Death of a hunter...

Matthew Gregory

Matthew Gregory

Chief Executive in charge of Entertainment
Joined
Jan 12, 2005
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As I was finishing up with an A5 belt and whisking over to the buffer with a sewn buff and some white compound, I noticed a small scratch... that continued on both sides. Not a scratch at all, says I, in dismay... nay, 'tis a crack. How ever could it have gotten there? Here are the clues, let's see what our resident sleuths might divine from rolling these bones!

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Tell me of what thine Oracle displays, oh Sayers of the Schools of Majick and Metals!
 
Forged or stock removal? Is it a grain thing? God I have a lot to learn...
 
Looks like it cracked from the spine down, for about a quarter of an inch, when
it was quenched. ...also looks like a fairly coarse cross section. Both can be
indications of overheating........So...

What kind of steel...?
Time and temp...?
What quenchant/at what temp...?
 
-1084 1/4" stock
-Watched the steel decalesce, so approximately 1500, soaked for a few seconds, quenched into 80 degree Park's #50 and tempered immediately upon steel arriving at 'holdable' temp.
 
Did you check with a temp probe or magnet? Looks like coarse grain from over heating or lack of normalizing/theremal cycling, and posibly a crack started from forging too cold, or maybe just a stress crack from lack of normalizing.:confused:

If I understand rite, Parks #50 is close to texico type A, I normaly quech between 130-160deg.F. Though a cooler temp should have caused a slower quench and less sever shock. But from the discoloration I'd beleive that the blade cracked in the quench.
 
Cracked in quench. Started at the spine and ended approx. 1/4" from it (due to the oil discoloring the steel caused by oil). Then you probably snapped the rest off.
 
I'd like to see a better photo of the crack. It may be that the crack was there before final quench !
 
I was thinking along the same lines as Mete. This may have been a situation created in the manufacturing process, which is not unheard of :eek:
 
Matt, That dark area makes me believe the crack was already there when you heated the blade. The picture's not great, but the grain looks large to me. You may have an overheating problem in addition to cracked steel. Time to get together with your friend and install that temp gauge so you can stop having to guess.
 
Will52100 said:
Did you check with a temp probe or magnet? Looks like coarse grain from over heating or lack of normalizing/theremal cycling, and posibly a crack started from forging too cold, or maybe just a stress crack from lack of normalizing.:confused:

If I understand rite, Parks #50 is close to texico type A, I normaly quech between 130-160deg.F. Though a cooler temp should have caused a slower quench and less sever shock. But from the discoloration I'd beleive that the blade cracked in the quench.
Click to expand...
Parks #50 is somewhere between spring water and thin sinus fluid in consistency and EXTREMELY fast.:D Visible MUCH thinner than Tough Quench. I have been using it at room......or more precisely, garage temperature on 1080 and it seems to work great. Now admittedly, a garage in sunny florida in late summer early fall may in fact reach the temperatures that you mention...lol;)
 
You guys are good!

As Chris' comment implies, I've been struggling with getting temps right in my forge. This is total proof of this, although it's also the worst I've had, so far.

There was a guthook on this knife previous to heat treat, and I guess there was a crack started in there before quench... I removed the hook AFTER quench, as it just didn't fit the knife. I also finished snapping the tip off when I saw the crack, to examine the break.

This knife was stock removal, btw.

Time to build a heat treat oven!!!!

Pretty impressive sleuthing, guys... there was a lot of info I didn't offer that was suggested. Once again, I'm impressed with this forums wealth of knowledge!
 
Bad day in the shop. We all have them from time to time. Sorry to hear that. Hard edge soft back is the way to go in my book at 1500 heat treat and 350 for temping for about 2 hours. Remember 1' inch per hour. for the hold time in heat treat. :yawn:
 
Not a bad day at all, guys - seriously! I'd rather have a failure like that --that points to an obvious weakness (and learn something in the process) --than to find the failure after it's in the hands of it's owner! I'm just amazed that the crack wasn't found by me until the very end...

There is no end to the learning in this stuff, and I'm happy I can struggle with it!
 
A gorgeous propane forge and, soon, a heat treat oven too.

God I'm jealous..................

Syn
 
Michael J. Spangler said:
matt just build the oven man... i'll send you the link, its easy and affordable.
digital controls man kick ass
Click to expand...

Do it, my man!


We need to talk about a sheath for that lil' guy I got from you at Ashokan... so far, it's just been sitting and staring at me! Not a good idea to carry something sharp and pointy in your pocket, you know?
 
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