Opinions needed on Magnacut.

HPD

HPD

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Quick background: I've been making knives as a hobby for a few years. I just purchased a 2x72 belt sander. Previously I was using a file jig and a 1x30. Consequently, in the past I've typically ground my bevels as much as I can pre-HT. With something like AEB-L, I've kept it pretty thick and managed to keep the warping to a minimum. With 1084 and 52100, I've keep them thin and had no problems with warping.

I've done two Magnacut blades with 1/8 stock.. The first one ended up looking like fried bacon out of the plates and I broke it trying to straighten it even though I had tempered it first. It was that warped. The second blade warped but not as bad. I had left it thicker. In fact, it was thick enough that a combination of straightening and grinding away material made a usable blade, a butt ugly but functionally excellent one. I did the standard recommended 2050 for 25 minutes and 350 temper.

Questions:

What are your opinions on the level of warping with 1/8 stock if I do my grinding post-HT?
What are your opinions on reducing my soak temperature to 2000 to avoid warping. Will that help or will it be unnecessary?
Any other tips on reducing the chance of warping?

I AM going to figure out Magnacut and it will be one of my go-to steels. I just need to figure it out.

Thanks,
S.E. Vines
 
I personally find a stress relieving step to really help with warp issues. I use a 500F ramp to 1100 and hold for 2 hours, oven cool.

Do you plate quench? I clamp blanks tight in the plates and let sit a few minutes before cryo.

For straightening are you trying to bend straight or using a peening hammer? Peening hammer would be the correct option for straighting.
 
Seedy Lot said:
I personally find a stress relieving step to really help with warp issues. I use a 500F ramp to 1100 and hold for 2 hours, oven cool.

Do you plate quench? I clamp blanks tight in the plates and let sit a few minutes before cryo.

For straightening are you trying to bend straight or using a peening hammer? Peening hammer would be the correct option for straighting.
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I do use peening and that is always the first thing I try (after tempering at least once). I also use the method where you clamp in the opposite direction and then temper. I do plate quench, but I don't have my plates set up in a vice. I might try that. Also, I have not tried stress relieving. I will definitely give that a try. Thanks for the suggestion.
 
You'll get a lot of valid opinions and options on this topic. But here's where I've settled on for MagnaCut.

I do the heat treat pre-grinding. Yup, I profile the knife, drill the holes, and pop it in the oven. I leave the blades in the quenching plates just long enough that I can touch it, but still warm. Then it goes into the LN. Larrin recommends doing this because if you wait too long, the cryo isn't as effective. However, warping is common. Then it gets tempered completely, warps and all.

I straighten with a carbide tipped hammer (I don't think a regular peening hammer is gonna work). Then I grind off the marks.

Now I finally mark the edge and begin the grinding. I start with a 36 ceramic grit belt, running fast. Then a 60 grit to get to the grind lines set and close to the right edge thickness.

Some folks have a bear of a time with hardened MagnaCut. For whatever reason, it's not an issue for me. Different abrasives are designed for different speeds and pressures. You have to find the combination of speed and pressure for the type and brand of belt you're using.
 
I’ve straightened magnacut quite easily with a carbide hammer, I use a 3/8” carbide ball. If you are using a normal hammer without carbide you will likely break every blade, if you are using carbide but it’s a sharp point or chisel that can also lead to breakage if you aren’t careful, if you are using a carbide ball on the peening hammer and still breaking blades you are likely hitting too hard or the warp is too severe due to the thin edge which could easily be fixed by leaving the blade thicker and grinding more after hardening. It helps to measure your pre ht thickness at the edge and share that info so people can help better provide advice. I typically grind my bevels entirely after hardening and find it doesn’t take any longer than grind pre ht then cleaning up post ht.
 
I don't think Magnacut is inherently prone to warping. I send mine to Peters, but I have done 8 knives in 0.093" stock, ground to about 0.020-0.025" at the edge before heat treat. They have all come back straight and only one or two had a torch mark on the spine as evidence of straightening and none had problems along the edge.
 
Sando said:
You'll get a lot of valid opinions and options on this topic. But here's where I've settled on for MagnaCut.

I do the heat treat pre-grinding. Yup, I profile the knife, drill the holes, and pop it in the oven. I leave the blades in the quenching plates just long enough that I can touch it, but still warm. Then it goes into the LN. Larrin recommends doing this because if you wait too long, the cryo isn't as effective. However, warping is common. Then it gets tempered completely, warps and all.

I straighten with a carbide tipped hammer (I don't think a regular peening hammer is gonna work). Then I grind off the marks.

