Which grade of steel do I need?

[JohnFParticipant @johnf59703]

Chris, I think welding may cause you more problems than you have already, personally I would not try to heat treat to whole tool, just do the cutting end. Looking at your photo suggests that the tool is not tempered evenly as one would expect if done in a oven ? The threaded end has been much hotter then the cutting end — blue // pale straw.

I would suggest heat the cutting end to cherry red and quench in oil [not water] then degrease, polish with new emery temper to a dark straw in subdued daylight, Don't heat the actual end, heat further back and allow the colours to run up the steel. Quench in oil.

Hope this helps

John

[JasonBModerator @jasonb]

As Ramon says your primary bevel looks very long, should be about 15deg included angle which on an 8mm chisel will be about 25mm long.

The secondary bevel which is the actual cutting edge should be according to my old school exercise book 65deg included for tool steels 40deg for mild steel or 30deg for aluminium

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Mike Poole on 23/07/2022 10:20:06:

Hi Nick, you could probably pound that all day with a 14lb sledgehammer without a problem, the chisel I had in mind was about 2ft long and 1/2 diameter, it was my grandfather’s who was a plumber by trade. Faced with some concrete chiselling for some new fence posts I bought a Screwfix cheapy SDS drill/ breaker, it did the job in style and if it never comes out of it’s box again it was worth every penny. Cast steel used to be the material of choice for cold chisels and was what my apprentice made chisel was made from, CrV seems to have become popular nowadays.

Mike

Hi Mike, I can understand that the 2ft x1/2" one would bend as the dia/length ratio as JasonB mentioned earlier, makes it prone to bending with heavy blows, most good chisels are not made of round material in my experience and are very often octagonal, hexagonal and flat. I have a 11 – 1/2" x 1/2" AF hexagonal unbranded one which is pretty good, but I wouldn't slog that with a heavy hammer, but my first 18" x 1" one did get some hitting with a 14lb sledge a few times without bending. The best cold chisel that I do have is Gedore 95-200 flat one Gedore 95-200 which is made from Chrome-molybdenum-vanadium air hardening steel and it holds a really good edge and are nice to use.

Regards Nick.

[HopperParticipant @hopper]

Posted by Chris Hunter on 22/07/2022 20:21:47:

 

p.s. I know this post will raise questions about why and what for but I really don't want to get into that as it will just raise other concerns. I am certain that this is what I need there is no other option but a circular 8mm hard resilient rod

Without knowing more about what you are trying to do, all we are doing is guessing in the dark.

It's impossible to offer meaningful advice on things like tool material or even how to grind the cutting edge when we don't know what material it is trying to cut, or how thick it is, or how securely it is anchored. And why is it limited to 8mm diameter when the tool in your photo has a bend in it showing it obviously was not constrained in an 8mm hole full depth?

For instance, depending on what the job actually is, you might be better off drilling it out with a long-series 8mm drill bit.

But if you really want to stick with the current, and so far unlikely to succeed method of hammering on a very long thin tool excessively, method, I would look at something like buy a good quality 8mm cold chisel and weld it on the end of an 8mm high tensile cylinder head stud/bolt from an automotive diesel engine. I have a box of them that came I think from a Toyota 4WD engine that would be perfect for the job. You would struggle to bend one of those puppies. Or you could use an 8mm high tensile Allen-head bolt.

EDIT: Also, Google "air chisel long bit" for a selection of commercial offerings that might help. You might consider getting the air chisel gun to drive it too.

Edited By Hopper on 24/07/2022 09:26:05

Edited By Hopper on 24/07/2022 09:26:49

[Chris HunterParticipant @chrishunter13136]

Again, thanks for the replies, I know that solutionising is the interesting bit but I was asking what would be the best material for to something akin to a cold chisel, i.e.something that is going to be bit with a hammer against a hard surface and is as tough as possible.

I guess I was hoping that someone would suggest a steel grade such as EN19 or EN24 or know what things like SDS drill bits are made from. I only mentioned the 8mm to avoid a lot of replies telling me the best material is a cold chisel or some engineering steel alloy that is not available in 8mm.

As I said for this application 8mm round section is the only option.

[Ramon WilsonParticipant @ramonwilson3]

Posted by Hopper on 24/07/2022 09:09:22:

Posted by Chris Hunter on 22/07/2022 20:21:47:

p.s. I know this post will raise questions about why and what for but I really don't want to get into that as it will just raise other concerns. I am certain that this is what I need there is no other option but a circular 8mm hard resilient rod

Without knowing more about what you are trying to do, all we are doing is guessing in the dark.

Afraid so Chris – asking for help goes without question on here but not giving the full story just leads to frustration on the part of those trying to help you.

You give us more questions than the one you seek an answer to.

As I said previously what is it you are cutting with this chisel ? A hard surface could mean anything.

Unless you are doing anything illegal try us – we're here to help but not if you can't help yourself by being open with us

Tug

[Chris HunterParticipant @chrishunter13136]

Just to round this off in case anyone comes across it in future it seems that EN-31 is a good choice for my application and is used for injection moulding ejector pins

[JasonBModerator @jasonb]

EN31 is an alloyed steel with chromium that was suggested to you yesterday. let us know if you find someone selling short lengths

" Good chisels will be some form of alloyed steel probably with vandium, chromium, etc"

Edited By JasonB on 24/07/2022 19:09:26

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Chris, the thing is it's not just the steel that counts, you will need the facilities and the skill to do the correct heat treatment also and I believe you have been told the diameter to length ratio makes it all the more difficult. Even good long screwdrivers will bend using them in a chisel fashion.

Regards Nick.

[Anonymous]

EN31 is similar in composition to gauge plate, minus the tungsten. It is hardened and tempered in a similar way. Like gauge plate it is formulated for oil quenching rather than water, at least for small sections. Hardening and tempering isn't that much different to silver steel in terms of temperatures. So if silver steel isn't suitable, or can't be hardened and tempered properly, I doubt EN31 will be any better.

Andrew

[Chris Evans 6Participant @chrisevans6]

Having spent my working life in the injection mould toolmaking I think you will find ejector pins are nitrided to give a hard working area. Believe me they will bend when they seize or the press malfunctions and they hit something solid.

Core pins are available through hardened and may be more like what you need.. Look up some of the industry suppliers of standard mould parts from the likes of "Hasco" "Diemould services" (DMS)"

[HopperParticipant @hopper]

I know of two steels that would do the job. One we used for making press tool punches for piercing holes in 1/4" steel plate in 100 ton presses running at 50 strokes a minute. The other is available from the US in imperial sizes so you might have to use 5/16" instead of 8mm.

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