Spyderco Forums

Hello all,

I've been using this M398 Mule for a few months now and the edge retention is awesome but the blade chips very easily. I have been cutting every cardboard box I can get my hands on with it and it will cut them forever without dulling but was looking closely at the blade one day and realized it has bad chips in it. I would not say that I have done anything abusive that would lead to chipping like this so I was very surprised when I noticed them. I have not sharpened the blade but I have stropped it once to restore the razor sharpness. I did not notice any chipping at that time.

Best regards,
Kenny

Looks more like a burr rolled at the front…wouldn’t call them chips, and with a factory edge that hasn’t been sharpened.

A few months without sharpening I think your doing good, as that’s not that bad…

No... not rolled at all... they're all chips. Here are more pictures from both sides. Some of the chips do reflect light but it is very hard to take a picture of them without reflections.

Best regards,
Kenny

Cardboard can hide a lot of nasty little surprises, so I wouldn't be surprised if you might have hit some inclusions that contaminated the pulp.

Can you reprofile it? I would probably take it to 20 degrees per side, or at least micro bevel it. M398 did come in pretty low in toughness on knifesteelnerds blog

Thanks for posting all 3 of you. MUCH appreciate the information...

akennyd wrote: ↑

Thu Aug 24, 2023 6:05 am

Hello all,

I've been using this M398 Mule for a few months now and the edge retention is awesome but the blade chips very easily. I have been cutting every cardboard box I can get my hands on with it and it will cut them forever without dulling but was looking closely at the blade one day and realized it has bad chips in it. I would not say that I have done anything abusive that would lead to chipping like this so I was very surprised when I noticed them. I have not sharpened the blade but I have stropped it once to restore the razor sharpness. I did not notice any chipping at that time.

Best regards,
Kenny

A few points...

Firstly, I'd want to sharpen the blade at least a half dozen times before jumping to any conclusions about the steel. This is needed to try to eliminate factory processing as a potential detriment to the steel.

Secondly, this type of behavior is entirely within the realm of expected considering the carbide volume of the steel. It's also possible that there is something going on at a microscopic level of the steel/heat treat that is causing further embrittlement.

Too early to say anything definitely until you resharpen and see if the behavior changes. Get a good coarse stone and grind away all the chips and reset the edge, I'd not go anything high polish on that blade personally as there's little benefit there.

One other suggestion I'd make would be to LOWER the edge angle if possible and RAISE the apex angle with a micro bevel to at least 20 DPS. This will not entirely eliminate chipping but may minimize it through less force required in cutting.

I never got around to doing toughness testing on mine. But I did have to raise my angle to about 15dps to have the stability I needed with my mule. In controlled cut testing it did well at 12 ish dps. But in real world use it wouldn't hold up so I had to raise the angle. I don't think it's fair to judge a steel until it's seen proper amount of mileage first.

I'd be enclined to sharpen the blade fully a good number of times too. I can't say for sure but it seems like a similar thing happend to me with my 4V Goddard. I had to fully sharpen it 2 or 3 times for the steel to start behaving more "like it should".

And it might be more subtile after the next sharpening, but I suspect it will show its edge stability and toughness improve over the next sharpenings too.

Thanks for the replies!!

Cardboard having some "nasty little surprises" is a very good point!!

The suggestions on resharpening have been noted and make perfect sense to me. Maybe I have jumped the gun on my opinions!! I will resharpen, maybe at a bit of angle change and see what happens. Thanks for pointing this out!

Best Regards,
Kenny

Anyone happy with the M398 edge retention?

Larrin on M398: “...toughness ... lower than any other available stainless knife steel, including S125V...” at around 3 ft lbs. Elsewhere: "The toughness of M398 is among the lowest I have ever tested..." Has large chromium carbides.

Bolster wrote: ↑

Thu Sep 07, 2023 9:48 pm

Larrin on M398: “...toughness ... lower than any other available stainless knife steel, including S125V...” at around 3 ft lbs. Elsewhere: "The toughness of M398 is among the lowest I have ever tested..." Has large chromium carbides.

Yeah, I know Larrin sort of gave M398 the cold shoulder, but I saw a Youtube video where the guy is hacking away w his M398 of maybe 66 HRC (something really high). It was really impressive.

Honestly I think Larrin´s review affected sales of the mule. I was very eager to buy one, and I think it is ideal for skinning dear... the perfect steel for a skinner or hunting knife.

In the end Im glad it didnt sell out so quickly, I had the chance to buy one :)

I havent seen any damage to my m398 mule yet. Spent almost 3 minutes whacking an ice block yesterday and it still passed my testing standards. I think M398 lacks stability at lower edge angles so twisting laterally during use will be the culprit for most visible damage.

Steeltoez83 wrote: ↑

Mon Sep 11, 2023 11:10 am

Screenshot_20230910-202831_Gallery.jpg

I havent seen any damage to my m398 mule yet. Spent almost 3 minutes whacking an ice block yesterday and it still passed my testing standards. I think M398 lacks stability at lower edge angles so twisting laterally during use will be the culprit for most visible damage.

Outstanding! I don´t think it´s as bad as they theoretically say

alphaneuron9 wrote: ↑

Mon Sep 11, 2023 8:12 pm

Steeltoez83 wrote: ↑

Mon Sep 11, 2023 11:10 am

Screenshot_20230910-202831_Gallery.jpg

I havent seen any damage to my m398 mule yet. Spent almost 3 minutes whacking an ice block yesterday and it still passed my testing standards. I think M398 lacks stability at lower edge angles so twisting laterally during use will be the culprit for most visible damage.

Outstanding! I don´t think it´s as bad as they theoretically say

Some folks "test" toughness thru batoning and measure damage on a knife that never had enough sharpenings or appropriate geometry. The ice I use hovers around the hardness of softer woods from my research. And my own testing is to see when the apex dulls not sustain damage. Now not being able to support lower edge angles is the only negative aspect I can say about this mule. For most mundane edc tasks it's gonna be just fine. As long as your not keeping edge angles too low and twisting in cuts. That's signs knife is dull anyways. Most important steps owners should take imo is to burrow thru the first few edges and remove any fatigued steel. Gives the user the best shot at avoiding damage.