Damascus Take-Down

tryppyr

tryppyr

Joined
Feb 5, 2010
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I've been giving some thought to the next project. I've been frustrated the last couple of attempts at making a take down, and I think I have a pretty good understanding of why I've been having problems. I believe a key part of my problem has been that I've been making blades using billets that were 1/8th inch, and that's not thick enough to have a reasonable threaded rod welded to it.

As it happens, I have two pieces of beautiful damascus from Mike Turner to work with, one of which is nearly 1/4 inch thick and 8 inches long. Those two dimensions, when put together, whisper the works "take down" into my brain, because the billet is too short to make a traditional hidden tang, and too thick to make a smaller type of blade. So I'll reserve about 1.5 inches for the tang, drill about a half inch deep hole in it and thread that hole to receive the 1/4 inch 20 twist threaded rod I have. That way, I won't be forced to rely on my pathetic welding skills, and can still make a functional take down.

I haven't given much thought to the blade design yet beyond the tang and rod connection, and certainly haven't decided on the handle or guard design. Given that the metal is so thick, I'm inclined toward a single edge blade (not a dagger, this time)... but might swing the other way once I start drawing.

Here's a look at the billet in question (1080/15N20 with 136 layers).

DSCN6147.JPG
 
Jim Siska always uses a stub tang with an extension but he cuts the end of the tang into a
dovetail and extension into a corresponding the dovetail, fits them together (hammer the
round rod in?) and brazes (or *hard* silver solders) the joint. That way the majority of
the stress is taken up by the mechanical connection and, if you fit things well, the sides
of the guard or ferrule.
 
Greg,
That won't work well.

Here is how to do it with even bad welding skills:
Before doing any cutting on the billet, draw the basic profile.
Leave the tang at least 1.5".
Cut a slot 1/4" wide and 3/4" deep in the end area where the tang center will be.
Take a 6-8" piece of 1/4" thread-all and set it in the slot.
Hammer the rod and the metal beside it to make it stay in place.
Wrap the blade portion in aluminum foil to keep the spatter off the blade area.
Weld the "U" around the sides of the rod, flip over and do the other side.
Grind off all the ugly stuff and then temper at 350 for an hour to remove any brittleness.
Cut and shape the blade as desired.
 
Greg- you kind'a lost me with the threaded hole thing. Standard practice for 1/4-20 threads, calls for a #7 or 13/64" tap drill. And, of course, has a major diameter of 0.250" So I'm not following why you'd want to drill "an almost 1/4" thick" billet for a 1/4-20 thread... ???

Your failed welds are due to weld prep and procedure, not the thickness of the material. From what I saw in the photos, it looks like you butted the tang and allthread together and welded over it, then ground most of the weld down. The pieces to be joined need to be prepped with a bevel--- think of two dull pencils butted up to each other, point to point.

In a perfect world you would preheat the high carbon blade steel prior to welding, and do a stress relief post weld also.

I prefer 10-32 threads for a threaded end also. With 1/4-20 threads, you typically end up grinding most of the threads off. A 10-32 has a major diameter of 0.190, so you usually wouldn't need to grind any of the threads off, and end up with MUCH more thread contact than a ground down 1/4-20. Also, IMHO, you only want a very short section of the tang to be that small---- the very end of it.

Just some thoughts about your recent struggles... :)
 
I have made many threaded tangs and have yet to weld a threaded rod to the tang. I just make the end of the tang as soft as I reasonably can and file it to size for the threaded part. Then I thread it with a die......either 10/32 or 1/4 28 depending on the tang. No need to jump through hoops welding a chunk of all thread on there.
Darcy:)
 
Thanks guys, great info on the bolt/thread size for take downs. I was thinking about starting a thread about that but now I may not have to. ;)
 
See... this is why I started this thread weeks before starting the knife. I knew I'd get useful information that kept me from accidentally making mistakes. Now I can make mistakes on purpose! :)
 
In agree that 1/4-20 is large. 1/4-28, 12-24, 10-32 are all sufficient for most takedowns. The same slot and weld technique works for all.
 
