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Ed Caffrey's Workshop Talk to Ed Caffrey ... The Montana Bladesmith! Tips, tricks and more from an ABS Mastersmith.

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  #1  
Old 05-22-2005, 04:49 PM
Dan Graves Dan Graves is offline
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Bubbles in billets

I have been making a lot of damascus billets lately and have been getting bubbles in the damascus (not desighn but bad weld) and would like to know any tricks on dealing with them and why do I get them sometimes and sometimes I dont? I always clean all scale off before folds. I start out with 1/8 thick stock and have used 3/16 stock to start. This happened yesterday at 128 layers. Any suggestions?


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Old 05-23-2005, 10:24 AM
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Ed Caffrey Ed Caffrey is offline
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Those annoying bubbles........

Hi Dan!

Generally those bubbles occur when there is a low spot between the layers. It usually occurs after the first re-stack/folding. When you grind the forge scale off before re-stacking/folding, make sure you grind a scarf into the pieces (the surface of the pieces are slightly convex, with the highest spot being along the centerline of the pieces. Another trick is to make sure the grind lines are running across the pieces (from one side to the other). This creates a capillary action for the flux, allowing it to be squeezed outward from the centerline of the billet. If your grind lines are running lengthwise on the pieces, there's a good chance that something will get trapped in there, creating a bubble.
Something else to think about are your dies (hammer or press). About a year ago I went for a couple of weeks where every billet I welded had a bubble in it.....it wound up being the press dies. There was a dent in the upper die, and it was actually causing the bubble. I replaced the dies and the problem was solved. And finally, one other possibility... sometimes bubbles are caused by trying to weld with drawing dies. The drawing dies do not draw all the layers equally...especially in a hammer. The drawing dies will draw the outer layers more so than the inner layers, and it will allow a gap/bubble to form, especially if it's an inital weld.

Hopefully you can sift through this and figure out what applies to your situation.

Let us know if you solve the problem!


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Old 05-23-2005, 10:47 AM
Dan Graves Dan Graves is offline
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Repairing bubbles

Once again you make things easier for my life. I do my welding with a power hammer with slight blows. Should I do my welds on the anvil? Also is there a way to repair a billet with a bubble? Is it important to grind mill scale off of the bars befor you stack? Finnally, is the dried Borax that much better than 20 Mule Team? I know its a lot of questions, but you the man with the plan. Double thanks!


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Old 05-23-2005, 03:24 PM
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Hi Dan!

If your hammer has drawing dies in it, then that is very likely the cause. You can do a couple of things to the dies..
1. If they are severe drawing dies, you can take them out and grind them to a less severe radius.
2. You can purchase a set of flat dies. I'm not much for that because it's such a spendy venture, but it will stop the bubbles.

About the only way you can repair those bubbles is to completley grind them out with an angle grinder, which is going to make a divot in the billet, and mess up the pattern, but if your making random, or haven't done any patterning yet, it won't be a big deal.

I never do grind off the mill scale prior to stacking and welding. I just heat it up and flux the daylights out of it......it's always worked well for me.

I personally think there is world of difference between 20 mule team and anhydrous borax. 20 mule team has so much moisture that it foams up and falls off before it can get any work done on the billet. Anhydrous borax goes on like a coating of honey, and works much better. You generally wind up using a lot less of the anhydrous too, simply because it stays on the billet instead of foaming up and falling off.


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Old 05-23-2005, 06:01 PM
Dan Graves Dan Graves is offline
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Thanks Ed. Guess I will get some new Borax.


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Old 05-24-2005, 08:52 AM
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I've had very good luck popping bubbles with a chisel or punch, fluxing, heating & using a ball pein hammer to lightly tap & weld all around the hole. Usually when you pop it a nice blue flame shoots out for a few minutes; burning off whatever gets built up in there. If I suspect a bubble due to a dark spot "in," the billet I heat to yellow, lightly tap on the suspect area, which welds the edges of the bubble in a little and puts pressure on the bubble, then go through a cycle or two of heating / cooling to yellow / dark red. Usually the bubble will inflate to the point of being very obvious and easy to pop. I've had billets with several bubbles that produced flawless blades using this method.


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Old 05-24-2005, 12:18 PM
Dan Graves Dan Graves is offline
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Mr. Loose, Thanks for the tip on popping those bubbles. Between you and Ed I just might be able to salvage the billet. Maybe do another fold after I pop the bubble. Is propane high or what? Need to make every billet count. Thanks


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Old 05-25-2005, 02:19 AM
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Dan!
After welding with powerhammer, when drawing out a billet and forging from edge, a hollow surface forms on sides. It's more prominent, when powerhammer is very small!
At the end of drawing, make sure to forge from surface to be welded together!!


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Old 05-25-2005, 08:16 AM
John Frankl John Frankl is offline
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Ed,

Where do you get your anhydrous borax?

Thanks,

John


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Old 05-25-2005, 10:54 AM
Dan Graves Dan Graves is offline
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Borax

Yes! Where do you get it? I have heard there was a way to make anhydrous borax out of 20 mule team but dont know how. Anyone heard of this? Also, when welding a billet, after the first weld do you turn your forge down? I like to forge hot and move metal, could this be another reason I get bubbles? Thanks


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Old 05-25-2005, 11:20 AM
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Ceramic supply outfits usually carry anhydrous borax. I've been getting mine for a place called Seattle Pottery. It comes in 50lb bags from them, and cost about $1.50 per pound.

If your fuel/air is correct on your forge, you can forge at very high heats all day long. As long as you remember to thermal cycle you damascus and undo any damage you did. I routinely forge at 2250-2350F when I'm welding/working with damascus.


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Old 05-26-2005, 11:04 AM
Dan Graves Dan Graves is offline
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Thanks

Thanks for the tips.


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