Introduction: TIG Weld a Broken Knife

Picture of TIG Weld a Broken Knife

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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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.


sourcesmith (author)2014-01-11

Hmmmmmm... A very helpful instructable. This will be very helpful in my next project:


Sometimes I wish I could "like" comments on this site.

chotzeny (author)sourcesmith2014-01-22


Wondering if TIG can Smelt a ring as well ?

ibwebb (author)chotzeny2014-01-22

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!

finton (author)sourcesmith2014-01-14

Rats! You beat me to it, sourcesmith! :]

thebluebulk (author)sourcesmith2014-01-12

BAHAHAHAHAHA thank you for that :-)

geekOmat (author)thebluebulk2014-01-12

Missed the comment from sourcesmith :-(

MajHunter (author)sourcesmith2014-01-12


Mig Welder (author)sourcesmith2014-01-12

Since I can't "like" your comment, I'll just say I lol'd :D

roballoba (author)sourcesmith2014-01-11


rostislav.tvaruzek made it! (author)2014-12-24

tig 18-25 A

Eh Lie Us! (author)2014-03-14

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.

rectora (author)2014-01-12

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...

ibwebb (author)rectora2014-01-22

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

ibwebb (author)2014-01-12

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!

ibwebb (author)ibwebb2014-01-12

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.

roballoba (author)ibwebb2014-01-21

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

ibwebb (author)roballoba2014-01-22

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!

The Lightning Stalker (author)2014-01-12

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.

Actually, I believe that was the stuff I used! Thanks for the tip.

Okay, because a thoriated tungsten will make the knife radioactive.

RetiredLE (author)2014-01-12

You could always grind a bottle opener cutout into the gouged out section.

roballoba (author)RetiredLE2014-01-21

I had seriously considered this idea at the time.... ;-)

geekOmat (author)RetiredLE2014-01-12

I like this idea very much!

really_grumpy (author)2014-01-12

had you clamped the knife down to a block of copper(or some other heat sink you would not have burned away the "thin bit". the weld would not have adhered to the copper

billbill11 (author)really_grumpy2014-01-18

The "BEST" learned skill, would be the use of a good copper heat sink.

As mentioned by, really_grumpy

Weld will not adhere to copper, and you even can fill a significant hole

in sheet metal.

I'm talking " bar stock' not thin copper sheet.

This is a "GOOD" Welders , tool box "thing".


ScubaSteve51 (author)2014-01-12

For being new to welding, you've got some nice gear! A PT 225, and what looks to be a Strong Hand table....lots of pros don't even have that caliber of stuff. Even so, you shoulda brazed, it bro! Plenty strong for kitchen use and you would be less at risk for overheating and losing corrosion resistance.

roballoba (author)ScubaSteve512014-01-14

that's the beauty of a community workspace like the TechShop! I can't wait to learn to use that stuff more - have tried aluminum and mild steel on there as well.

as for the knife... it is really a crappy Ikea bread knife... I have no worry for it's future abilities.

dooleyfive (author)ScubaSteve512014-01-14

Scuba That's wrong info.... GTA welding process will have less HAZ then brazing.

Snidely70448 (author)2014-01-14

As a practice project, an admirable success. However, if I had a knife that broke from dropping on the floor I would have trashed it immediately. Junk

Ricardo Furioso (author)2014-01-13

Thank you for sharing your success and learning.

apu2010 (author)2014-01-13

nice DIY, but for a knife buying a new one will be cheaper unless no more knives are available

graydog111 (author)apu20102014-01-13

Instructables is not about "saving money and buying a new one". I may be wrong, but it's more about taking something useless and making something good.

ned103 (author)graydog1112014-01-13

Also, in my case, I have some knives that are antique and irreplaceable. But by golly, they are great knives. I still use them. That would also be worth repairing. Honestly, I have a knife that I use regularly and still really holds an edge that was made in the 1920's. It's always a good idea to be able to repurpose things. Personally, I like his "nice handled box cutter" comment. Made me laugh and think of knives I have thrown away. LoL

dhanhurley (author)2014-01-13

Hi from Tübingen University, Schwaben, S. Germany.... Have you heard of ATOMIC HYDROGEN WELDING (electrolysed from water,spark-gap etc.....very hot)... BROWN'S GAS ( CHEMALLOY ( Friedman Metal)... Enjoy ... Dhan

graydog111 (author)2014-01-13

Great post. I weld with a MIG, an stick welder, and acetylene / oxygen, but I would love to have a TIG. You might try clamping thin pieces to a piece of brass or aluminum as a heat sink. It works for me.

