Advice on how to thin a bush hog blade for a Kukri

[norrin_radd]

I came across an old bush hog blade similar to this:

The end of it is worn more to blunt point but its the basic same thing. I thought this would be good to make one or two big Kukri's out of, my first ones, but I think its a little too thick at a 1/2".

 

Im still a newb, so my dumb question is should I just heat it up and start beating on it with my regular 3lb forging hammer or should I use something like a flatter to try to get it to around 1/4" thick before I start to get the kukri shape that I want. I dont have a power hammer and have never used a flatter so I thought I would just see what the pros would suggest before I get started with this rather large piece of steel.

Might be easier to just make some big a' viking axes out of it, i dunno.

thanks for any advice.

[ThomasPowers]

Flatter is only for dressing the surface at the very end of forging.  I would suggest cutting off a strip sufficient to your needs and convincing some friends that it would be fun to use sledge hammers striking for you.  (Note using a whonking big chunk of steel rather than your anvil may be indicated if your strikers do not have much control---I would suggest having them always hit the same point on the "anvil" and you move the workpiece back and forth....)

[Charles R. Stevens]

Drawing out I's a basic skill. Wich can be done in many ways, efficiently in a few ways. This is what cross pein, strait pein and fullers are designed for. A bit more experienced smith may use the horn, off edge of the anvil or the edge of his hammer to acomplish the same thing. As Tommas points out, cutting a peice out to start with, then drowning it out with a fuller and a striker is one if the more effecient ways to do so.

[Crazy Ivan]

Just want to point out that the standard issue Khukri  has a 3/8" spine. 1/4" would be fine but less hammering and more authenticity sounds like a win to me!

-Crazy Ivan

[norrin_radd]

Just want to point out that the standard issue Khukri  has a 3/8" spine. 1/4" would be fine but less hammering and more authenticity sounds like a win to me!

-Crazy Ivan

I had thought about making one that thick but I was afraid it would be too heavy for backpacking type useage. I was shooting for at least a 12" blade. I might try the first one at the 3/8" though. There is plenty of material in that blade for 2.

thanks for the replies.

[ThomasPowers]

I was checking stats on some new kukri pages and they had some heavier than medieval swords were!

[VaughnT]

I wouldn't even attempt it.  Thinning down a piece of .5" stock to make a blade is a metric ton of work.  And the blade is only going to be roughly .250" at the spine; the rest is tapered to zero.

 

Burns up a lot of time and fuel, and you're left with something that might not even be hardenable.  Maybe it will require an air quench or water quench.  Can you hold it at temperature for the required soak period?  Can you forge it in the right temp zone for that alloy?

 

Whole bunch of questions..... but the big one that you don't ask is:  How is burning up $50 worth of fuel and $50 worth of time to make a piece of .250" steel better than spending $10 to buy a piece of known-alloy steel that's already close to finish dimension?  

 

That thick blade could be used for other tasks, like a guillotine or bolster block.  Making it into a knife, though, is, in my estimation, a fool's errand.

[norrin_radd]

Well then...thanks for the reality check. You've given me something to think about. I actually had wanted to make a guillotine a while ago, probably a better use for it. I may have let my desire to make a huge knife cloud my judgement. Every time I thought about it I knew it was going to be a huge pain.

Thanks for all the advice.

[VaughnT]

Don't mean to sound rough, but wanted you to know what you're getting in to before you get in to it.  Lots of folks think using "free" metal is saving them a ton of money, but good carbon steel like 1084 isn't expensive.  You can get a foot of 2"x.25" delivered to your door for pennies.  More importantly, it's a known alloy that you can heat-treat at your house and have a very good chance of coming out with a great blade.

 

To give you an example.....  a "friend" took a lawnmower blade and made a knife out of it.  It was already a perfect thickness for a small blade, so he didn't have to do any work to thin it down.  Finally gets it done and is proud as a peacock over it.  Probably had about twenty hours worth of work in it, mostly stock removal with files and sandpaper.  Lots of sweat, a little blood, but good times.

 

Gets it all the way to the point where it's time to sharpen it.... and he can't get it to hold an edge.  Take it down to a mirror shine on the bevel, but it's no different than sharpening mild steel.  What happened?  Dunno.  All those hours of work just to end up with a glorified butter knife.

 

Sometimes mystery metal can be a great thing.  That blade is probably a pretty tough steel and would make great bits for a guillotine tool, bolster block or nail header.  I could definitely see you using the worn down edge to make a wall-mounted bottle opener.  Overkill, definitely, but we're men and overkill is good for us.

[Broomhead]

To give you an example.....  a "friend" took a lawnmower blade and made a knife out of it.  It was already a perfect thickness for a small blade, so he didn't have to do any work to thin it down.  Finally gets it done and is proud as a peacock over it.  Probably had about twenty hours worth of work in it, mostly stock removal with files and sandpaper.  Lots of sweat, a little blood, but good times.

 

Gets it all the way to the point where it's time to sharpen it.... and he can't get it to hold an edge.  Take it down to a mirror shine on the bevel, but it's no different than sharpening mild steel.  What happened?  Dunno.  All those hours of work just to end up with a glorified butter knife.

 

Been there, done that. It was my first knife, back before I had any knowledge of knifemaking, and I was excited with how it turned out. It looked really good, nice design, great handle shape, even made a sheath for it. It sharpened up great the first time, and a few days later, and a few days after that... I'm sure you get the point.

 

Lawn mower, bush hog, and other landscaping blades are meant to be tough but still bend/deform when they hit something hard. If they were made of knife quality steel, they would most likely shatter when you hit a rock. Just because a piece of metal seems strong, tough, handles a heavy load, etc, doesn't mean it's good for a knife. As was said, use it for tooling or even as a bolster material, with some type of patina/bluing/coating/acid etch to help protect against rust.

[Stormcrow]

A fellow in Australia who hangs out on another board that I do contacted me for advice while working up prototype blades to be manufactured by one of the khukuri manufacturers that sells in the U.S. a lot.  It let me get a few interesting glimpses into their process and business.  One thing that I hazarded a guess about that the Australian confirmed is that one of the reasons that khukuris tend to have such massive spines is that they're being forged by hand from 1/2" truck springs.  The labor to work them down to a blade thickness with muscle power is tremendous.

 

I don't know if they ended up doing so, but I recommended they see about ordering some 1/4" 5160 from Aldo Bruno.  They were certainly interested in doing so; I just don't know if they followed through.

 

The owner seemed to be fairly forward-looking.  He apparently owned the only CNC milling machine in Nepal, not only for his own business, but would hire it out to other businesses.  They were investigating power hammers too.

 

If you are going to use salvaged steel for a blade, I'd recommend going with pickup leaf springs.  They tend to be a much more workable thickness and should be good blade steel.  Not guaranteed, though, and there's always the possibility of microfractures in a used car spring.

[Charles R. Stevens]

Or spend the 20$ to order a genuine nepolise kirk

But we're blacksmiths ;-)

[ThomasPowers]

My suggestion is to visit a spring shop and buy drops---unused steel of known type(s) in convenient sizes.  Talk about smithing with them and you might have to flee before they can load you down with freebies---at worst I paid their scrap rate for it.