Stubborn Steel

D

drlozier

Joined
Jan 4, 2010
Messages
158
So after making about 20 knives out of known steel, I am inspired by this forum to make a knife from an old file. I heat it up to past non-magnetic and let it slow cool three times. I profile it and grind it out and then I try to drill some holes to mount the scales. I can't drill holes through it...it is still too hard. I even tried new drill bits and different size bits but nothing seems to work. So I heat it up again three times....still I can't drill it. Any ideas or suggestions...I never experienced this before...Many thanks !!
 
This is one of the common problems with working a file.

By heating hyper-eutectoid steel above Ac1 and then slow cooling it multiple times, you created fine laminar pearlite. It is fairly hard stuff. The way to anneal hyper-eutectoid steel is to heat it to 1200F ( below critical) and cool it to about 900F, then quench. Do this three times and you will have a spheroidal structure that drills easily.
The stickys have a piece called "Working with Three Steels" that covers all this in detail.
 
Thanks Stacy. I followed your instructions and finally managed to get to a steel I could drill. Much appreciated.
 
I'm curious how you tell it's below 900F? 1200-1300 is visibly a very dull red, but it gets black pretty quickly.
 
mgysgthath said:
I'm curious how you tell it's below 900F? 1200-1300 is visibly a very dull red, but it gets black pretty quickly.
Click to expand...

For the first of three quenches, I heated in my forge until my thermometer read 1200 and then turned the forge temp down and waited until it cooled down and read 900. This gave me a good idea of what 900 looked like in dull light. (it looked like the last hue of red just before turning black) I used this appearance as the benchmark for the second and third quenches which I really "guessed" at.
 
It helps to observe the steel in a dark corner of the shop, steel can look black in a lighted area, put it in shadow and plenty of heat color left. I just guess at the temps for this process and it works well.
 
Salem, that's about what I do, is turn all the lights off except for the forge, so I don't overshoot a very dull red. It's amazing how it disappears under even a little light, still looks black in the forge. It's too bad high temp IR thermometers are so expensive. I wonder if there's a good way to interface a thermocouple probe right to the blade after it's outside the forge, like a glob of solder or something..
 
Doing HT and other related tasks is best done in low light at night.
When I have a special project, I save the final forging and HT for a night that has a thunderstorm. The lightening and thunder just make the whole process sooooo coooool. Tai will agree, I'm sure.
The real, advantage is being able to see steel colors as they really are. I turn off the smithy lights, and forge by the forge flame plus the light spilling out the grinding shop door.
 
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