Cracked Blade

[dhannon]

Ouch! I've cracked a blade! Can anyone explain what went wrong (guesses)?

I forged a simple blade out of 1095 bar stock, 1/8 thick x 1-1/4 wide. Not much forging, but a first try. It took many heats as I only had a 12 ounce claw hammer at the time. I forging heat was from 1500 F to light glow. I packed the blade at the light glow range then annealed. I roughed the grind then heat treated. I quenched in 70 F olive oil and tried to differentially quench (the edge half of the blade in the quenchant). After cleaning up the blade prior to tempering I noticed a crack starting at the edge and going 3/8 inch toward the spine (half way down the blade).

Can too many heats cause this? Any guesses as to a possible culprit?

Thanks,

Dan

 

[raker]

There are several things that can cause the blade to crack. One is that the temperature you quenched at was too high and caused the grain structure to become enlarged. Two is that the rough grind may have been too much and the edge was too thin. Three, you could have produced a hairline crack in the material by hammering too cold. Four, if you didn't normalize before annealing, sometimes the grain is still to large and will cause the blade to crack or break.
The best way I know to assure a good heat treat every time is to use clay and a magnet. The clay will keep the back of the blade from getting too hot and cooling too fast and the magnet will keep you from overheating your blade. 1095 requires a very fast cooling rate and it may be better to heat your oil to about 140 deg. before quenching. Hot oil cools faster than cold oil. The temper will determine final hardness and edge holding characteristics.
If I knew more facts about exactly how you went about it, it would be easier to pick out the problem.
I hope this will help some.

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Ray Kirk
http://www.tah-usa.net/raker

 

[Darrel Ralph]

The forging temp is to low!
This will cause 1095 to crack every time.
You are forging to cold!
Get some 5160 for now to start with. Its much more forgiving. Was the anvil pre heated?
This will cause problems also.
You will need to normalize the blade after you have it to shape. This will set the grain back to normal before heat treating.


The oil temp as Ray said helps also.



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Web Site At www.darrelralph.com
MADD MAXX !

 

[dhannon]

Thanks guys. This was the first attempt at forging, having all other knives made by stock removal. I've got much to learn. I'd say that probably all of the above could have happened on this one forging. So much for only reading before trying. Nothing can replace the experience.

Thanks,

Dan
Hannon Bearpaw Knives