I understand the importance of wood shrinkage... in walls and floors... in joinery, especially when glue is present, the wood is properly air or kiln dried, and the joint is tight, this is not important whatsoever in my experience. Add a good poly glue to the mix and forget about it. I would have more concern with the bottom of the tenon being too close to the thin lower edge of the mortise.?
Taylor Donsker
www.tdonsker.com
818.424.9046
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On Apr 7, 2021, at 8:34 AM, Mark Kessler <mkessler10@...> wrote:
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Splitting a wide tenon (>5¡± maybe) into two narrow one solves two potential issues, reduces wood movement and increase the strength the mortised peice
On Apr 7, 2021, at 10:48 AM, imranindiana via groups.io <imranindiana@...> wrote:
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Joe,
I agree. Was sharing what some claim on WW forums.
Imran
On Apr 7, 2021, at 10:28 AM, Joe Jensen <joe.jensen@...> wrote:
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Its seems to me the tenon would move by the factor times the tenon width and splitting the tenon into two parts will not change anything as the two
tenons are still attached to the single board.? The whole board will move but only calculate to movement of the tenon on the width of the tenon, or if two then the width of the two tenons and the gap together.
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[Edited Message Follows]
Mark,
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I prefaced with this may serve as a starting point. I did not do exhaustive search but this one article seem to cover all aspects so I decided to save it and use the info as a reference
only. I included all ¡°details¡± so what I excluded, I do not think was important but here is the link. Would not be the first time I missed something.
I thought it came from FWW but it is from Popular WW. I have added the link in presentation so another update is attached.
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Few other interesting rules I cam across:
- An article stated that 3¡° or 4¡± max tenon width is too conservative and 6¡± max is fine.
- Another interesting idea is to make the tenon width equal to the rail width minus it¡¯s thickness. So 6¡± wide rail in 8/4 stock will have a 4¡± wide tenon per this rule. 2¡± wide rail of ? stock will
get 1 ?¡± wide tenon.
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As far as dividing the tenons due to rail width is concerned, some claim that the tenons see less movement when divided even though the total width is same. In example below, the
claim is that tenons on right will see less strain. I do not understand that. The 6¡± wide rail is going to expand or shrink (in width) in both case the same therefore the extreme ends of tenons (across the width) should see similar strain. There probably is
some relief in the 2 tenon case as there is not a continuous 5¡± wide tenon pushing but I am not sure if that is significant.
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In my mind moving the tenons significantly away from the ends of the rail (as shown in your example below and may be required in extra wide rails) will introduce the possibility
for the rail to rotate. This however, can be countered in many ways. I have a continuous stub tenon running the entire inside of the stile. So there is a short tenon for the entire width of the rail that should counter that possibility, haunching is another
way as mentioned by the author of PWW article.
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<image004.png>
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I have not found a rule for placing 2 tenons in parallel. For my door, I have room to have a 2¡± wide tenon in the 3.5¡± wide rail and stile. This is more than even the rule of half.
So I am considering two ?¡± tenons in parallel.
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Imran
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From:
[email protected]
On Behalf Of mark thomas
Sent: Tuesday, April 06, 2021 6:17 PM
To:
[email protected]
Subject: Re: [FOG] Calculating Wood Shrinkage #wood_shrinkage_Mortice&Tenon
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Do any of the references cite reasons for their rules?? Some of those don't any sense that I can see.
Using one of your example dimensions of 6" wide rail and 1/4" tenon allows this result, which makes no sense:
<image004.png>
Now partly that may not make sense because the right hand tenons are too close together, but your rule just states that the left hand version is too wide and you "have to" be break into two tenons, but it says nothing about spacing of the two tenons.? Maybe
you didn't include his full rule, or maybe a more full understanding of his rule is conveyed in his drawings and was lost in your translation to text.? So let's assume he wants them space further:
<image006.png>
But why?
