Forging a Double Bit Axe

In the lofty pursuit of forging all the tools I will eventually need to timber frame a workshop, I have worked my way into the variety of axes. Starting with the small ones, this time I made a double bit axe. More of a proof of concept and to experiment with dimensions, it won't be doing much of the heavy lifting but is designed for light trimming and the like.

The size of the stock is 5"x2"x,75" mild steel, nothing special. The other axes I have made were done using the fold/wrap method where the poll is forged out of the middle of the piece and the edge is made from the two ends. This time, I slit an eye in the middle and the ends will become two edges instead of one.

All the tooling I used for this I made in the shop over the last few months. From left to right, there's a hot cut hardie, centre punch, hot cut chisel, small drift, large drift, hot cut (without the handle) and a pair of double calipers. On top is the pair of hammer eye tongs. These are great for this, and having only recently finished them 8 months after forging the two halves, I am incredibly glad I did. 

First step is to mark the centre of the billet. 2,5" in from the ends, I marked both sides. This is because slitting from both sides separately and meeting in the middle is generally cleaner and prevents one side from getting too thin if the entry is off kilter.

With the hot cut handled, it's onto slitting the eye. Flipping the piece around (or the hot cut) helps keep it all centred. I took the entire first heat to setting the line properly in the centre of the billet and across the dot I marked earlier. The setup is the most important part, as doing it off angle or off centre will be difficult to correct as the eye opens. If it is at an angle, it will tend to stay at an angle until either you reach the other side or it comes out the face of the billet.

Here it is with both sides slit. Were I to make the hot cut again, I would round the edges a little and make it more oval rather than rectangle so there are no sharp corners on the inside of the eye. This width of steel is on the cusp of being too thin for this size of a hot cut, and as a result, a small tear formed in one of the corners. Nothing catastrophic, but it would have been prevented with rounded corners on the hot cut.

Next up is drifting it open to size. By hammering the drift down into the eye from either side, then forging on the cheeks, it spreads out and widens. Do not use the drift by simply forcing it down through the eye and stretching it to shape that way, it will rip the steel somewhere with it being this thin. 

After moving through both sizes of drifts (you can get away with one or none depending on how you make the hot cut/punch/whatever), the eye is mostly done. Here, it is still thick because I want to do a few things to the rest of the axe body without distorting it unduly.

Before slitting the ends to weld bits into, I tapered the ends a tad. Looking back, it would have turned out better had I left it the original dimension, because the extra mass would have made welding in the bits easier and the subsequent spreading to shape easier.

To open the ends, I used the hot cut again, holding it on edge in the leg vice. I would have gone considerably deeper with the slit had I a better way of holding it or a second set of hands, but the limitation left it about half as deep as the bit of rasp I was using as the edge steel.

Cut on both ends, it looked something like this.

For the edge, I used the aforementioned rasp. Cut a little long to give room for error in alignment, it will be trimmed neatly after welding. I cut this one on the hardie hiding out in the shadow in the top right of the above. Having a narrow bodied hot cut is extremely useful for cutting thick stock (not this, but it also works great for thin stuff) that a butcher won't do without heavy distortion.

And, a fair bit hangs out. I could and probably should have forged it down to about half that width and doubled the length so I only had to use one piece, but the teeth of the rasp helps hold it in place while setting the weld.

Setting the edge hot locks the bit and the body together because the cold rasp's teeth bite into the hot steel of the body, which keeps it from sliding all about. 

A few careful heats to set the weld, then another few to shape it, the first side is set. Some of the excess is trimmed off here, but more sill go to clean up the edges.

Now comes the second. The easiest way to judge if the piece is welded with steel this thin is to let it cool. If shadows form anywhere when everything else around it stays hot, there is probably a weld flaw underneath. Even cooling indicates good welds, but obviously there can still be problems.

Back to the trusty hot cut, the excess is removed and it starts to look like the thing I am trying to make.

Unfortunately at this point I had to close the shop and didn't have the chance to take any more pictures, but a little more work was done on the eye, the last bit of profile forging, and a quick trip to the old hand crank grinder to true things up. I may end up going back and forging it a little thinner all around, but it feels good as it is...