How critical is moisture content of hafts?

T

Twindog

Gold Member
Joined
Apr 6, 2004
Messages
3,982
As I've been learning about axes, I've read and heard that one of the main reasons for heads to come loose is because they were hung while the moisture content of the haft is too high -- apparently more than 10 percent. When you use that axe in dry weather, the wood shrinks and the head can loosen up.

My long-time user axe -- a Collins from the '90s that sits in my outdoor shed -- has a moisture content of 19.6 percent.

My new House Handle hafts that have been sitting inside for a couple weeks have a moisture content of 10-15 percent. A couple rejects that have been sitting on the floor by my stove, read 6-10 percent.

My Granfors Bruks axes, which I keep inside, read 6.3 to 10.6 percent.

My Wetterling, which is fairly new, reads 7.4 percent.

My Helko axes, which are new and inside, vary from 6.3 to 11.9.

My cabin is all raw wood on the inside, and the paneling (T&G pine) and desks and such (Doug fir) are 6 to 10 percent.

I live in a rainforest, and my cabin is extremely well insulated, so I don't run a fire much.

I was wondering if people pay much attention to the moisture content of hafts and if you only hang axe heads on low-moisture hafts.
 
With a seasoned handle, moisture is only critical in the tongue when hanging an axe. Moisture can be removed with a heat source after the handle is fit, just prior to wedging.
 
It's not something that I ever considered before. Your comment made me wonder if moisture content varies along the length of the haft.

On an axe that I just hung and sanded the varnish off, and that has been sitting not far from the fire for a week or so, the moisture content does vary a little.

Butt: 10.8 percent
One-third up from butt: 10.8 percent
Two-thirds up from butt: 10.7 percent
Just below the eye: 12.1 percent
Top of eye: 12.7 percent

I don't know what to make of that, nor am I sure what the proper level of moisture is and how much of a difference it makes. In the past, I've always hung a new axe on a nice sunny day, and then left the axe in my shed, where the humidity would be high year round.
 
Seeing as you live in a high humidity area merely warm up (ie home kiln dry) your nicely fitted handle in a 180-200 F oven overnight and then set the wedge. The wood will swell back up again to lock the head into perpetuity for where you live, unless you decide to move to Arizona.
 
300Six said:
Seeing as you live in a high humidity area merely warm up (ie home kiln dry) your nicely fitted handle in a 180-200 F oven overnight and then set the wedge. The wood will swell back up again to lock the head into perpetuity for where you live, unless you decide to move to Arizona.
Click to expand...

Thanks for the tip.

It seems as though it could make a bid difference, maybe a 16th of an inch total, especially when both the wedge and the haft are shrinking.

Radial shrinkage (the width of a normal wedge) could be 2-8 percent. Longitudinal shrinkage (the deepness of the wedge) is much less, less than 0.2 percent.


shrinkage2.jpg



If both the haft tongues and the wedge shrink by 5 percent, that would be be enough to loosen a wedge.

http://www.wood-database.com/wood-articles/dimensional-shrinkage/
 
Moisture content (mc) can certainly have an effect when a head is hung. Axe handle stock is undoubtedly kiln dried, reducing mc to an "overdry" state. The wood then gains mc depending the humidity and temperature of where it is stored. That is it reaches "equilibrium moisture content" (emc). See a related article to the one in your post #6: http://www.wood-database.com/wood-articles/wood-and-moisture/. There is a graph there that relates emc to relative humidity.

My suggestion is to compare the current mc in the handle to what it will be where it is stored. You may not need to dry it further. For example, 10% mc would be maintained at a relative humidity of approx. 47%.

Bob
 
If things such as this really worry you then don't cut the wedge off flush when you think you're done. Leaving it 'proud' (1/8 to 1/4 inch) will allow you to tap it in further at a later date, or pull it out (for replacement) if you think something isn't right. Don't forget that a driven wedge imparts a lot of pressure and how resistant to compression a haft (and the wedge) are over the long run determine how tight a hang remains.
Wood is absolutely wonderful material and until over-stressed or rotted away lives and breathes (shrinks and expands) continually, and some types are way better than others.
 
It's not that I'm overly worried, I'm just trying to learn the proper way to hang an axe. It's a big thing to get all the small things right.

I noticed that Gransfors Bruks also recommends that the haft and wedge be dry:

"It is important that the axe handle is of high quality. The handle and the wooden wedge have to be very dry when fitting. If not, they will dry and shrink later, loosening the head."

http://www.gransforsbruk.com/en/axe-knowledge/caring-for-your-axe/fitting-an-axe-with-a-handle/

Mostly, I was looking for a number corresponding to the proper moisture content, such as 10 percent moisture content, that I could check before hanging an axe.
 
Hi there. New to the forum here. I've seen some great advice. Ben Orford of the UK has a video about making axe handles and says that to dry the wood after the handle is made simply leave it by the wood stove or another heat source. First weigh it and continue checking the weight. When it loses no more weight then hang the head.
Well it is a humid summer hear on the east coast of Canada and so I put the handle of the axe I am working on by the dehumidifier in the basement. (Because I'm not using heat right now!) I have been weighing it but I just don't trust it. It is so humid and the dehumidifier is filling constantly. The wood wasn't losing much weight. Could be the humidity, could be that it was dry enough to begin with.
So I decided to google the issue and found this thread so helpful. 300Six thank you for the oven trick!!! I hadn't thought about that! Twindog thanks for asking the questions. Soon as I saw this I knew it would work because of my woodwork training and experience. Just one of those things you need a reminder of once in awhile.
 
You must log in or register to reply here.
Back
Top