Straightening via peening

HSC /// said:
You are saying that peening doesn’t fix the warping.... but at the same time you say that you peened the side of the blade until it was quite straight.

So it does work and you are likely inducing a bend during surface grinding

I think the peening works great and it’s highly reliable and predictable and it’s been a huge benefit for me

Recently I just heat treated two thin Magna Cut kitchen knives and they came out with huge banana bends that wouldn’t straighten with shimming during tempering but straighten out just fine with peening
Click to expand...
It does straighten them while the peening remains and yes it works great... But when I grind the peening out it has a warp again. I'll double check but I think it's the same direction. I also have coolant I can use to keep everything really cool so I'll double check it's not any heat build up too.

On your kitchen knives are you leaving the peening or removing it completely to finish the knives?
 
Hubert S. said:
It could mean a lot of things, e.g., that 14c28n and AEB-L are more popular and that's why you see more posts about them...

I would still like to know what the "more expensive and at the same time much better" steel is that you had in mind when you posted that working with "cheap steel" does not pay off.
Click to expand...
I don t think that we are on same page ? If other more expensive steel wrap that easy like this **** , I m sure that knife makers should post about that problem .It is popular because it is cheap . What i was saying is this....AEB-L is cheap steel and that is fact , right ? AEB-L like to wrap like no any other steel and that is fact , right ? AEBL- don t hold edge as other more expensive steel and that is fact , right ? So why i should waste so much time with all trouble he give to HT ? Things like annealing that steel /as suggestion to do against wrap/ before HT process last hours in oven ? Same with peening , grinding after that take lot , lot of time ? That steel wrap if you just grind bevels on it ? One pass for one side , then turn other side make one pass on other side so MAYBE it would not wrap ? Are you kidding me ?? With what thickness of AEB-L should I start so at the end I have 2mm. thick knife at spine ? With 5 mm ?
Anyway this is just my observation from reading here about that Aeb-l .And from what I read here my choice of stainless steel would be S30V , if I ever want to use stainless for knife .
 
Last edited:
REK Knives said:
It does straighten them while the peening remains and yes it works great... But when I grind the peening out it has a warp again. I'll double check but I think it's the same direction. I also have coolant I can use to keep everything really cool so I'll double check it's not any heat build up too.

On your kitchen knives are you leaving the peening or removing it completely to finish the knives?
Click to expand...
I Remove the peen marks by grinding
 
i make mine from a hardened profile with the 45 degree starts on the edge. i got sick of the warps and doing my tapered tangs twice, even though the company "straightened" them after heat treat. peters.
 
Most steels grow when hardened and shrink back a little when tempered but with a net growth. Any decarb at the surface will not grow at the same rate as the center causing stress. Uneven grinding and internal stress also cause warping.

If you ever get a blade that comes out straight, consider yourself lucky. We spend a lot of time making things straight and keeping them straight.

Forging blades adds a whole other set of things that causes warping.

Stay strong 💪.

Hoss
 
DevinT said:
We spend a lot of time making things straight and keeping them straight.

Hoss
Click to expand...
Awhile back, I was told here that straightening steel is the hardest easy thing that I would learn to do. I didn't believe it then but I do now. Straightening, easy. Keeping things straight? Well...
 
It's just one of those things. I was surprised how many quality industrial knifes (I am not talking Henkels but 1 or 2 price ranges up) have a kick to one side. Once you take it in, you see it as a part of the process, especially with large kitchen knifes (in stainless).
 
Scaniaman said:
You have a point. Even with the more expensive and maybe better steel in my shop (RWL-34) I have to do quite a bit of straightening though, cryo warps that steel too.
I am only doing this for a hobby, so time isn't as "valuable " for me as forsome others.
Straightening is mostly a time consuming problem with long chef knives though. And 14c28n is just an excellent excellent steel. I am amazed at how well it performs at 61 Hrc.

We should ask PEU PEU about this, he has a significant production volume and still uses a lot of 14c28n.
Click to expand...

Hi Guys, yes, I bought 200kg+ of 14C28N in 2mm and yes, it warps, you have to deal and be proactive in every step of the process to minimize warpage, but it happens way more often than desired.
I have a cooling press next to the oven, and I do pre process the whole batch with a 850C heat, room temp cooling, reheat at 650C and slow furnace cool to improve my chances of getting them straight.
Peening is part of the work, and I do my best to leave the blades straight as arrows. Most of the times I succeed, sometimes at the expense of leaving the peening marks in the final blade. I used to dislike this finish, but its slowly growing on me, so time will tell if I leave them as a feature.
Its a great steel to work and make knives with.
A colleague here in Argentina told me once that bead blasting has the same effect as peening, but I can't test this because I don't have a beadblasting setup. You guys may want to test this and report back.


Pablo
 
Watch this video from 4.55 , they use ordinary hammer with ball head .Steel is hardened ? Ball shaped head can t leave mark on that steel ?
 
Scaniaman said:
Would be nice with more info on that hammer. I can't make it out really. Interesting!
Click to expand...

What i can see on that video it is big radius ?
try to google hammer with round head come out a lot and different shape .
Maybe something like this would work
CTmbH22.jpg
 
Keep in mind that exact zwilling knife is only hardened to 58-60, and they straighten before grinding full flat grinds, you can do the exact same with a carbide hammer with more fine control then do full flat grinds and all peening marks disappear. The key is to still grind evenly after peening, if you try to just remove material from one side to remove marks you’ll most likely warp the steel just due to uneven grinding. I can pre grind aebl and oil quench with no plates and fix any warps in 30-60 seconds after tempering then grind evenly on both sides and it stays straight the whole time. On the other side of that I make some nakiris from 1/16” stock and do a chisel grind and I straighten 3 times as I’m grinding and often will pre bend the blade to account for movement during grinding since I’m only processing one side.
 
Natlek said:
Watch this video from 4.55 , they use ordinary hammer with ball head .Steel is hardened ? Ball shaped head can t leave mark on that steel ?
Click to expand...

If you slow the video down to 1/4 speed, you can see little marks on the blade when the hammer strikes, but they don't look like divots. The narrator mentions they check them after the blades are annealed twice. Maybe the grid pattern on the blade helps hide the strikes before final grinding? Interesting to see the process. A ton of engineering involved.
 
Hi folks, here in Brazil its very common straightening blades with this special hammer.
We use after quench and temper, but during the grinding process sometimes the blade warp again.
You can use the hammer for 1 or 2 times again, but if you do many times the blade will crack, specially near the point.
So when it happens i generally grind a little bit each side to keep almost the same amount of material and heat.
About the hammer, i made mine with an old piece of round car spring, with a point radius about 4 mm and quench this point.
Reaaally simple and effective! Sorry for any english mistakes, im avoiding use the translator!!

Regrads!
 
You must log in or register to reply here.
Back
Top