Do Your Cheeks Have Dimples?

A couple weeks ago, I posted about making a new carving axe from an old carpenter’s hatchet. The axe has gotten quite a workout since I made it, and I couldn’t be happier with it. One curious feature of this old axe head is a couple of dimples on its right cheek. I’ve seen similar dimples, years ago, on the back of a chisel. I can’t remember who first told me about their purpose, but I suspect many of my readers already know.

One clue about their purpose lies in the form of a faint color change in the steel about 3/4″ from the cutting edge. This line demarcates the change between hardened steel and the softer steel.

The hardened/unhardened steel combination is found in many tools, from chisels to knives to plane blades, but it serves an absolutely critical function in a striking tool such as an axe. The cutting edge must be quite hard to remain sharp after repeated blows into wood, but unfortunately there is a positive correlation between hardness and brittleness. If we made the entire axe head hard enough that the edge stays sharp, we also increase the likelihood that the blade will crack during use. On the other hand, if we make the steel soft enough that brittleness is not an issue, we also resign ourselves to a blade that will not hold an edge for more than a few minutes. The solution? Combine a soft but malleable steel body with a hard but brittle edge. The softer steel supports the harder steel to create a superior tool.

There are many ways to accomplish this task. Traditionally, a blacksmith would forge weld a piece of tool steel within a wrought iron sandwich to make an axe head. This works well and yields a robust blade, but it’s also labor intensive (and therefore expensive). The modern method is to forge the entire axe head of tool steel, then harden only the outer edge of the blade. This is the method that was used for my axe.

So what does this differential hardening have to do with the dimples on the axe cheeks?

Notice in the picture above that the smaller dimple is located well within the hardened steel area, while the larger dimple is located just on the other side in the softer steel.

Those dimples are the vestiges of hardness testing done by the manufacturer to confirm that the axe head was hardened to certain specifications. In modern parlance, we tend to refer to steel hardness on the Rockwell scale. The higher the number, the harder the steel. Chisels and plane blades may measure around 60-62 Rockwell hardness. Axes will be a bit softer to remove some of the brittleness – 55-57 is typical for a well-made axe. Saws are softer still, since they must be sharpened by a steel file, rather than a stone, and “set” (that is, the teeth bent by a specific amount to either side), which a harder steel would not allow. A hardness of 50-52 is normal for saw steel.

Hardness is measured by forcing a very hard object (often diamond or tungsten carbide) of a specific size and shape into the object to be tested using a specific amount of force. The size of the the depression that is created provides a measurement of the material’s hardness. In the case of my axe, the depressions indicate that the object used for testing was spheroid, which means that a Brinell hardness tester was used. The formula for determining harness using the Brinell test is:

Which is a fancy way of saying: the smaller the indentation (Di), the harder the steel. So, looking again at the dimples in my cheek, we see exactly what we would expect. The dimple near the cutting edge is smaller (and therefore the steel is harder) than the dimple right behind it. It’s pretty intuitive, actually. Unfortunately, we don’t know the diameter of the indenter (D) or the force used by the test (F), so we can’t estimate the hardness using the information available to us, but still…Go science!

I can anectodally state that the steel in this axe head is quite good. I would assume that a manufacturer that cares enough to test its blades is probably more likely to be one that will make a good blade in the first place. So, do any of your cheeks have dimples?

 

Turn a carpenter’s hatchet into a carving axe.

You’ve probably seen them stuffed piles in the cluttered tables of an old antique store or flea market. Kicking around your grandpa’s barn. Maybe you keep one in your camping gear (like my Dad does) for driving tent stakes and splitting kindling. I’m talking about the once-ubiquitous carpenter’s hatchet. These little guys were useful for trimming odd bits of wood to size or driving the occasional nail, but most carpenters these days wouldn’t know how to trim a piece of wood with a tool that didn’t have a cord or a battery pack, so these things mostly languish unused in forgotten corners.

I’ve had a carpenter’s hatchet head kicking around my toolbox for who knows how many years, always meaning to put a handle on it but never quite getting around to it. I’m glad I waited, because I finally figured out what to do with it.

For the last five years, I’ve been using a Gransfors-Bruks hunter’s axe  that I picked up for $50 (used) for spoon carving. It’s a great little axe, but the handle is about six inches too long so I always have to choke up when I use it. It’s not a convenient length for packing up when I want to do a bit of spoon carving away from home, either. Something needed to be done. I though about buying a new, smaller axe, but good ones don’t come cheap. Then I remember my old carpenter’s hatchet:

It’s a terrible shape for spoon-carving. The hammer head places the balance too far back, the wide blade gets in the way of your fingers when you want to choke up on the handle, and the straight bevel makes it difficult to carve curvaceous spoon profiles. No problem though; I own a hacksaw.

The hammer head is the first to go.

