Differential heat treat

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Are all axes differentially heat treated (harder edge than eye)? If properly made, should all axes be differentially heat treated?
 
It depends, I don't think commercially produced axe heads would be differentially heat treated (too expensive). Some of the custom makers of tomahawks etc around here will either or both harden the cutting edge or use a harder steel for the edge(1096, L6 etc) and use mild steel for the eye (1050 or so).
All differentially heat treating does is make the eye area more prone to bend or deform then break.
 
These should be helpful-

From RMJ's FAQ

Heat Treatment

A blade cuts only as good as the steel, the edge geometry and the heat treatment that goes into making it. If one of these factors is neglected or compromised the quality of the blade suffers. Heat treatment plays a major role in how the Shrike tomahawk performs. The Shrike goes through seven specific heat treat operations including four tempering cycles. The entire tomahawk is first hardened and double tempered to a hardness of 30 Rockwell C. This is an extremely tough and springy temper that gives the tool a lot of shock resistance. Next the tomahawk cutting edges are through flame hardened and double tempered again to a hardness of 55 Rockwell C. This hardness is good for cutting into materials such as sheet metal, brick, wood, etc. without losing its edge. This differential heat treatment, much like that of the Samurai swords of feudal Japan enables the tomahawk to have a tough, shock resistant body with hard cutting edges.

Why do you differentially heat treat your tomahawks?

The Rc 55 striking surfaces allow you to cut through hard materials such as concrete and steel without wearing out or chipping the edges. The Rc 30 handle and center of the head allow for higher shock absorption as well as more toughness in the stress bearing areas of the tomahawk.


What is “through flame hardening”?

Unlike some forms of heat treating which only harden the surface of the metal, through flame hardening hardens the metal all the way through, from one side to the other. This causes the metal to truly be harder, not simply have a hard outer shell. If you were to slice the spike in half on one of our tomahawks and test the Rc of the center, it would be Rc 55, just like the surface.

Many manufacturers use a higher Rc than you. Why are your tomahawks not harder?

From our observations and rigorous testing, we have determined that Rc 55 is the optimal striking surface hardness for breaching applications like, cutting through concrete and steel. When you begin approaching Rc 60 the metal becomes not only harder, but more brittle as well. This creates a higher risk of failure under heavy use, such as chipping of the blade, and even a chance to shatter if an very hard surface is struck with enough force.
 
Much of the reason that the old axes were typically made with a wrought iron body and high carbon bit was because with pre-Bessemer smelting techniques, you get much more wrought iron than you do steel. Steel was much more valuable, and would be only used where necessary for an impact surface or cutting edge. Hammers would be made with wrought iron bodies and steel faces, as would anvils. Even scissors often had wrought bodies with a thin piece of steel forge welded along the main blade for the cutting portion.

Wraparound 'hawks really lend themselves to the inserted bit. Axes and 'hawks with punched eyes are easier to make from one homogeneous piece of steel.

My take on it (as someone making punched-eye axes) is that the head is tempered tough to withstand the tremendous forces of chopping hardwoods, so with a tough steel given a tough temper, there's not a whole lot of necessity to differentially temper. YMMV.

By the way, oldschool45, 1050 is not mild steel but medium carbon steel that in itself should make a decent ax or hammer. Mild steel is going to typically be under .3% carbon, commonly 1018 with approximately .18% carbon.
 
A quality axe whether new or old will be either differentially treated or have the bit inserted as previously described. I like to buy old axes and heads. Most that I encounter are differentially heat treated. You can see this by soaking a head in vinegar overnight. The head is mostly gray but the harder area is darker, almost black. You can look at older threads here and see plenty of examples. If it has a bit inserted, it is inlay or overlay, depending on which was split to receive the other. You can see this by looking at where they meet especially on the top & bottom edge
 
Most that I encounter are differentially heat treated. You can see this by soaking a head in vinegar overnight. The head is mostly gray but the harder area is darker, almost black.
Click to expand...

Alright. No wonder you could see on the edge and spike of the CS Trench Hawk, the tip is indeed darker compared to the neck.
 
We dont make that many mono-steel head hatchets/axes but heres on I made a long time ago..Its made from 4140. If you look you can see the temper line about an inch back of the edge. the edge and the poll face were hardened and tempered..Edge tempering is easier than hardening the whole head and then drift tempering or oven tempering..To me it is anyway..I personally prefer welding a bit in myself..
newpics078-1.jpg
 
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