Posts filed under hatchets

Axe Handle Breakage, Designing For Resiliency, Weak Links and Stress Distribution

An axe head with a wooden handle has some inherent problems. The head and handle are made of very different materials that behave differently. Steel has a very high density compared to wood. Wood is much more flexible than steel and will dent and break more easily. When using an axe, these differences can cause problems, such as the wood being damaged by forceful contact with the hard unyielding metal head, or the relatively high density of the steel head behaving differently than the handle, thereby putting stresses on the weaker wood. Breakage just below the eye is a very common occurrence. This article and video are an attempt to explain some common reasons why axes frequently break near the eye, having to do with design, or perhaps lack of design in some cases. Breakage in the main body of the handle can of course also occur, but I’m not really dealing with that here. I’m pretty sure that the greater percentage of axe handle breakages are initiated right where the handle meets the bottom of the eye, or within the first few inches of handle, especially if the breakage is not due to wonky grain or other defects. Shear stresses seem to be particularly high in this part of the handle.

In this article, I will be assuming that we are dealing mostly with American axe head patterns, which tend to have thinner eyes than European and Scandinavian axes. Even though American axe styles migrated back to Europe (many axe patterns on that side of the pond are actually American or modified American patterns) the axe eye sizes largely remained bigger than American axe eyes. This is an important point when we look at overall handle design, because with any given axe head, the eye shape just is what it is, and the size and shape of the wood where it enters the eye is therefore pre-determined. Some of these problems are obviated by the use of tapered axe eyes, in which the handle feeds in from the top and fits by friction, but that is a separate subject also. The assumption here is that we are dealing with American style patterns that are wedged from the top. For whatever mix of cultural and practical reasons, these axes have pushed the limits of strength and resilience of the wood used in handles, by evolving toward a small eye.

Aside from the size of the axe eye being fixed, there are two other things that are pretty much givens as well.

One is that the section of handle just below the eye, lengthwise (poll to blade) is wider than the rest of the handle. If the whole handle was the same front to back dimension as the eye length, it would be unusable, so the body of the haft has to slim down soon after leaving the eye.

Predetermined factor number two is that we need a slight flair in handle thickness just below the eye at the back of the handle, as well as on both sides, so that the head seats firmly around the bottom as it is driven on. The front edge of the handle can come straight out of the eye if desired, with no rise, but the other three sides need at least some flair, though not very much. In my view, it is always unnecessary, and also a detriment, to come out of the front of the eye and then immediately outward, forming a shoulder. I see no reason to do that, and every reason not to. If the handle isn’t completely straight coming out of the front of the eye, the rise is best made as a gentle transition.

WE CAN CONSCIOUSLY WORK AROUND THESE FIXED PARAMETERS. IN OTHER WORDS, DESIGN AROUND THE THINGS WE CAN’T CHANGE.

A Few Common Axe Handle Mistakes and What to Do About Them

On a recent snowy morning I answered a YouTube comment on axe handle breakage that led to a one take video shoot with a beautiful snowy background.  Being conceived and shot in one morning, this is just a partial snapshot of the subject.  It revolves around the specific problem of design factors contributing to handle breakage just below the axe eye.   It could easily have snowballed into a multi-part series on axe handle function and design ideas, leading to yet another video or series on user contributions to breakage; but the snow melted and I couldn't throw out that beautiful backdrop, which some people actually thought was done with a green screen!

This is viewed primarily from the perspective of American axes, which are evolved in the direction of high performance with the consequence of increased delicacy.  At least that is my current take on it.  An axe is a system composed of a handle and head which creates some inherent problems.  In America, the European axe systems that migrated here with early colonists eventually evolved toward higher performance creating narrower eyes that are inherently weaker than the wider ones they descended from.  European axe eyes seem to have remained wider for the most part, often even when copying American patterns.  In fact, I think the standard American axes are refined to a point where the handles could not be much thinner at the eye without becoming impractical for use with wooden handles, and some might argue that they already have become too thin.  That is a subject for another time though.  For now we will just look at, common problems that we see from both manufacturers and folks producing handles at home, which are easy enough to fix with some tuning up. 

