Soldering stainless steel

kenhills

kenhills

Joined
Dec 17, 2007
Messages
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Hi All,

OK so I am making some hunters along the lines of some of the WW2 fighting knives. That means the blade (ATS-34) has a stub coming off the back passing through the stainless guard (416) and then is soldered to, in this case a stainless All Screw which passes through the handle and threaded through a stainless butt cap (416 again). I know what the blade is made from ATS-34 I have no idea what the All Screw is made from. After a number of unsuccessful tries using silver as well as gold solder I got nowhere. Off to the PC and Utube which is what I should have done in the first place.

So here is the problem: is it even possible to solder dissimilar stainless together, what is the best solder to use and what is a technique and flux that you have had success with. Its easy enough for me to make full tang knives but with some of the steels starting to get pricey I am looking for alternatives. Any input would be appreciated.

Thanks, Ken
 
You're talking about a low temperature silver solder , 400 + F. The flux MUST say 'made for stainless steel ' .Best gap is 0.003" for strength and capillary action. Heat the steel then let the steel melt the solder .
 
I'm not sure I'd trust a solder job on that joint. What you're after is called silver
brazing and its high temp 1200+. Silver braze will join most any disimilar metals.
Ken.
 
I have simply given up soldering ATS and stainless guards/bolsters. I now "oversize" the back of the guards and form a recess and use JB weld and pin. Solder would flow but not stick well. If you want to keep it up and keep trying I found using a heat gun was best for stainless to stainless, were i have traditionally used a butane gas for other fit ups.
 
Low temp? I keep hearing about that. But as KC says thats going to be a "soft" connection. There is quite a bit of pull on that joint when I tighten up on the butt cap. I have high content silver solder 70% or something like that. Cost a fortune. Trooper go on a little more about your method. I am not quite visualizing it. Thanks
 
Just an update I did finally manage to hard silver solder the blade to the All Steel. Had to get paste flux meant for stainless and used my 70% silver solder to do it. Pricey but it worked. No go with a propane flame. The oxygen-acetylene torch did the trick. In keeping with what I read and saw on u-tube I used the outside cone on a loose flame which got the stainless hot enough to flow the solder but not so hot as to have it popping on me. I also kept the steel when it was ground for soldering very clean. The final clean up was with alcohol and I was wearing surgical gloves as a precaution so as not to get any oil from my fingers on it. Hope this helps someone else. To those who offered advise thank you for setting me on the right path. This the best knife forum out there the members are the best., Ken
 
High temp. silver solder is fabulous stuff. I still use jeweler's solder now and then for stuff like that.
You can also fix various cast materials with it- I repaired an antique trivet not long ago with SS.
It's called "solder" but it's actually a brazing material...not to be confused with the equally fabulous stay-brite silver bearing solder.
 
elementfe ...What is the melt/flow temperature of the solder you are using? How will it effect the H/T of the blade?

I have found that "Stay-silv" ( not "Stay Bright) black flux is great for soldering ferrous metals at high temperatures. It is a paste flux that will withstand the heat necessary for silver soldering ferrous metals without burning off before the solder flows.
 
Just to clarify for you folks who didn't get it:
Ken is hard soldering the threaded rod to the stub tang. It is also called silver brazing. The hard solder is 70% silver and quite strong. It flows at around 1250°F. These joints are usually made after HT.

I prefer to weld the tang extension on with my MIG wire welder using flux core wire. This allows the tang extension to go on either before or after HT. Below is the method I use.

Ken - The best way to do the joint you are working on is to entrap the thread-all into the stub. Cut a 3/4" long slot in the tang that is just right for the threaded rod to sit in. Set the rod in the slot and give it a few whacks with a hammer on the anvil. This will make it a pretty tight fit. Now you can braze or weld the rod to the tang quite strongly.
 
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Reading the thread I hope you understand and appreciate the need to use proper terms .There is "Soft Solder" a low temperature melting alloy such as 400 F. There is "Hard Solder" melting in the range of 1000F or more. A big difference there ! Bye Bye
 
Thanks for the clarification Bladsmth the tread was sort of wandering. I will use your technique the next time beats mine time wise I think. My final solution was to grind the end of the tang and the end of the All Screw half way through, creating two half rounds or looked at from the side two Ll shaped ends. Those two ends were fluxed then placed together one on top of the other and there was a clean match. Flow the silver solder with the torch and done.

There was a question up there about how it affects the HT. This had to be done after the HT. With ATS-34 the HT goes up to 1950 degrees or so, much to hot for the solder joint. But to answer the question specifically, the actual soldering or brazing happens very fast with the oxygen-acetylene torch. There was not a lot of heat migration from the joint to the blade. Within about a 60 seconds I could hold the blade in my hand. So probubly no effect on the HT. Thanks all., Ken
 
Will do that on the next one. Thanks for the input. I have said it befor and I will say it again. This is the best knife forum out there. Ken
 
I know it would limit the material to the blade type and also the size of threads and cap nut, but would there be anything wrong with just threading the tang itself? Using 1/8" stock you should be able to use a #10 die. I am working on a knife currently that I had thinned the tang and used a #8 to thread the last 1/2" of the tang.

Chris
 
Not quite following you. If you are suggesting that I extend the tang to the butt end of the knife then thread the end to accept a # 8 or 10 nut, well yes that would work. But in this case I am trying to minimize the amount of expensive steel that is "wasted". I have threaded the end of the tang about an inch behind the end of the blade then used a long nut to join it to a piece of All Thread, then to the butt of the knife and another nut. I just dont like having all the hardware inside the handle. Actually I tend to tap the butt plate so I am not limited to using washers and nuts. Did I answer the question??, Ken
 
I appreciate the clarification here, mind you I have been reading the thread after a long day ...... what I have done before is cut a slot into the end of the tang wide enough to accept a tap, tapped it then simply screwed the threaded rod or whatever you have made, into the slot. I have coated everything with locktite or jb weld and NEVER had a issue with it coming loose or out. No heat no mess.
 
McMaster has grade 8 all thread.

Just a suggestion, I bury the blade in heat sink and weld 'er up. No chance of it coming apart, quick and easy

I think the grade 8 all-thread is the ticket.
 
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