Square_peg
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Good informative discussion, guys. Kudos.
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A source for decent wood wedges...?
- Thread starter chevyguy72
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The paper is not about drying lumber (green to dry). It's about shrinking and swelling of already "dried" lumber. That movement is not taken directly from Appendix III. An Appendix III value is only a relative factor used to calculate that movement.
To calculate this movement, Eckelman presents this equation under the subtitle "Quantitative Amounts of Shrinkage":
AW = W[(SC) / 100] × Amc / 30
Where:
"SC = the appropriate shrinkage coefficient given in Appendix III."
"Quantitative
Quantitative information or data is based on quantities obtained using a quantifiable measurement process. In contrast, qualitative information records qualities that are descriptive, subjective or difficult to measure."
https://en.wikipedia.org/wiki/Quantitative
The "green to dry" values (Appendix III) used are known (quantitative) values. Those shrinkage percentages represent the maximum percentage that a particular wood species can move. Green (largest dimension) to dry (smallest dimension) for that species.
The equation uses a known value (largest to smallest) to calculate the value that wood will move within a smaller range of movement (eg seasonal movement in a given location).
As a practical matter, if I bring a "dried" piece of wood into a particular environment and location and let it acclimate, how much will that piece move in the following year?
Would you use the equation Eckelman presents in the paper to obtain that information?
If not, what is the mathematical/physical reason, why not? And what would you use instead?
Do you have an alternative set of quantitative coefficients? What are they? Where do they come from? How are they used (i.e. a mathematical equation)?
I am more than willing to go wherever the numbers based on empirical evidence and logic (mathematics) take me on this subject.
Bob
Whoooh. We were on to wedges at one time. Sure they'll want to move to some degree due to humidity but when you figure they're only 3/16 to 1/4 inch thick just how much (or how little) is that? Could be that Yellow Poplar is traditionally used for wedges because it remains springy despite being thoroughly compressed when it's driven in.
Interesting - I had missed that the author is correcting for exactly what I'm talking about --> he's dividing the green to dry figure from the table by an estimate of the fiber saturation point (mentioned in the section before that formula). I think that's what he's doing anyway, since he divides by 30 and mentions that 30% is a reasonable assumption of FSP for wood in general. Hardwoods will tend to be lower, but only down to 20% or so.
Take that 0.63"/32" for his maple top example and what percentage does it work out to? 2% - roughly what experience leads me to guess you'd see - I would actually expect around 3/8" to 1/2" for maple, but adjusting the FSP for something more in line with hardwoods could correct that.
So yes, you can use that formula to adjust for the range of emc you'll actually see in use of dried wood.
Glad you stuck with it - you made me read more closely and learn something!
(and thumbs up )
As an aside, I went and found the writeup of that informal experiment I mentioned. I still wonder if the guy let his samples acclimate long enough, as the percentages he came up with seem a bit on the low side - but then I've not made a close study of it.
https://woodgears.ca/wood_grain/shrinkage.html
EDIT: Had to ditch the quoted part, all those brackets seemed to be confusing the quote syntax.
Take that 0.63"/32" for his maple top example and what percentage does it work out to? 2% - roughly what experience leads me to guess you'd see - I would actually expect around 3/8" to 1/2" for maple, but adjusting the FSP for something more in line with hardwoods could correct that.
So yes, you can use that formula to adjust for the range of emc you'll actually see in use of dried wood.
Glad you stuck with it - you made me read more closely and learn something!
(and thumbs up )As an aside, I went and found the writeup of that informal experiment I mentioned. I still wonder if the guy let his samples acclimate long enough, as the percentages he came up with seem a bit on the low side - but then I've not made a close study of it.
https://woodgears.ca/wood_grain/shrinkage.html
EDIT: Had to ditch the quoted part, all those brackets seemed to be confusing the quote syntax.
Yeah, if it moved 2% from summer to winter that would only be 0.005" on a 1/4" wedge.
I just made some beech wedges yesterday for a Hudson Bay rehang I'll do soon. I wonder now if I ought to scare up a bit of poplar instead
I think you may be right about the springiness.Yeah, if it moved 2% from summer to winter that would only be 0.005" on a 1/4" wedge.
I just made some beech wedges yesterday for a Hudson Bay rehang I'll do soon. I wonder now if I ought to scare up a bit of poplar instead
One decent suggestion that was made on this forum awhile back was to use wedges of a material that is softer than the hickory (or whatever) haft itself. Old_Axeman himself (if I recall) was on side in this regard although I think he's also a fan of Poplar. Walnut, cherry, soft maple and whole bunch of others fall under this category if you're insistent about using a hardwood. Much as folks tell me otherwise I have personally always used hard wood wedges (made thinner than those you get from the store) and have never managed to split an axe head or deform an eye because of wedging action. Sock the oil to the hang once your done and keep oiling the eye whenever you get a chance. If you can displace the air voids in the wood then it cannot move very much anymore after.
I'm pretty sure I have a decent scrap of poplar around, I just don't use it often enough to have much. Beech isn't exactly what I'd call springy, it was just the first scrap I grabbed out of the bin. Might try walnut too, I have plenty of that on hand and usually a wide range of scraps in the kindling box.
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You may be surprised by searching "green woodworking".
