Instructables
Picture of TIG Weld A Broken Knife
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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.
 
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Step 1: Set up welder

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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

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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

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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

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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.
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sourcesmith7 months ago

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

-Elrond

Narsil.jpg

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

Briliant...

Wondering if TIG can Smelt a ring as well ?

ibwebb chotzeny7 months ago

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!

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

BAHAHAHAHAHA thank you for that :-)

Missed the comment from sourcesmith :-(

Hilarious!

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

roballoba (author)  sourcesmith7 months ago

Ah HA HA HA HA!!! YES!!

Eh Lie Us!5 months 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.

rectora7 months ago

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 rectora7 months ago

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

ibwebb7 months ago

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 ibwebb7 months ago

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)  ibwebb7 months ago

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

ibwebb roballoba7 months ago

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.

roballoba (author)  The Lightning Stalker7 months ago

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

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

RetiredLE7 months ago

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

roballoba (author)  RetiredLE7 months ago

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

I like this idea very much!

really_grumpy7 months ago
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

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".

f

ScubaSteve517 months ago

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)  ScubaSteve517 months ago

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.

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

Snidely704487 months ago

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

Thank you for sharing your success and learning.

apu20107 months ago

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

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 graydog1117 months ago

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

dhanhurley7 months ago

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 (eagle-research.com).... CHEMALLOY ( Friedman Metal)... Enjoy ... Dhan

graydog1117 months ago

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.

jimcathers7 months ago
Thanks for sharing your mistakes. Often times mistakes are the most important part of the learning process.
caruncles7 months ago

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) 7 months ago

Behold! favorite steel from Ikea!!!

It cuts bread again!!!

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.

Wroger-Wroger7 months ago

This is how you get smart - by capitalising on an opportunity.

Kind of like spending $30 on bearings to refit a $25 router.

Great for a once off....

Then we go all technical and see what the welding has produced within the metal - the heat affected zone, crystal and metal types etc...

If it holds up - fine - if not... that is fine too.

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