Now I finally mark the edge and begin the grinding. I start with a 36 ceramic grit belt, running fast. Then a 60 grit to get to the grind lines set and close to the right edge thickness.

Some folks have a bear of a time with hardened MagnaCut. For whatever reason, it's not an issue for me. Different abrasives are designed for different speeds and pressures. You have to find the combination of speed and pressure for the type and brand of belt you're using.
Click to expand...
If you look at page 289 of Larrin's book you have a bit of time before you need to get blade into cryo.

I put the quench plates with balde still clamped between into a 5 gallon bucket of ice water for a couple minutes before cryo to bring the blank temperature down a little more.
 
HPD said:
Quick background: I've been making knives as a hobby for a few years. I just purchased a 2x72 belt sander. Previously I was using a file jig and a 1x30. Consequently, in the past I've typically ground my bevels as much as I can pre-HT. With something like AEB-L, I've kept it pretty thick and managed to keep the warping to a minimum. With 1084 and 52100, I've keep them thin and had no problems with warping.

I've done two Magnacut blades with 1/8 stock.. The first one ended up looking like fried bacon out of the plates and I broke it trying to straighten it even though I had tempered it first. It was that warped. The second blade warped but not as bad. I had left it thicker. In fact, it was thick enough that a combination of straightening and grinding away material made a usable blade, a butt ugly but functionally excellent one. I did the standard recommended 2050 for 25 minutes and 350 temper.

Questions:

What are your opinions on the level of warping with 1/8 stock if I do my grinding post-HT?
What are your opinions on reducing my soak temperature to 2000 to avoid warping. Will that help or will it be unnecessary?
Any other tips on reducing the chance of warping?

I AM going to figure out Magnacut and it will be one of my go-to steels. I just need to figure it out.

Thanks,
S.E. Vines
Click to expand...
Are you wrapping the blade in heat treating foil to prevent decarb?

Hoss
 
Seedy Lot said:
If you look at page 289 of Larrin's book you have a bit of time before you need to get blade into cryo.

I put the quench plates with balde still clamped between into a 5 gallon bucket of ice water for a couple minutes before cryo to bring the blank temperature down a little more.
Click to expand...
Joshua Fisher said:
I’ve straightened magnacut quite easily with a carbide hammer, I use a 3/8” carbide ball. If you are using a normal hammer without carbide you will likely break every blade, if you are using carbide but it’s a sharp point or chisel that can also lead to breakage if you aren’t careful, if you are using a carbide ball on the peening hammer and still breaking blades you are likely hitting too hard or the warp is too severe due to the thin edge which could easily be fixed by leaving the blade thicker and grinding more after hardening. It helps to measure your pre ht thickness at the edge and share that info so people can help better provide advice. I typically grind my bevels entirely after hardening and find it doesn’t take any longer than grind pre ht then cleaning up post ht.
Click to expand...
I think I went to .025 on the first blade. On the second one I went to .040 if I remember correctly. I will just learn to grind post-HT once I get time to set up my 2x72. I'm used to grinding way the last 20-40 thousandths with the 1x30 and have gotten pretty good at that, so I suppose the learning curve on the 2x72 won't be too bad. Thanks to all for the free advice.
 
HPD said:
I think I went to .025 on the first blade. On the second one I went to .040 if I remember correctly. I will just learn to grind post-HT once I get time to set up my 2x72. I'm used to grinding way the last 20-40 thousandths with the 1x30 and have gotten pretty good at that, so I suppose the learning curve on the 2x72 won't be too bad. Thanks to all for the free advice.
Click to expand...
I’ve done pre ht grinds on magnacut to .050-.060 and it’s been pretty stable, I still prefer grinding hardened steel but can understand on the smaller grinder wanting to do more before hardening. Making sure your grinds are extremely even on both sides also helps prevent warps if you grind pre ht.
 
I've done just a bit more than half a dozen MagnaCut blades, .110 and .125, I've done initial grinds prior to HT and had them heat treated prior to grinding. I prefer grinding post HT now. I do use a misting system that keeps the blades nice and cool. I've not had any issues with warping but JT does an amazing job on heat treating on MagnaCut. I've had him do some K-Tips at 63-64 and 62-63 and some hunting knives (the thicker ones) at 61-62.

I can certainly recommend grinding post HT, not much more difficult to grind than prior to HT with good new ceramic belts. Certainly easier to keep from warping and no chance of bacon edge.
 
Magnacut does not need any pre treatment before heat treating. We have done a ton of magnacut and yes it’s not as prone to bowing as AEBL but does like to bow more then some of the More simple CPM steels. The trend we see is if you grind the mill scale/finish off you increase the bowing risk. So generally we recommend just profiling and drilling your holes and then heat treating. And plate quenching is a must. Then after all your tempering is done then surface peen to straighten and your golden.
 