jimcathers (author)2014-01-13

Thanks for sharing your mistakes. Often times mistakes are the most important part of the learning process.

caruncles (author)2014-01-13

TIG welding is on my to-do (and to-buy) list. As you said, this was good practice and know absolutely nothing about. However, as has been stated, the welded knife may not be safe to use. One reason is that a good blade is tempered and the welded portion won't have the same tempering as the rest. Cutting it down and making a paring knife wood be a good save for the blade, but I understand you needed a welding project! All good. I learned from your Instructable and also from the posters who replied. Good job!

roballoba (author)2014-01-10

Behold! favorite steel from Ikea!!!

It cuts bread again!!!

inthedesert (author)roballoba2014-01-13

Yep, you gotta be careful when using it for real sword fights, but for bread, it will probably have the strength for a couple loaves before complete metal fatigue ;) - ignore the haters.

I think this was a great instructible. Looks like you did something new, probably had fun, and learned a bit. Sounds like an ideal Saturday to me.

Tin Man (author)2014-01-13

I did a TIG welding course at my local Tech College and I can vouch that TIG is great for nearly everything, I love it!

(If I could afford a Lincoln welder though, I'd throw all my cheap knives away, as they are a potential safety hazard). I once dropped a kitchen devil knife on the floor and it snapped at the handle; the danger to me was in jumping sideways to avoid the falling blade, I bashed my elbow!

Jack of Most Trades (author)2014-01-12

"Seek the Sword that was Broken. In Imladris it dwells..."

Even though Elrond beat me to it...

And all you haters out there, why don't you get back to welding on your mechanical girlfriend projects or something?

welderbot (author)2014-01-12

How many people have access to a tig welder? I've been welding for 20 yrs and can

tell you no welder can weld everything. The jerks out there that criticize every ones

solutions probably are envious and don't know what they are saying about a very

deep subject. Yes heat is involved and will affect the properties of the material.

How long do you want the instrument to to last, one fix or forever. I still continue

to research how to assemble and repair, be it with adhesives, fusion or nano.

So back off know-it-alls and let people learn by doing and suggest some advise

to improve.

jbkinn (author)2014-01-12

nice try. Great equipment. Since a knive is not used much by the handle I was thinking you could cut the blade after the gap and match the cut as close to the handle as possible. Grind the handle end to match the width of the blade. Then TIG weld with argon and the proper settings on the welder for thin metal. Also clamp a piece of al or cu to such the heat and reduce the HAZ. U should be able to reduce the damage to the metal of the good part of the blade. One I inch from the handle the blade should be fine. The balance of the knife will change but WTH,

ScubaSteve51 (author)2014-01-12

Since you're just experimenting: I watched Jody on build up a damaged propeller blade. He just built up the lost metal with the appropriate filler rod. That would be a fun experiment. You could even get a thick piece of copper plate as a backer and weld it that way. The steel won't stick to the copper because of heat conduction and then you could just grind and sharpen the fresh metal.

marshall p (author)2014-01-12

Nice welder -- got the same one myself but man you shure butchered that weld , After purchasing my welder I took a course on tig welding at my old high school which really helped . One thing that would of helped keep the edge would have been to start the weld at the thin edge with minimal current and increase as the metal got thicker . Also use filler right at the start and put the knife on a piece of copper to take some heat away .

iceng (author)2014-01-12

Impressive heliarc welding

Do you think a further reduction in current as you approached the knife edge would have been able to reduce that erosion ?

rjohnson45 (author)2014-01-12

I'm sorry but if a knife breaks under regular conditions It's just not worth it. Good knives have good alloys and should be reliable.

rocksalt2342 (author)rjohnson452014-01-12

having a knife is like being in a relationship, it's much more rewarding to learn how to work with its special quirks and secrets than having the perfect trophy knife.

Kpax7 (author)2014-01-12

Nice one :)

About This Instructable




Bio: Trying to learn faster than I forget. It will be cool to make some stuff along the way.
More by roballoba:Fix a TrellisFlame Grilled Oreo Cookies - S'Mores Are Gonna Hate This One.Fix a Broken Stud / Remove a Broken Bolt
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