In need of MagnaCut grinding advice

M

MM52100

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Dec 29, 2020
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18
When making a standard chef knife I can get 2ish maybe 3 AEB-L or 52100 knife’s out of a 2x72 36 grit Cubitron 984F belts. All grinding post HT. I just did the same knife out of MagnaCut and I went through 3 36 grit belts and an 80 grit getting it to near final geometry.

I know the belts are on their way out when the blade starts to get small flats. That is, they wouldn’t grind a full flat on the blade. It would take small bites, regardless of pressure. Put on a new belt and they would grind the whole blade again for a while.

Any recommendations for belts, procedure, etc for grinding a MagnaCut blade? I would like to continue to use the steel but what I’m doing seems inefficient.

Thanks!
 
I’ve ground a decent bit of magnacut at this point. I’m using vsm 880 or 885 belts and tend to prefer 50 grit over 36. I do all of my grinding post ht from full thickness and use a mister on full blast to keep everything cool. I primarily work with nitro-v and magnacut for stainless steels and expect about double the abrasive cost for magnacut, both steels I shoot for 62-63rc. Magnacut other than just being more abrasion resistant to start with also seems to clump and clog belts while grinding so I will use a rubber belt eraser frequently to clean the belt and this helps me get a bit more life from a belt. If you are freehand grinding it could also be a case of using a belt that you won’t be able to get the best performance out of, the 3m cubitron belts need high speed and really heavy pressure to break down and keep cutting. They are designed for automated grinding where a robot can put as much pressure as needed. I’ve never had good results from those lines of belts for freehand work. I’d try the vsm belts, you’ll likely go through a similar number of belts but your belt cost will be less than half what the 3m cubitron belts run.
 
Not sure I can help, never used MC, yet....
But I do grind Very Hard high alloy steels.

Are you free hand grinding with light pressure?
Maybe you are glazing your belts.

High belt speed, heavy pressure, light passes, wet coolant

Edit.... I also like 50 better than 36.

Agree with Josh, he beat my posting... ;)
 
Also maybe try a 50 grit belt, again for freehand work I find it’s harder to get enough pressure on the larger 36 grit grains to keep them fracturing and sharp but a 50 grit belt seems to wear much better for me. I save 36 grit belts for use on a surface grinding attachment.
 
for me it's VSM XK870 40 grit. low speed. a good value belt
use of a Desmond beltabrasive cleaner
once or twice touch up of the belt (as it starts to wear down) with a diamond dressing tool
also you can try splitting the belt when it gets dull to a 1" wide, might sound ridiculous but give it a try.

When I started with Z wear and Magnacut, I was like you, 3 belts etc.
Now I can grind either wear resistant steel in one 40 grit and then use that belt for other simpler steels.
as the bevel and edge is close to getting thin, I switch to a new belt which cuts sharper and cooler.

But the biggest efficiency improvement is a surface grinder attachment.
With the SGA I can (reasonably) quickly and accurately grind in the distal taper which greatly relieves the bevel grinding.


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I use the VSM 890 or 885 in 36 grit, but it sounds like I need to try a 50! I run the belts a little slower too, not always full speed. I run Magnacut at 64 HRC and it is much more wear resistant than AEB-L or 52100 by far, but not quite as bad as CPM 20CV or S90V post HT. When I grind Magnacut, S90V or CPM 20CV post HT and then go to another steel like 52100, 80crv2, Nitro V, etc post HT, I think I forgot to harden the blade at first!
 
I grind down to roughly 0.05" pre heat treatment on pretty much all my blades. It provides for much longer belt life for me and I have plenty of room to correct little warps.

I use VSM XK870's and start with 50 grit for the pre heat treatment grind. I can get a couple of blades rough ground out of one belt. Post heat treat I can start with 60 grit which are a fair bit cheaper than the 50's. Then go to 80 and then 120 for final bevel grinding. I then use AO belts 120, 220 and 400 for belt finishing.
 
I’ve done 2 magnacut chef knives (64 HRC) and I will say you will certainly go through more belts than with AEB-L or 52100. However those belts aren’t shot they will still cut lower carbide steels they just loos their cutting speed due to the higher carbide content of Magnacut. I typically pregrind some before heat treat to save time grinding. After heat treat it’s a fresh belt or mostly fresh belt to finish the primary grind. Then I use a 2 fresh belts one for each side of the knife to grind the distal taper.

It’s worth adding I’ve done 2 CPM-154 63-64 hrc chef knives that also took 3 belts each.
 
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Awesome feedback, thanks everyone. I'll order some VSM belts, especially 50 grit, and try your methods. Much appreciated!
 
I've had the same experience as far as 40 grit belts of the same spec staying sharp longer than 36 / 24 grit when grinding without a lot of pressure goes

Btw cubitron 784f are also a good option, you can definitely feel in the prolonged that they are made for low pressure applications as opposed to the other cubitrons I used which felt rounded over after half of a knife (don't remember the number but it started with a 9)
 
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