I have dedicated a big part of my life working with different metals, starting from regular mild steel up to stainless and damascus. As you all of you probably know, blades are a passion of mine, and sadly, few weeks ago I managed to drop and break one of my favorite blades. It has a crack about 1/3 of the width of the blade running from the bottom, right around the middle of the knife itself.
After pondering for a while I thought maybe it is possible to fix the blade. I did some research, but as it turns out, there is not a whole lot of information about that on the internet. After few more days I reached out to my friend Daniel from WeldingMania to ask for advice. To give you a short answer, I got my blade fixed, and also decided to write a post about if it is possible to weld a broken blades because it might help some of you who are in a similar situation.
Thing to consider before turning to a welder
I am no expert in welding nor forging, but as far as I understand, welding a knife blade is not something that should be treated lightly. As a matter of fact, a good blade should not break after a fall. That indicates the blade is poorly forged and it might have unrelieved stress in the material of micro cracks. For that reason, blade smiths never weld their blades because it is easier to avoid the hassle and potential risks that come with such jobs.
What I am trying to tell you is that unless the blade you broke is very expensive or have sentimental value for you, you should not weld the blade.
In my case, the blade has a huge sentimental value and that is why I decided to go with welding. I also accepted the fact that I would never use the knife.
Alternatives to welding the blade
Unless you broke the tang off your blade or cracked it from the middle, you still might have one more option to fix the blade and that is reshaping the blade by grinding the blade smaller.
For example if you chipped away a small piece of the blades edge or the tip of your knife. In that case it would be much easier to just grind out the damaged area. Depending on the size of the chip, it will reshape the knife a little bit, but as long as it is not a huge chunk of the knife, that is the route I personally would prefer.
Welding method to fix the blade
Now as we got all the essential thing out of the way, let’s talk briefly about the welding methods that are suitable for the project. Maybe you are a hobby welder and would prefer to tacker the job yourself?
Well, unless you are good at TIG or MIG welding kiss the idea of welding the blade yourself goodbye. Many weekend welders and enthusiasts are marrying metal with either stick welders or with flux core welding machines and neither of these methods is suitable for the job. I am not very familiar with the details why, but as I heard both of the methods are way too messy and difficult to carry through precisely.
Actually the precision part also goes for MIG welding, but since it does not produce any flux, it would be preferred over stick and flux welding every day of the week and twice on Sunday.
The most suitable, and the only method that I would let anyone use on my blade would be TIG. This welding method is precise and actually designed for such delicate work. It has many advantages like better control over the heat going into the blade and whatnot.
Before we go into the whole procedure to welding your blade, I think it is important to note that if you have a Damascus blade that you want to fix, then regular arc welding will not cut it (no pun intended). Damascus can only be forge welded.
If you are familiar with welding and understand the basics of metallurgy, the process itself is not very difficult to understand. To give you a brief overview, let’s simplify the whole process and go over the steps to successfully weld your blade. If none of the things mentioned in this part make sense, then better take your blade to a professional.
- First of all, since you are dealing with a knife blade, it is more or less high carbon steel that has been heat threated (varies from blade to blade). To relieve the stress and avoid cracking the blade even more, it should be tempered. I am not saying it is always necessary, it depends on the material from which the blade is made, but just to be safe before welding it, temper it!
It is important to note that even if you choose not to temper the blade beforehand, it will lose it’s hardness from the welded area. The hardness of the blade might not be important to you, so I would say if you are sure you are not welding very high carbon steel, you can skip the first part.
- Now comes the part that is tricky. You need to find the right filler wire. The filler wire needs to be on point to avoid ruining the welded area after hardening the blade by quenching. Dissimilar metals act different when heated and cooled down and quenching might result in brittle weld.
- If you are a welder, I am probably not in a position to teach you, but from the theoretical standpoint, you should tack weld the blade one tack at a time and let the blade cool down naturally between each tack. That’s necessary to minimize deformation of the particle structure in the blade. After you are done welding, grind down the excess metal and you should be ready to harden the blade.
If you got everything right, after hardening the blade, it should be good to use, but I would not. If you have a blade that broke one time, and it important to you enough to go through fixing it, I would not risk breaking it again.
Worst case scenario – If you messed up somewhere down the line either with welding, hardening it or grinding the bead, the welded spot will be visible to the naked eye. Another thing possible is that when you start using your blade, you might find out that the welded area is brittle. That might result another crack right next to the welding bead.
Generally welding a knife blade is not recommended but I would say that if you have a really expensive blade that you can not replace, it is worth giving a shot to repair it. However, materials that knife blades are made out of vary a lot so it might not be possible to weld yours. If you are not sure if it is possible to save your blade, consult with a professional blade smith or a welder, they should be able to help you out.
Daniel from weldingmania https://www.weldingmania.com/