Tempering first experiments => first problems/questions

[Mihai4Z]

My first post so hello to everyone,

Intro:

Started forging a year ago, practiced it for a maximum of a dozen times, then the winter came and having no indoor possibilities I stopped.
I restarted again this weekend. Meanwhile I tried to gather some information.
I pretty much want to go through making as much as I can (especially tools: woodworking, metalworking, glass, stone etc.)
It's kind of difficult to find guidance (face to face) as very few people do this sort of thing in my city/country (Bucharest/Romania).
Still, fortunately I will probably be able to play with forging more than just in the weekends.
I'll stop here, as I intend to communicate a lot on this forum... many questions and hopefully much to share as I go along.

First attempt at forging:
Improvised a forge: refractory bricks on a metal foil base, a square pipe full of holes and a hairdryer fan connected to the socket through an adapter. - will detail in another post.
The forge works but can still be improved - it specially needs changes for particular projects.
And a railroad track improvised anvil.

Second attempt at forging:
Just experimenting with mild steel, flat, round and square stock... practicing turning/coiling, bending, flattening, punching, cutting, drawing out etc. mostly basic stuff.

Still have to try in future attempts:
Welding, hardening, tempering


The "problem"/challenge:

I decided to try and make a draw-knife out of an old rusted file because:
1. I need a draw-knife.
2. I would go through the process of heat treating.

Haven't started working on the file yet (of fear of destroying it - question no.1: what would happen if I heat it to much - being a high carbon steel), instead I used a scrap piece of high carbon steel.
Hardening seems relatively simple (as in no problems so far), from what I gathered, simply put, you heat it up to the point when it looses its magnetism (seems to be a red - orange color) and then quench (I used water, not sure if it's OK, seemed alright).

The part that actually took me all day (literally) and with no result at the end was the tempering part.
I am really insistent on not using the oven, or a torch or heat-insulation (clay or others) for my first try but instead use the most rudimentary method (I'm thinking of the forge itself) AND THIS, well this has been and still is a mystery to me.

1. I thought that I will be able to get the temper by just putting the "file" on the fire on it's side and watch the colors(of course after cleaning it). Result: It generated "random" colors because of the non-regularity of the flame, higher flame resulted in the blade becoming all blue, smaller or less intense flame resulted in that, during same amount of time, it got yellow and in the end instead of a gradual pattern from back to blade I actually got a Mosaic of colors, mostly blue.

2. I tried using another piece of metal (tried thin, thick, mild, high C), which I heated up to red hot and then took it of the fire and placed the file over it. Result: as soon as I took it out of the fire it started to cool, also the small imperfections in the levelness(=> no contact to file) of the support metal resulted in no temper color. I tried even getting mild steel to orange-yellow hot and still no result.

3. Variation on 2 after heating the support metal I left it in the forge and placed the file over it. Of course that the heat from the forge generated the result from 1. I also tried simply heating up the forge and then placing the support metal over the fire in the forge. This time because I didn't envelop the metal in charcoal it never got hot enough to generate the temper colors on the file.

4. I also tried playing with the fire bricks, creating different heat areas trying to control the distribution of heat in order to only affect the spine of the future draw-knife.
As in almost all the other examples the very small imperfections in the heat distribution (caused by cracks or dents in the bricks) resulted in a very non uniform temper pattern.


Main question: how can I get a uniform, full length, one shot, progressive temper color pattern on a longer blade (particularly: draw-knife ~ 10 inch) using a forge and watching the colors run.

Hopefully tomorrow I will also take pictures of the setup and every method I tried (more or less skillfully) and share. Even if I couldn't use so far the methods maybe someone else will correct them or learn from them.


Observation:
- for forging colors you need darkness (unfortunately I cans only use the outdoors to forge so it's a little bit cumbersome)
- for the tempering colors you need light (I cannot see a thing inside the forge I actually need to make the fire more into the sunlight)
Those two don't mach up until now.

Probably for someone with more experience this might seem silly or even foolish... (sorry if it really is) but by just experimenting with it and having almost no experience I kind of got stuck looking at the forge. Tomorrow is another day... hopefully I will come up with something. Anyway I plan on starting the day by actually shaping the draw-knife... this way at least I will get something done.
Sorry for the long post, being my first one I kind of wanted to say more, I will keep it concise from now on.

Thanks,
Mihai

[jmccustomknives]

Well, your forge just needs to get hot enough to move the metal, my first wasn't much different. As far as hardening, sounds like you've done a little homework but I wouldn't quench in water. A water quench can come back to haunt you (experience talking). After hardening I would put it in an oven for an hour but since you are dead set at doing it the old way heat up a peace and lay the back of the knife on the hot metal (cleaned up of course). Your temper colors are delayed so don't rush it or you will over heat the piece before you realize it. It takes a lot of practice to do it this way, that's why I don't use it as the primary method of tempering. Good luck.

[bigfootnampa]

Here's a way for you to use that won't be quite so difficult. First get some oil to quench in... water is too fast and especially for thin items likely to cause more problems than it solves. After oil quenching IMMEDIATELY, with the metal still in your tongs, go to the forge and heat it till the oil flames. Pull the blade out of the forge and let the oil burn off in the air. Dip it into the oil again and cool for a few seconds and then burn off again as before. Repeat this process till you have flamed off the oil about 6 times total. Now let it cool and you are done! This whole process takes about 2 minutes. It is NOT an optimal system for those who have to have an exact Rockwell hardness or a rich looking hamon,.. but this method is likely to get you consistently good results with little equipment and a minimum of skill and practice. I use it myself for most items and it additionally has the advantage of tempering the blade so quickly that rarely is a blade lost in the process. Of course this is not for EVERY steel but it works well for medium to high carbon steels in the 1040, 1090, 4140, 5160 ranges. I personally once spent around 2 hours heating the spine of a small (1 1/2" long) carving knife blade with a TINY flame on a small propane torch... I got a near perfect temper on that blade and it holds an edge better than any I have ever made since... I never even think of doing more in that way now though. This method is controlled by the flame point of the quenching oil and I use motor oil but most common oils are not that far different. Doing it this way you are not dependent on colors... so no grinding, dim light okay.

[bigfootnampa]

BTW as I am an expert draw knife user I can tell you that some sort of super hard edge is quite unnecessary, I put many hours of hard use on my draw knives edges between sharpenings. Most of the work is splitting rather than cross grain slicing and the edges seem to wear forever. A super sharp edge does not seem to be optimal for the work anyway... most of mine are probably overly sharp. Do try to keep your bevel all on one side though and fairly steep with a softly rounded back edge (to keep from marring the work... the bevel acts as a fulcrum to control the cut depth).

[pkrankow]

Sounds like you have a good grasp on hardening. Water may be a good choice for this batch of steel, but oil may be a better choice for another batch. Make near-shape samples and test both oil and water to see which gives desired performance. Use the more gentle option if both, as the likelihood of breaking in quench is lower.

Instead of reheating the blade in the forge, heat a piece of bar stock and press it to the spine of the blade. The colors will run much slower. When the desired color reaches the desired point, quench/cool the blade. File the blade again, and heat the next area until the entire edge has been tempered to the desired color. That you are not tempering the entire blade at once will not make a difference, as long as the entire blade gets tempered.

If you find you are doing this frequently then a set of tempering tongs may be in order, they have pieces of bar stock fastened to the jaws so you just grab the spine after they are heated.

Phil