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I was going to make some videos of knives at different sharpnesses to show how I judge sharpness. On forums it's hard to "see" what someone means when they talk ab out some things. But I found this out and decided to do a video on just the edge retention of the M4 on the GB. This is one of my first videos so please forgive the darkness or poor quality.
Thanks for the great video Jack. Now I see why my Gayle Bradley doesn't seem to ever get dull. I've cut a considerable amount of cardboard boxes up and other than staining the blade, the knife never seems to get less sharp by any measurable amount. I noticed over a year ago that most of the top competitors in the cutting competitions switched over to M4 and stopped using D4 and some of the other tool steels that had been use by top competitors for a couple of years.
In Oct 2013, I happened to be in Sevierville, TN at Smokey Mtn, Knife Works one Saturday morning and witnessed a cutting demonstration put on by the guy that placed 2nd in the 2013, world championship. He was using an M4 blade (he made his own blade and the blades for other competitors). He told me that prior to the switch to M4, he had to re-sharpen/touch up his competition blade after each competition. After switching to M4 he only re-sharpens once mid-way thru the season. Anyway, that got me interested in finding a knife with an M4 blade. I thought CPM S3V was good, but I have to say M4 is even better from an edge retention angle---not sure if it is as tough as S3V though? I notice my M4 Bradley's blade seems to get stained up worse than some of the super stainless blades when slicing lots of cardboard, but a little elbow grease with some SemiChrome polish seems to return it to new looking condition. Again, thanks for the video. Wes
I forced a patina on my GB blade the other day. Patina (which is good corrosion) is supposed to help prevent bad corrosion (rust). That may help with the staining but your blade will be much darker. Tuf-Glide is great for corrosion control. In fact I used Tuf-Glide on my GB when I first got it. I tried to force a patina on it then but was unable to. The Tuf-glide and cloth made it impossible to force a patina which is a form of corrosion as I understand it. If Tuf-glide makes it hard to intentionally cause corrosion, I feel pretty safe about it protecting against rust.
I should have posted a couple of other videos I did right after I made the GB one on edge retention. They were a Cold Steel Mini-lawman and an Opinel with a carbon blade. They did ok I guess but they got dull MUCH MUCH sooner than the M4 did. I'll try to post them just for comparison.
Cold Steel mini-lawman with AUS-8A blade steel and Opinel w/carbon blade videos for comparison to the CPM-M4.
I think CPM-M4 may be the best blade steel I've used. Stays sharp and is easy to sharpen. Another blade steel that stays sharp a long time is ZDP-189 but it can be a bear to sharpen. For that steel (HRc around 64-66) you need really good, clean stones. Even then it take a while because less steel is removed per stroke. M4 is MUCH easier to sharpen and takes a razor edge that is hard to beat. Probably why it is used in competition. I can't think of a better recommendation for a blade steel than it being chosen for competition. The only other good recommendation might be if someone makes a video of scraping a really nice edge on a really great knife across a metal work bench he made. LOL I don't think I need to share how I "felt" as I scraped the edge along the metal. :)