While there are a lot of people that understand some of this intuitively and practice it, I don't recall seeing it spelled out anywhere.  It is my hope that this information will spread and eventually reach manufacturers, many of whom who are clearly not axe users.  Most axe handles will need work out of the factory and that is fine, but the mistakes that are greater in concept and scale are costing a lot of handle breakages at the eye that are totally unnecessary.  The essential problem is that manufacturers think they can just increase the thickness of the handle body to decrease handle breakage.  When viewed as a dynamic system though, it quickly becomes obvious that doing so puts undue stress on the thin eye portion of the axe, instead of sharing the stress across the length of the handle. At some point, continuing to thin a handle will obviously reverse that problem and create excessive vulnerability in the handle's main body.  That is really another level of this discussion though and one I purposefully avoided in this presentation.  Another issue is that there are other types of stress that are incurred from different types of use or mishap that may be more likely to break the body of the handle.  The grain of the wood and it's character is also at play.  We are dealing with a tool that sees different types of stress at different times, has inherent problems that are not entirely solvable and involves an inconsistent natural material.  Wood of even the best quality has fatal faults.  We continue to use it for the same type of reasons I continue to use vacuum tubes in my stereo and guitar amps, and that is user experience.  I personally also like wood because I can cut down a tree and make a new handle without relying on industrially produced products that I have to buy.

There is a lot of forgiving grey area in this problem and we don't have to engineer a perfect handle.  But, we do need to avoid the largest mistakes being made and if we get a handle that has them, we can tune those problems down until we have something that is more comfortable to use for long periods of time and also reduces stress on the eye.  I don't think I've seen a handle yet where the problem encountered was too little wood to work with!

Enough said here.  While this video is incomplete, it presents some ideas that I think are important and which can go a long way toward practical solutions. 

Axe Buying Checklist Series, #1 Damage and Wear

This is a series on common problems found with axes from craftsmanship to use and abuse.  There are many points, like a checklist of things to look at when picking up an axe or axe head which few people are savvy enough to know to look for all of.  After this series, you'll have that mental checklist. 

The four video segments are on:

Wear and Damage,

Symmetry,

Handles

Options and Axe Hunting

Most used axes are either worn or abused in some way.  Fortunately, they are often perfectly serviceable anyway, usually after a little work.  New axes can have various issues and seemingly perfect axes seem to be the exception. 

This links to the video playlist.  One video will come out every day for the next few days.

Penetration, Saturation and Coating, 3 Main Factors in Oiling Wooden Axe and Tool Handles

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Over the years I keep evolving and refining my methods and understanding of the process of oiling tool handles.  Although it is painfully simple, the obvious is not always so obvious.  I've been soaking my handles pretty deeply with oil for a long time, but still have had something of a fixation on coating them with a protective coat.  Until, I realized that a well saturated handle is it's own finish, and more.

a Coating ona a handle is a barrier between the wood and the environment.  But does it achieve that goal well, and what is the goal anyway?  The goal is to protect the handle from environmental changes in moisture basically.  Moisture swells the wood, and when it leaves, the wood shrinks.  When wood shrinks, it is stressed and those stressed can lead to cracks.   For some reason cracks seem more likely to form if the wood swells and shrinks repeatedly.  If the wood swells within the eye of a tool, the wood compresses against the hard metal of the eye walls, becoming crushed.  When it shrinks on drying again, it many shrink smaller, than it was before it expanded.  That is why soaking the eye of a tool in water when it is loose will eventually make it even looser.  A good thick coating of cured linseed oil can help prevent the entry of moisture, and anytime oil is used on a handle, some of it soaks into the wood to some depth, bringing in the factor of penetration, which must help some.  A coating is basically still very thin though and will wear off over time.  These are handles remember,  They are essentially rubbed over and over again.  And although some penetration is always occurring, the questions to ask is how much good is penetration when it is shallow and of a low saturation.

Enter Saturation.  Saturation if you look it up, basically means full or at maximum capacity.  But it is commonly used with a quantifier or clarification like partially, mostly, completely.  If I soak a handle numerous times with linseed oil, it will penetrate to a certain depth, but unless it is applied regularly and in quantity, it will have a very low saturation as the oil spreads itself out deep into the wood structure.  Eventually, it either reaches the middle or some unknown depth and starts to increase it's saturation eventually filling the wood to the point that no more will soak in.  This 2 minute video shows the process I pretty much use now.  If you get tired of adding expensive oil to a handle, try stopping for a month to let the oil in the handle cure and penetration should slow down.  Some handles will take a lot of oil.  Fortunately, oil is light.

Now if we think about a handle that is fully saturated with oil, for even 1/8 of an inch deep, let alone more, we now have something like the equivalent of a 1/8 inch coating.  But even more cool, it is actually protecting the wood itself by filling the pores and structures that water would fill.  If you leave such a handle out in the weather, water droplets just bead up on it and sit there.  Not recommended, they aren't necessarily immune to moisture, but it's telling.

droplets on a well saturated knife handle.  Two hours later they were still there, though smaller, but I have little doubt that at least the majority of missing water left be way of evaporation and not penetration.  That is a test better done in high humidity, not on a warm breezy morning.  This handle has probably not been oiled since it was originally treated 2 or 3 years ago.  After all, the treatment cannot wear off.

droplets on a well saturated knife handle.  Two hours later they were still there, though smaller, but I have little doubt that at least the majority of missing water left be way of evaporation and not penetration.  That is a test better done in high humidity, not on a warm breezy morning.  This handle has probably not been oiled since it was originally treated 2 or 3 years ago.  After all, the treatment cannot wear off.

