Hi

Assuming I have a piece of mild steel plate and want to put a sharp edge on 
it, how do I go about it?

The sharp edge isn't a problem, how do I harden the steel to keep it sharp?

Heat it up & plunge it in oil/water etc???  What colour  - red hot, white 
hot?

Dave

On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
 wrote:


>Hi
>
>Assuming I have a piece of mild steel plate and want to put a sharp edge on 
>it, how do I go about it?
>
>The sharp edge isn't a problem, how do I harden the steel to keep it sharp?
>
>Heat it up & plunge it in oil/water etc???  What colour  - red hot, white 
>hot?
>


Way OTT!

You are taking me back to metalwork lessons 40+  years ago.

The colours I recall refer not to incandescence but to the colour of
the oxide film on the surface of the workpiece.

However looky here: http://web.cetlink.net/~farrier/glossary.html

"HARDEN: To render a given piece of steel to its hardest possible
condition. This is accomplished by heating it to cherry red (or until
a magnet will no longer stick to it), then cooling it very quickly,
usually by quenching in liquid." 

Grind it sharp afterwards.

HTH

DG

"david lang"  wrote in message
news:7irQe.57312$Il.46527@fe2.news.blueyonder.co.uk...

> Hi
>
> Assuming I have a piece of mild steel plate and want to put a sharp edge
on
> it, how do I go about it?
>
> The sharp edge isn't a problem, how do I harden the steel to keep it
sharp?
>
> Heat it up & plunge it in oil/water etc???  What colour  - red hot, white
> hot?
>
> Dave


Normally you cannot harden mild steel, you require a high carbon steel, but
a quick search on google "harden mild steel" does show a 'super quench'
method.
The way I have done it in the past is to use Kasenit compound and follow the
instructions on the tin.

Regards Jeff

On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
 wrote:


>Hi
>
>Assuming I have a piece of mild steel plate and want to put a sharp edge on 
>it, how do I go about it?
>
>The sharp edge isn't a problem, how do I harden the steel to keep it sharp?
>
>Heat it up & plunge it in oil/water etc???  What colour  - red hot, white 
>hot?
>
>Dave
>


When I was at school we used some hardeing compound that I seem to
remeber you dipped the hot metal into. THis was called by our teacher
case hardeing.

Rick

On Mon, 29 Aug 2005 07:44:15 GMT, Rick  wrote:

| On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
|  wrote:
| 
| >Hi
| >
| >Assuming I have a piece of mild steel plate and want to put a sharp edge on 
| >it, how do I go about it?
| >
| >The sharp edge isn't a problem, how do I harden the steel to keep it sharp?
| >
| >Heat it up & plunge it in oil/water etc???  What colour  - red hot, white 
| >hot?
| >
| >Dave
| >
| 
| When I was at school we used some hardeing compound that I seem to
| remeber you dipped the hot metal into. THis was called by our teacher
| case hardeing.

Case hardening is a tricky process, IMO best avoided.   
Get a bit of better steel.

-- 
Dave Fawthrop <dave hyphenologist co uk> 
"Intelligent Design?" my knees say *not*.
"Intelligent Design?" my back says *not*.

On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
 wrote:


>Assuming I have a piece of mild steel plate and want to put a sharp edge on 
>it, how do I go about it?


You can't harden mild steel.  It won't harden on its own, and you'll
have a hard job finding Kasenit these days. I suggest you search out the
rec.knives FAQs, which have a great deal of information.

The _best_ steel to use for this might be O-1, which is an oil-hardening
steel available from good engineerng suppliers. It's surface ground
already and is the standard workshop material for making hardened jigs
etc. OTOH, not exactly cheap (but not too bad).

The _cheapest_ material for big stuff is van leaf spring from a scrappy.
This is probably a bit thick though.

The _easiest_ material may be old kitchen knife blades, drum lawnmower
blades, woodworking chisels, or general scrap steel that you know was
originally intended to be hardened.

The other way is to hard-surface the steel by running a good bead of MIG
weld along the edge, then working on that. Lots of people hereabouts
have little benchwork equipment, but do have welders.

Harden it by heating to a moderate red on the kitchen cooker, then oil
quenching. Old motor oil in a tin box with a lid - yes it will light,
just shut the lid down and leave it to get on with things.

A more accurate temperature gauge is by heating to just above the "Curie
point".  Fasten a magnet to a bit of coathanger wire and heat the steel
until it stops being magnetic. Then quench.

Tempering is a much harder task and needs some knowledge of what you're
using it for. If it mustn't be brittle, then temper it. If it needs to
be sharp rather than strong and your hardening is a little dubious
anyway, then don't try it.

