Photos Deep Pitting

SpokaneMatt

SpokaneMatt

Joined
Aug 24, 2019
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This is my second forged knife and both have the same issue.I am using 1084 steel on a small home-made coke forge and keep getting these deep burns in the steel. I am only heating to just above ACL but both knives had these deep burns. I have to grind form 1/4 inch down to 1/8 in just to get to unburnt steel.
Does anyone have any suggestions on how to keep this from happening?

Thanks
 
SpokaneMatt said:
This is my second forged knife and both have the same issue.I am using 1084 steel on a small home-made coke forge and keep getting these deep burns in the steel. I am only heating to just above ACL but both knives had these deep burns. I have to grind form 1/4 inch down to 1/8 in just to get to unburnt steel.
Does anyone have any suggestions on how to keep this from happening?

Thanks
Click to expand...
Here is a picture of the blade
 
The solution to this is - Don't burn the steel.

Seriously, it sounds like you are really overhreating the steel in forging. Another thing that can mess up a forged blade is not brushing the scale off the blade and anvil before each heat. If you don't, you forge the scale into the surface and make deep pits.
 
Thanks Stacy!
One problem I have is I'm fairly colorblind, so determining the heat of the blade is pretty tough by sight. So I want to pull it from the fire before I see any dark spotting on the blade?
 
I'll be honest - colorblind and working a coal/coke forge is a bad combination. I would look into building a propane forge. You also might consider making it PID controlled.

You want to learn how to move the blade in and out through the firepot in order to evenly heat the blade. Figure out what is the right loo0k for when it is at forging heat. If you see sparklers, you have burned your blade badly ( usually the tip).

When you pull the blade from the forge, brush off with a wire brush to knock off scale and cinders. After each heat, wipe the anvil surface clean of all scale and debris.

For HT, you either need good color recognition if using the forge, or a HT kiln with temperature control. By far the better way to do HT is with a controlled kiln.
 
SpokaneMatt said:
. I have to grind form 1/4 inch down to 1/8 in just to get to unburnt steel.
Click to expand...
I'm not sure how much grinding you're doing here. Are you grinding a 1/4" billet down to 1/8" billet to remove all the pits? OR, do you have to remove anywhere from 1/8" to 1/4" of metal from the billet to remove pits? The first is only 1/16" from each side which is darn good. The second of removing 1/4" is still only 1/8" from each side of billet.

As Stacy says be sure to remove scale each heat - one problem I have with my inexperience at forging is putting hammer divots in the metal that has to be ground out. I use a flattening iron to help with that, but still removing scale is VERY important to prevent the scale from putting divots in the billet.

Good luck.
 
Thank you for the advice!
I have been seriously looking into a propane forge....does anyone have experience with Hells Forge forges?
The double burner looks very enticing.
 
Overall, they are OK. You will need half a dozen or so firebricks to close the front and back as needed. The wool needs to be coated, cured, and fired. It isn't hard to do, but it is still a semi-kit.

Take a look at the Atlas forges, especially the recently improved Graham forge. Very popular and well made. Great customer service and always working to improve a good product to make it better. It's a better forge for the same money.
https://usaknifemaker.com/atlas-stainless-graham-forge.html
 
Is a single burner forge good enough for making 10 inch chefs knives or similar sized blades?
I noticed the dual burner they have is listed as a sword forge...
 
It is plenty suficient. You don't really need two burners if the forge is properly built until it gets over 16" long. I have done a sword in an Atlas Graham forge.
 
Matt
I'm sure there are others who forge with coal on a regular basis that can better address your difficulties, but since none have tried to help you I'll throw out a few things. It has been over 20 years since I forged with coal so take this for what it is.

You said you were using coke, if you are making your own from coal, make sure the green/yellow gas has dissapeared before you try to heat steel with it. It is full of sulfur which is very bad for steel.

Kill or reduce the forced air to the forge before inserting the steel, this will reduce scaling. It will also help you to not over heat the steel.
If you pull the steel from the forge and sparks are jumping off the edges, throw it away, you are burning it.

I do agree that propane is the way to go, cleaner, easier to buy, easier to store. Faster to light and to turn off.

If you look up some of the local knife makers who forge ( Knives 2019) (or any other year) and give them a call, some of them may invite you to come watch them forge so you can get a better idea of what the proper steel temperature looks like and the good points and bad points of their particular forge.
Happy forging!
Jim A
 
Thank you Jim, I appreciate your input!
I believe you have struck on the cause of at least some of the burning....I have been using a lot of air through the forge, actually with the knife I posted I was using a single speed shop vac to supply the air. I thought I needed that fire as hot as I could make it.
I am going to keep the coke forge and continue playing with it, but I am also going to either purchase or make a propane forge for everyday use. It looks to me like using propane is a better way for me to learn the heat needed, the color of the blade (as I see it) to begin hammering, and the basic forging skills. Then move those skills to the coke forge, and make changes to that forge to improve the fire.
 
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