Bladed scarf joint questions

[Jim_Rogers]

That picture was taken 15 years ago, and it was at a Timber Framers Guild project. We took a barn down in one town. Moved it to another town, repaired or replaced all missing timbers, and put it back together again.
I donated a week of my time cutting joints under the direction of the head man just to learn how to do things like that.
And that joint can be cut into a post in a standing barn:



 

You just have to understand the step by step procedure to do it.

When anyone ever asks me: "how'd you learn all that stuff?" I always reply "by joining the Timber Framers Guild."

If you're not a member and you want to learn more I suggest you join.

Jim Rogers

Jim-  Is there a thread somewhere on this forum that discusses the cutting of this scarf, as well as others?  I have lots of questions, but don't want to muck up Jim's build thread with them.

One of the questions I have is that, since I can't see how you cut that scarf joint, what keeps the beams together side to side, sliding out sideways?  Is there some sort of key in the middle of the joint not shown?

Thanks,

Jeff

I'm not sure if I ever posted anything here about how to cut this bladed scarf joint.

But the joint is pegged to prevent it from coming apart.

We used three pegs in that picture. One straight in, one pointing to the left and one pointing to the right, so that if not peg fell out (which is highly unlikely) the others wouldn't.



 

Here is another one showing two different peg hole locations:

 

 

Above it one of my favorite pictures.

If you want to learn more about doing this scarf joint send me a pm and/or your email address and I'll send you some information about how to learn how to do it.

Jim Rogers
(the reason for the PM or email is that advertising a product you sell is not allowed on the forestry forum threads)

[jimdad07]

How does that scarf perform for a top plate compared to a stop splayed and undersquinted scarf?

[Jim_Rogers]

You have to understand what is going on in a frame and where to use what scarf joint.
For example, in your "tie beam" you used a stopped splayed tabled scarf with undersquinted butts and wedges because your "tie beam" could be considered "in tension" as it is supposed to be "tying" the two long walls together.

In a plate there shouldn't be any tension from gable to gable. So you could use a bladed scarf joint there.

The next questions comes is "which way" up and down or left and right.

Well let's think about that.

If the blades are up and down, vertical, then the strength of the joint is relying on the pegs holding it together.

If the blades go left and right, horizontal, then the timber will have to split, as well as the pegs have to bend in order for the joint to fail. Most likely it will not if placed properly in the length of the plate so that it is supported by a brace.

In both the pictures I have shown the timber was a post. And the new wood was a post bottom being added onto an old post that had a rotten bottom, that was cut off.

If you are interested in learn about the many different types of scarf that could be cut you should get the book written by Cecil A Hewett titled English Historic Carpentry:



 

It has a huge section in the rear about the history of scarf joints and many different types.
I found it very educational.

Also there is a section on scarf joints written by Jack Sobon in the Historic American Timber Joinery it is part # 6. Free download off the web.

Jim Rogers

[jimdad07]

Thanks Jim, great information.  I'll check that literature out. Can't know too much in this world.

[Jim_Rogers]

If you go to the for sale section and look at my timber framing tools for sale list (https://forestryforum.com/board/index.php/topic,50674.0.html) you'll see an item ID # M326**
It can be emailed to you.

Jim Rogers

[Shandog]

I have to lengthen two 8x8 post the problem is that there is mortises from the knee braces two foot up from the bottom of the post what's the shortest length I can make a bladed scarf joint ? I need to add about 44" to the post 
Thanks 

[Jim_Rogers]

I have to lengthen two 8x8 post the problem is that there is mortises from the knee braces two foot up from the bottom of the post what's the shortest length I can make a bladed scarf joint ? I need to add about 44" to the post
Thanks

You'll have to do what you have to do. the new piece could have the brace mortise in it as well.
Jim Rogers