CPM REX 45 | Edge Performance

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Deadboxhero
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CPM REX 45 | Edge Performance

Postby Deadboxhero » Sun Aug 12, 2018 12:16 am

I want to share my experience with Rex 45 so far

I feel the best way is to compare it to CPM M4 which is a steel we are all familiar with and gets compared often to Hap40/Rex 45

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First testing is sharpening to a high sharpeness freehand on benchstones and comparing small differences in the edge quality and other characteristics.



Using a 1000 grit CBN waterstone the factory bevel scratches where removed and the knives where fully Apexed and deburred off the stone.

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Some quick notes on testing.

-Bigger burrs were made then I usually do in order to clean out the deep factory grind lines.

-1000 grit was chosen since it highlights the best comprise between toothy bite and polished precision.

-both blades were new and unsharpened by me before I tested.



Before sharpening I noticed the factory edge on Rex 45 had less aggression at the edge then the M4. It was Sharp but had less bite when gently sliding my finger pads down the edge.

Rex45 grinds very easy on the stones and wants to polish well. The M4 was also good in this regard and noticed the M4 was softer because the stone had more "grip" on the bevel then the rex45. I could feel more cutting on the M4.

*Rex45
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*M4
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Both had a stubborn burr that had to be feathered off on a worn scotchbrite pad after being weakened and reduced on the CBN stone. For M4 this is common if you create a larger burr (of course the burr isn't truely stubborn like 8cr13mov but it's noticable when compared to the top steels) as for Rex 45 I'll need more Sharpening on REX 45 to confirm if this is the norm since it was the first sharpening from the factory which always has a little overheated metal to remove by hand Sharpening and because I made a larger burr then normal. Neither of these steels deburr as good as Cruwear.

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The edges were both sharp and crisp off the stone, the REX 45 was noticably less aggressive. It took a very keen edge but had less bite compared to the M4. This tells me that more of the carbides in the REX 45 are finer then M4 and used to promote the higher hardness by strengthening the grains of the matrix.
However in M4, I feel its more aggressive due to larger carbides with more volume just hanging out and promoting more wear resistance and edge aggression over stability and keeness but we'll have to test more to see.

Both edges were treetoping sharp and would catch free hanging hairs immediately after 1um diamond stroping.
The M4 had more "grab" yet the REX 45 seemed keener.



At 0.5 um diamond that magic happened for Rex45, feathered the hair like a boss and took a nice polish at the bevel from the strop.

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The M4 could not feather after 0.5um the M4 was just too aggressive and kepted popping the hairs rather then curling it into a ribbon desipte going back several times.

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M4 needed those carbides smoothed out more so I jumped to 0.25um diamond to feather.

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Rex 45 at 0.25um very very keen, I was able to whittle a hair into a little Christmas tree.

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So far, I'd say people will enjoy the properties of Rex 45, while M4 prefers a more toothy finish Rex 45 will prefer the opposite which is unique amongst Crucible steels let alone US steels. It's interesting to a US steel closer to the properties of a japanese steel which have more of a bias toward Polished edges.

I'm going to do a rope cut test next when I get time, before I got to try the knives I was guessing Rex45 would out cut M4 on rope due to the chemistry and hardness. However based on what I'm seeing off the stones I don't think Rex 45 has the aggression to smoke M4 with a toothier edge on manilla rope. We'll see what happens.

After that it will be interesting to test the edge stability and toughness with more controlled destructive edge testing.
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The Mastiff
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Re: CPM REX 45 | Edge Performance

Postby The Mastiff » Sun Aug 12, 2018 12:46 am

Thanks for taking the time to write up your findings so far. I haven't had mine long enough to even get it sharpened yet . It's funny you are comparing it to M4. I had went to my knife box earlier today to get my Gayle Bradley to do something similar ( don't have a M4 P2). My new P2 came very sharp ( robot sharpening?) but I always end up tuning the edge for my needs. Reading this has me looking forward to getting into mine. :)

Joe

Deadboxhero
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Re: CPM REX 45 | Edge Performance

Postby Deadboxhero » Sun Aug 12, 2018 1:01 am

Thanks Joe, I think you'll like it alot, the edge comes up like 3v but a little keener
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Deadboxhero
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Re: CPM REX 45 | Edge Performance

Postby Deadboxhero » Sun Aug 12, 2018 1:24 am

A note on the hardness,
@frankie_blades on Instagram who does amazing custom work on Spydercos did a hardness test with his Ames portable Rockwell tester and got 64 HRC he didn't do mutiple tests to average but he did calibrate his tester with the testing block before testing. For comparison he got 61.5 HRC on Spydercos M4.

I'd be curious to see averaging with more tests on the blade but he has given us an excellent data point.

Check out his custom work on Instagram, very cool. The copperwash delicas look rad

Image



Hardness isn't everything and it will be interesting to see how these para 3 edges hold up to more edge abusive testing.
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Triple B Handmade Knives

Para3
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Re: CPM REX 45 | Edge Performance

Postby Para3 » Sun Aug 12, 2018 1:46 am

Deadboxhero, Thanks for the feedback on the Rex 45, I've been waiting to hear what others thought about it. Looking forward to hear on your performance testing.
Native5-S110V, PM2-S30V, PM2-Rex 45, PM2-52100, PM2-S110V, PM2-S35VN, Para3-S30V, Para3-S110V, Para3-M4, Para3-BD1N, GB2, Dragonfly, Manix2-S30V, UK Pen Knife-S110V, Delica4, Para3-Rex 45, Para3-52100, Manix2-S110V, Stretch 2-ZDP-189 G10, Stretch 2 FRN-VG10.

