TIG Weld a Broken Knife




Introduction: TIG Weld a Broken Knife

About: Trying to learn faster than I forget. It will be cool to make some stuff along the way.

A panicked scream came from the kitchen and thankfully there was no bloodshed. A kitchen knife had slipped and fallen on the tile floor.

Broken in two this would either be trash, a nice handled box cutter or a new TIG welding project.

I tried it as a box cutter and it was awesome, but I really wanted to practice TIG welding on stainless steel.

TIG is short for Tungsten Inert Gas. It is an electric welding process that heats an area of metal with an electric arc. The arc is shielded with an inert gas - in this case Argon. The gas shielding will protect the molten metal from becoming oxidized during the welding process. The power is adjustable and as you may guess, the bigger the spark, the deeper the weld. You can weld two parts together with capillary action pulling molten metal from both parts, or add a filler rod of suitable material.

I am quite new to TIG welding, so bear with me... this one is gonna be a bit rough.

Step 1: Set Up Welder

Set up welder according to the charts for the material. I set the welder to DC power and dialed it down to 60 amps.

Step 2: Clamp the Two Parts Together

I clamped the parts together and made sure the piece was grounded to the table.

Step 3: Tack Weld the Two Parts Together

A quick zap held these parts together so I could undo the clamp. No filler used in this step, but you can see how the metal has pulled in from the edge.

Step 4: Weld

My first pass wasn't that pretty so I did it twice. I learned that my power was fine for the thick part of the blade, but once I got to the thin stuff, it burned right up. Now I think of it as a battle wound.
This weld was given just a little bit of filler rod.

Step 5: Grind and Finish Sand

Grind off the lumps and finish sand. I used the rough and fine bench grinder and finished up on a belt sander.
As you can see, the discoloration gets sanded away in the process.

Step 6: Enjoy Your Knife

This knife has new life once again. It's a bit sharper now than it was before too!
There are still blemishes, but there is also a lesson learned and a skill practiced.

I did this project at the Tech Shop in San Carlos California.

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73 Discussions

When I was in a vocational school my junior/senior year taking Auto Collision we had a test of these to build certain shapes without any other material (it was to show control of the welder and the heat we used) and I can tell you that I DID make a ring as a joke at one time. I do not have it anymore.. that was a long..long...long time ago!

I opened this instructable because I was AGHAST that you didn't make it into a cool Halloween prop, coat hanger or 'damaged car' prank but, i'll be dmned, you actually put something back to work for it's intended purpose. something about that is very impressive.

I see a lot of yacking and critiques ( mostly in good humor) but not one image from anyone displaying their fine welding work... Just saying...

1 reply

THANK YOU! I posted about the LACK of positive/constructive criticism on this. but not a lot of agreeance on that yet.

roballoba: Nice instructable and PLEASE accept the comments as 'constructive criticism' as much as you can. Although you DID mention you were new to welding and it DOES say that the project was done at the "Tech Shop in San Carlos California"; it seems you are the only one being real honest/constructive here. Well, I do have to say sourcesmith gets points for his. That was genious and funny, I don't care who you are (<-say it with a lame Larry the Cable Guy voice and it'll be just like in my head). ANYWHO, I am willing to bet that everyone that blasted your welding job didn't ace their first few welds.. I sure as heck didn't! The ones that have only commented about your 'nice equipment' (I hope they are talking about the welder too) are just jealous that you have access to that stuff. I try to stay positive that they actually read your instructable and saw that you did this somewhere not in your garage, but who knows. Good start and keep it up and it'll get better and better. Thanks for the instructable and idea too!

3 replies

In my err (I'm sure I will hear about it..) I forgot that I wanted to remind them all in the above about this bit "We have a be nice comment policy. Please be positive and constructive." IMHO riding your but or telling you that your welding is horrible is NOT constructive. How about offering tips on how he could do better! Yes, I did notice some of you did.. that is why I am not pointing this at those people.

It's all constructive in my eyes... Thanks for your time in the experience.

I am glad that you are taking it as constructive roballoba. I would have for someone to be run off by others being rude. Heck, for reason other than lack of want I have not posted my first yet, but I have followed many others to make theirs and loved it! Keep up the good work!

If you ever plan on cutting food and serving it to others with that, you should use 316 filler rod and a lanthanated or cereated electrode.

The "battle wound" can be taken out with some sheet cut to the right shape, or just built up with filler metal and ground down.

2 replies