I just finished working on a 120 layer billet made from 1084 and L6 with a simple twist pattern. Everything went fine with the twist and forging the bar back into square under the power hammer. At this point from what I was told I should have taken the billet to the grinder and cleaned up the edges where the twists could cause shears. Well this is my first piece of damascus and I got carried away and went staight to the hydraulic press and started flattening the bar and ended up with a 3/8" x 1" bar with what appears to be bad shears or shunts along the twist lines. I'm thinking that they don't go in very far and that I can grind them away ending up with a bar that's oval in cross section which I can then continue to press flat. Alternatively I was told to soak it in battery acid and try another welding heat and press it in from the edges in the hope of closing up any shears.
I realize it's great to learn from our mistakes (and I've learned a lot from this first bar of damascus!) but if anyone can see another alternative or thinks one of the above options is better than the other I wouldn't mind the advice!
At this point I'm leaning towards the grinding option with the assumption that the shear/shunt lines are surface cracks only (I'm not usually such an optimistic fellow!)

Guy Thomas

Hi Guy well I have also had the same things happen when I twist. You are correct in that most of the time the shears are not very deep and after twisting and resquaring I usually grind away the shears till I no longer see them. Then forge from there into the knife. Another thing I do that seems to help is too grind off or forge down all the square edges before twisting or twist a hexagon instead of a square. Also when flattening keep the billet at a welding heat and take a little at a time instead of trying to take it all at once until you get the flats well established. Hope this helps I am sure Ed has more tips.

My solution to that problem was to never twist anything square. I get my billet(s) to the desired number of layers, and then using the flat dies on the press, I knock down the corners, creating another set of flats on the bar, I then continue that process until the bars is very close to round. (this usually only takes one heat. From there I do whatever twisting I need, then flatten out the twisted round bar into stock. Nothing worse than sheared welds! :mad:

&nbsp &nbsp &nbsp &nbsp After making a couple billets with cold shuts as a result of twisting square and flattening I started grinding square to round. After grinding down the edges of a couple billets I realized I was wasting considerable time and material, so...

&nbsp &nbsp &nbsp &nbsp I forge to round before twisting also. I find that when I do a really good job of it there are no cold shuts, shears or surface inclusions. Even a slight concave surface ( such as in between the initial corners ) results in a valley that tightens and deepens as you twist. Usually these are very superficial cold shuts on the final squared billet, but they do lend themselves to shearing.

&nbsp &nbsp &nbsp &nbsp BTW on the subject of shuts/ shears I find that the edges where you overlap your billet before it is rounded/ twisted are also prime spots for cold shuts as you square things off after each weld. Sometimes one layer sticks up a little more than another and as you flatten them you can merely push one over another. I often grind the overlapped sides clean for the first couple welds. After that it seems less of an issue.

Thanks for the info guys, I think I've decided to grind away the edges and see what I've got, the more I look at the surface area that I did grind (I couldn't resist a quick etch to see my first damascus pattern!) shows the cracks disappearing within a few thousandths of and inch. The edges of course are deeper than that but grinding won't do more than reduce the bar to a nice oval cross section. (And hopefully useable stock to make several knives!) My fingers are crossed however. I sure know I'll take care of those edges either by grinding or forging round next time! This stuff takes to much work and time!

Guy Thomas