Next I turned my sights to a nice cutout for my fingers when I need to choke up on the handle:

At this point, it’s still pretty rough-looking, but twice as functional as it was 15 minutes ago. I couldn’t resist prettying it up a bit with some work on the belt sander and some 220-grit hand-sanding. I also re-ground the straight cutting edge into a gentle curve:

That shiny look is nice, if that’s what you’re into. I know better than to think it would look like this for long, though. A clean metal surface like this is a magnet for rust when carving green wood. I gave it a soak in diluted vinegar overnight to tone down the shine.

Much nicer, in my opinion. All that’s left to do is give it a handle. I shaved some riven hickory to an octagonal shape, then dried it in my kiln for a couple of days before hanging the head.  I also darkened it up a bit more (and added some more rust protection) with some cold gun blue:

Not bad. But how does it work?

Very nicely. Very nicely, indeed.

I’ll admit, it will take some getting used to the shorter handle after 5 years of used a sub-optimal size. I think once I get the hang this one, though, it’ll easily be my favorite carving axe.

So, what have you got to lose? Hatchet heads like these are $5-10 at flea markets and on eBay. Maybe you’ve even got one in the junk drawer of your shop (like I did). A couple hours of work is all it’ll take to turn that forgotten tool into a fine carving axe!

October was made for camping. Camping was made for carving.

Ahhh! October. Best month of the year, as far as I’m concerned. At least it is if you live in the Deep South. The heat and humidity of summer finally breaks, beckoning even the most climate-control-loving indoor enthusiasts into the open air. It was a month made for camping, so this past weekend, we headed for the oaky woods of Georgia with a few friends and pitched some tents by a lake. I packed a few simple tools – a small axe, a Sloyd knife, and couple of bent knives – and spent Saturday whittling by the fire.

I love my workshop, but sometimes at the end of a long work session, I gaze at my bench stacked haphazardly with so many complex tools – metal planes with a couple dozen precision-made parts, taper-ground saws,  micro-adjustable marking gauges, multiform chisels and gouges all of different shapes and sizes – and I marvel at the hundreds or thousands of hands and minds that coalesced to create this toolkit that allows me to create a simple (or sometimes not-so simple) piece of wooden furniture.

When I carve spoons, the tools are so simple so few that the opposite feeling is invited. One man at a forge could easily make in short order all of the tools that I need to turn a crooked branch to a ladle. I find few things more primally satisfying than taking a few pieces of sharpened steel and a stick of wood and carving something useful and beautiful.

Choosing a branch for spoon-carving is a good way to start any morning. It’s just a walk in the woods with a purpose. The woods around my campsite were filled with oak, hickory, and ash. All of them have large open pores, but I want a close-pored wood for carving spoons (It’s a preference, not a necessity. Some of my favorite spoons are catalpa and sassafras, which have big, open pores but the golden glow of the heartwood makes up for it). Sweetgum and blackgum were plentiful. Both have small pores and are easily carved, but they don’t split well due to interlocking grain so I passed them up (they are pretty homely woods, too, unless your sweetgum has rich reddish brown heartwood, but they don’t develop heartwood until they’re pretty big). I found some chalk maples, too. Maple makes a good spoon but chalk maples (Acer leucoderme) are a species of hard maple, and hard maple is, well, too hard. I prefer red maple for carving. The understory was filled with sparkleberry, and the occasional wild plum, crabapple, and hawthorn. All of these species are perfect for spoon carving. Close-grained and attractive wood.

My walk in the woods yielded a nice length of sparkleberry.

Crooks always yield interesting shapes, and sparkleberry always has plenty of crooks. Sparkleberry (Vaccinium arboreum) is a species of blueberry, and one of the few that reaches the size of a small tree. I’ve carved it before – the wood is hard and dense and honestly one of the tougher woods I’ve ever used – probably close to hard maple or yellow birch in hardness – but it has a lovely pink color that makes it completely worthwhile. Since it was the most plentiful, it was the easiest to find a branch that was worth carving.

The grain of this branch was particularly sinuous, so I took care to follow the grain perfectly. Not only does this result in the strongest spoon, it also creates an eye-catching shape. It’s slower going than carving straight-grained wood, but I love the end result.

I have never left the pith (the very center of the branch) in a spoon before, but for this spoon, it was too eye-catching to whittle it away. It’s wide and bright red and completely solid. I took special care to leave it on the underside of the handle. Sparkleberry has an eye-catching ray fleck as well, somewhere between maple and sycamore.

After I finished up the big serving spoon, my friend (a coffee aficionado) mentioned that he could use a replacement for his plastic coffee scoop. So I took a straight-grained section of wood and tried to carve something that was more worthy of his prized Guatemalan java beans.

He deemed it a success.

Both spoons, underside.

And topside.

This trip wasn’t all about woodworking, though. We still found plenty of time for hammock nonsense,

Stacked 5-high!

Cooking over an open fire,

My friends have an awesome blacksmith-made spit that I am officially coveting…

And enjoying the sunset by the lake.