Hammers to Use With Chisels Part 2 – Hammer Faces

The Jabberwock! Not just a beautiful face.

Beware the Jabberwock, my son!
      The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
      The frumious Bandersnatch!

Lewis Carroll

This is the second post in our six-part series about hammers to use with our chisels. As with all the tool-related articles we publish, this one is based on past communications with, and in response to direct questions from, our Beloved Customers. Your humble servant hopes that not only Beloved Customers (may the hair on their toes never fall out) but Gentle Readers too may gain something from these articles.

We sell limited quantities of hand-forged professional-grade chisels to professionals who use them to please their customers and feed their families.

We are tickled pink when amateurs purchase our products, but our target customer is the experienced professional woodworker. If you do your part our chisels will provide faithful, reliable service until, after many decades, nothing is left of the blade but a nub. But to achieve this longevity, and to avoid smiles turning upside down, we insist Beloved Customers use flat-faced hammers to motivate our chisels as a condition of our warranty. It’s that important, at least for the professional that uses his chisel even after the blade and handle become hot.

375gm gennou by Kosaburo with a black Persimmon handle resting on a Go board. The head is a classical style seldom seen nowadays.

In the previous post in this series we looked at the Japanese gennou hammer with its two faces: one domed and the other flat. In this post we will examine these two styles of hammer faces in more detail. We will leave waffle-faces to the Belgians for now.

The Domed Hammer Face

Does this domed face look perfectly centered to you? Does it looks smooth? Can it be improved?

Few people in industrialized countries outside of Japan have any experience with flat-faced hammers since manufacturers automatically grind a convex or domed striking face on their hammers nowadays. It’s simply what consumers are accustomed too. But I daresay few have ever considered the ramifications of the dome.

A domed face on a hammer has some advantages, of course. For instance, when one needs to “set” a nail with it’s head just below the flat surface of the piece of wood into which the nail is driven. But does a domed face help the hammer drive nails faster or straighter? Does it help reduce the ratio of bent nails to straight nails? Does it motivate chisels more efficiently? No, no and no.

Another more questionable feature of the domed face (depending on your viewpoint) is that it makes it difficult to judge the accuracy of one’s alignment of the centerpoint of the domed face and with the centerline of the hammer head. Who, pray tell, profits from this ambivalent construction? I’ll give you one guess, and it ain’t me or thee.

Indeed, if your working hammer tends to bend a lot of nails, I recommend you carefully examine its face with a square for centricity and uniformity. “Doh! (palm to forehead). No frikin wonder,” may well be your genteel reaction.

While it may seem passing strange, we strongly recommend Beloved Customers use a hammer with a flat striking face to motivate our oiirenomi chisels, atsunomi chisels, and mortise chisels.

So why is a domed-face hammer a problem when striking Japanese chisels? Simply because it tends to focus the impact forces on a relatively smaller area on the wooden handle than a flat-faced hammer does accelerating the wear and shortening the life of the handle.

In addition, and especially if you are skilled at hitting the handle dead-center a high percentage of the time, a domed face will actually encourage the crown to try to jump off the handle and to become beaten up, sometimes even dangerously deformed, eventually damaging the handle.

The Flat Hammer Face

While your humble servant is inordinately fond of the Japanese gennou hammer, it is by no means the only viable option. Indeed, you can easily modify most any decent-quality, properly-hardened hammer to have a flat face by simply abrading it with a grinder or sander.

Be sure you make the new face planar (flat) and truly square to the hammer’s centerline because a tilt to the left or right will make doing precise work inexplicably difficult and may lead to insanity. I once knew a “frugal” carpenter (read “cheap jackass”) who insisted on using a hammer with a skewampus face. The cumulative corrosion to his confidence caused his wits to wander into the weeds (iambic pentameter?). A sad but too common story, I fear.

If you are modifying a standard hammer with a standard handle, you may benefit from tilting the face’s plane a bit inwards towards the handle, but there is not adequate space in this post to discuss this modification in more detail.

Whatever you do, be especially careful to avoid overheating the hammer’s face while grinding/sanding it; Too hot and the temper will be damaged softening the hammer’s face and ruining it. Seriously. Even a wooden chisel handle will eventually mushroom a steel hammer that has lost its temper. Here’s a guideline: If the hammer’s face becomes becomes too hot to touch with your bare finger, its temper is at serious risk.

Finally, once the face is as flat and square and smooth as you can make it with your grinder or sander, be sure to polish the face because a smooth face wears out the chisel handle slower. A final polish with 320 grit W/D sandpaper is adequate. We polish ours even finer on sharpening stones. Overkill? Yup. Why bother? Because we like purty hammers and they deserve our love. Don’t worry, the polish won’t make the hammer’s face slippery, unless you spread butter over it as the March Hare did to his watch.

By the way, once you your flat-face hammer is ready, try driving nails with it. You will find it works a lot better for everything except setting nailheads below the board’s face. A nailset works better for that job anyway.

We hope our Beloved Customers will take this article to heart for the sake of their chisels.


In this post we reviewed two types of hammer faces: domed and flat. We also considered the advantages and disadvantages of each, and explained why a flat face is best for beating on Japanese chisels, and gave an example of the brutish damage a domed face can inflict on a poor innocent chisel. Like me, some of you may have shed a tear at the sight, but I bid you take heart because we also instructed you in how to convert a common domed-face hammer of any sort to a more genteel and polished flat-faced hammer at no cost, one that will also drive nails better without butter. O frabjous day! Callooh! Callay!

To motivate chisels efficiently, the hammer must not only have a flat face, but it must be of the appropriate weight. Of course, the harder the wood, the deeper the cut, the wider and heavier the chisel, the heavier the hammer needed. But what is an efficient hammer weight? We will examine some options in the next post in this series. Please stay tuned, my beamish boy.

Until then, I have the honor to remain,


A hand-forged square gennou head by Hiroki with a handle made from a traditional Japanese handle wood called “Kamatsu” (Pourthiaea villosa) meaning “sickle handle, also called “Ushikoroshi (“cow killer”). Despite the appearance, the head is one-piece of uniform steel, not a jigane body with forge-welded steel faces. BTW, if someone tells you that hammers with forge-welded faces are superior, direct them to the closest legal marijuana dispensary so they can maintain their waking psychotic dreams.

If you have questions or would like to learn more about our tools, please click the see the “Pricelist” link here or at the top of the page and use the “Contact Us” form located immediately below.

Please share your insights and comments with everyone in the form located further below labeled “Leave a Reply.” We aren’t evil Google, fascist facebook, or thuggish Twitter and so won’t sell, share, or profitably “misplace” your information. If I lie may a Bandersnatch fruminate all over my face!

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