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timber frame brace

Started by danwhitejr, September 09, 2004, 05:30:40 AM

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danwhitejr

I am cutting the beams for a frame addition and would like to use red oak for the braces,and would like to know if not boxing the heart for 4 x 6 braces would create any problems.I have some 20" dia. logs that I would like to cut as many braces as I can out of each log.

Jim_Rogers

Dan:
Good question!
The standard answer is that it could create some problems. It really depends on the quality of the logs. If they are good quality then there may not be any problems. If they are low quality they may.
Handling of the lumber after it is sawn and before the braces are cut can help or hurt the brace stock. Proper stacking of the pieces with good support is needed, along with weight on the pile to hold them in place.
Usually brace stock is mill oversize in thickness. What that means is if you're intending to layout your brace tenon 2" of the layout face and then make the tenon 2" thick, you've got to insure you have 4" of wood. If you mill your stock to 4" thick and it shrinks with age, then you don't have enough to create a proper brace tenon or in the proper location.
We always mill brace stock at lease 1/8" over in thickness to account for shrinkage with age.
So when we cut a brace tenon we first establish that the tenon is offset off the layout face by 2". Then we hand plane the back side of the brace to make the tenon 2" thick. This hand planing of the back side, which is the inside of the building extends a few inches or more beyond the end of the tenon creating an un-noticeable change in thickness.
If the area that is hand planed seems to be noticeable, we sometimes hand plane the entire inside surface of the brace to dress it up.
Depending on the actual brace over all length you usually try to create two brace blanks from one longer timber. When we layout a brace on a long piece we look for defects in the long piece and slide the layout location away from the defect hopefully eliminating it. To do this instead of sawing out 8' brace stock for two 4' braces we mill out a piece 10'. This extra length will be needed went sliding the brace location back and forth to eliminate the defects that fall in the tenon areas.
Because of the way lumber shrinks and distorts as it shrinks it's best to try to plan your brace stock location in the log in advance.
I usually try to create multiple pieces out of one log by placing them in a location in the log that will reduce the amount of distortion as the lumber dries.
This drawing has been shown in many places for many years:



Because the lumber will distort when cut out of a log, I try to place my timbers in these positions:



If you create your brace stock timbers in the clock face positions of 12, 3, 6 and 9, as well as the center you will reduce the amount of distortion that these timbers will move when they dry, (the center spot usually is of very low grade).

Good luck with your project.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

danwhitejr

Thanks Jim,  
The brace will be cut over size and then planned to 4" x 6" and will be put into the bent within 1 week.  I have cut the mortise & tenon at 1-1/2" and is 2-1/2" from the layout face with  a  3/4" shoulder. The logs are of good quality with no knots and can be cut as the drawing is shown.My biggest concern was with the brace bowing towards the exterior or interior of the frame or twisting really bad.

Jim_Rogers

Dan:
If you are using a inside shoulder then there is no need for milling them oversize, unless you truly want to plane them.
With the time table you have said, they should twist much between milling and insertion.
And if you cut them as you plan then once in place the tenons will hold them from twisting.
Good luck with your project, and post some pictures when done.
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

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