Mysterious lines (perpendicular to grind lines) appear on bevels

[t1mpani]

`Hey everyone,
So this is one of my modified karambits that I've made quite a few of, out of 3/16" AEB-L, HT to 61.5 by Peter's HT, and though I got it back a few months ago I'm just getting around to finishing this one. I used a green scotch brite belt to clean the HT coloring off of it, just a few seconds on a side (and my thumb is always on the opposite side of the blade so it never gets all that hot) and then cleaned it up, etched it, and put it in the rocks to tumble. When I took it out, there were some longitudinal scratches that I THOUGHT were possibly from shoving the knife into the rocks too hard, so I kind of repeated the scotchbrite cleanup, etch etc and then gently set the knife in with the stones and covered it up, did a tumble again, and this time the lines are EXTREMELY prevalent. They seem to follow the contours of the blade, especially around the plunge lines. Have you ever seen anything like this? Could the acid etch have damaged the steel in such an odd way?
Thanks very much in advance,
Warren

 

[Lorien]

is it carbide banding?

 

[t1mpani]

Wow---I don't know, it may be. I've heard of it in forged carbon steels but not stock removal stainless. It actually reminded me of the multiple lines on the knives made with the Ed Fowler multi-step HT. I wonder if this knife is even viable going forward... I wonder if I should return it to Peter's, not "for a refund" but so they can look at it and see if they've encountered it before. I mean, they've done so much for me, I'm not going to spit nails over one HT mistake, if it is indeed a mistake.

 

[DevinT]

You should do your final grinding after heat treating.

All steels have a slight amount of decarb after heat treating.

I believe what you’re seeing is part decarb and part banding.

Hoss

 

[t1mpani]

Hmmmmm. I’ve always been afraid of grinding on steels with relatively low tempering ranges after they’ve been tempered. It may be that I’ve produced dozens of knives with this very same thing but the lack of etching didn’t bring it out. Only the fourth knife I’ve etched and tumbled.

Edit to add: I mean, they’ve always looked decent enough to me, but now I really do wonder. This one was a couple weeks ago, same steel. I’d look closer but I’ve already shipped it.

 

[Huntsman Knife Co. LLC.]

Did you tumble the blade before HT?

Tumbling unhardened steel can cause gouging, then if you do an acid wash, the color will stay in the gouged out areas and not get cleaned off by the stones. If they are deep enough, the scotchbrite belt wont touch them.

I'd recommend hitting that bevel with a quick grit progression and then etching to see if the lines are still visible.

 

[t1mpani]

No, only tumbled after HT. Okay, well I’m giving up for the night and heading to bed, but thanks everybody for the input! Now I have to emotionally gird my loins for taking a shot at NOT moving the currently-symmetrical center ridge of a dagger point.

 

[JV Knives]

The uniformity of the lines definitely leads me to think that it is showing layers in the steel similar to the way Damascus shows. Certainly more pronounced from an etching process than would normally be observable. As to why in AEBL, could be many things but likely all from the foundry side ,in my opinion.

 

[Tom Lewis]

I had some of that with 26c3 steel. I contacted Alpha, they checked into it and said it was most likely alloy banding.

 

[t1mpani]

The customer actually likes it, and asked me if it’s a problem. While pondering how to say “hell if I know” in a way that sounds professionally reassuring, loud thunder surprised me and I dropped the damned thing from a little above waist-height and it landed edge down (not sharpened yet) on the bathroom tile floor, from which it very loudly bounced about six inches before clattering to a halt. There is no damage from it (except a chip out of the tile) so I’m mildly reassured that it isn’t a severely weak, embryonic-cracks type situation. I mean, with a 2.5” blade it was never going to be a chopper but I had wondered. I’m not saying this is in any way a scientific test, but if the customer is excited about the look…

 

[Stuart Davenport Knives]

It really looks like carbide (alloy) banding to me as well. I prefer a more homongenous steel matrix, but no it is not a problem at all. Most steels that have vanadium, even trace amounts, will exhibit banding to some degree or another. I agree, it looks cool, but will not affect performance negatively.

 

[t1mpani]

Well, apparently I’m leaving it as is per customer request—but thanks everyone (as always) for being the well of wisdom.

 

[A.McPherson]

The customer actually likes it, and asked me if it’s a problem. While pondering how to say “hell if I know” in a way that ... but if the customer is excited about the look…

I was just going to comment that you should see if they like it. I think it's pretty cool looking...
If it's functional and the banding doesn't result in a weak knife, why not just embrace it and drive on!?

 

[Larrin]

The fact that the lines follow the grind and not the rolling direction makes me somewhat skeptical that it is entirely from banding.