my weekend project (it's your fault!)

T

Tommy_Atkins

Joined
Jul 27, 2003
Messages
134
Okay...

after a couple of weeks' reading through the HI forum, and the HI website FAQ, and spending the GNP of a small jungle nation on HI steel, I decided to try my hand at the legendary, yet elusive, "convex edge".

firstly, I have no concrete idea what a "convex edge" actually is. I have inferred from reading through the forum archives that the cross-section of a convex-edged blade would kinda look like an elongated watermelon seed, with no discernible bevel toward the edge, but rather a gradual, inverted-teardrop shape from the knife's spine to the edge.

I have this "Genuine Gurka Issue Kukri Rare L@@k!!" that I bought from eBay (yes, I'm gullible; shut up.) a few weeks ago before the HI forums showed me The Way. I shoved it way back in the darkest corner of my linen closet out of embarassment...I didn't want to have to explain to my HI Khukhuris why I allowed such an ugly specimen to share their living space. I planned to give it to some poor, unenlightened sucker as a gift or something ("here dood; just like them Gurkas carry, happy Arbor Day!), but after reading about how y'all carve up your khuks, I decided to use it as a Guinea Pig in my own little convexing experiment. It's full tang with an ugly, hourglass-looking handle with giant steel pins in it. The blade itself is nowhere near as thick as an HI Khuk; it's a blade of much more conventional dimensions.

I used a mill file, some sanding sponges, a drywall sander with various grit papers and water. Fueled by beer, I was an unstoppable grinding machine!

Eventually, I got the convex profile that's so widely touted hereabouts. The original edge bevel is gone, and the blade kinda tapers smoothly toward the point. I used a Gerber diamond sharpening rod to put a nice edge on it, and put it to the test.

Even without the heft of an HI blade, it made short work of a 1x4 pine board and a 3" thick hardwood log. After that abuse, its edge was still keen enough to snicker-snack effortlessly through the stems of some really big, dying elephant ears in my back yard.

I feel pretty good about this project. I managed to convert a useless hunk of tourist crap into a workable blade, and in the process learned (or began to learn) some of the necessary techniques for maintaining and improving a good knife.

My next project is a certain Pakistani Bowie of dubious provenance that I intend to convert, at least in shape, into something resembling a Cherokee Rose. I need to build some sort of rudimentary forge or furnace for tempering blades, but...one step at a time, right?
 
What's so hard to understand about the convex edge? It's simply a lenticular shape!
;) :p :D
 
Originally posted by Tommy_Atkins
Fueled by beer, I was an unstoppable grinding machine!
Click to expand...

When I see things like this, the next line I expect is either:
1. "The next thing I knew I was waking up in the emergency room", or
2. "The next thing I knew my knife was the size of a cocktail spear"
:D :D :D

Sounds like a good start to working on your blades!
 
Originally posted by Tommy_Atkins

"here dood; just like them Gurkas carry, happy Arbor Day![/i]),


Happy Arbor day!!!!!
Not if you're a tree :eek:
I hope a few of you see the irony in that......
Click to expand...
 
I have one of those humbler khuks too, and it has come in handy as a "test khuk" for the slack-belt grinding process. It makes no appology to the other khuks it hangs next to, because the task to prying rocks out of the tiller is a dirty job but something has to do it.

Recently I have been thinking about using my wood-burning tent stove as a forge for re-tempering some old axe heads. Don't know how well this will work, but it would be an easy solution.
 
Originally posted by cliff355
Recently I have been thinking about using my wood-burning tent stove as a forge for re-tempering some old axe heads. Don't know how well this will work, but it would be an easy solution.
Click to expand...

Hey, that's a pretty good idea! I was considering an old Weber grill, but dunno if it could withstand sustained temperatures as high as those necessary for tempering.

I think I can get 'hold of an old army issue potbelly...they're nice and thick.
 
An old BBQ can apparently work just fine if the interior is insulated by a thick layer of dampened wood ash that has been packed in and allowed to dry.

