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Forge and filing problem.


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So i wanted to make a knife for my mom to use in the garden.  I opted for a tanto style just for fun. I forged it out of a coil spring, forged in bevels.  Then i drawfiled it, making the nice partially unfinished knife here.  Picture 1 and 2

Then i made this filing jig. Then i filed one side (sort of) to a flatish bevel (it came out of the drawfiling slightly convex)  picture 3

Then, using the same bevel angle on the other side, i did a more thorough job.  To my dismay, 1/4" deep of my edge had rolled over and was useless, leaving the blade shape below.  I will have to start again...... picture 6

So i want to diagnose the problem.  Some factors to consider.  

1 the plunge line is far deeper on the second side i did, i removed much more material. (This could also be as a result of being shy on the filing near the plunge)  *Picture 4 and 5

2 the knife was not completely straight or flat when i started filing, it still isnt.  

3 due to the use of a plywood jig, the c-clamp accentuated the problem of non-flatness, so depending where the clamp sat, the blade was at a different angle.  

My working theory is that the bevel on the first side was not completely accurate, so when i did it on the other side it was too much.  I think this was accentuated by the lack of flatness.  

What are your thoughts? I would like to not have this happen again. :)

Thanks in advance!







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If you want consistency the first order of business is to get the stock as nearly perfectly flat and uniform thickness as possible from forging.  Small variations can be removed with the file, but anything significant that makes one side stick up higher than the other when it's clamped in place will inevitably result in non-uniform bevels at the end.

If you get it flat and uniform thickness, then you can use a magic marker or something like Dykem on what will be your cutting edge.  Use calipers or other method of finding and marking the center of the cutting edge the full length of the blade.  Determine where you want your plunge lines.  Use a chainsaw file to cut your plunge lines in on both sides down to about a dime's thickness.  That will establish your desired thickness and it should help you figure out the angle needed on your filing jig to set the bevel where you want it.  Watch as you are filing.  If you reach the edge thickness you want before the bevel is up as high as you want it on the blade then you will need to lower your eye bolt height.  If you reach the bevel height you want on the blade before reaching the edge thickness you want then you'll need to raise your eye bolt height.  Whether you use a jig or do it all by eye it will take some practice to get the results you want.

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Lots of good advice already. One other thing I would add, look for a more ridged backer to clamp your blade to. Two inch structural angle iron  or something of that ilk can be scrounged in most industrialized areas without breaking the bank. Mild steel drills easy but a thick enough cross section will be much more ridged so you eliminate one issue and then can concentrate on maintaining the correct angle without having to wonder if the problem is you or the jig.

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On the few long ago blades I've forged I used a flatter to true up the faces before I even looked at the grinder. Uh. . . Draw filing IS regular filing. There are probably hundreds of types of file stroke depending on the cut. Practice on something other than a blade you want to use. Get good with a file THEN do fine finish work with one.

Frosty The Lucky.

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Thanks guys, i will definitely flatten my future knives with a flatter to true everything up and smooth out the bevels.  Then i'll file completely flat.  Then i'll mark centre and set plunges with chainsaw file, then judicially file with the jig.  I rushed that one a lot!!

I will post the next knife and i guess we'll see how it turns out!  

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