels of a khuk blade are awkward to accomodate on the flat bed of a belt-grinder; you have to use the roller end, and you risk the hills and valleys effect, grinding bumps into the flats of the blade, when using such a small contact area.
Accordingly, I took the grinding disk off of the angle-grinder and replaced it with a flap-wheel; flaps of hard-wearing abrasive cloth overlapping each other like the blades of a fan. The flap-wheel scours off firescale in a spectacular shower of orange sparks (dont forget your eye protection!) but only skims off the minimum amount of metal; there shouldnt be any deep scratches scored into the blade, and you can follow the contours of the flats and bevels and so avoid rounding off the pronounced edges.
With the firescale gone, I could see what lay beneath. At first sight, it wasnt promising. As well as a whole lot of dings and dents where the edge of an uncrowned hammer had dug into the metal during forging and planishing, there were a whole lot of my pet hate, scale inclusions (this is where bits of scale and clinker from the fire have been hammered down into the steel during forging; theres not a lot you can do about this problem except keep your anvil clean of scale flakes, and wire-brush the scale off of the hot metal before you hammer it; also some types of spring steel seem to attract scale more than others - old Victorian cart springs, such as I mostly use, shrug off the scale, whereas modern car and truck springs scale up for a pastime) Also there were places where the original steel had been rust-pitted, and the pitting had been forged in to the blade.
Time for a policy decision. I could grind out all the hammer marks and scale inclusions, and thereby lose about 25 thou of metal from each side (reducing the thickness from 0.395 to 0.345") in order to get a mirror finish; or I could leave the dings, inclusions and pits alone and get an ugly but entirely functional blade.
I compromised. I ground the blade down to 0.375", which took out nearly all the marks while still leaving me with plenty of blade. The remaining marks are plainly visible and they bug me, but I dont want to waste those precious extra thous of thickness. After all, this blade is going to work, and work hard; itll get scuffed and scratched and sharpened with coarse stones, so putting an exhibition finish on it would be a waste of time anyhow.
The back of the blade was pretty straight, but the cutting edge was slightly adrift, tending to lie over to one side in the last 4 inches. I couldnt fix this by tapping it over with the hammer, as I would with one of my own blades, since of course the khuk had already been hardened; and I didnt want to lose valuable hardened cutting edge by grinding it straight. Again, a compromise; a little careful work on the belt grinder has trued the edge up to a certain extent, without sacrificing too much steel. I can live with the remaining deviation.
Next step was to grind out the grind-marks left by the flap-wheel. These marks were shallow enough to come out completely, being only a thou or so deep. Step one was to take off the new flap-wheel and put on an old, half-worn flap-wheel for a couple of passes each side. This got rid of most of the marks and left me with a surface I could just about see my reflection in. Next, I put an abrasive rubber wheel in the Dremel and scoured all over, leaving a smooth but smeary-looking dull finish. Finally, the buffing-wheel, mounted on my bench grinder; I charged it with lots of heavy gray buffing soap and buffed till the blade felt like glass to the touch; then changed wheels and charged with the pink polishing soap to get the proper HI mirror effect. The remains of the scale inclusions &c were still visible, but not nearly as bad as they had been - the buffer actually cleans out the inside of the affected areas, to a certain extent.
Last step in preparing the blade was to make and set the edge. I did this with the bench-grinder and the roller end of the belt grinder to get a rough edge, then finished by hand with six grades of stones. The edge was now quite sharp, but not razor; I left the final whetting and stropping until later, since Id be handling the blade a lot while making and fitting the furniture.
At this point, I stopped and thought about design considerations. The khuk was going to be point-heavy compared with the 25", so I needed to pull back the centre of balance. On the other hand, I wanted to fit a handguard - my only major beef with traditional khuk design is that theres nothing to protect your knuckles and fingers - bad news when youre hacking brambles, thorns &c. I decided on a small circular hilt, like a Japanese tsuba. This meant adding weight behind the elbow, which was good, but in front of the hand, which wasnt; so Id have to counterbalance all this forward weight with a pommel.
Another compromise. Ideally Id have liked a big disk pommel, as fitted to medieval European swords, to give me weight plus comfort on the back of my hand; but khuks only have a little thin tang, and putting a big hunk of steel on the narrow end of a thin tang is asking for real trouble because of the effect of vibration running up the tang on impact; too big a pommel and Id be risking a sheared-off tang.