These videos may not be you cup of tea, but others may find them interesting. Good information on wood grain and a wee bit of axe work in them:
"THE WOODWRIGHT'S SHOP
Paneled Chest with Peter Follansbee
A master joiner shows Roy Underhill how to make and fit the beveled panels and storage till into a framed chest from the Pilgrim era."
pt 1 http://www.pbs.org/video/2365021510/
pt 2 http://www.pbs.org/video/2365079634/
Paneled Chest with Peter Follansbee
A master joiner shows Roy Underhill how to make and fit the beveled panels and storage till into a framed chest from the Pilgrim era."
pt 1 http://www.pbs.org/video/2365021510/
pt 2 http://www.pbs.org/video/2365079634/
Bob
I may watch those if I have time this week. I'm pretty sure that the green work is limited to riving the wood in this case - that would has to be dry before you build a chest out of it, even if it's a paneled chest. As far as I know, actual green woodworking is limited to a couple specialized fields of chairmaking & what I would call twig furniture for lack of a better term.
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"For the past eleven years, I have worked at Plimoth Plantation in Plymouth, Massachusetts, as the joiner and turner. In this position, I meet thousands of visitors each year, who come into the shop and see me at work on all stages of making the reproduction furniture used in our re-created seventeenth-century houses. Because of the popularity of woodworking in general, there are visitors every day who have some knowledge of the craft, but have not usually seen someone working with hand tools, nor with green wood. A certain number of visitors, both woodworkers and non-woodworkers, are astounded at the level of complexity possible with only hand tools. When I describe that the stock is riven, or split, from the log, and worked from green wood, they are further surprised."
Peter Follansbee
Bob
Peter Follansbee
Bob
So are you saying he builds the chest out of green wood?
Or rives the billets green, perhaps rough dimensions them green, then lets them air dry before final dimensioning?
I probably won't have time to watch those vids before tomorrow night or perhaps later in the week. I'm sure he outlines the process there as well, but you won't spoil it by spilling the beans now
Or rives the billets green, perhaps rough dimensions them green, then lets them air dry before final dimensioning?
I probably won't have time to watch those vids before tomorrow night or perhaps later in the week. I'm sure he outlines the process there as well, but you won't spoil it by spilling the beans now
You'll want to be a master craftsman, or better yet a magician, if you figure on trying to build furniture out of 'green' wood. Sure, if everything is equally 'green' you'd think it ought to uniformly stay together as it cures but lengths behave quite different from widths and there is no getting around those properties nor is there any foolproof technique for fully being able to account for such movement either.
Ok, had time to watch the first one. Not green woodworking. There is absolutely no advantage to making a frame and panel chest of green wood, but there are several distinct disadvantages.
It did not appear to me that he was riving green either, but who knows. I would imagine that you'd dry the wood billets first in any case, to reduce checking in the finished piece.
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I think it would be useful to define "green woodworking".
First, I would define "dry" wood (YMMV) as wood that has lost all of its free water and the bound water has come into equilibrium with the relative humidity of the air surrounding it.
So, I would think of "green wood" as not "dry".
He does rive from freshly cut logs.
Another video in which it is quite clear about the wood.
[video=youtube;x_BGZHP6r2E]https://www.youtube.com/watch?v=x_BGZHP6r2E[/video]
Bob
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Not entirely, the mortice and tenons are cut, drawbored and assembled in the still "green" state.
Result:
"I mark out the joint with a mortise gauge, awl, and square, then chop the mortise with a chisel and mallet. Maybe some work with a paring chisel afterwards to clean up the insides of the mortise a bit...not too tidy though. Green wood cuts the easiest. A little drying beforehand is not a bad thing, but its still wet inside."
Bob
Peter Follansbee' blog: https://pfollansbee.wordpress.com/
Jennie Alexander: http://www.greenwoodworking.com/Home
Not entirely, the mortice and tenons are cut, drawbored and assembled in the still "green" state.
Result:
"I mark out the joint with a mortise gauge, awl, and square, then chop the mortise with a chisel and mallet. Maybe some work with a paring chisel afterwards to clean up the insides of the mortise a bit...not too tidy though. Green wood cuts the easiest. A little drying beforehand is not a bad thing, but its still wet inside."
Bob
Peter Follansbee' blog: https://pfollansbee.wordpress.com/
Jennie Alexander: http://www.greenwoodworking.com/Home
Interesting method, but riskier than using seasoned wood - ie "dry". The reason it's risky is that if you do not gauge the drawbore offset just right, you risk breaking the pin as the piece dries and attempts to bend the pin, pulling the tennon along with the shrinking leg. I've broken drawbore pins before, it sucks.
The other risk is that you have panels that rattle, but he doesn't seem too concerned about that - back when I did this stuff for a living, building rattly furniture was a sure way to get a stern look and perhaps docked pay from the boss.
I gather the reason to take these risks, and others, is that if you're going to build with quartered oak you normally would have to sand a lot - the stuff is terrible for tearing out on you as you try to plane it. I didn't know anyone took it to that extreme, green casework still strikes me as a headache waiting to happen.
Sorry I didn't watch the whole thing, I kinda prefer doing to watching - I was out in the shop making a handle for my S&N Hudson Bay axe!
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Undoubtedly with kiln dried sawn stock, power tools, and lots of sandpaper.
Bob
Fitting and hanging a 'green' handle conceivably could be accomplished but would require seating the head gradually plus using cross wedging that is able to be replaced or driven in further over the course of at least a few years. Rule of thumb for 'air drying' is one year per inch thickness. 10-15% shrinkage is hugely significant if you're trying to keep something tight!