Welding on a tang with a MIG

B

bennett

Joined
Sep 22, 2005
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212
Evenin', ya'll.
I'm forging a blade tomorrow, and want to try welding a piece of mild steel on it for the tang. I've heard (and read) that you can forge a "stub-tang" onto a blade, and weld a piece of mild (softer) steel onto it when the blade's finished, to create a stronger, more springy tang. I've even heard of some guys welding a bolt onto the stub tang. My question is, can the mild steel be welded on with a MIG welder, or does it have to be silver-brazed or "stick"welded? So far, all of my forged knives, and stock-removal knives too for that matter, have been full-tang style, forged or ground from the same bar of steel. I want to make a hidden stick tang with a threaded end, for a special piece of antler I've been saving, and thought I'd try welding the softer steel onto the blade, just not sure if I can do this with my MIG welder or not. Anyone know if it'll work? I plan on heat-treating/quenching before wlding the tang on. I'm thinking that the weld should survive tempering in the oven. Should the tang be welded before heat-treating/quenching? Any advice on this matter would be most appreciated!
 
You can weld it with mig, stick or torch, but it's a lot easier to silver braze. For one thing the heat generated welding makes for very large grain in the weld so it needs several normalizing heats and even then it would be kinda iffy on strength. Remember your welding a high carbon to a low carbon steel. If it were me and I was going to weld extra tang length I'd leave at least an inch of tang, weld it up and weld again to leave excess weld then forge the weld down and go through the thermal cylcles prior to heat treating.

Silver brazing is what I do and even then I like to give the joint several blue temper draws with a torch, especialy on an air harding steel like 52100 or 5160. The way I do it is to put the gaurd on, sharpen the tang to a flat point, split a bolt or piece of all thread and mate to the gaurd. Wrap a wet rag around the gaurd to keep heat from traviling to far, silver braze the bolt/tang joint. Let cool down, keep adding water to the rag around the gaurd till it's cool. Brigten the tang up with sandpaper and heat till it's a nice shade of blue, repeate at least twice. Adding a split bolt this way means you can have full threads instead of just the thickness of the tang for an end cap. If I'm making a heavy duty knife with an end cap I silver braze a threaded coller to the end cap and screw on the split bolt thread to suck everything up tight. For a light duty/small knife with antler and a but cap I make sure the tange goes most all the way through the antler and silver braze a "tang" about an inch or so long to the but cap and clamp everything up tight with accureglass epoxy.

Hope this helps
 
Just a couple of points if you weld on mild steel, mild steel is not springy. It is strong enough to hold the end on most of the shear strength is needed at the area where the handle material meats the guard so I think you should leave enough forged tange to get past the main stress area.

Second I do weld some extentions to tangs. I have a sheat of copper plate 1.5 or 2 mm thick. I belted a round rod into the sheet between my vice jaws and made a groove all the way across the 60 or 70 mm sheet. Then flatten ths sides down level with the thickness of the rod/tang.THe groove width is the same size as the tange. clamp the tang in one end with the section to be welded in the middle of the groove. I put a bit of a beval around each of the ends to be welded.

What happens is as the tang and weld are molten they fill the groove. The copper holds it in shape and fills a good full weld without the sides falling away to make week scollops in the sides.

Weld will not stick to the coper and it pulls/ falls away when unclamped. The groove keeps it aligned and any exces is filed off.

Remember the welders will spray some spatter so protect your blade.

WHen should you weld? If you weld on an extention as soon as possible after
forging you can use it as a handle to help as you shape the blade. Depending on your style and equipmemnt.

I leave the handle a bit longer when hollow grinding the blade free hand because for my style I can hold on and steady the blade better. Up to you what clamps and jigs you have.

There are many right answers some are just wrong for our needs. Do what suits you.
 
I use two plates of aluminum to clamp the blade between if it has already been HT'd. This keeps the blade cool enough to handle with bare fingers when I am done with the MIG.
 
Just thought I would suggest another option. If you don't want to weld. Leave an extention on you tang the width of the bolt you want to use. Cut the head off the bolt. Mill an open ended slot in the shoulder of your bolt the width of your blade. With the bolt mounted in place on the blade, drill two holes through the shoulder area of the bolt and through your soft blade. These can be .093 or .125 in diameter. Now you can rivet the bolt to the blade after heat treating. You don't hurt the temper of your blade or introduce any stresses from the welding.
 
There have been many good suggestions here, and any one of them should work out nicely.
Another idea you might ponder is using grade 5 or grade 8 bolts. When I weld a bolt to the end of a tang, I aneal one, split it and then tig weld it on the tang. the higher carbon content in the graded bolts is more like the blade steel, and there seem to be less problems with a weld cracking later. I then normalize and heat treat after the bolt has been welded on.
 
its not difficult to weld to carbon steel. but you do need to preheat it in most cases to avoid huge differences in carbon structure between the disimular metals. which would cause a crack. try welding spring steel to see what i mean. you will probably need to preheat to 400-600 degrees depending on the metal. for example when i made backhoe buckets for ford tractor we preheated the cutting lip to 600 degrees before welding it to thebucket itself. this will require using a preheat chart, or some experimenting. id preheat to around 400 for something this small then weld it. then you should cool it slowly. afterwards do your heat treat and tempering. should come out ok, but don't quote me on this.
 
Just wanted to say thanks very much for all of the great advice.:thumbup: Sorry I haven't been able to post for a while, but had to make a last-minute work-related trip to Tijuana. I'll post a pic of that (and some other knives I've done since joining the forums) when it's finished.
 
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