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Author Topic: General Rules for Joinery Design  (Read 47211 times)

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Offline Jim_Rogers

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Re: General Rules for Joinery Design
« Reply #20 on: February 15, 2010, 07:50:18 AM »
Quote
Unless I were to offset the tenons and lap them on either side of each other in order to run the tenon past the centre(Canadian spelling) of the 10" post. How common is this?

I'm not totally sure how common it is but when I questioned Jack Sobon about how to get the relish needed on tenon he suggested an over and under tenon set up:



and to see through the joint:



Quote
Should one consider a spline joint instead?

Each frame and each joint depends on a lot of factors. Each has to be evaluated based on size, location, load, type of wood are a few things on the list. So a general answer would be maybe.....

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Is this tiresome answering similar questions from different people over the years?

No, over the years we have all learned more and more. Timber framing is a life long learning process, experiences add to your knowledge base.

Quote
Am I cheating by asking questions here instead of taking a design course?
 

A design course will help you understand more than you can learn by reading posts on forums. But keep asking questions.

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Should I just trust the Eng.?

Yes, but you may want to help educate him in timber framing basics if he doesn't have a lot of experiences with timber framing.

Quote
Should I just stick to nails and 2x4s? (please no!!) 

Every type of construction is something to learn......
Whatever you do, have fun doing it!
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Offline Aikenback

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Re: General Rules for Joinery Design
« Reply #21 on: February 15, 2010, 12:06:31 PM »
Hi Jim, Thanks for all your help. This is great.  After looking through some other pictures i saw the over/ under tennon. there is always a solution.  I'm Gratefull. The engineer I use is listed in the TFG.



Blake.
P.S. I don't dislike stick framing that much It's just too much of the same old same old. It's a trade that is under appreciated by many.
no whining.

Offline baryon

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Re: General Rules for Joinery Design
« Reply #22 on: April 27, 2014, 09:15:47 AM »
I am about to start cutting the 3X5 oak knee braces for a TF project. After drying and lightly planing they measure 2.75X5.    If I keep a 1.5" deep face for the brace surface what would be the implications of using a 1.75" tenon in a 1.5" mortise ?

Offline baryon

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Re: General Rules for Joinery Design
« Reply #23 on: April 27, 2014, 09:20:00 AM »
Correction!!! ---   The tenon would be 1.25" in a 1.5" mortise ---

Offline Jim_Rogers

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Re: General Rules for Joinery Design
« Reply #24 on: April 27, 2014, 07:01:39 PM »
Have the mortises been cut?
If they have then you're going to have very loose and sloppy tenons in the mortises.
If they haven't been cut then cut them to fit the tenons.

Jim Rogers
Whatever you do, have fun doing it!
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Offline baryon

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Re: General Rules for Joinery Design
« Reply #25 on: April 29, 2014, 07:17:35 PM »
THANKS Jim--- The mortises have not been cut yet.    You are very helpful  and down right knowledgeable. !!     Baryon

Offline rjwoelk

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Re: General Rules for Joinery Design
« Reply #26 on: June 15, 2014, 11:04:54 AM »
Why do timber framers work with big timbers?

They are bent that way. :D
Lt15 palax wood processor,3020 JD 7120 CIH 36x72 hay shed for workshop coop tractor with a duetz for power plant

Offline Magicman

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Re: General Rules for Joinery Design
« Reply #27 on: June 15, 2014, 05:41:53 PM »
Hello rjwoelk, and Welcome to the Forestry Forum.
Knothole Sawmill, LLC     '98 Wood-Mizer LT40SuperHydraulic   WM Million BF Club Member   WM Pro Sawyer Network

Never allow your "need" to make money to exceed your "desire" to provide quality service.....The Magicman

Offline dad2nine

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Re: General Rules for Joinery Design
« Reply #28 on: January 11, 2016, 11:37:58 PM »
Jim is there a general rule for depth of a given mortise or length of tendon?

Offline Jim_Rogers

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Re: General Rules for Joinery Design
« Reply #29 on: January 12, 2016, 09:36:39 AM »
Yes, but it is not a simple answer.
It all depends on the location of the tenon and mortise. Each joint has to be reviewed as to how much stress or load is on that joint.
Then the tenon has to be long enough to provide enough "relish" beyond the peg hole to have the strength to not "blow out" the tenon and split it along the grain.
The basis for this is something like at least 4 diameter's of the peg beyond the peg hole. But it could be more. I'd have to look up the standard rule, but I don't have time right now to do that.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Offline 1234wood

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Re: General Rules for Joinery Design
« Reply #30 on: October 08, 2016, 10:27:58 AM »
Hi jim? I plan on building a saw mill building   24x30  10 x10 beams pine vertical  post set on concrete pillars with strong ties  in concrete  10 ft spaceing with rafters not sure on size probably 7/12 or should I have someone draw it up I need a 21 ft opening  for logs near middle of 30 ft side of building

Offline Jno wood

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Re: General Rules for Joinery Design
« Reply #31 on: May 01, 2018, 11:46:11 PM »
Yes, but it is not a simple answer.
It all depends on the location of the tenon and mortise. Each joint has to be reviewed as to how much stress or load is on that joint.
Then the tenon has to be long enough to provide enough "relish" beyond the peg hole to have the strength to not "blow out" the tenon and split it along the grain.
The basis for this is something like at least 4 diameter's of the peg beyond the peg hole. But it could be more. I'd have to look up the standard rule, but I don't have time right now to do that.

Jim Rogers
I am following along all these rules and based on this I have come to the following conclusion:
I have a 6" post, and a 4X6 knee brace with 3/4" pins.
This means:
1. the tenon should be 1" thick (1/4 the thickness of the knee brace)

2. the tenon needs to have 3" of relish (4x 'the pin')

3. the tenon need to be 1.5" from the edge (2X pin)


So in this case the tenon is 1" thick X 4.5" deep

Did I get it all right?

Some more notes:

- By the "peg rule" this peg actually should be 1/2 x tenon thickness or 1/2" and this would change all the numbers - 3" deep tenon???

-I have read that relish should be 3.5d - 7.5d for softwood

Offline Jim_Rogers

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Re: General Rules for Joinery Design
« Reply #32 on: May 02, 2018, 09:04:22 AM »
There are exceptions to every rule. Understanding when the apply does take some research and experience.
On a 4x6 knee brace we do 2" flush tenon and 1" peg.

Also, we normally make the tenon length 3".
Recently in a discussion with another designer he felt that 3" brace tenons were too short. I believe he uses 4".
Braces are strong in compression and that's their job. Lack of pegs in braces have been found in many old barns and structures.
Some people say that the peg in a brace tenon is there to just hold the brace in place during raising.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Offline Jno wood

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Re: General Rules for Joinery Design
« Reply #33 on: May 02, 2018, 09:48:24 AM »
Thanks Jim. One thing about the project I am working on is all the joints are under compression, so it should be a very forgiving project as far as pins go.

 


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