Blade cracked during grinding?

A

avs3323

Joined
Oct 28, 2015
Messages
29
Hi all,

I was grinding a blade earlier today, when it developed a pretty big crack at the spine of the blade.

Is this normal, or is there anything I can do to avoid this? I wasn't doing anything crazy with the blade, it was .110 thick Nitro-V stock that had been heat treated by Peter's.

Here is an image of the crack

54hqNDl.jpg
 
I have seen that happen and it's happened to me befor but normaly becaus it was not tempered befor grinding. Befor tempering there is a ton of stress in the blade waiting to be released and once you start grinding away steel the stress goes out of blalnce and you get a crack. But if was heat treated by peaters so I'm not sure. It would be worth running a hardness test on that blade to see how hard it is.
 
We need to know the steel type, HT method, tempering specs, and when in grinding the crack happened.
 
Hi,

Thanks for the replies, it was a piece of .110 Nitro-V that I had sent off to Peter's to be heat-treated to 62 HRC.

I was trying out something I had read on the forums here, where someone had used a contact wheel to hog off most of the steel before flat grinding (That is why there are a bunch of stacked grind marks on the blade).

I was dipping the blade after every pass, so the blade wasn't getting too hot, I am still new to knifemaking in general but I don't think I was doing anything out of the ordinary
 
I've only had a crack show up during grinding that was already there, but I didn't see it at first. Nothing major like that though.
 
I recently got my blades back from Peters' and I found a couple of the blades with a crack; one NitroV blade the spine and another NitroV blade with a surface crack. Both were about 70% pre-heat treat ground and I didn't touch them since I sent them out for HT. I found the cracks today and searched to web to see if this is a common issue, found this post and decided to reply. I'll post pics later when I can.

http://digsfossils.com/knives/BladeForum/20170909_153958.jpg
http://digsfossils.com/knives/BladeForum/20170909_153924.jpg
http://digsfossils.com/knives/BladeForum/20170909_153854.jpg
 
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Nitrogen could cause brittleness in steel, however it is used in the makeup of good steels like AEB-L and 12c28n in place of some of the carbon, to lessen the corrosion and recover hardness.
I wonder if the "marriage" between steel and nitrogen could lead to mischief in case the steelmaking procedure was not totally ok.
 
stezann said:
Nitrogen could cause brittleness in steel, however it is used in the makeup of good steels like AEB-L and 12c28n in place of some of the carbon, to lessen the corrosion and recover hardness.
Click to expand...
AEB-L does not contain nitrogen.

Chuck
 
DigsFossils-n-Knives said:
I recently got my blades back from Peters' and I found a couple of the blades with a crack; one NitroV blade the spine and another NitroV blade with a surface crack. Both were about 70% pre-heat treat ground and I didn't touch them since I sent them out for HT. I found the cracks today and searched to web to see if this is a common issue, found this post and decided to reply. I'll post pics later when I can.

http://digsfossils.com/knives/BladeForum/20170909_153958.jpg
http://digsfossils.com/knives/BladeForum/20170909_153924.jpg
http://digsfossils.com/knives/BladeForum/20170909_153854.jpg
Click to expand...
I think CMFTW aka Charlie Mike Charlie Mike was having some cracking with Nitro V
 
NJSB.

I also got a bunk order of A2 from them. Out of 9' of the stuff, I was only able to salvage 2 blades. Everyone had cracks.

A2 is the steel I use the most. I've never had an issue until this order. I purchased some from AKS and no cracks.

All sales final at NJSB. I just tell myself the $500 approx bunk A2 was just a bad trip to the casino.
 
This is weird. A2 is normally really stable and I always look forward to heat treating it. I hope the nitro-v cracks where just a fluke. I'm talking to a potential HT customer that has 20 nitro-v blades. I have only had AEB-L black once and that was because it had such a crazy bow. Like crazy bad and we lost it during tempering while trying to straighten it. Hope this is figured out, nitro-v sounds like it has good potential.
 
Likely that the bad batch of A2 wasn't rolled at a hot enough temperature. Thats what Edward Braun told me.
 
I have the luxury of being able to acquire steel direct from the rolling mill. I understand that most don't, BUT, here's my take on this, and why I'm reluctant to get it any other way than I do, with a handful of reservations...

I usually get sheets, or at least biggish strips. One of the great advantages to this is that the material has the type, thickness and processing stamp on it.

37020048632_440176acdc_c.jpg



That may not always be the case, though, as sometimes I get it and it's been run through the Timesaver, or precision surface ground, at which point I try to keep a record of the material through receipts. I think I'm not talking out of turn here, but I'll bet that the guys at Niagara Specialty Metals could trace it back. Im also willing to bet that would be true for most of the distributors, assuming they keep records as well.

I don't always get stuff this way, but it's certainly reassuring to know that what I'm getting can be validated, or traced, should there be an issue down the road.


Matt, who is Edward Braun?
 
Hmm.. i myself just got 6 blades of nitro-v back from Peters..hardened to RC 63-64. I also had ground them about 50% of the way pre heat treat. only a couple of the blades had needed the localized heat/ straighten. I will take a closer look them later. I had a few nitro v blades hardened by Tru Grit a month or two ago though and they finished out well enough, although they came back with a distinct bend.
 
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