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Re: CPM REX 45 | Edge Performance

Postby AlexRus » Sun Aug 12, 2018 5:08 am

Thank you for sharing!

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abbazaba
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Re: CPM REX 45 | Edge Performance

Postby abbazaba » Sun Aug 12, 2018 5:56 am

I was eagerly waiting for this thread, thanks for posting!

Glad you picked some recent M4 to compare it to, which has been probably my favorite steel to use. Looking forward to seeing more opinions/data on Rex 45.

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Re: CPM REX 45 | Edge Performance

Postby Woodpuppy » Sun Aug 12, 2018 6:24 am

Thank you! I knew nothing about rex45. Now it seems I should have bought one!!
:spyder: My other blade is a Kelly Perfect :spyder:

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Re: CPM REX 45 | Edge Performance

Postby The Meat man » Sun Aug 12, 2018 6:32 am

Thanks for sharing your experience Shawn. Good insights here.
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"What is a man profited, if he shall gain the whole world, and lose his own soul?"

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Forest Green
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Re: CPM REX 45 | Edge Performance

Postby Forest Green » Sun Aug 12, 2018 8:14 am

I was wondering how others were liking Rex 45. Thanks Deadboxhero! I was surprised how much more I enjoy Rex 45's edge compared to the Hap40 Lum Chinese Folder, but then it seems all the Para 2's & 3's edges are my favs (Maxamet, Cruware, S90V, M390). Maybe blade geometry?

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Re: CPM REX 45 | Edge Performance

Postby FK » Sun Aug 12, 2018 8:19 am

Thanks for posting Shawn, excellent discussion.
Awaiting your further observations.

Regards,
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blendergasket
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Re: CPM REX 45 | Edge Performance

Postby blendergasket » Sun Aug 12, 2018 9:27 am

Deadboxhero wrote:
Sun Aug 12, 2018 12:16 am
Both had a stubborn burr that had to be feathered off on a worn scotchbrite pad after being weakened and reduced on the CBN stone.
I'm a very novice freehand sharpener (got a dc4 from massdrop a couple weeks ago and a worksharp field sharpener just came in the mail yesterday) and have been having issues with burr removal on my esee.

Can you please explain how you do the above? Also, I love your videos. They've been very helpful for me. I would love to see a video on different methods for removing a stubborn burr.

Thanks!

BTW that steel looks awesome and your Christmas tree is very inspirational.

Deadboxhero
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Re: CPM REX 45 | Edge Performance

Postby Deadboxhero » Sun Aug 12, 2018 9:50 am

Burr removal quick guide

Make the smallest burr possible on both sides to confirm that the bevel is set and the edge is fully Apexed under the burr. I weaken and reduce burr with edge trailing passes (some do edge leading, no biggie) alternating sides with zero pressure. When the burr is reduced or weakened enough and straightened out you can dust it off on worn scotchbrite, cloth, towels, draw through cork, draw through wood, or power stroping. I've met alot of Sharpeners and they each have preference, whatever works.

You can't use those "cheater" methods though on a strong burr so reducing and weakening on the stone is the most crucial l. This is a big mistake I see newer Sharpeners doing. They go through the sematics without adjusting the process to what is happening and results in not getting good effect.

There are no numbers or specific amounts of passes. It's done to effect and based off of feel and experience. Just know that not hitting the same angles kills your edge so use sharpie to see where your hitting on the bevel and adjust accordingly.
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blendergasket
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Re: CPM REX 45 | Edge Performance

Postby blendergasket » Sun Aug 12, 2018 11:37 am

Thank you very much for the thorough and helpful answer! I'm gonna get one of those sponges. I'll also use the sharpie more. I think that's going to be key to keeping a consistent angle across the whole process. I'm used to the knee where I use it at the start and then trust the system from there on out. I definitely am looking forward to building freehand skills. Thanks again!

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Re: CPM REX 45 | Edge Performance

Postby wrdwrght » Sun Aug 12, 2018 12:04 pm

The things we can learn here. Thanks, Shawn.

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Re: CPM REX 45 | Edge Performance

Postby Dudemac333 » Sun Aug 12, 2018 12:08 pm

Nice writeup! Look forward to getting mine on the sharpener.

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Re: CPM REX 45 | Edge Performance

Postby Bloke » Mon Aug 13, 2018 1:31 am

Thanks for sharing Shawn! :cool:
A day without laughter is a day wasted. ~ Charlie Chaplin

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Bloke
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Re: CPM REX 45 | Edge Performance

Postby Bloke » Mon Aug 13, 2018 1:32 am

Whoops! :o
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ejames13
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Re: CPM REX 45 | Edge Performance

Postby ejames13 » Mon Aug 13, 2018 9:59 am

Thanks for that analysis and testing!

Do you have a Cruwear blade you could test REX 45 against? I would really like to see how the two compare.

Deadboxhero
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Re: CPM REX 45 | Edge Performance

Postby Deadboxhero » Mon Aug 13, 2018 12:52 pm

ejames13 wrote:
Mon Aug 13, 2018 9:59 am
Thanks for that analysis and testing!

Do you have a Cruwear blade you could test REX 45 against? I would really like to see how the two compare.
Yes, however I chose M4 because I felt the chemistry was closer and people have a better feel for how M4 behaves.

I really like the Para 3, it's very exciting that Spyderco has made it a flagship model with a huge variety of steels just like the PM2. I'll just keep building up a collection of para 3 for testing steels. Also it's just my favorite model, especially with a deep carry clip.

More testing when I get time.

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Big Brown Bear
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