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EN42J heat treatment

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Robin Graham24/06/2020 21:58:37
755 forum posts
186 photos

I've been thinking about using spring steel for knife blades, but I don't know much about the stuff. My local ME supplier stocks EN42J , but searches haven't revealed anything better than 'consult your heat treament specialist'. Has anyone here worked with it?


Oily Rag25/06/2020 08:45:28
123 forum posts
57 photos

Yes - EN42 grades are generally considered nitriding steels. That is probably why the searches state 'consult your HT specialist' as there are several techniques for nitriding and not all HT specialists can handle these processes. For instance, there is the oldest but rarer nowadays treatment which employs ammonia atmosphere system where the component is placed in an ammonia atmosphere at around 800C for between 24 and 36 hours to absorb the Nitrogen, there is a process which uses a Carbon/Nitrogen rich soak, and various other variants such as TCN. Due to the energy costs this is not a cheap process or a home workshop capability. It will probably carbon harden or oil quench but not as favourable as other steel grades.

The steel is used in crankshafts and gears where extreme hardness is required - nitriding will impart a surface hardness of typically 900 VHN yet allow a core toughness which gives components immense fatigue resistance.

Edited with additional points and spelling mistkaes!

Edited By Oily Rag on 25/06/2020 08:49:34

Edited By Oily Rag on 25/06/2020 08:51:29

Circlip25/06/2020 09:55:41
1180 forum posts

Don't know about todays materials but EN42J was the main material used for Circlips. Basically they were passed through a gas furnace heated to red and then dropped into a "Low temperature" salt bath to quench, barrelled to clean and then tempered to "Dark blue". Can't remember the various temperatures (It was sixty years ago) but nearly sure we were "Austempering"

Regards Ian.

JohnF25/06/2020 10:01:50
1013 forum posts
143 photos

Robin, I have no experience of EN42 but use EN45 & 47 regularly for springs and the carbon content in EN42 is sufficient for “normal” hardening, I would suggest heat to 850 C and quench in oil then temper to desired hardness, for knives I would suggest 280 C but you may have to experiment. This would be far too hard for a spring ! You need to temper to 340/350 C for Springs

Look at **LINK** for some info

There a couple of knife makers close to me, one uses files to produce unique products the other uses tool steel, aka gauge plate. Lots of info on the web if you dig around


Edit spelling & typo errors 

Edited By JohnF on 25/06/2020 10:03:55

Tony Pratt 125/06/2020 10:15:09
1195 forum posts
5 photos

I would have thought gauge plate [O1steel] would be the 'go to' material for knives. Easy to obtain & h/treat


Plasma25/06/2020 17:13:15
440 forum posts
53 photos

I guess it depends on the type of knife and what you want it to do and look like.

I make blades and back springs from 01 tool steel, it polishes up beautifully but obviously rust is a problem if you want to use the knife wet. I have bead blasted some blades and got a slightly more resilient finish for a work knife.

Hardening has always seemed a dark art for anything more exotic than tool steel and beyond my home made knife skills.

I believe that most of our Bowie blades were made of EN 42 and were hardened by a specialist heat treatment firm in Sheffield. Again not stainless but just as good looking as long as they are cared for properly.


David George 126/06/2020 12:16:56
1305 forum posts
447 photos

I have some CSM420 steel it is used for toolmaking as it is a type of stainless steel and a few blokes made knives from it. It holds an edge and polishes up great.


David George 126/06/2020 19:42:04
1305 forum posts
447 photos

Robin I have sent you a message on this site at top of page.


Robin Graham01/07/2020 23:54:34
755 forum posts
186 photos

Thanks for replies, and apologies for not following up on this sooner. I was struck down by some sort of bug - not Covid the Dr says - which jellified what remains of my brain.Seems to be recrystallising a bit now though.

I've made some blades from O1, and they are OK, but quite brittle - fine for plane irons which are supported close to the edge, but not so good for kitchen knives. The reason I was thinking about spring steel is that I'd seen stuff about people in '3rd world' countries making functional knives from Landrover springs etc, and thought I'd like to try something like that. But I haven't got a Landrover to take the springs from.

Especial thanks to David George for offering some 420 stainless for me to work with - I couldn't make use of it because it was round bar, but the offer was much appreciated.


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