Tempering.... and home made tools.

[Jow]

ive been experimenting with tempering home made tension wrenches and have found that its almost not worth doing. I started making them out of sweeper blades by heating them in a similar method to pyros video. then heating them till red and quenching in water. this made a very stiff but extremely brittle wrench.
ive been doing a little reading on tempering and it seems that quenching the metal at different heats as changes its colour from brown to blue through to red will render different characteristics.
my home experiments are a little un-scientific as im currently using a gas stove as a heat source which gives an un-even heating to the wrench.

does any one know much about tempering and or how to do it correctly and or what properties different colours will yeild?
from what ive found the cooler the metal when quenched the softer it becomes.
any one have an oppinion on the optimum colour for a: picks and b: wrenches.

joe

[TOWCH]

I don't know about the signifigance of color but I had a soft homemade peterson reach style hook that was too soft. I ended up hardening it with a lighter and immediately quenching in water. It was my favorite pick up until a day or two ago when it snapped due to brittleness. In the future I plan on trying a five second delay and if that is too soft and 2.5 second delay. If five is too brittle trying 10 and so on.

[Jow]

i talked to a blacksmith years ago and he used to use the colour of the steel to temper with. for example with knives i think he said hed heat the tip till blue and the bade till brown then quench so the tip was softer that the blade so it wouldnt break off as easily, yet the blade was hard enough to maintain an edge.
i like the idea of your timed tempering... be sure to post results.

[Jow]

Pale yellow - hardness 750-800 Vickers - Still quite brittle but very hard.
Pale straw - hardness 720-770 Vickers - Suitable for machining mild steels. Low resistance to fracture.
Dark straw - hardness 700-750 Vickers - Suitable for home made taps, scribers and the like.
Purple-blue - hardness 650-700 Vickers - Suitable for chisels and punches.
Dark blue - hardness 640-690 Vickers - suitable for springs.

this is the best i can find on the net.
it seems its not how long you wait to quench but the heat you heat up to.

[TOWCH]

I have actually played around a bit with heat coloring in the past when I was making chainmail. My understanding though was the color was an indication of the temperature the steel was heated to, more than it's temper. I'm really not sure though because I let all the rings I did this to cool down by themselves. I remember there being a table that showed the temperature and resulting color somewhere. I'll go look.

[TOWCH]

Looks like you beat me to it but here's the one I was talking about http://www.anvilfire.com/FAQs/temper_colors.htm

[Jow]

exactly.. the colour give a hint of the temperature. thereforee you can heat to a given temp and quench resulting in said properties.

[D_Shane]

this is a brief description of tempering and the theory behind it.

http://w3.uwyo.edu/~metal/heat.html

I have a few manuals on metalurgy and "home" tempering, and I'll try to go through them and put up some of the pertient info.

[Beginner]

When you are heat treating your picks and wrenched i suggest that first you heat the metal so it has bright orange color and then quickly cool it with cold water.

Then comes the important part, you have to heat the metal again (tempering) so it will be gray, NOT too hot. And let it cool down, DO NOT dip it to water or anything to fasten the cooling process.

Tempering will then take the brittleness of the metal and it becomes more durable and it wont brake so easily. The temperatures when tempering is important, but the rule of thumb in this situation is that when it comes gray it haves right temperature.

And i learned this in school.

[Beginner]

I made some test with street-bristles and tempering them.

Here's the pic

http://tinypic.com/k000m

One on the right hasn't tempered at all, i just took couple of pliers and twisted it and it was quite tough but it did broke.

One on left was heated up to orange color and cooled down in water, then i again twisted it with pliers and it broke down immediatly.

And center piece was tempered with the instructions in above post, and it was very tough and hard piece of metal. It didnt broke even when i rolled it down and then unrolled it a littlebit and then rolled it again with pliers.

Conclusion is that when you temper your metal proprietry it will last even harder twisting in locks

[MrB]

Excellent information.

That picture goes so well with the text that it deserves to be permanent rather than a temporary link. Does someone know better than I do how to make the picture a permanent part of the post?

[Chucklz]

the IMG tags work very well, except that tinypic does not seem to support them.

[Jow]

so "Beginner", you heated the middle piece till grey than let it cool in at air temp?

the pics really show the difference and benefit of this process. nice one!

[zeke79]

When you are heat treating your picks and wrenched i suggest that first you heat the metal so it has bright orange color and then quickly cool it with cold water.

Then comes the important part, you have to heat the metal again (tempering) so it will be gray, NOT too hot. And let it cool down, DO NOT dip it to water or anything to fasten the cooling process.

Tempering will then take the brittleness of the metal and it becomes more durable and it wont brake so easily. The temperatures when tempering is important, but the rule of thumb in this situation is that when it comes gray it haves right temperature.

And i learned this in school.

are you sure this process is tempering and not stress relieving?

[Chris B]

Good evening,

I used to make my own cylinder picks and 'harden then temper' them, they worked quite well without breaking.
The method that I used was to heat to red heat and quench in oil, moving quickly between the flame and the oil. It slows down the cooling process better than water or air.
Polish the tool back to a silver colour then carefully reheat the tool until it turns light brown [you'll have to experiment with the shade of brown] and quench again.
If the shade of brown is too light, the tool will remain brittle, and if too dark the tool will loose it's hardness.
Different types of oils will also alter the cooling rate so you could change the types of oils that you use.
This is a totally agricultural way of doing it, but it works.
Hope that this helps.
regards from Chris