Add a piece of pipe for a tuyere and an old or cheap hair-dryer for a blower and it's good to go.

looky here:

http://www.ckdforums.com/showthread.php?threadid=10293

14071417-d247-01F40177-.jpg


He burns charcoal (not briquettes). Seems you can buy it from restaurant supply houses. Wood also.

When hardening, he places the blade in-side of a pipe heated by the forge so as to heat evenly. Lots more details in the link.

Those who really know this stuff can add more or correct me, but I don't think a wood stove will get hot enough without a blower, and one would probaly want to line it with refractory. This looks simpler to me.
 
My hats off to you Mr Atkins:>
I have the highest respect for someone who goes at this with hand tools alone. A convex edge is simply IMO the strongest sharpest edge that can be put on a blade. Even with a good grinder and new belts they are a pain in the ARS to do. But if properly done they will take a fantasticly strong edge that will be razor sharp.
As for what it is, it is more of an apple seed shape done to zero.
When you get ready to put the finishing touches on the net one try this. Get good quality cloth backed sandpaper and run it up and down along the edge in whatever grit your at, untill you get a burr. move to the next grit and so on. Using an up and down motion like you were buffing a shoe only keep it at about a 20 deg angle or so. The paper will form the convex as you go. Be sure to do each side evenly with each grit. I would go to about 1200 and then (Blade down) obviously you VERY lightly buff off the wire edge with a buffer if you have one.
If not use a superfine ceramic hone.
Excellant edge for an excellant type blade.
 
Firkin:

Thanks for posting that link. I'm sure not going to hook a blower up to my stove because it would soon be glowing like a lightbulb and I would be down one stove. The forge-b-que seems like a simple enough thing though.

The axehead in question is a cheap axe which came with a cheap handle which broke. I burned out the stub in a fire and when the head was fished out of the coals it was glowing bright orange. So, I thought a wood fire might get it hot enough to manipulate the temper, but maybe not. It is certainly something worth further study.
 
"I'm sure not going to hook a blower up to my stove because it would soon be glowing like a lightbulb and I would be down one stove."

Exactly. Unless you line it with firebrick or other refactory. And then you'd still be down one stove--then you'd have an oven!:)


The threads in that forum have a lot of infromation on very simple ways to get the job done. As I understand it, unless you can get carbon steel heated hot enough that it becomes nonmagnetic and quench it, any high temperature treatments that don't get that hot are only going to make it softer regardless of how it is cooled. But I don't know a lot and have done even less.
 
Here's another interesting forge (by Raymond Richard on ShopTalk):

PDRM0430.JPG



It's made from an old propane tank.

Here's the info:

This is a new forge I made over the weekend out of a 3 gallon propane bottle. Think it may be number 9 or 10. I find the three gallon bottle works best for the forging I do plus its real portable. Its also got the back door so longer blades can be done in it. Pretty much like Don Fogg's except its totally contained. I made the cut on this one at the bottom for easy fix and repairs. Its held on with a few tack welds.

...and thread:

http://www.bladeforums.com/forums/showthread.php?s=&threadid=267817



...and a personal response from Ray:

Most the propane bottles I get are from a dealer that other owners have turned in. 90% of the time the valves have been removed and there is no gas what so ever. Ones I've made out of my own bottles I'll hook up a weed burner to them and make sure there empty. I'll drill a small hole in afterwards as another precaution. The one in the picture I used a saber saw with a metal cutting blade to do most the cutting. Just go slow and they work fine and don't have the blade going to fast.

This is a propane forge, the pipe that is welded on the left side is the sleeve that I stick my ventura burner in. I've made a number of them out of the propane bottles and for general use this one is the best as far as size and the way it functions and is really tuned with the style burner I use.. I've always tried to come up with something that burns the least amount of gas and produces the heat I need. Normally what I see is guys using way to big of a forge for what they are doing and it don't need to be this way. I'm just guessing but I don't think this forge weights more than 20 pounds if that much.

If you have anymore questions let me know and I'll try to answer them. BTW is also lined with cerramic insulation and coated with clay mortar...
 
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