For the hilt, I went through my scrap pile and found some 2.5" squares of quarter-inch mild steel plate Id scrounged from a local machine shop. Just the job; so I drilled a 3/8" central hole for a mandrel, mounted the square plate on the lathe and turned off the corners, leaving a 2.5" disk; then over to the Bridgeport to mill out the slot for the tang to go through; file to fit with a foursquare file. After that, back to the lathe to turn up a steel bolster, 0.900" internal diameter and 0.050" thick, to strengthen the weakest part of the wooden grip. I knurled both the bolster and the hilt; no reason, I just like a diamond cross-hatch finish on steel.
Next step will be to turn a wooden handle, drill and slot it to take the tang, make the pommel (probably out of a 5/8" thick slice off a cute little round bar of 1 ½" brass Ive been saving for a rainy day), forge a karda and chakma, then make and cover the scabbard. So far its been a lot of work and a lot of fun. If I dont contrive to mess it up at some stage along the way, the result should be a wholly functional khuk, modified and balanced to suit the sort of work itll end up doing.
If anyones been considering tackling a blade-only project, I heartily recommend it; as well as being surely the best value for money deal in big knives youll ever get anywhere, its a thoroughly enjoyable experience.
Remarkable what a difference even a few thousandths of an inch can make. The blade only was (obviously) an inch shorter than my beloved 25" Kobra; also slightly thicker (0.395" at the elbow, as against 0.350") with rather less distal taper towards the point, and a tad wider from elbow to point. Theres also a more pronounced upsweep at the point, so that the fuller-profiled cutting edge at the point end more closely resembled a Japanese kissaki. Minor differences; but I could tell as soon as I opened the box that this was going to be a very different tool from the 25".
Heavier, stouter, more weight-forward; potentially even more slicing and shearing power, because although the blade is shorter, because of the extra width the cutting edge is actually longer. I was already beginning to see this khuk in terms of a heavier-duty application - maybe for felling, lopping, trimming and shaping lumber, rather than clearing brush. Of course, the 25" fells, lops, trims and shapes like a lightsaber already - but nothings so good it cant be improved, right?
First job was to clean it up. The blade as it came out of the box was beautifully and symmetrically shaped, coated all over with firescale and a little rust. For those of you who havent encountered firescale, its the baked-on residue of the forge fire, slate-gray in color and hard enough to turn a new, sharp file. Horrible stuff.
Getting rid of it can be a real problem. Hand-sanding or stoning it away is a heartbreaking job. The kamis grind it off with a bench-grinder, but unless you have a very light and sure touch (as they have) you risk scoring up the blade with deep, ugly grind marks thatll have to be ground out in turn, costing you precious blade thickness. Same goes for an angle-grinder with a grinding disk. A belt-grinder whisks off firescale fairly quickly, but the curves and bevels of a khuk blade are awkward to accomodate on the flat bed of a belt-grinder; you have to use the roller end, and you risk the hills and valleys effect, grinding bumps into the flats of the blade, when using such a small contact area.
Accordingly, I took the grinding disk off of the angle-grinder and replaced it with a flap-wheel; flaps of hard-wearing abrasive cloth overlapping each other like the blades of a fan. The flap-wheel scours off firescale in a spectacular shower of orange sparks (dont forget your eye protection!) but only skims off the minimum amount of metal; there shouldnt be any deep scratches scored into the blade, and you can follow the contours of the flats and bevels and so avoid rounding off the pronounced edges.
With the firescale gone, I could see what lay beneath. At first sight, it wasnt promising. As well as a whole lot of dings and dents where the edge of an uncrowned hammer had dug into the metal during forging and planishing, there were a whole lot of my pet hate, scale inclusions (this is where bits of scale and clinker from the fire have been hammered down into the steel during forging; theres not a lot you can do about this problem except keep your anvil clean of scale flakes, and wire-brush the scale off of the hot metal before you hammer it; also some types of spring steel seem to attract scale more than others - old Victorian cart springs, such as I mostly use, shrug off the scale, whereas modern car and truck springs scale up for a pastime) Also there were places where the original steel had been rust-pitted, and the pitting had been forged in to the blade.
