Need help with my fish mouthed banana blades

Wade Jones

Wade Jones

Joined
Nov 1, 2009
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183
Trying my hand at forging and the results have been depressing thus far.
Figured I better look for some help before wasting anymore steel.

I can't seem to avoid the fish mouth. I've been holding the steel on my makeshift anvil (sledge hammer head in concrete) at an angle and hammering back towards the legth also at an angle (45°ish on both). This is what I read and see in the videos, but I must be doing something wrong.
One tip a was able to bang out sort of OK, but the thing banana'd badly on me when I tried to taper the edge down. I see people mention straigtening as you taper the edge, but I don't fully understand how this is done.

I know this stuff is probably hard to put into words, but any help would be appreciated.
-Wade
 
Well it's pretty flat, there's a little radius at the edges, but I try to stay centered on it where it's flatest... I guess I never really gave it much thought before.
How would I straighten it? I can't imagine I'd do well with my angle grinder.

I've been looking for a real anvil, but they are few and far between and really expensive.
 
Wade, I've seen people knock in both corners to form a point in the middle, and I've seen people knock in one point and form the point towards the remaining corner. This is actually how I prefer to do it as it also matches my blade style. I'd also recommend "cheating" a bit, especially as you're learning (like I am). This involves lightly rounding off the corners at the end of the bar with a grinder prior to forging your tip. It just makes things easier and helped me decrease the fish-lips as you don't have to hammer that sharp point of the corner back into the bar.

As for avoiding the banana blade, some people straighten as they go when forging bevels, but I prefer to do a pre-bend. So, after you have your point and very rough profile forged in, you actually forge a bend in the blade that goes in the opposite direction of the typical banana you've been getting. So the cutting edge looks like it's the inside curve of a boomerang. Then, as you forge your bevels in, the blade gradually bends back to near-straight. The pre-bend is typically done over the horn of the anvil, but you could get by with what you've got.

--nathan
 
Hi Wade.
Are you using flat stock that is cut at a right angle on the ends? If so, that is a tough way to start. Try cutting the tip first at an angle or radius before starting to forge.

As for the curvature that comes from forging the bevels you can correct it a few ways. You can first "precurve" your blank into the future edge. As you forge the edge bevels it will straighten out. Alternately, you can forge in the bevels and then forge in distal taper along the upper portion of the blade. This will also straighten the blade to a degree. Lastly, you can put the blade on a wooden block or stump, curved edge up, and strike down on it. It will want to twist and the edge will deform, so alternate between the edge and flats to correct as you go. Hope this makes sense.

Edit: Nathan gave a better description of the prebend method as I was posting. Also, an angle grinder could flatten your anvil just fine. If you have a hand held belt sander that will be easier to keep things flat.
 
I'll add this: Remember when you directly strike hot steel with a hammer, the steel moves in all directions, not just in one or two directions. Imagine a pile of silly puddy sitting on a table that you smash with your fist. It expands in all directions. This explains why the blade banana's on you when forging your bevels. As you are hitting the steel to thin it out towards the edge, it's also expanding towards the tip and ricasso at the same time thus actually lengthening your bar near the edge.

--nathan
 
Thanks guys.
Yes I am using square cut bar stock. I shall experiment with what you have advised and see if I can make something work. The corner cuts make a lot of sense.
As far as doing the pre-curve, are you just hitting the "spine" along to bend it out? I'm envisioning myself using the radius on the edge of my sledge to get a decent curve.
Thanks again, big help!
 
I too do a prebend because the edge beveling will bend it back the opposite way. I use a couple logs to form a gap and a third log as a hammer to bend it. The wood won't deform the metal, just bend it.
 
stevomiller said:
Hi Wade.
Lastly, you can put the blade on a wooden block or stump, curved edge up, and strike down on it. It will want to twist and the edge will deform, so alternate between the edge and flats to correct as you go.
Click to expand...

I like this method quite a bit for forming pre-bend. I have nice horns on my anvils, but still often use this method. I took a pretty fair sized round of unsplit firewood, and hollowed the top out slightly with the nose of my chainsaw. You can use a round piece of hardwood, such as a 4" or so round branch, as a hammer. A 2x4 works in a pinch.

Set the blade on spine down over the depression, and hammer the edge from the top where you want the apex of your pre-bend to be. Flatten on the anvil. It works well since the tongs don't have to grip as hard; when using the horn you are hammering against your grip. Even holding your tongs strategically fails to entirely mitigate this difficulty.

This method also works well after forging your main bevels in case you need to tweak your profile a little. It will bend (correctable) your edge, not mushroom it as hitting it with the anvil and hammer would.

When forging a tip onto a square ended piece of flat stock, I find it more effective to hammer from the top only. I hold the piece flat to the anvil; the hammer can be directed at the tip at a 45 deg. angle, (or steeper as needed) and be more effective than if the piece was angled as well. The point is more firmly supported by the anvil this way, yielding more work done for your effort. The hammer can be angled sufficiently this way, and hit hard without necessitating contortions on your part.

For a clip point, forge your tip down to pretty sharp, leaving a definite shoulder at the top where it meets the back of the straight portion of the stock. For a drop point, form a continuous curve from the straight stock down to the tip. After forging the tip in, the tip can pretty easily be bent to your desired shape.

Remember to forge the tip a bit more narrowly than you want it to be when finished. Forging the bevel will widen it. And, after forging the tip, I often leave it as forged- that is, wharncliffe looking. I pre-bend the rest of the edge. Then, when forging the bevels the main body of the blade and the tip tend to come back to roughly the shape I've planned. If necessary, I finish profiling by tweaking a bit using the stump method.
 
Sounds like you don't have a lot of time or steel to waste trying to figure this thing out, get some plasticine and practice your forging. A little mineral oil on the face of your hammer and your anvil will keep it from sticking, just don't hit it hard or you will splatter it ;D
seriously, hot steel moves like modeling clay so I was teaching a class in a church where I couldn't use fire, so I got some modeling clay and taught the class with it.

-Page
 
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