Wood Scale Shrinkage

JackstrawIII

JackstrawIII

Joined
Jan 25, 2015
Messages
429
Hey fellow makers,

Now that it's cold up here in NY, I've noticed an issue with some of the wood-handled knives I made over the summer. On some of them (not all) the wood appears to be shrinking. I can now feel the corners of the exposed tang and the pins are no longer flush. I secure all my scales with G-Flex epoxy in addition to the pins, but this is still happening.

Is there something I'm doing wrong, or could be doing differently in order to minimize this issue?

Thanks in advance.
 
Being in Iowa/Wisconsin where my knives see a potential swing between a humid 100+ in the summer and a very dry -10 or lower in the winter deer season I only use professionally stabilized woods. Even then with some woods I have seen a small amount of shrinkage on a knife or two.
 
The wood will expand and shrink with the enviroment if it is not stablized.

it is the nature of the beast.
 
Not wanting to hijack the thread but is there any way to stabilize wood scales on a hobbyist level ?


Sent via telegraph with the same fingers I use to sip whiskey.
 
Have seen stabilized wood shrink if it has not set awhile. You don't have a clue when it was cut . I have found wood, mammoth and walrus ya need to let it set for atleast a year if its a big piece of wood or ivory of any type the year doesn't start untill it cut in scale size pieces.
 
With non stabilized (untreated) wood you can control shrinkage or minimize it with a good finish.
Some of the guys here like to go unfinished but they will have shrinkage and wood movement.

How are you finishing the wood?
Most woods do well with a Danish or Tru-oil finish.
 
I have a piece of spalted pecan, it's from a tree that fell in my yard. I blocked it up about 6 months ago and split some not long ago and I fell in love with the spalted grain. I know it's not the best handle material out there but it's gonna be a personal project. I haven't done much woodworking but have had good success refinishing a couple gunstocks with TruOil so that's what I planned to use if there were no better suggestions.


Sent via telegraph with the same fingers I use to sip whiskey.
 
I believe you will find the softer woods move more than the hardest. Pecan is a medium or soft/hard wood imo. It will expand/shrink more than something like desert ironwood.
 
Get the moisture out, keep the moisture out, and that's about the best you can do. Moisture is what is going to cause the most expansion and contraction. It may seem like temperature swings are doing it, but when they're warm, pores and vessels and spaces open up and draw moisture from the air. When it's cold they contract and expel moisture to the air.

It's like a sponge in a ziplock bag. Squeeze the sponge, seal the bag, and the sponge stays. Hot cold warm wet doesn't matter. Leave the bag open and it does whatever it does.

Or stabilize the sponge and you can use it as a bludgeon :)
 
i bet the wood was too wet. i had that happen in the past, bought a wood moisture meter. 5-8% moisture is the right area.
 
Come summertime the AC will fix it. :very_drunk:

3fifty7 you can send your wood to be stabilized if you want. It needs to be dried to under 10% first. K&G is a good place to send it. http://www.kandgstabilizing.com/
 
What was mentioned above is true. We used kiln dried wood at work building trusses for the housing market (MSR wood, but it was softwood not hardwood). This stuff comes out of Canada on rail cars, but it ships into Tucson. No matter how "dry" it was from the kiln, it would shrink once it got into town & sat in 100+ heat @ 6% humidity for a while. Once the summer rains started, it would swell a bit due to the humidity in the air. It was nice clean, straight grain wood, but it would always move. Wood moves more across the grain than lengthwise.

For knife grips I use hardwood which has been sitting in the shop for a few years, but it can still change dimension with a change in relative humidity. The hardest woods tend to move less. Epoxy on the blade at the joint & a good oil finish (a complete saturation of the wood fiber to help keep out the moisture, Danish or Tung oil) will help prevent movement, but it can still change seasonally. Ironwood which is dry is pretty stable, as well as some of the more oily woods, but encapsulation in a resin is about the only way I know of to keep wood from moving.

If you start with a good, dense, dry, hardwood, then glue & pin it in place with epoxy & use an oil or epoxy finish, that's as good as you will get on a blade, without a commercially stabilized wood. I'm lucky to live in a climate where we don't have as much shift in humidity as some places do. Try ironwood or ebony for something hard & stable, but make sure it's completely dry first. Cellulose will wick moisture out of thin air if there isn't a "barrier" to protect it.....
 
There is stuff called "Cactus Juice" and some simple homemade appratus, one can accomplish DIY stabilization.
One could potentially treat a finished knife in the stuff.
 
I do a fair amount of stabilizing myself with Cactus Juice. I wouldn't recommend trying to do a finished knife. Baking to cure would kill your epoxy joints for starters, but also likely there would be dimensional changes as it heats and cools during the curing process that would effect the pin holes, guard/bolster fit, etc.
 
I thought even stabilized wood can shrink and expand a little bit, too. The resin used can vary greatly in physical properties.
 
Everything can. Your blade steel will shrink or expand. A 6.000" long blade at 32 F will be a 6.0065" blade at 100 F. But stabilized woods, whether professionally done or with something like Cactus Juice, or engineered wood products, seem to move significantly less than their counterparts.
 
As someone who has done a lot of wood work, I find that the vast majority of handle scale failure is not due to changing humidity, but rather to not using dry wood in the first place.

The shrinkage and expansion is a percentage of movement, so a 3 foot wide table is going to move maybe 1/4-1/2 of an inch with a pretty big seasonal change. A handle is going to move very little. The big issue is that people buy exotic wood and figure it must be dry. Most of the time, it's not. I mostly buy very very old wood, things that I know have been in the U.S for at least a few decades, but when I get newer wood, I wax the ends and leave it alone for 2, 3 or even maybe 4 years to make sure it is dry.

Exotic woods ate inherently very stable when dry, but pronever to cracking when they are drying from being green.

The answer is to either buy dry wood, or wait a good long while. If a piece of exotic wood is really cheap, think about it. It's a lot cheaper to gethe a piece of wood in, dunk it in wax and send it out the door then baby it with drying and then cut away any cracked areas.
 
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