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Grain in blade that was broken


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Hello all, I made a couple of blades for a Buck 501 knife that had a broken blade.  This photo is what the two blades looked like before final finish. post-23496-0-57538400-1360119586_thumb.j

The next 3 photos are of one blade after heat treating.  Normalizing twice by taking to non-magnetic, then cooling.  Then to non-magnetic and quenching in canola oil.  File wouldn't cut at all - just slide. Then bake in oven for 1 hr at 400ºF for 1 hr- did that twice.  Then for final finish.  I took the one blade, clamped pointy end in vise about an inch from end, grasped other end with channel locks, bend over until break.  Top section has a nice bend before breaking just above vice jaws.

 

 

post-23496-0-28260100-1360119624_thumb.j post-23496-0-08693000-1360119632_thumb.j post-23496-0-38357100-1360119642_thumb.j

 

The 3 views are at about 15X under microscope (a stereo microscope I use for SMD work) - USB camera isn't very good.  Those images are the best I could do.  

 

My question: can ya'll tell anything about the grain size?  Does it look "ok", is there anything obviously wrong with the looks?  OR perhaps the images just are not detailed enough to make a judgement call?

 

Thank you for any suggestions and help,

 

Ken H>

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While I am no expert that grain seems okay to me.  Are you surprised that you could break them this way?  What kind of steel are they made of?  Your heat treat seems okay to me but was it appropriate to the steel that you used?  I would expect most good blades to break given the test that you applied!

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Thank you for your comment - and Ooops!!!!  In trying to put all the pertinent details I forgot one of the most important of all - what type of steel.  It's 1084 that I ordered from USA Knifemakers.  I was pleased with how tough the steel is when heat treated.  It took more pressure than I expected to bend far enough to break.

 

I did the brass rod test, and it did seem to pass ok - I could see the edge rolled a bit, but not stay rolled over.  I've read so much about keeping a small grain structure I was curious how that compared - AND "IF" the photo was clear enough to actually see the grain enough to judge.  From what I've looked at in photos, and what my meager experience tells me - it seemed good.

 

Thanks again for the comments.

 

Ken H> 

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Yep, I know 1084 is one of the simple steels - that's why I chose it over 1095 or 5160.  I've got a piece of 1095 I plan to try before long.  I've got a coil spring from a farm implement of some type. The coil steel about 1/2" in diameter when cut and straighten out - I've made a couple of blades from that and it "seems" like it might be 5160 - I heat treated as if 5160 and got the expected results.  Those blades are pretty tough - not tested one to destruct..... yet.  I heated in forge and pounded steel rod until it looked like a knife blade, then finished on 2"X72" grinder.

 

I'm sure having fun with this knife making<:)

 

Reading in this forum has given me a LOTS of knowledge on how to work steel.  Built several burners for gas forge, built 2X72 KMG clone, just lots of fun things.

 

Ken H>

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grain size could be smaller ...  it looks big in the pic

 

crack a file in half... notice how fine the grain is there...   thats what it should look like

 

do 3 normalize cycles... and you start higher and go lower

Kevin has good stuff on his site

http://www.cashenblades.com/steel/1084.html

http://www.cashenblades.com/heattreatment.html

 

good luck

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It is so nice to see a post from someone that is actually doing shop testing to see that wot they wish a knife to do is capable with the process' used in HT.

one key to this that I am sure you already know is to keep acurate records for each and every steel type you use. And for " mystery steel" like  a spring,,the result will hold true for the rest of that particular piece of spring.

If you have not yet looked at the knfe making chat logs they are posted in the forum. We have a new session each wednesday at ten  pm, EST.

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Rich, Thanks for the idea of comparing grain - why didn't I think of that.  I found the broken blade from the Buck 501 knife, clamped both broken ends together under microscope - the Buck grain is smaller than the 1084 grain.  

 

Kevin has some really good info on his website and I used it for the tempering temp.  I'd sure like to be able to control temp while normalizing to the degree required, but at this time I can not.  Just heat to non-magnetic, cool -  then try for a "tad" less temp.  I'm working on a "K" thermocouple for my gas forge, but doubt I'll be able to control temps as close as required.  I've read (depending on steel) 1525ºF for first, 2nd at 1500ºF, then 1475ºF for 3rd and final heat - then to 1500ºF (again depending on steel) for quench.

 

I'm sure having fun learning all this good stuff - fortunately I've just retired and don't have to sell anything<:)

 

Ken H> 

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I've read about those temperature crayons, but never looked into them.  I just did a quick check of the tempil.com website.  They have 1400ºF, 1450ºF, 1500ºF, 1550ºF range of temp sticks - AND, they are $130 or so per box of 10.  Perhaps I can find them at welding shop where I could buy single crayons.

 

Thanks for the reminder - that would be good to double check the K thermocouple reading I get.

 

Ken

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