Softening a Hidden tang for drilling

Brian Avila

Brian Avila

Joined
Jan 2, 2011
Messages
1,286
I was hoping to get some experienced smiths to discuss the softening or drawing back of the hardens of the hidden stick tangs that Nick Wheeler was talking about in his awesome WIP. He said that Mike Vagnino taught him about it.

I was wondering what you are really looking for in the color when you do it? And why did Nick do it three times? Can a propane torch be used to do this method compared to an OA set up?

- Brian -
 
I take it to gray (past blue) once for carbon steels and that's usually enough to drill. Sometimes you have to do it twice, but a sharp drill and hard feed rate will get 'er done.
 
Hi Brian,
What color I look for is a dark blue. I use 2 propane torches to speed the process. I put the cutting edge in a trough I made out of 1.5" angle iron filled with water. I do it at least 3 times. O-1 takes me 3 or more times.
1084 is easily done O-1 is a real pain so when I harden the O-1 I try to keep the tang out of the oil.
When softening the tang let it cool off slowly for better results.
Dave
 
Thanks guys!!!

Can you give me a reference for order the colors start? I know blue isn't the first color.

I don't know about the fast feed rate for the drilling though, I find that I get way better results with "pecking" and not laying into the drill, even on annealed steel.
 
And since I have double read this, can you tell me why the O-1 is harder to soften then the 1084, David?
 
Hi Brian,
There are charts on line http://www.anvilfire.com/article.php?bodyName=/FAQs/temper_colors.htm
But for a fun experiment make your one chart by taking a piece of the same metal and heat up one end to a dull red and watch how the colors travel and change.
Based on the blades I have made in O-1, it has a tendency to air harden enough to make drilling a real pain. But it does not air harden enough for a cutting edge. Put it in oil at the quench and you will get it to fully harden.
Dave
 
I draw the tang to a medium blue color. The triple cycles are done because you can't hold temp using a torch, but the temper benefits from time at temp, so instead of trying to hold at the right temp, we just try to hit that temp multiple times.
If you want easier drilling you can anneal further by heating to dull red (below critical) and air cooling, but I only do this at the very end of a tang for threading or peening. If done to the entire tang it will be softer than you want it. Again, this will benefit from multiple cycles.
 
O1 is one of the original modern "tool steels". Meaning, it was designed for tooling that cuts other hard materials. (mills, drills, etc.)

TheWeatherman said:
And since I have double read this, can you tell me why the O-1 is harder to soften then the 1084, David?
Click to expand...

Chromium and tungsten. Sometimes a bit of vanadium, depending on who made it.

All those alloys are added to O1 to make it form carbides, give it more wear-resistance, and most importantly to help it harden all the way through the part during austenitization and make it more "red-hard" or resistant to high temperatures. That means it's less likely to lose its hardness when used in high-speed/high-heat cutting applications, and that even as it wears down or gets sharpened several times, the part or blade will still have the same hardness.

It also means that O1 is somewhat easier to quench, or harden from a high-heat state. It can work-harden from friction (drilling or grinding) more easily than simpler alloys like 1095 and 1084, though not nearly as much as high-alloy steels like CPM-154. So, spot-annealing or -tempering O1 with a torch and letting it cool in air isn't as effective as it would be with 1084 or other alloys with little or no high-temp alloying elements.
 
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David Loukides said:
Based on the blades I have made in O-1, it has a tendency to air harden enough to make drilling a real pain. But it does not air harden enough for a cutting edge. Put it in oil at the quench and you will get it to fully harden.
Dave
Click to expand...

What is actually happening is lamelar pearlite formation. You are slow cooling a hypereutechtoid. I had that issue when I was using O-1 and not quenching the tang. The only solution once you have that is to follow the directions in the "Working with the 3 steel types" sticky and spheroidize anneal. You can avoid it by hardening and tempering the whole blade including the tang then doing a "subcritical anneal" of the area you want to soften

-Page
 
sunshadow said:
What is actually happening is lamelar pearlite formation. You are slow cooling a hypereutechtoid. I had that issue when I was using O-1 and not quenching the tang. The only solution once you have that is to follow the directions in the "Working with the 3 steel types" sticky and spheroidize anneal. You can avoid it by hardening and tempering the whole blade including the tang then doing a "subcritical anneal" of the area you want to soften

-Page
Click to expand...

Page, just so I think I know what is going on. Say you are working with 1084, you can do the torch method. but when you move to hypereutechtoid steel like O-1 and W2, it is better to use the spheroidize anneal the tang area?
 
Ideally, I try to spheroidize anything I am going to drill or machine (yes 1084 too) of course I try to predrill whenever possible and sometimes I don't have time to do a serious spheroidize, so I do a quick torch heat to dark blue, quench, sand off the oxide, heat to blood red oxide, quench, then straw, and quench. usually does the trick

-Page
 
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