To temper it, let it cool and then polish the surface shiny with some
emery or wet-and-dry.  Then heat it gently and watche for the oxide
colours forming. Yellowish brown for sharp stuff, blue for anything
you're likely to break. Then quench in water.

Accurate heat treatment is of course rather more complex than all this.


-- 
 Cats have nine lives, which is why they rarely post to Usenet.

"Dave Fawthrop"  wrote in message
news:gef5h15jm8djb8jcii9pn1d167co10t1om@4ax.com...

> On Mon, 29 Aug 2005 07:44:15 GMT, Rick  wrote:
>
> | On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
> |  wrote:
> |
> | >Hi
> | >
> | >Assuming I have a piece of mild steel plate and want to put a sharp
edge on
> | >it, how do I go about it?
> | >
> | >The sharp edge isn't a problem, how do I harden the steel to keep it
sharp?
> | >
> | >Heat it up & plunge it in oil/water etc???  What colour  - red hot,
white
> | >hot?
> | >
> | >Dave
> | >
> |
> | When I was at school we used some hardeing compound that I seem to
> | remeber you dipped the hot metal into. THis was called by our teacher
> | case hardeing.
>
> Case hardening is a tricky process, IMO best avoided.
> Get a bit of better steel.



You can't harden mild steel without increasing the carbon content using some
form of case hardening compound. That's no good for tools because the
instant you sharpen it you'll grind through the thin case-hardened layer
back into the soft steel below.

You need a high carbon steel.  Round stuff usually sold as "silver" steel
and the flat stuff as "gauge plate".  People like J&L Industrial sell it.
Can be hardened and tempered as described in any basic metalwork book.

"Dave Fawthrop"  wrote in message
news:gef5h15jm8djb8jcii9pn1d167co10t1om@4ax.com...

> On Mon, 29 Aug 2005 07:44:15 GMT, Rick 
wrote:
>
> | On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
> |  wrote:
> |
> | >Hi
> | >
> | >Assuming I have a piece of mild steel plate and want to put a
sharp edge on
> | >it, how do I go about it?
> | >
> | >The sharp edge isn't a problem, how do I harden the steel to keep
it sharp?
> | >
> | >Heat it up & plunge it in oil/water etc???  What colour  - red
hot, white
> | >hot?
> | >
> | >Dave
> | >
> |
> | When I was at school we used some hardeing compound that I seem to
> | remeber you dipped the hot metal into. THis was called by our
teacher
> | case hardeing.
>
> Case hardening is a tricky process, IMO best avoided.
> Get a bit of better steel.
>
> -- 
> Dave Fawthrop <dave hyphenologist co uk>
> "Intelligent Design?" my knees say *not*.
> "Intelligent Design?" my back says *not*.


Case hardening is dead easy with the simplist of equipment. Heat item
to cherry red - dip in Kasenit compound - reheat to cherry red -
plunge into water. That'll give you 2-3 thou of higher carbon steel on
the surface. Repeat to increase the case depth. The surface after the
plunge should be glass hard and will turn a file.

WWll prisoners used to case harden mild steel for wire cutters using
sugar as the carbon source and heated with a spirit blowlamp - if they
could do it with such basic kit, given a tin of Kasenit it's a doddle.

AWEM

"Andy Dingley"  wrote in message
news:p1p5h1lo6vgom8hk35tkhq4a61ntl1rc47@4ax.com...

>>SNIP<<

>
> You can't harden mild steel.  It won't harden on its own, and you'll
> have a hard job finding Kasenit these days. I suggest you search out
the
> rec.knives FAQs, which have a great deal of information.
>>SNIP<<



Kasenit equivelent from Chronos

http://www.chronos.ltd.uk/acatalog/

1 KG Case Hardening Compound(Reference #CHD3)
This case hardening compound is specially formulated to give an
acceptable depth of case hardening to small metal pieces where
production time is very short. The powder is produced from top quality
raw materials giving a consistent material which reproduces good
results every time you use it.


Price inc UK mainland carriage:  21.24 24.96 Including VAT(appl
European union only) at 17.5%


AWEM

On Mon, 29 Aug 2005 13:23:36 +0000 (UTC), "Andrew Mawson"
 wrote:


>Kasenit equivelent from Chronos


Chronos' site is broken, but I bet that stuff's the same as the modern
"Kasenit-lite", not the old stuff. It'll work in a reducing atmosphere
(so the "packed tin in a furnace" method works)  but it's no longer any
use for the "heat and dip" method. If you see old Kasenit around, snap
it up.

