Saturday, November 2, 2013

Axe Handle

I found two forged steel double bit axe heads pitted with rust and forgotten on a shelf in a barn. It's hard to find forged steel axes (now expensive and rare) so I took the time to clean the smaller of the two and put a nice handle on it.

Most modern axes are cast. During casting molten metal is poured into a clay or sand mould and left to cool before final shaping is done by removing excess metal by filing or machining. When casting, the metal in the axe ends up being homogeneous and of a type that can reasonably hold an edge, somewhat tough and somewhat brittle. Trade-offs are made. In contrast, forged axes are created by heating and pounding metal into shape. When done in mass production, as this axe head was, it's usually not a person doing the pounding but rather a giant mechanical hammer. Forging requires that the metal be somewhat malleable (aka tough) so it won't tear during the forging process. Since malleable steel doesn't hold an edge, a more brittle piece of steel with a higher carbon content is forge welded to the edges of blades. Metal also has "grain" much like wood does. Forging metal stretches and aligns this grain with the shape of the object. The forging process results in a nearly indestructible axe head that will keep a razor edge for a long time. I know, axe heads aren't necessarily known for being fragile, but realistically there is no chance of hair line fractures in the metal near the handle since it is a tougher metal in the center. The axe can also be made thinner and lighter since the center part won't crack if misused as a hammer or when accidentally striking a rock.  For a more in depth explanation of these concepts, check out this great video by Ben Krasnow on heat treating metal. I took some care to avoid unecessary heating of the metal to avoid changing any of the temper.

If you spend any time shopping for a serious axe for wilderness treks or
timber work, you'll note they are all forged and cost several hundred dollars. Of course, if you don't care about any of this you can go to home depot with 30$ in your pocket and walk away with a cast axe to thump away at stumps in your yard. It will be over-built to compensate for the brittle metal and not keep an edge very long, but they're great for banging off rocks while cutting roots. I have one of those sitting in the corner of my garage covered in mud. This axe will lead a very different life. There is a maker's mark on one side of the axe and a Flint Edge logo on the other. Some online searching and I discovered that the latest this axe head might have been forged was 1949, but it could be a few decades older. All this considered, I was excited at the chance to bring this beauty back to life and own a quality unique axe that's also a piece of history.

The lines near the edge of the blade edge (visible in the image to the right) are where the high carbon steel was forge welded to the rest of the axe head. Both pieces of steel were heated to near melting, covered in a flux (common household borax works), and pounded together. I like that the lines are so clear on this axe; they speak to what it is.  The red oak should be better than the osage at resisting over-strikes, and I think the osage is a little lighter and more flexible than red oak. If I ever do any serious timbering it will be with a chainsaw, so I made the overall length more like a smaller forest axe as opposed to a long felling axe. It's 29 inches long. I think this is the perfect size to put in the truck for longer camping trips, fishing, or in the canoe. Short enough to pack or split kindling semi-safely, but long enough to get a good swing at something big.

The video starts off with me showing how to pound off an axe head without destroying it. I rarely see an older axe head that isn't deformed from hammer on blade contact. A safer and less destructive way is to drill it out and use scrap wood to protect the blade from the hammer. If you look closely you'll notice the head I remove is on backwards. I didn't record the original separation and it was easier to put it back on that way. Both of these axe heads have an aggressive reverse taper inside them. I ended up compensating for this by pounding wood wedges soaked in wood glue into the final axe. The glue soaked wood slivers nicely filled up the top of the axe and filled out the rest of my shim slot. It was easily trimmed back with a saw blade and made uniform with a quick touch from an angle grinder with a wire wheel. This head will never come loose, move, or let moisture get under it. I made the metal shim by putting a taper and some grooves on a piece of scrap metal (forgot to record that). The process of banging on the head and the shims ended up destroying the bottom of the axe handle. That was another reason to put the extension on with the box joint jig. I think this concession wouldn't do for a real axe connoisseur or even for a serious axe; but I did the work and I know the joints are solid. I don't think it will break even under severe use. It's far away from any critical stress points in the handle. Plus, I think the contrast makes it look good and will leave most woodworkers puzzling over how I was able to make such a clean joint with those dimensions. If I ever do this again I'm going to make the handle longer and wider than needed and cut it to length and shape it after the head is on and the shims are in. Or spend more time custom fitting the head; I may have made this all go together a little too tightly.

Functionally and aesthetically I think this turned out to be a great tool. Axes are most useful when chopping the sap free wood of fall and winter while camping. The leaves are turning, maybe I'll get a chance to test it out soon.

Update: I put a handle on the other axe head today. I ended up not sanding it, just wire wheeled the rust off. For ten dollars at tractor supply I scored a hickory axe handle with hickory shim. It took me less than 10 minutes to fit it with a file then glue and pound in the shim. Practical, but less fun than making one from scratch.  After the glue dried, I took the time to sand off the polyurethane coating and cover it in some danish oil. The reason for an oil finish is repair-ability as opposed to durability. If I nick the handle, I can just dab some oil on it and it's protected; surface coatings are not as resilient or easily repaired.

While sharpening I noticed that the steel was much harder than any of my other axe heads. The file didn't want to bite into the metal while sharpening. A skittering file is a common way to diagnose a hard steel. I ended up using my orbital sander to shape the initial edge. I'll wander into the garage and finish off the edge later this week. Here's a picture: