Appears to be roll chatter defect from a millOk I have an update. I was able to get one on the chuck and prep both sides. For a reference we don’t leave scale on the back side of blades before testing. We use a scraper if it does not pop off in the quench.
I took the top surface down till the test groove and test dimples where removed. I’m guessing it was about .020. But I snapped a few pictures while grinding because the sparks coming off the grinder looked really good. I have had some that sparked like mild steel. Come to find out it was and was sold to him as high carbon on eBay. So I worked my way through the grits up to a norax 5x which is 3000grit. Once I got up to the norax 45 I found that I could start to see patches showing up. I have seen this before on some steel that was sent to me in the past so I’m not Surprised at all. I guessed from the beginning that it was full of soft spots. Here are the pictures
This is the first pass taking off about .005
The next pass I snagged a close up shot of the sparks.
The patches and vertical bands are clearly visible in person but harder to catch on camera because it’s so damn shiny. Took it out side to get better lighting.
we then took it inside and ran it through the demagnatizer and tested it.
you can see the tests change when going from a dark to a light spot. On the tang where I had ground and tested before I got 37.5 now. Before all this, that spot measured 37rc. So I do not find any fault with my current testing and prep procedures. Here is a picture of the blade before all this grinding.
here is a quick video showing the final grind and just how polished that surface is.
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More 1084 weirdness
- Thread starter JTknives
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Someone should use this weird numbers to make combination for Lotto ticket , I can bet they are winningThe only possible logical, scientific explanation is obviously that the batch of steel is cursed.
I'm waiting for some logical explanation of what happened...looks like JT is used clay for differential hardening ...Zebras type
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They have tested EVERY blade I have ever sent them, and it even says so on their web page, they straighten (if needed) and hardness test every blade. The grind is indeed a shallow hollow grind. It obviously is....there is no other way to create that test spot (as shown in the posted photo) OTHER than a hollow grind. It’s 220 grit, BTW. If it was flat ground, the whole tang would be polished. Get your facts straight before posting nonsense.
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The only possible logical, scientific explanation is obviously that the batch of steel is cursed.
i want that as my new avatar pic lol
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They just really like you Stuart, They didn't test everyone of my blades always, sometimes they did, sometimes they didn't.
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Ha ha. I've sent over 10,000 blades to Peters in the past 12 years - welcome to fact country. They don't hardness test every blade (not even close in my case), maybe they do for you, but your knives are not "every blade," are they? They grind the area with one of these. It's not a hollow grind. Let me know if I can clear anything up for you.
10,000 blades.......................
If i was the one who heat treat them for you , after first 1000 I will do that blindfolded and no need for that HRC test anymore
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A little mini flat disc? I'mma have to try that, had no idea
Thank you so much for the update JT, and I do think you've more than proven the steel is the issue. The spots do show up so well in the polished blade, and they are right where the low Rc reading is. As Larrin asked, are you able to do a quick etch on the blade?
Larrin
Knifemaker / Craftsman / Service Provider
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Etching is a very good idea, but it was Dad's idea not mine.
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You're right Larrin - I respect both of ya'll so much in knowledge and sharing of knowledge I might get ya'll mixed up sometimes. I'm sure ya'll look alike {g}
Either you don’t know or you’re being funny. Larrin is ~5’9” and 165#, I’m 6’1 and 310# and old. My other two boys look more like me, Larrin took after my dad.
Hoss
Hoss, I've never seen photos (have seen your photo on your website) or met either of ya'll in person. my meager attempt at being funny I guess, and you can see why I didn't quit my day job to work as a comedian {g}
My Dad and I bore a strong resemblance - Looking at photos from a trip and saw an old gray haired man sitting on a bench so it must be my Dad, and what was he doing on that trip? Yep, it was me!
My Dad and I bore a strong resemblance - Looking at photos from a trip and saw an old gray haired man sitting on a bench so it must be my Dad, and what was he doing on that trip? Yep, it was me!
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There was a batch of 1084 from 5 or 6 years ago I bought a bunch of, that needed excessive normalization/thermal cycling or it had some big issues with inconsistent hardness and huge un-attractive banding though. Was fine if it was heavily forged or made into damascus, no problems would show, but if you just followed normal HT regime (i.e. normalize twice, decending thermal cycle, austenize from the usual temp), and did stock removal, it would show up. Simply re-harden, and it would go away and be completely "normal" in terms of appearance and uniform hardness. Although lots of pucker factor rehardening finish ground blades the first couple of times. It wasn't obvious until hand sanding (these were mono steel so no need to have etched them, which would have shown the issues yes), then it was clear as day. In those cases I had done cursory single point hardness tests and just gotten "lucky" where I tested. So, this could be a similar case?
That said, I'd highly recommend grinding below the final dimples after you etch, then re-check hardness and then re-etch. Would expect to see splotchy etch this time, but wouldn't be surprised at all to see this go away the second time. People highly underestimate how deep decarb can run under the wrong circumstances, and unless you're getting ground decarb free (and described as such) stock, you shouldn't assume there isn't already 20 or 30 thou decarb on each side, to which heating continued heating, is only going to exacerbate.
That said, I'd highly recommend grinding below the final dimples after you etch, then re-check hardness and then re-etch. Would expect to see splotchy etch this time, but wouldn't be surprised at all to see this go away the second time. People highly underestimate how deep decarb can run under the wrong circumstances, and unless you're getting ground decarb free (and described as such) stock, you shouldn't assume there isn't already 20 or 30 thou decarb on each side, to which heating continued heating, is only going to exacerbate.
You know what I think what happen here ,well one of the possibilities? JT has long HT oven with heat elements/coils/ only on top of oven ....looking in this numbers on blade , tip of knife/deep in oven/ HARD ...then SOFT ..then HARD ........maybe ,maybe blade was hold to short in oven so HT elements heat blade in spots /zebra type/ in right temp , while rest is still not on right temp? Bad explanation but I think it is understandably what I think ?