And you can't case-harden with plain sugar either. You need to burn the
sugar first (use fag ash as a catalyst(sic) )  and also add grated
fingernails.

Yes, last time I did any case hardening it began with a hoof rasp and a
donkey  8-)

"Andy Dingley"  wrote in message
news:u656h15l9g0g2qrogfsjia4l3oseja9umf@4ax.com...

> On Mon, 29 Aug 2005 13:23:36 +0000 (UTC), "Andrew Mawson"
>  wrote:
>
> >Kasenit equivelent from Chronos
>
> Chronos' site is broken, but I bet that stuff's the same as the
modern
> "Kasenit-lite", not the old stuff. It'll work in a reducing
atmosphere
> (so the "packed tin in a furnace" method works)  but it's no longer
any
> use for the "heat and dip" method. If you see old Kasenit around,
snap
> it up.
>
> And you can't case-harden with plain sugar either. You need to burn
the
> sugar first (use fag ash as a catalyst(sic) )  and also add grated
> fingernails.
>
> Yes, last time I did any case hardening it began with a hoof rasp
and a
> donkey  8-)


Nope - I have a tin and it's fine for 'heat and dip' With sugar they'd
heat the item, dip in sugar then continuously reheat so obviously the
sugar burns to a gooey caramel gunge. For the 'pack a tin and bake'
method leather is good. as is bone so I suppose your fingernails are
similar.

AWEM

In message , Rick 
 writes

>On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
> wrote:
>
>>Hi
>>
>>Assuming I have a piece of mild steel plate and want to put a sharp edge on
>>it, how do I go about it?
>>
>>The sharp edge isn't a problem, how do I harden the steel to keep it sharp?
>>
>>Heat it up & plunge it in oil/water etc???  What colour  - red hot, white
>>hot?
>>
>>Dave
>>
>
>When I was at school we used some hardeing compound that I seem to
>remeber you dipped the hot metal into.


Jones from 3B for example


-- 
geoff

On Mon, 29 Aug 2005 14:50:32 +0000 (UTC), "Andrew Mawson"
 wrote:


>For the 'pack a tin and bake' method leather is good. as is bone so I suppose your fingernails are
>similar.


Fingernail (or hoof) works better than leather or bone. Rawhide is
better than leather, but both of them really need some calcining
(roasting) before being used. 

Bone is pretty much useless, unless you're working on an industrial
scale. There's just not enough organic material in it, compared to the
minerals.

"raden"  wrote in message 
news:2CRGsVMMrzEDFwA5@ntlworld.com...

> In message , Rick 
>  writes
>>On Sun, 28 Aug 2005 22:56:03 GMT, "david lang"
>> wrote:
>>
>>>Hi
>>>
>>>Assuming I have a piece of mild steel plate and want to put a sharp edge 
>>>on
>>>it, how do I go about it?
>>>
>>>The sharp edge isn't a problem, how do I harden the steel to keep it 
>>>sharp?
>>>
>>>Heat it up & plunge it in oil/water etc???  What colour  - red hot, white
>>>hot?
>>>
>>>Dave
>>>
>>
>>When I was at school we used some hardeing compound that I seem to
>>remeber you dipped the hot metal into.
>

Ditto, it was probably powdered hoof. AFAIK all you need is carbon but there 
may be a technological reason why hoof is better than charcoal. I believe 
the depth of case-hardening is controlled by the rate of diffusion at the
temperature the process occurs, that is to say, if you can keep the article 
hot for longer, say a few hours, you will get a deeper layer of carbon 
steel.

Andy

On Mon, 29 Aug 2005 15:04:43 +0100, Andy Dingley
 wrote:



>Yes, last time I did any case hardening it began with a hoof rasp and a
>donkey  8-)


I thought all you needed was a steady supply of slaves into whose
giblets you could plunge your blade?


-- 
Peter Parry.   
http://www.wpp.ltd.uk/

On Tue, 30 Aug 2005 23:26:31 +0100, Peter Parry 
wrote:


>I thought all you needed was a steady supply of slaves into whose
>giblets you could plunge your blade?


That's tempering, which relies on a copious supply of URHB (urine of a
red-haired boy, the rec.knives mythical panacea tempering fluid).

One of my older sword books does have a suggested diagram for how to get
most efficient use of a condemned prisoner for sword testing.

Andy Dingley wrote:

> One of my older sword books does have a suggested diagram for how to get
> most efficient use of a condemned prisoner for sword testing.


Very useful thing to have, especially now that condemmed prisoners are 
in such short supply.

Owain