Welding threaded rod to tang for takedown dagger.

H

HallHandmade

Joined
Jun 5, 2012
Messages
1,071
I am starting a project on a takedown dagger. One of the things I still need to figure out is welding the threaded stub to the tang. I'm using S35VN for the blade, and probably 304 or 316 stainless threaded rod. I'm an experienced TIG welder so the actual welding is not a problem. I'm going slot the tang and do a u-shaped fillet weld on each side to attach the rod into the slot on center with the blade. I do have some other fuzzy spots though. I know that 309 filler is recommended for dissimilar metals, including when joining different stainless steels.

It can be very challenging to weld heat treated steels without cracking, so I probably should have the HT place leave the tang soft I assume? I would just weld the threaded stub on first, but I'm afraid of them fouling the threads with tongs/pliers. I also would rather not have the actual working area of the thread be oxidized.

Also, being that the whole assembly is under tension, it should be inherently strong as long as everything seats properly. With this in mind, how far down do I need to go with the tang? Should I bring it as far down as possible and then only have the threaded stub at the end?

Thanks in advance for your time and help/advice. :)
 
You should preheat the piece to around 500f and then after the weld heat it to read and let it cool very very slowly slowly even if it has never been HT. Most high alloy stainless steels recommencement 50F per hour rate of cooling to anneal.
 
SteelSlaver said:
You should preheat the piece to around 500f and then after the weld heat it to read and let it cool very very slowly slowly even if it has never been HT. Most high alloy stainless steels recommencement 50F per hour rate of cooling to anneal.
Click to expand...

Ok thanks. I think that with it done in foil, oxidation on the threads should be minimal if I do the weld prior to HT. I don't think anything will happen to the threaded rod, it just won't harden, correct? I almost feel like it might be better to weld post-HT. I might need to get a crappy die to run over the threads to clean out the oxide that is there though, if I go with doing the weld after.

I have had success with pre-heating when joining already tempered steels, but sometimes they are just plain ornery.
 
You probably know this, but if you are using stainless, you have to use silver, or nickel silver to braze. Brass and bronze won't work. Use a braze rather than a solder.

I just noticed you plan to TIG it. I think brazing with a good flux is easier on the steel. It will cool slower. Most guys doing bicycle frames silver braze ( with lugs) or fillet braze with nickel silver rather than TIG weld.
 
Thing about this that makes me wonder is welding to an air hardening tool steel. It is going to get hard and brittle from the weld heat and cooling off. I have welded to steels like 1095, 01, 1085 1095/15N20 damascus and their brothers and come out with a good solid piece after doing a preheat then a post weld stress relief. (Aneal). Things like San Mia made with tool and mild steels work out fine, but I wonder about air hardening steels. If I was at home I would try it with scrap D2 and simple Stress reliefs. It is not the weld that worries me it is a good stress relief. I will call my brother and talk to him today. He is a Certified Welding Inspector and gets stuck with finding the procedures for all kinds of welds. Although I am a not one to believe welding to high carbon steels is impossible and a bad idea, this may be an instance where silver braze maybe better. You know that if you put a bit of a "head" on the threaded piece and the slot in the tang has a wide spot for that head and it is soldered in place it will be very strong.

I was once told by a smith that a welded joint was more prone to failure than a mechanical joint or soldered one. This came from a guy who made blades mosaic type blades that had wrought iron portions. Why did he believe that he could forge weld dissimilar metals and I could not arc weld them with the proper procedure?
 
I am no expert on this,? But I have googled it many times. I look forward to what you find out. There are very specific rods I found, and my local welding supply didn't stock them. I had no need for 10lbs of these rods either. From what I have read, the more localized the heat, the higher the stress from heating and cooling. Soldering, and brazing distributes the stress over a wider area. It's basically opposite from mild steel welding, where you want to localize the heat. Preheating, and slowing the cooling are strongly recommended.
 
SteelSlaver said:
This came from a guy who made blades mosaic type blades that had wrought iron portions. Why did he believe that he could forge weld dissimilar metals and I could not arc weld them with the proper procedure?
Click to expand...

Funny how some folks think about certain things eh? ;) :)

My #1 recommendation is to simply run the tang long enough that you can grind the last bit round and thread it. Just remember to leave a little extra length initially, so you can taper the end a bit to help get a nice easy, square start with your threading die. You can always shorten it up later.

Don't worry about scaling the threaded portion. S35V HAS to be austenitized in a foil wrap, an inert gas atmosphere, or salt bath, so you're only going to see some discoloration on the threads... no scale.

#2 recommendation- would be to braze the joint if you're going to use a separate threaded piece.

From my experience, Jim hit the nail on the head by pointing out the concern of welding an air hardening steel.
 
Braze or hi-temp silver solder it for sure. Makes a very strong joint if done right, which is not hard.

I like to make a keyhole type slot in the tang end, shape the end of the threaded rod so that it press fits into that, and then braze it. Some use this type of connection without even brazing, but i like the belt and suspenders approach. Plus, it holds the joint right where you want it while you are brazing. It only works if your tang end is wide enough to allow cutting a keyhole in. I just drill a hole and bandsaw into it.
 
You must log in or register to reply here.
Back
Top