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Best way to flatten a knife?

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So ive forged a few knives lately and Its been pretty difficult to flatten them out.

The knife i forged is a little thick in the tang then it gets thinner that the thickness goes into the tip. Its not too bad but Im not sure how to get it all to even thickness

any ideas? besides sanding :rolleyes:


How expensive would an old used manual surface grinder be? 

Thanks in advance.

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You can use some cheap calipers to check the thickness, dont forge too hot and hit the steel flat so you dont ding it. I mostly just eyeball the thickness, I recently forged a chefs knife and I made it a little over 1/16" and used calipers to make sure the whole thing was close.

If I want to thin the spine of a blade I forge with the spine facing me so I can see it.

Taking a step back in the process, you should first forge a preform, this is a knife like shape that when the bevels are forged you have your blade without having to taper a complex shape like a blade and if the bevels are even the profile will be good also.

A preform can be tapered to make a tapered blade or flat for a flat blade.

A preform can have a tapering profile that when the bevels are forged in, if the width of the blade is constant, you will have a distal taper to your blade.

A preform is basically a rectangle with a point on one end, it may have profile taper or distal taper. When beveled, everything falls into place together, there is no back and forth.

A preform is something i have trouble describing, but forging from preforms was a big step up for me.

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What Alan said! There is no better, easier or faster way to forge closer to final shape than practice. If you don't have a hi power 2x72 that's all the more reason to hone your hammer skills. I mention this because most often when I hear this question it's because someone isn't happy with their metal hogging equipment. If on the other hand you have the best grinders and want to speed up production you may be ready to build a rolling mill. Hot rolling is a form of forging, usually at the level of heavy industry, but I have seen some really slick ones built from industrial parts for use in a smithy. A rolling mill wont give you a bevel but it will bring the stock down to uniform thickness suitable for grinding to shape, or final hand forging of tangs and bevels etc. For most people the best fix is simply dressing their hammer face and practice.

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I still put my hammer on the anvil to get a feel for what flat and level is, it really helps. You can register against the blade too, if its tapered then registering against the anvil will make you hold the hammer wrong as the blade will be angled in relation to the anvil.

A little extra detail, to register the hammer against something lay it on the piece and try to feel the center of the hammer, relax your hand and let the hammer lay as it wants, if you are tense your muscles will pull to the side and you will fight to stay centered. But its really more of a full body thing, like aiming a firearm or a saw. Close your eyes, hold out your hammer like its on the anvil, and see where youre body is pointing. That relaxed body position is your center, when you are centered you arent fighting against unbalanced muscle forces so you can do things straighter, if that sounds too much like hippy bs just pretend I called it your point of aim and said tactical a few times. I consider it more of a martial arts thing, I learned it shooting air rifles in njrotc in high school. I think it might help to step into position rather than shuffling around in one place, no big deal if you have to step from forge to anvil but I dont have the space myself.

I flatten blades at around 1500 degrees, cherry red maybe, I like to use water on the anvil too. The low temperature reduces scale and the water takes care of the rest. 

Sometimes when I am taking out the dings from a blade it gets all bent out of whack, especially blades with a convex distal taper, but they can be straightened after the dings are out. 

I wish I could describe preforms better, they really help but I am a fool when I try to explain them.

Sometimes I think that forging miniatures really helped with my hammering, but little doll knives arent for everyone. Hopefully thats the last bit of help I have.

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Conner, serious thickness differences should be addressed at the anvil not at the grinder. Good hammer control and technique (something I admittedly lacked for years) is the best means to achieve uniform thickness. Understand though that this is only required along the spine for a short distance and across the ricasso (if you have one). The spine should taper down towards the point and the tang should taper down towards the other point.

I have a video on my channel that shows how to "surface grind" on the 2x72 and the technique is equally valid on a cheap 6x48 belt sander. I started using a cheapo 6x48 from Harbor Freight Tools, and I still use it occasionally to smooth out the surfaces on some knives. 

You can see the video here.

If you are talking about smoothing out the bevels, I use a very heavy plastic faced mallet as a planishing hammer.

Josh pic 1.jpg

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This is what I was trying to say back when you were gonna buy your cheap belt sander. 

Good tools are only as good as the operator. It might seem like you're wasting time by taking it slow without the best equipment, but you're actually learning more than you think. Get a good foundation before you go trying to learn everything at once. Maybe even try forging things other than knives.

Patience will take you further than any tool ever could.  

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