oh.....shards!!!

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cmott69

cmott69

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Sep 11, 2004
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:mad: :mad: hell of a day

been working on a big knife (khukri style) for a few weeks now.
Got every thing like I wanted it, handle fitted all of the major scratches sanded out time for heat treat. (rigged up a small forge a while back so I could beat it into rough shape)got forge up to a good heat, got blade to non-magnetic(leaf spring steel-5160?) quenched in brake fliud(had alot on hand) PING!!! :eek: fractured in 2 places.

Any one know a maker in the little rock area that has a forge that reaches welding heat, I would hate to chunk this one. :(
 
If it fractured, it's not repairable. You cannot forge weld it back together.
Circular fileing is the only option... :rolleyes:
 
Ah, what a kicker... That sucks. Like Howie said though, nothing you can do but try to grind it back behind the cracks, and try it again. Not easy, not fun but sometimes you'll find that what you didn't want to do actually makes the knife better.

Darryl
 
Why quench in "brake fluid"? That stuff is hydraulic fluid, and is very nasty.:eek:
Use cheap olive oil, and preheat it to 125-160 degrees F, before quenching.

A handle would be fitted up after heat treatment, and finish sanding were done, as many things can change during those processes, as you've found out.
Now you'll have a tough time using that material on something else, unless it's the exact same shape as the knife you cracked.
Get back to work and do it over!:eek: ;)


Edited to add; You say it was 5160 "leaf spring material", do you mean it was a vehicle spring, or just 5160 steel? Because, if it was a spring, you have to anneal them properly before working.
 
In general I would avoid grinding past cracks to make a failed knife into a new knife. For every crack that you can see, there may be several microscopic cracks that you cant see. I dont like it when a knife fails, and a big kukri that may be used for hacking at tree branches and stuff, may fail more easily than a knife that someone uses to gut the occasional fish. just my two cents.
 
Lets see now,
First the Brake fluid may have been to fast of a quench,Just a guess as I have never tried it.Old burnt motor oil works great and even better if you add a little transmission fluid with it,Vegetable oil or cooking oil of any kind works also.
Second,I have had this problem with recurved edges myself.When heat treating after grinding I would have the front part of the recurve try and curve back up like a katana does and thus crack the edge in a few places.I solved this problem by forging the blade then doing the heat treat before I did any grinding.Just grind slow and easy,keeping the blade coole off as you grind,get a wicked edge and when you are done grinding you just finish out the knife.

You can save the handle work you have done by forging another blade a little over sized of what you have now and finish the blade out by using the dimensions of the knife you cracked.Save that blade untill you start making Damascus and weld it into a billet and make another knife with it that way,I wouldn't try and save it any other way than that myself.
Bruce
 
cmott69 said:
Thanks for the input guys :D

oh well back to the drawing board.
Click to expand...

Above all, don't get discouraged. This happens to everyone - even accomplished smiths. Leaf springs can sometimes have microfractures simply from years of use. The cracks become evident when you begin to transform them into something else. :)
 
i was just working on a big kuk myself, and i didn't notice anything till i got to the actual tempering part. because i did it in an oven, the whole thing blued quite nicely, but there are a buch of purple streaks running all kinds of directions, but mostly in line with the length of the blade. now im just softening it up some more in hopes that it won't break. what was odd was that all of the streaks were in the middle of the blade face, not by the edge... idk why that happened
 
Nine year old thread. ----- Thread Closed. Please look at the date of a thread before resurrecting it.

The rainbow of colors ( usually blue, purple, magenta) seen on a blade after tempering are not important. They are caused by oils and other things. Just sand them off.
 
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