Try it on a handle and see what you think.  It is a long process and the oil is not always cheap.  many tools are also not subjected to much in the way of atmospheric changes, so it's not something we have to use everywhere.  I'm pretty sold on it though and any axe that I plan to keep and use gets the full treatment now.  Dudley cook recommends the same basically, but he maintains with an occasional coat, which I think is unnecessary if the wood on the outside of the handle is well saturated.  The wood essentially becomes it's own finish.  If the wood will ever take oil on and soak it up, do it, but it it doesn't, there is no need to keep coating it. 

I use food grade linseed oil (usually labeled as flax oil, which is the same thing) anymore and have found ways to pick it up cheap enough.  Boiled linseed oil is toxic and I think it probably dries too fast.  Prices change on amazon constantly, but this brand is usually about the cheapest, but do your own research.  I've also found flax oil at the local cheap food outlet where they send overstock and expiring stuff.  Other oils can be used as well, walnut, hemp, poppyseed and tung oil should be adequate, but I really haven't used any of them enough to say for sure.

For handles that you don't need to saturate, I recommend a thin coat of oil once or twice a year, or better, just whenever you have an oily linseed rag.  Raw linseed oil will cure, it just takes longer.  So called "boiled linseed oil" contains metallic driers and solvents that speed curing time.

I have more ideas and experiments brewing around this problem, and no doubt you'll hear more about it in the future.

Of Sharp Tools and Dummy Rules, A Safety Framework and 1/2 Hour Video Just Talking About an Axe Handle

Here is something I recorded regarding safety when using sharp tools.  I hope it conveys my basic approach and philosophy regarding the subject.  I'm much more about a general approach and philosophy adopted as a framework in which to approach work than I am about sets of rules.  Most rules that are stated as absolutes need all kinds of qualification that they don't always get.  Not only is that ineffective when engaging in real world work, it can be dangerous.  What I like to call dummy or boy scout rules are generally stated in absolutes like never and always.  That discourages intelligent engagement with the work at hand and defers your safety to an authoritative statement or entity.  The idea seems to be that if you just do this one thing, you will be safe.  If you're doing real work in the real world, you'll find that most of those rules will be broken, and some frequently, in order to carry out work at all or to do work more practically or more efficiently.  It would be more constructive to state these as guidelines and be realistic about the risks involved and strategies one can employ to ameliorate risk when doing things that are dangerous, or when using sharp tools in the grey area that exist between the very safest ways to do things and the most effective.  The usual black and white approach can lead, I believe, to unsafe work approaches when trying to bend your self and your work to static and overstated rules which experienced craftsmen and workers may not actually follow.  In the future I'll get more specific on knife and axe safety, but this is actually some of the more important part to me.  

Also, I forgot to post this video on the husqvarna axe handle.  It covers various points regarding the handle and planned modifications and as a matter of course addresses some stuff about axe handles in general.

Pocket Axe Strop Production Part 1, Introduction, Liming Hides and Selecting Wood

This is part 1 of my project to build up Pocket axe strops from scratch as incentive/rewards for the Axe Cordwood Challenge.  I may also sell some on the website depending on numerous factors.  For those who don't know, a strop is a device for polishing or refining a sharpened edge.  it is the last step in many sharpening sequences and can also be used to touch up edges, especially if polishing compound is used.  It usually involves leather, which my design of course does, but the act of stropping can also be done on wood or even cloth.  In this project, I'm building strops from the ground up, which involves, tanning, glue making and working up some wood from it's raw log-like state.  There should be no materials used in these strops that were not processed by me here on the homestead, down to the lime and fat used in preparing the leather.  The project will span an undetermined number of videos, as well as a short version of making an easy high quality hide glue from scraps that most hunters or butchers of animals typically throw away.  Almost anyone who is not me should learn a lot from this series and I hope to learn some stuff too! ;)  Feel free to vote on names for the pocket strop or think of new ones... Stropet, Pocket Strop-It, Pixie Paddle (the woods are a dangerous place full of mischievious pixies!).

Vintage Swedish Hatchet Restoration Part 1: Making the Handle Blank

This is the start of restoring a vintage hatchet.  Actually I'm going to modify the head quite a bit, so what I'm really doing is trying to improve it and make it functional.  In this video I make the handle blank which is now seasoned and ready to make into a handle.  Other steps will be to modify and refine the head, shape the handle, put the handle on, oil it and make a sheath.  I'm not sure when I'll get all that done, but this was the first step....