Author Topic: Extremely hard steel - CPM REX 121  (Read 2912 times)

Offline Sharpco

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Extremely hard steel - CPM REX 121
« on: November 11, 2018, 11:15:05 am »
Do you know what is the most difficult steel for sharpening? Maybe this is it.

http://zknives.com/knives/steels/cpm_rex_121.shtml

My customer said it's even much harder than ZDP-189 and asked me if I could sharpen this steel. I think my CBN wheels can grind it. But I don't think my leather honing wheel & PA-70 can hone it.

Has anyone sharpened this steel with Tormek? Do you think plenty of PA-70 can be solution?

Offline kwakster

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Re: Extremely hard steel - CPM REX 121
« Reply #1 on: November 11, 2018, 04:19:51 pm »
Haven't sharpened CPM REX121 steel yet, but your CBN will certainly grind it as it is much harder than both the steel matrix as well as all it's alloying elements.
For deburring however i would definitely also use fine CBN (or diamond) compounds to cut through the large amount of vanadium carbides, which will provide for the best possible edge that will also last the longest.
PA-70 being aluminium oxide is literally unable to cut through vanadium carbides.

Offline Ken S

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Re: Extremely hard steel - CPM REX 121
« Reply #2 on: November 11, 2018, 04:48:51 pm »
Good reply, Kwakster.

We should mention that PA-70 was not designed for steel this hard.

Ken

Offline Jan

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Re: Extremely hard steel - CPM REX 121
« Reply #3 on: November 11, 2018, 05:17:33 pm »
Good reply, Kwakster and Ken.  :)

The attached graph shows, that aluminium oxide is harder than tungsten carbide but less hard than vanadium carbides.

Jan
« Last Edit: November 11, 2018, 05:20:07 pm by Jan »

Offline Sharpco

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Re: Extremely hard steel - CPM REX 121
« Reply #4 on: November 12, 2018, 08:29:33 am »
Thank you everyone.

Offline Fernando

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Re: Extremely hard steel - CPM REX 121
« Reply #5 on: November 16, 2018, 10:09:02 pm »
Good reply, Kwakster and Ken.  :)

The attached graph shows, that aluminium oxide is harder than tungsten carbide but less hard than vanadium carbides.

Jan

remain with the doubt of where the carborundum is, I know that it is above the aluminum oxide but I do not know if it is harder than the vanadium carbide

Offline kwakster

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Re: Extremely hard steel - CPM REX 121
« Reply #6 on: November 17, 2018, 11:24:38 am »
Carborundum = Silicon Carbide


Offline Fernando

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Re: Extremely hard steel - CPM REX 121
« Reply #7 on: November 19, 2018, 05:51:11 pm »
Carborundum = Silicon Carbide



Good information, thanks for sharing

Offline Sharpco

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Re: Extremely hard steel - CPM REX 121
« Reply #8 on: December 16, 2018, 12:47:04 am »
https://youtu.be/o2FHwnTH_sE

He honed the REX 121 steel with the PA-70.