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Controlling Scale

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Posts: 775
Noble Member Apprentice Bladesmith
Topic starter
 

I have always had a problem with what I believe to be excessive scale on my forged blades. Not only does this require a good bit of grinding but keeps me from forging as close to final shape as I would like. Typically what I will do once I have a blade forged to shape is to brush off as much scale as possible (while at forging temp) and sticking the blade in a bucket of lime to cool. What more (or differently) can I do to eliminate more of the scale from forming? Is it the lime that is my problem?

I would appreciate any insight or techniques that will help.

Thanks,

Gary

 
Posted : 12/12/2011 3:19 pm
Lin Rhea
Posts: 1563
Member
 

Gary,

Are you running your forge slighty gas rich? (you need to), this might help a little. Also, you may have heard of forging at reducing heats. The technique of using finishing blows works well with that method. When you get the majority of the forging and metal moving done you might turn down the forge a little and finalize you shaping at a color shade lower in temperature. Then turn down the heat a little more for your straightening stage, just a low red heat. Also use light taps for your finishing blows to smooth the surface and refine the finish. Dont be tempted to do any substantial forging at this low heat. I routinely use this technique. It takes a while to cover the entire surface, lightly heating and applying these light fast blows, but it will clean and smooth the surface. You'll have to wipe the loose scale off the top of the anvil often. For kicks, take it to a wire wheel and see how it shines when you work through the last thin layer of scale.

Lin Rhea, ABS Mastersmith

[email="[email protected]"]Email me[/email]

www.rheaknives.com

 
Posted : 12/12/2011 8:24 pm
Posts: 775
Noble Member Apprentice Bladesmith
Topic starter
 

Thanks Lin. That makes perfect sense. I am running the forge gas rich but have been forging pretty hot.

Gary

 
Posted : 12/12/2011 8:58 pm
Kevin R. Cashen
Posts: 735
Member
 

|quoted:

Gary,

Are you running your forge slighty gas rich? (you need to), this might help a little. Also, you may have heard of forging at reducing heats. The technique of using finishing blows works well with that method. When you get the majority of the forging and metal moving done you might turn down the forge a little and finalize you shaping at a color shade lower in temperature. Then turn down the heat a little more for your straightening stage, just a low red heat. Also use light taps for your finishing blows to smooth the surface and refine the finish. Dont be tempted to do any substantial forging at this low heat. I routinely use this technique. It takes a while to cover the entire surface, lightly heating and applying these light fast blows, but it will clean and smooth the surface. You'll have to wipe the loose scale off the top of the anvil often. For kicks, take it to a wire wheel and see how it shines when you work through the last thin layer of scale.

Very good tips Lin, I use the lower finishing heats myself to cleanup and keep from dinging the work all up. Ken Mankle gave me the best name for this when he told me that he called it "hammer polishing".

Also, when all done,and before you go to the grinder, soak the blade for a few hours in a strong sodium bisulfate solution. Don Fogg has recommended it for years, it is the chemical industry uses to strip scale when pickling and you can buy the crystals anywhere they sell pool or hot tub Ph supplies. It it will eat through any scale and leave you with a clean gray blade that is much easier on belts.

"One test is worth 1000 'expert' opinions" Riehle Testing Machines Co.

 
Posted : 13/12/2011 9:42 am
Admin_DJC305
Posts: 1999
Member
 

Thank you Kevin! I am actually in Home Depot at the moment and checked the ABS Forum on my IPHONE and saw your post. Sally located a bottle of sodium bisulfate in the store in the pool supply aisle. I will use it on my next forged blade.

Dan Cassidy
Journeyman Smith
Send an email to Dan

 
Posted : 13/12/2011 11:48 am
Posts: 0
New Member Guest
 

Does anyone use water on the anvil and hammer during the low heat "hammer polishing" to bust off scale?

 
Posted : 14/12/2011 3:16 pm
Lin Rhea
Posts: 1563
Member
 

I sometimes use water but only at forging heat. Water is just on the hammer or the anvil or both. The blade just barely contacts it steaming it away immediately which is why the scale pops off. I dont use water on low heats because the water might over run the low heat on the thin edges. That may not be a big worry, but it's where I draw the line. From there I use finishing blows at a low red heat. That is a blacksmithing technique from days gone by before wire brushes.

Lin Rhea, ABS Mastersmith

[email="[email protected]"]Email me[/email]

www.rheaknives.com

 
Posted : 14/12/2011 7:00 pm
Posts: 32
Eminent Member Journeyman Bladesmith
 

Lin, I've heard something about about vinegar for removing scale. If this true, how do you use it and when? Thanks-Bill

 
Posted : 27/02/2012 3:07 pm
Lin Rhea
Posts: 1563
Member
 

I believe thats talking about softening the forge scale before grinding.

Lin Rhea, ABS Mastersmith

[email="[email protected]"]Email me[/email]

www.rheaknives.com

 
Posted : 27/02/2012 7:26 pm
Mike Barton
Posts: 54
Member
 

I have a container full of white vinegar that I use, and it removes over 90% of the forge scale before I put the blade to the grinder.

Mike

 
Posted : 27/02/2012 8:29 pm
Posts: 307
Member
 

Yup, white vinegar in a container after the forging is done. Before I had access to a grinder, I was draw filing and I learned quickly that scale is REALLY hard on a file... I just leave the blade in the vinegar for a while then wipe and wash the goop off. Saves on belts, too.

Jeremy

Jeremy Lindley, Apprentice Smith

 
Posted : 27/02/2012 9:03 pm
Posts: 1
Member
 

Kevin Do you have to dip the blade in ammonia or baking soda to kill the bisodium sulfate after the scale is gone?

Thanks Lonnie Crabill

 
Posted : 28/02/2012 11:04 am
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