Time for a policy decision. I could grind out all the hammer marks and scale inclusions, and thereby lose about 25 thou of metal from each side (reducing the thickness from 0.395 to 0.345") in order to get a mirror finish; or I could leave the dings, inclusions and pits alone and get an ugly but entirely functional blade.
I compromised. I ground the blade down to 0.375", which took out nearly all the marks while still leaving me with plenty of blade. The remaining marks are plainly visible and they bug me, but I dont want to waste those precious extra thous of thickness. After all, this blade is going to work, and work hard; itll get scuffed and scratched and sharpened with coarse stones, so putting an exhibition finish on it would be a waste of time anyhow.
The back of the blade was pretty straight, but the cutting edge was slightly adrift, tending to lie over to one side in the last 4 inches. I couldnt fix this by tapping it over with the hammer, as I would with one of my own blades, since of course the khuk had already been hardened; and I didnt want to lose valuable hardened cutting edge by grinding it straight. Again, a compromise; a little careful work on the belt grinder has trued the edge up to a certain extent, without sacrificing too much steel. I can live with the remaining deviation.
Next step was to grind out the grind-marks left by the flap-wheel. These marks were shallow enough to come out completely, being only a thou or so deep. Step one was to take off the new flap-wheel and put on an old, half-worn flap-wheel for a couple of passes each side. This got rid of most of the marks and left me with a surface I could just about see my reflection in. Next, I put an abrasive rubber wheel in the Dremel and scoured all over, leaving a smooth but smeary-looking dull finish. Finally, the buffing-wheel, mounted on my bench grinder; I charged it with lots of heavy gray buffing soap and buffed till the blade felt like glass to the touch; then changed wheels and charged with the pink polishing soap to get the proper HI mirror effect. The remains of the scale inclusions &c were still visible, but not nearly as bad as they had been - the buffer actually cleans out the inside of the affected areas, to a certain extent.
Last step in preparing the blade was to make and set the edge. I did this with the bench-grinder and the roller end of the belt grinder to get a rough edge, then finished by hand with six grades of stones. The edge was now quite sharp, but not razor; I left the final whetting and stropping until later, since Id be handling the blade a lot while making and fitting the furniture.
At this point, I stopped and thought about design considerations. The khuk was going to be point-heavy compared with the 25", so I needed to pull back the centre of balance. On the other hand, I wanted to fit a handguard - my only major beef with traditional khuk design is that theres nothing to protect your knuckles and fingers - bad news when youre hacking brambles, thorns &c. I decided on a small circular hilt, like a Japanese tsuba. This meant adding weight behind the elbow, which was good, but in front of the hand, which wasnt; so Id have to counterbalance all this forward weight with a pommel.
Another compromise. Ideally Id have liked a big disk pommel, as fitted to medieval European swords, to give me weight plus comfort on the back of my hand; but khuks only have a little thin tang, and putting a big hunk of steel on the narrow end of a thin tang is asking for real trouble because of the effect of vibration running up the tang on impact; too big a pommel and Id be risking a sheared-off tang.
For the hilt, I went through my scrap pile and found some 2.5" squares of quarter-inch mild steel plate Id scrounged from a local machine shop. Just the job; so I drilled a 3/8" central hole for a mandrel, mounted the square plate on the lathe and turned off the corners, leaving a 2.5" disk; then over to the Bridgeport to mill out the slot for the tang to go through; file to fit with a foursquare file. After that, back to the lathe to turn up a steel bolster, 0.900" internal diameter and 0.050" thick, to strengthen the weakest part of the wooden grip. I knurled both the bolster and the hilt; no reason, I just like a diamond cross-hatch finish on steel.
Next step will be to turn a wooden handle, drill and slot it to take the tang, make the pommel (probably out of a 5/8" thick slice off a cute little round bar of 1 ½" brass Ive been saving for a rainy day), forge a karda and chakma, then make and cover the scabbard. So far its been a lot of work and a lot of fun. If I dont contrive to mess it up at some stage along the way, the result should be a wholly functional khuk, modified and balanced to suit the sort of work itll end up doing.
If anyones been considering tackling a blade-only project, I heartily recommend it; as well as being surely the best value for money deal in big knives youll ever get anywhere, its a thoroughly enjoyable experience.
