Tried something different today.....did a little welding on a knife.

[Triple_D]

Yep, it sounds crazy. Ruin the heat treatment, and all that. But sometimes you just have to go for it.

This pilot's survival knife was issued to me more than 40 years ago.

The pommel had become a little loose, and was quite annoying. It has a slot in the butt end, and is simply slid over the end of the tang, and then the tang is peened flat. I guess the leather has dried, and shrunk a little, causing the problem. I was unable to peen the tang any tighter, so I decided to fix it with a MIG welder. Basically, I snugged the pommel down tight against the stacked leather handle, and then stitch welded it to the tang. I took it slow, and after each small tack, I dunked the blade in a small bucket of water, and blasted the weld with compressed air. The pommel barely got warm, and the blade stayed cool the whole time. It was a bit of a slow process, because I made sure everything was cool before I hit it with another weld tack. Anyway, it worked fine, and I almost positive I didn't do any harm to the heat treatment. I'm 100% positive that the pommel doesn't rattle around anymore.

I forgot to take any pictures until I had ground the excess weld smooth, but here it is in raw steel, and with a coat of primer on it. I'll hit it with some paint in a day or two. Should be good for another 40 years.

 

[tinfoil hat timmy]

Nothing ventured, nothing gained my man.

looking good.

 

[davek14]

You could have submerged the blade in water and welded it, maybe.
I've had good welders weld a thumb clip on a knife and I could lay important parts of the blade on my arm when they were done. I've seen welders who had to get the whole thing damn hot. It's black magic to me.

 

[Cementite]

You could have submerged the blade in water and welded it, maybe.

...or stuck the blade end of the knife into a soup can filled with wet sand...this might prevent there being a "hard change" from super-hot to cold, which could conceivably turn into a stress riser where it might eventually crack/break.

I have a similar Case XX USMC "Ka-bar" style knife (1095 steel), and I've considered tigging on a pointed "nut" to the pommel end ... if I ever try it, I will probably use the "wet sand" idea...

Whatever method is used, I think the key is to get in and get out fast -- use a ton of amperage to make a puddle ASAP and then get out. The whole operation should take no more than 1-2 seconds of arc time. If it does, then weld 1-2 seconds, then cool back to ambient, then weld again, then cool again before welding any more. This will minimize overall heat input and HAZ.

Since the knife is made of high-carbon steel (1095 in my case), I would also recommend what once was known as "25-20" filler (ER310) which is about 25% Cr and 20% Ni ... the use of this filler (along with welding FAST) helps prevent carbon from the parent metal from getting into the puddle and (due to the "quenching" effect of the cold part of the knife chilling the weld puddle) making it brittle (the same thing that happens when you quench hi-carbon steel without later tempering it...it ends up too hard and brittle)...for more on this, see the chapter on high-carbon steels in the Lincoln Welding Foundation's excellent little handbook called "Metals and How to Weld Them"...screenshot from Google Books below:

 

[Triple_D]

I thought about submerging the blade in water while welding, but in the end I don't think it mattered. The blade never even got warm. I just stuck it in the water after each tack, as a precaution. The pommel acted as a pretty good heat sink, and even it never got so warm that I couldn't handle it without a glove. I did get "in and out" fast, and each tack only lasted a second or two.

Just a fun little project, and not a big deal if something went wrong in the process.

 

[Grasshopperglock]

Mig welder in taps, no problem. If you put it to it, get it glowing red. Looks like it worked.

I TIG weld. I can offer advice.

The way to control heat from seeping into areas you don't want or it'll harm a temper.

You don't need the water.

Use cooling bars. Slabs of aluminum or copper contacting the areas you don't want getting hot.

I've found the heat sinks on old computer CPUs to be handy. I also use an aluminum plate. Other heat sinks for things I weld. You'd be amazed at how you can control the heat.

 

[davek14]

.

Use cooling bars. Slabs of aluminum or copper contacting the areas you don't want getting hot.

I've found the heat sinks on old computer CPUs to be handy. I also use an aluminum plate. Other heat sinks for things I weld. You'd be amazed at how you can control the heat.

I've seen that done a lot, that's actually the most common solution. The welders where I used to work had big aluminum jaws that fit over a vise.
Done it myself when just grinding on a part to dissipate heat.