San mai help.

[jdale]

I started working on my first San mai blade yesterday. I welded 2 pieces of 1084 to a core of 15n20. I was planning on forging out the blade but I'm unsure of how to get the 15n20 to show up on the finished blade. Do I forge it to shape but not forge in the bevels, do I grind down some of the 1084 then forge in the bevels or is there some really simple solution and I'm over looking it?

[jmccustomknives]

Stock removal will bring out the most from your billet. It really boils down to they style of knife and the thickness of the billet to how things pan out.

[Ray Rogers]

Assuming you welded three equal sized plates together then, as James said, stock removal is your best choice. As you grind the bevels the outer layers will be removed from the edge up and that is what you want to see. If you forged the bevels only a small amount would be removed at the edge when you did the final clean up by stock removal.

If you want to forge the bevels on a san mai blade you would need to weld two narrow bars onto a wider bar....

[jdale]

Originally Posted by Ray Rogers

If you want to forge the bevels on a san mai blade you would need to weld two narrow bars onto a wider bar....

Good, I didn't think about that. It just so happened that my 15N20 was wider than the 1084 I used. Looks like i am going to forge some bevels

[jdale]

My biggest worry with this blade is the weld, it looks ok but I am just unsure about how hot my forge is getting. I am able to limit out my pyrometer at 2000 deg F, but i cant get steel to get close to sparking. I think there is also an issue with the psi gauge i have on the setup, i cant maintain a fire if the gauge reads anything under 30psi and i have to ave my blower at the lowest setting and the flow tube close to 90% blocked off. I might have to buy Ray's DVD

Ray does your DVD have a section on properly tuning the forge?

[Ray Rogers]

QUOTE: Ray does your DVD have a section on properly tuning the forge?

Not really but, unless you are trying to build a fancy venturi burner there isn't much tuning to be done. In the video, I try to show a first time forge builder several simple ways to quickly and cheaply build a forge that can be used for forging or heat treating without having to deal with complex tuning issues. So, the venturi I build basically just has one setting (which is all it needs) and the forced air burners don't require anything special because they are adjustable as you use them.

I can say that if you are running forced air at 30 psi then something is very, very wrong. Forced air rarely needs to run at more than 5 psi and most will run at 3 psi. Some pictures of the forge and a description of how the burner is built might be useful at this point.

Also, 2000F should be enough to weld those steels. If the steel is sparkling its losing carbon - sometimes we have to use those temperatures but for welding simple san mai you don't really need to be that hot. Your 2000F , some good flux, and most importantly good hammer technique in establishing the weld is all that should be required.

For any new makers considering their first effort at forge welding let me give you the secret to getting the weld to take:

First, some clean smooth metal is a good start. Then, enough heat, you need some color in the steel but it doesn't need to be yellow and throwing off sparks.

Second, some forge borax for flux. When the borax sitting on the steel is bubbling the steel is hot enough to weld.

Third, and most important: the first hammer blows must be done lightly! Newbies usually try to smash the pieces together and that simply will not work. Light, firm taps all over one end to the other to force the flux out while the steel is hot will set the weld. Its a good idea to go through this process at least twice. After that you can hit harder and do whatever shaping you need but work up to it, don't try to get it all done at once or the weld can be torn apart. Once you think the weld is solid you can turn the piece on its side and hammer from the side to see if the weld will separate - if it holds, you're good to go ...

[GHEzell]

I do a mix of stock removal and forging with san mai. Forge the blade to profile, then grind a 45 degree bevel along both sides of what will be the edge, then forge in the bevels. This guarantees you'll have the center steel along the edges.

It might be simpler to forge the profile and stock remove the bevel, though. I just prefer to play with fire and hit things with a hammer over grinding...

[Crex]

Listen to Ray about the initial weld. You are more just "pushing" the steel together. If the heat is right and the steel is clean it will pretty much weld itself. You are just pushing out the residual flux.

You're going to know pretty quick if your welds took when you start forging in your bevels. It will either hold as it should like one solid piece of steel or......separate. Simple as that.