Power Hammer class has moved onto the toolmaking part of the curriculum. We’re practicing making tools in mild steel and then moving on to tool steel versions.

Hot Tools

We’ve used 4140 steel to make tools for hammering into and through hot metal. The process starts with forging the tool to shape, trying to do it in as few heats (trips to the furnace) as possible, to keep the number of heat cycles the tool steel goes through to a minimum.

Three pieces of steel. They have 3/4" round shafts and three different shapes at the point. One is a cone, the second is flat and widens slightly towards the tip, and the third is a blend of the two, a flattened taper.

Because 4140 is fairly hard, we “air quench” these by just letting them cool off. Then we refine the working features by grinding.

The three tools polished and ground. The cone has a flat end and the half near the tip is polished. The flattened one has been polished throughout and has a distinct chisel-shaped edge. The blended one is polished, but its shape hasn't changed much.

Finally the struck end of the tool is rounded off on the grinder so that it doesn’t chip when you hit it with a hammer.

Finished tools

An end-on view of the tools described

These are a Hot Cut (for cutting a piece of hot metal by hammering a wedge through it), a Round Punch (for punching a round hole through a piece of hot metal by hammering a circle through it) and a Slot Punch (for punching a slot through a piece of hot metal by hammering a bar through it). We don’t heat treat these tools because they’re going to be subjected to high heat and their temper would be quickly ruined. Instead, we assume they’ll deform over time, and we’ll reshape them.

Cold Tools

Next we moved to W1 tool steel to make tools for marking cold metal. Again, we’re forging the tool into shape in as few heats as possible. Then we bring the tool back up to forging temperature and stick it in an insulator for a while to anneal it. There are tubs of vermiculite in the shop, and we bury our pieces in them until they fully cool.

A blackened steel bar. It tapers to a point at one end, while the other is blocky and has circular indentations.

This metal is in a very soft and workable state, so it’s a good time to clean it up by sandblasting, grinding, and filing.

The steel bar is bright and matte. The dark oxides have been sandblasted away. The taper can now be seen to have a slight octagonal cross-section. Chamfers are what separate us from the animals, as Blondihacks would say.

The tool is now mostly polished to a shine. A steel tool that tapers to a chisel point. Unlike the other, some black oxide remains.

Next it’s time for heat treating. We get the working end of the tool (which we want to be very hard) up to the temperature where it stops being magnetic, and keep it there for a few minutes. We learned two ways to do this: using the induction forge we can heat just the working end of the tool. Using the gas forge, we need to heat the whole thing on the “porch” of the forge.

An induction forge with the first tool in the copper coil. Within the coil, the metal is being heated by the current passing through the coil. The tip of the tool is glowing red Fire bricks outline the aperture of a forge. It is orange-hot inside, and a tool rests at the boundary between the high heat and the outside.

Then we quench the tool. The W in W1 means that this alloy can be water quenched, so we dunk it in a bucket of water until it’s cool enough that it gets wet. This leaves a very hard but also brittle metal. We temper it to make it somewhat softer and much tougher. This is done by heating the struck end to red and then letting that heat seep through the tool until the appropriate temperature is reached at the working end. You can judge this by the color of the oxides that show on the surface.

The blocky back end of the first tool is in the induction forge and is red hot. Midway down the tool, there is a rainbow of temper colors. Closest to the tip are straw, gold, and blue, followed by purple and brown. The tip of the first tool above a quench bucket. The straw and gold colors extend all the way to the tip. About an inch in, there is blue.

We’re aiming for a straw-to-gold color for these. We then quench the parts again in water to stop the tempering process, and toss them in an oil bath to cool down.

A tool in a metal mesh strainer held above the surface of a barrel of oil

Finally, we grind in the final shape and test the tools.

The first tool lies on an anvil, with a hammer next to it. There's a strip of flat metal with three circular marks on it. The second tool lies on an anvil with a small chunk of metal next to it with three linear cuts.

These are a Center Punch, used to mark metal with a point, and a Cold Chisel to mark lines.

Bonus: Touchmark

You may have noticed that my cold tools have circular marks near the struck ends. This is to identify them. This is essential when everyone is making the same tools and throwing them into the vermiculite at once. It would be cooler if I had something more distinctive…

I bought some 4140 at a near-ish metal shop (the one that’s actually nearby wanted to sell me 12’ when I only wanted 12”), and took it to Asmbly to do some work on the Tormach.

A vise on a fixture table with a small rod of steel standing up, held in place with a V block A strap clamp has been added to stop the V block from being lifted by cutting forces. A screw stops the V block from moving horizontally. A second V block has been added in the vise, with another piece of steel. This stops the vise jaws from closing asymmetrically.

It took me a bunch of tries to figure out how to properly hold the piece so I could machine it, and I had to use a tiny end mill (1/32”) to carve the details. They sell these end mills in packs of 5, so that when you break one basically on first contact with the work, and break a second just loading it into the tool holder, you still have a chance of finishing your part.

The spindle of the machine with a tiny end mill in it. The point of the end mill is comically small compared to what's around it. Oops. This view shows the part, with a bit of the end mill sticking out of it, while the rest of the end mill is still in the spindle.

The tip of the touchmark. It has three triangles carved in it A CAD view of the three triangles. If you squint, you can see the letter A in the negative space between the triangles, and with more creative squinting you can see an N on the left and a Z on the right.

Unlike the hot tools, which were also made of 4140, I want this to be quite hard so it leaves a good mark. Because 4140 is an oil quenched alloy the process is: heat until non-magnetic, quench in the oil barrel, then temper.

The touchmark held in tongs in front of the induction forge. The oil barrel smokes. The touchmark is in the strainer. The touchmark is held in the tongs so that the back end of it is barely in the coil. The back is red hot.

It works pretty well! If only I’d finished it in time to mark my center punch and cold chisel…

An anvil with a bar of steel showing the three-triangle mark. The touchmark is held nearby

Why yes, that is a stylization of my name! You’ve got a good eye.