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MCalvert

First knife in the new forge

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Posted (edited)

I just got done making a multi-port gun forge, and I have been wanting to make a large kukri (sp?) to use at work. This is the largest knife I have made yet, and first attempt at a kukri. I started with a .250" x 2" flat bar of 1095 from NJ steel baron. I cut the opposite angle off for the tip and stretched it back down. I am not sure what that process is called, but I am a fan of Walter Sorrell's and emulated one of his knives in this regard. The overall length is 18 inches. The belly was drawn out, and I tried forging in the bevels some. These steps went fairly well. Two major failures.. First and most frustrating was the failed curve in the mid-blade. I tried and tried to get it to happen, and all I have to show for it is the slightest angle change. The second failure was a twist that developed while drawing out the belly. I thought I had it corrected, but found it to still exist when inspecting the blank today after grinding scale off. The handle was roughed in on a band saw.

So I have some questions, first being how do yall get the  blade to have that beautiful change of angle when making a kukri? I thought of using one of my solid fuel forges to make a small hot spot and hammer the spine to get the steel to expand there.. I just dont know how else to go about it from a flat bar.. Second question: will grinding the minor twist on the edge half of the belly cause a warp during hardening since one side will have seen so much more belt? I have tried thus far to hammer and grind both sides evenly.

The pictures are from post-forging with most of the scale ground off so I could see a little better. Black table is pre-profile grind, brown table is post-profile grind. The edge picture is an attempt at capturing the belly twist.. not a good attempt as it turns out.

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Edited by MCalvert
Forgot to add a dimension

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I havent made too many blades over a foot long but one thing I found that helps keep it straight during the heat treat is just after I quench it I lay it on my cement floor and place something flat and heavy on it. I use a piece if 3/4 in mild steel. The cement pulls the rest of the heat from the blade and the weight helps keep it straight as long as both sides are ground fairly evenly

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Well I haven't done any heat treating yet. My concern was that grinding one side significantly more than the other would cause issues during hardening... going forward I am planning on grinding more this afternoon (finally on my weekend again) and seeing how it straightens out through the first few passes. I could put it in the vertical mill but that seems excessive. If I am not liking how it is looking I will just put it back in the fire. If the grinder does the trick, I might normalize tonight and harden tomorrow. Still up in the air on handle material.. I keep going back to bloodwood and gaboon ebony. I also like the idea of cratemurtle and gaboon ebony for the contrast. I will post pictures tonight for an update on my belly twist and how it gets fixed. I appreciate your reply/advise Scanlan, and will try it out.

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You are much further along than I like to be when putting the bend in a kukri blade.  I keep it simple.  I heat up the area I want to bend  and then I hold what will be the tang end and slam it edgewise where I want the bend to be over the horn of the anvil a few times.  Once I have the bend then I can move to the profile and getting nice straight lines on the spine.

Since you already have the profile close to where you want it except for the bend and you have bevels started I'm not sure how well that technique would work for you.  You could try heating the area you want to bend, support the two ends on some pieces of wood and smack it where you want the bend with a wooden mallet to keep  the deformation to a minimum.

As for the grinding part I'm not sure I can give you a definitive answer.  In general if you have a perfectly symmetrical blade, regardless of whether it was forged to that point or ground, and you do proper normalization cycles there shouldn't be much warping, but so many things come into play.  If you get one side just a bit hotter than the other, if both sides aren't exposed to the quenchant equally, if you move the blade side to side a little while it is still cooling in the quenchant, etc., you can still get warps.  For large blades you can even get a warp just pulling it out of the forge for the quench if the spine isn't perpendicular to the ground.  Gravity can be a harsh mistress.  If it were me I'd do my best to get everything centered and symmetrical, prepare something to keep it flat and straight after the quench, do the normalization cycles, quench and immediately get it into the "straight jacket."  And of course temper immediately afterwards.

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Posted (edited)

So instead of trying to grind the belly twist out, I bit the blade (har har) and got the metal hot again. It was relatively easy to get the belly of the blade properly straight (according to my eye at least), so I did some drawing on a 1in round for some tongs while I thought up a way to try and get the angle in the mid-blade without ruining it. I decided to make a little jig using two 1x3x12ish bars in a vise. I clamped the tang end of the blade between the bars just in front of where I wanted the bend. I then used a blowtorch to heat that spot in the blade before putting it in the forge, and I made sure the bars soaked up a good bit of heat to ease the leeching during clamping. This caused a hot spot where I wanted the bend, and with a little hammering, it finally broke over. The blade was straightened again using an idea from Buzzkill, profile ground, and scale removed. I am planning on starting bevels next weekend, and if I can get through the coarse belts to 200ish, I will normalize. The blade didn't take as drastic an angle as my pattern, and is closer to a real kukri I have in my display cabinet. All in all I am happy with where the blade is at, although I'm not as far along as I wanted to be today. Pictures below show the corrections.

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Edited by MCalvert
Giving buzzkill credit

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That's a definite improvement to my eye.  The flow of the curves is more appealing for sure.  I'm looking forward to seeing the finished product, but I don't think I'd want to see it coming at me.  That thing looks like it will be wicked!

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Fortunately it's just for injured deer we have to put down after they get bumped on the roads. Animal control refuses to respond to deer after business hours.. just too many. Tis a shame we cant donate the meat. :wacko:

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