Hey guys. As someone who has welded most things from carbon to stainless, I feel inclined to chime in. First I have a question. What are you using to weld the 1/8th steel with? You may have already stated in a previous thread. I just cannot recall. If you are having trouble with burn through, you are welding way to hot. If you are not achieving a good weld, the prep is off somewhat. Like stated above, think of bevels. Nick said two pencils. That is one hell of a way to put it. Weld from the lowest point and work out. When pipe welding we call it root, filler and cap. The same process applies here. Another way you can try is to make your hidden tang. Right in the center of it cut a wedge out, 1/2- 3/4 inch, take your all-thread and make it a wedge. Take the all-thread and put it in the tang. Tack weld the tip to the blade, flip over and tack this side also. Make sure the rod is where you want it. If it is, tack end at the rear of the tang, flip, tack. Now go slow. Tack, flip, tack flip. After you are sure its where you want it. Weld it going slowly. Remember that the tacks are to keep the sides from drawing alot. Once its welded. Grind it down. If you see any voids fill them with a tack. It may not affect the tang at all to do it this way, its just something that I do. Now normalize the blade several times.
While I am in no way an authority on the aspects of bladesmithing. I am however one hell of a welder and have done it for years in the industrial field. Just my .02.
 
I appreciate the advice. I'm not sure what half of it means, but I'll try to explain the problems I've had before.

First, in answer to your question I'm using a cheap HF 90A MIG flux wire welder (no gas). I also have an OA torch and some welding rods, but have not yet fired that up.

On the last attempt I was trying to weld a bolt to a blade that had already been heat treated. I tacked it in place and tried to aim the weld so it went from the tack down the edge to the end of the join, then dipped it in water to avoid having the heat of the tang break the temper of the blade. I repeated that process on the other side. When that was done I sanded off the slag, and the weld looked okay and felt sound. It was only during handle fitting that I had a problem when I put too much repetitive stress on the small bolt.

On the second attempt at welding it in place I used the larger threaded rod and followed a similar procedure, but the resulting weld was very brittle and the first time I put any stress at all on the weld it snapped above the weld, revealing a very large grain pattern on what was left of the tang. To me the message was clear... "stop trying to weld things to this piece of metal!"

Maybe some day I'll follow the advice to spend time learning to weld. I'm just not there yet, and these recent frustrating experiences haven't given me the desire to pursue that at this time.
 
I do not understand why you aren't silver (my choice) or brass brazing. It's sufficiently strong, easier on the material and to do, otherwise just thread the parent stock.
 
Gotcha on that welding rig. You can do it with that. Its just not gonna be the prettiest in the world. Mr Dwyer asked why you are not brazing. Thats an idea you may go for. With the torch and all its easy to practice on mild steel. Trust me, brazing rods are way cheaper than damascus.
 
Doing small welds on dissimilar metals with a little machine like that, even a little bit of preheat with a propane torch will do wonders. If you're using zinc (galvanized) all thread, take care not to breath the fumes, they're really bad news. If you smell that sickly sweet odor, get a fan going.
Andy G.
 
Incidentally, I've decided to use this billet to do a half scale Musso Bowie. It was already the perfect width for that, and only slightly over the thickness I would have targeted for a perfect scale model. This will have more of a tang than the original design, for obvious reasons.

So far here's what's done:

Step 1: Review plans
Step 2: Take measurements
Step 3: Mark up the billet for cutting
Step 4: Mark and drill the pilot hole for the all-thread

DSCN7073.JPG
 
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Very nice billet there Greg!! Mike does great work.
Thats gonna be a through tang musso right? Or are you building a frame to incorporate the take down aspect?
I use all thread but i "hide" it in epoxy filled handles, the thought of telling someone to go ahead and take it down, only to expose a stick of all thread maybe jb welded at the tang to counter the twist to break it free doesnt seem right, imo.
However a tang either stock removed or forged with a nice little nub of hand threaded steel of sorts begs to be appreciated! Brazing is the bees knees Greg dont give up on it get a cheap O/A set up, a 0 tip, run it at 10 and 5 psi, and start brazing nuts and bolts to stuff!
Greg
 
To be sure, I was not planning on gluing the rod into place. Oh, and I do have an OA torch with the tanks... I just never used it (and damn sure won't on this project without a significant amount of practice on lesser pieces).
 
There is another solution that I saw Kyle Royer do. He to cut a 3/8 in long vertical slot in the tang. He then ground down the sides of his threaded rod so it would slip fit into the slot. He drilled a hole through both pieces and pinned the rod in place. The rod worked like a hinge and easily allowed him to line up his handle material, especially in something like a stag taper.

Just make sure to cut the slot before heat treat.
 
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