possible cracked blade

[J. Doyle]

Hi Ed and anyone else.

I made a drop point hunter today and quenched it. Everything went well and looked good. I cleaned it up just a bit and got it in the oven to temper. When I pulled it out, I etched it in ferric chloride just to see where the hardening line was at. I noticed what looked like a hairline crack running up near the plunge line. I sanded it out and re etched and now can't see it. Man it sure looked lick a crack to me and it went almost to the spine. I did everything just right as far as edge thickness and even grinds and I took it to 400 grit prior to HT. My plunges were nice and even and rounded out.

I put the knife in the vice just below the crack and flexed it quite a bit. I heard no cracking sound and the crack didn't reappear. I didn't flex it all out because it had only one temper so far.

My question is this: Is there a sure way to tell if it's a crack before I just destroy the blade? It's supposed to go to a customer and I do not want to send out a cracked blade but like I said, I can't seem to see it now even after etching again. Still makes me nervous though. Also, if it was cracked and almost to the spine, wouldn't it have snapped pretty easy in the vice?

The steel is 1080 quenched in warm mineral oil by the way. This is potentially my first cracked blade. Any ideas?

[cdent]

Hi John,

If you have a decent finish on the steel, you might try a little diesel or kerosene on the area. Wipe it off so it looks dry. Then blow a little compressed air across where you think the crack is. Hold it so the light is good, and you can see a little tail of kerosene lift out of a crack that you couldn't see by just looking at it.

Don't know if it'll help, but it's worked for me. I don't know if you might not just listen to that voice in the back of your mind. Chances are other folks will have better ideas.

Good luck with it, Craig

[MLAZYB]

John, Wrangling with this kind of problem can be mind boggling. Here is my take. First if knife does not have a crack then great your good to go. Next if you think there is a crack will you be comfortable sending it to a customer? These are questions you have to decide the answers to.

Has this happened to me? Yes and I didn't notice the crack ? until I had finished the knife. As this pained me I destroyed the knife only to discover that it was actually a 100 grit scratch. The positive out of my situation was that all things considered. My knife passed the destructive test. Sometimes we have to take one and do just that. I would rather destroy a knife in my shop than send one out and have it fail in the customers hand.
Good Luck and let us know how this turns out

Bing
MLazyB Custom Knives
ABS Journeyman Smith

[Ed Tipton]

I guess that in the absence of confirmation, then you have to let your conscience be your guide. I have had blades crack to where there was no doubt, and then I've had them appear to be cracked...but cannot be sure. For me, it's destructive testing time. Either way, all doubt is removed and I'm able to salvage something positive from it.....either way I'll know if it's definitely cracked or that I had made a good blade. If it was cracked, then I have the confidence that it was caught by me...and not a customer. If it is a good blade, then I also get confidence from that. It's a win-win situation for me.

[J. Doyle]

Hey guys. Thanks for the suggestions and responses.

I want to say first that I would absolutely not want a blade to crack in a customers hands. And, as mentioned, if there was even a doubt in my mind remaining, it would not get shipped out.

And I do regularly test my blades to destruction to make sure I have confidence in my blades and the heat treat.

All that said, I am now 100% sure that this blade is not cracked. I went ahead and triple tempered the blade and hand sanded to 600 grit, etched again, and sanded again then examined the area with heavy magnification. No sign at all of what I thought was the crack. The 'crack' ran parallel to the plunge but did not go to the edge. Never heard of steel cracking just out in the center and not to the edge. The mark in question turned out to be a leftover ragged file mark from cleaning up the plunge line that was filled in with firescale. After all the hand sanding it was removed.

Once again, I appreciate the comments but am also sure and relieved that this was not a crack.

[tomh]

John I quench my knives at 50 grit. I have only ever had one crack and it was because I was using parks 50 that was too warm, and it was like quenching in water. And it was obvious that it was a crack once I started grinding.

I would guess it is a scratch line, not a crack. if you are worried about it, do some destruction testing on the blade, and make your customer a new one. it is just a little steel and time brother!