Metal Testing

[Sniper]

I have a couple of "souviniery knives" if that's the right word which come from India and fancy having a go at turning them into something usable. Question is how can I tell if the blades are
A. Tempered?

B. Carbon steel or just mild steel?

C. If I attack the blades with a grinder how would I go about retempering if I had to anneal them in order to reshape with the grinder?

I don't have a forge or anything I could make one from.

Could any of you makers out there do this for me if I could not manage it myself, and if so any ideas as to how much you would take for doing it. I really would like to turn them into users. TIA

 

[Bernie Garland]

I have a couple of "souviniery knives" if that's the right word which come from India and fancy having a go at turning them into something usable. Question is how can I tell if the blades are
A. Tempered?

B. Carbon steel or just mild steel?

C. If I attack the blades with a grinder how would I go about retempering if I had to anneal them in order to reshape with the grinder?

I don't have a forge or anything I could make one from.

Could any of you makers out there do this for me if I could not manage it myself, and if so any ideas as to how much you would take for doing it. I really would like to turn them into users. TIA

Hi Sniper take some pics of them and email me the pics,and i'll see if i can help you out.

Bernie

 

[robin wood]

First step would be to test them with a file. You don't need to actually cut the metal, just kind of rest the file on the edge and just see if it will catch as if starting to cut. With a little experience its possible to judge quite well the hardness of a tool this way. If it is very hard (too hard) the file will scate off as if it was glass. Too soft (or mild steel) and it will bite easily. Just right and it should sort of just think about biting. Try your file on different bits of metal of known properties to get a feel for it.

 

[mick spain]

The easy way is to test it with another knife that you know is ok say something like an Opinel up against the edge if it cuts into it easy, you know it's no good, if it wont touch it then it's probably too hard
It's a simple way but it works similar to using scratch gauges

 

[Sniper]

First step would be to test them with a file. You don't need to actually cut the metal, just kind of rest the file on the edge and just see if it will catch as if starting to cut. With a little experience its possible to judge quite well the hardness of a tool this way. If it is very hard (too hard) the file will scate off as if it was glass. Too soft (or mild steel) and it will bite easily. Just right and it should sort of just think about biting. Try your file on different bits of metal of known properties to get a feel for it.

I've just tried this with a nail file (don't have any other type) and it seems to pass the test but I'm really not sure what I'm doing with this. email sent Bernie

 

[crwydryny]

I may be wrong but I think a nail file may be too soft for this test (I'm sure someone else can confirm if I'm right or not) what you need is a metal working file (any ironmonger/hardware store will have one or you could try asking you local mechanic) the other way is to scratch it with an object (such as another knife which someone else has suggested) where you know the temper. if it scratches it's softer than the object used to scratch it. if it doesn't scratch it's harder.

 

[Sniper]

If memory serves me correctly when grinding metal bright sparks indicate carbon steel and dull sparks indicate mild steel is this correct? It's been many years since my apprenticeship days.

 

[Bimble]

If its non magnetic, then it’s stainless. Some stainless are slightly magnetic get a feel against a can of beans and your magnet if it clamps on it's carbon/mild steel.
As for temper, use a fire steel. If is showers sparks easily its hard enough for a knife blade, carbon or stainless. (Some people think stainless won’t generate sparks, but it will if it’s hardened knife steel.)
Without writing chapter a verse on metallurgy, you can harden and temper any blade by the following:
1) Light the BBQ
2) Insert blade in coals
3) Fan until blade glows ‘cherry’ colour (hair drier good for this), best at night as you can see colour.
4) Drop blade in tray of old engine oil (not water) to quench.
5) Now put blade in your kitchen oven at 200C and heat for an hour (tempering), then let cool slowly.
6) Polish off the burnt oil if needs be.
7) Never expose the blade to temperatures above boiling point after that.
8) Sharpen.
This method will be good enough for an outdoor knife with most heat treatable steels, certainly anything a knife is made from.