Seedy Lot said:
If you look at page 289 of Larrin's book you have a bit of time before you need to get blade into cryo.

I put the quench plates with balde still clamped between into a 5 gallon bucket of ice water for a couple minutes before cryo to bring the blank temperature down a little more.
Click to expand...
Thanks S Seedy Lot . Good info!

At the top of page he writes: "When there is a delay in time, even at room temperature,... the cold treatment becomes less effective. But later he's more specific: "When using LN there can be a delay of approximately one hour." I missed that part.

While, that comment was not steel specific, it gives me lots of room to do more experimenting. Longer in the plates might be less warpage.

BTW, this is another reason I grind bevels after HT: for us plate-guys, the whole blade is in contact with the plates and not just the spine. And it's not the spine I think about hardening, it's the edge. I'm sure the edge on pre-ground knives comes out fine. But, I'm just overly cautious. Like, I test the hardness near the edge, before I begin grinding bevels.
 
Sando said:
Thanks S Seedy Lot . Good info!

At the top of page he writes: "When there is a delay in time, even at room temperature,... the cold treatment becomes less effective. But later he's more specific: "When using LN there can be a delay of approximately one hour." I missed that part.

While, that comment was not steel specific, it gives me lots of room to do more experimenting. Longer in the plates might be less warpage.

BTW, this is another reason I grind bevels after HT: for us plate-guys, the whole blade is in contact with the plates and not just the spine. And it's not the spine I think about hardening, it's the edge. I'm sure the edge on pre-ground knives comes out fine. But, I'm just overly cautious. Like, I test the hardness near the edge, before I begin grinding bevels.
Click to expand...
I use 3/32" Magnacut and grind post heat treat as well. But you will be surprised just how fast a pre ground edge gets to black heat once pulled from an oven. It is an air hardening steel, the plates just help to keep warping down.
 
I second not grinding the mill finish off before HT. I did that on one out of 6 blades. Apart from warping, there was also terrible foil welding that had to be ground off. I did 1120 C, plates and cryo.
The other 5 came out with very little warp and no foil welding.
 
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I cold stamp my work with makers mark so it is better if I remove mill scale before heat treat. I also freehand grind and I really appreciate starting bevels preheat treat, I will grind 10dps bevels down to around 0.020 inch. With this I will experience warp if I do not run a stress relieving cycle and still occasionally experience some warp but easily fixed using the peening hammer I bought from Joshua.

I use 309 foil and never have experienced it welding itself to my blanks even when running oven temps up to 2150 F, 1176C.
 
Scaniaman said:
I second not grinding the mill finish off before HT. I did that on one out of 6 blades. Apart from warping, there was also terrible foil welding that had to be ground off. I did 1120 C, plates and cryo.
The other 5 came out with very little warp and no foil welding.
Click to expand...
I've got a 1/8" x 1.5" bar from Alpha and like all of their Magnacut offerings, it comes flat-ground. Where do you get you supply? I see NJ Steel Baron/Aldo's has unground bars. What's their track record with Magnacut? I haven't purchased anything from them since I first got interested in knife making in 2015.

When I make a knife with the Alpha bar I plan on stress relieving at 1100 or 1200 (wrapped in 309 foil even though I suspect that's not necessary at those temps, but I'm not sure so I will) for 2 hours with an oven cool. I'm shooting for 61-61.5 RHC with maximum toughness (16+ ft. lbs.). The knife will be for hiking/LIGHT batoning and kindling prep/bow drill making). I think I will drop the temp a little bit, say maybe to 2020F and temper at 350-360F. Maybe the lower Aust. temp. will help with warping? Maybe it will make no difference and I should just stick to 2050/350? There's a video of Medford talking about this (I bet he rubs some people the wrong way but I appreciate his honesty). I will definitely leave the blade in the plates a little bit longer too, but not too long as I'll be using dry ice/iso for the cold treatment. Also, making sure the foil seals aren't thicker than the knife blank so that I get good plate contact, and also grinding everything post-HT. Fingers crossed.
 
Scaniaman said:
I second not grinding the mill finish off before HT. I did that on one out of 6 blades. Apart from warping, there was also terrible foil welding that had to be ground off. I did 1120 C, plates and cryo.
The other 5 came out with very little warp and no foil welding.
Click to expand...
This....also for me. My sample was 0.1" from NJSB....also foil welded. First time I have ever had that and only on one of the 2 pieces I did. They both turned out straight though....just a pita.
 
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