I am brand new to TF and the forum having just discovered it two days ago and have a question about cutting timbers from logs. I have a Woodmizer sawmill and was just given a big red oak log by a neighbor. I plan to make a TF covered porch off of my stick built house as my first project and plan to start my timber collection with the oak. I planned to split the log down the middle and saw two beams from top half and two from the bottom thereby keeping the center out. This is based on my experience that sawn boards with the log center usually have large cracks. Then I read pg 80 of Jack Sobon/Roger Schroeder's book where they say that large beams should be center-cut but small ones like braces need not. Q1 - Is it desirable to keep the center in large timbers or really not important? Q2 - I have a lot of sweet gum trees that are big enough to make timbers - any reason not to use them? Thanks for the advice.

Center cutting or box hearting timbers usually starts with the timbers are 5"x5" or greater. If the braces are 3"x5" then they usually aren't center cut/boxed heart.
In an oak log if you make one large cant and then cut it down the middle to make two each one could bow due to stress in the log.
If it was me, I'd make one center cut/boxed heart timber, if it is going to be larger than 5"x5".
Checks or surface splits are part of timber framing....
I've never used sweet gum so I can't help you with that....

Like JR, I have no experience with that species, and I DO think that matters. I work primarily in Eastern White Pine and Douglas Fir. In fir, we prefer FOHC (free of heart center), and in pine, we prefer boxed heart, becuare the two species behave differently as they dry. In general, the fir will check less and shrink more in dimension. The Pine will shrink less dimensionally, but instead will open up larger checks. By using boxed heart for the pine, these checks won't penetrate all the way through the timber. In fir, the dimensional shrinkage will tear apart a boxed heart timber, as the center doesn't dry as fast. This will lead to a really big check on at least one face, and creating a... somewhat non-rectangular cross section. You'll need to find out how your species behaves. I'd start with a local sawyer, if you don't get any advice here. CB.

Sweet gum is very unstable in large sections -- I would not use it for timber framing. Or anything else for that matter.

What I have done with really large oak logs is cut brace stock off the sides (3x5) and leave one timber in the middle at least 8x8. As Jim said, when you halve or quarter an oak log, the timbers bow tremendously (usually right on the mill).

gabel

I cut up one huge red oak log last winter, got a ton of 1x boards off the outside, and six 6x7 floor joists out of the middle. None of them bowed or twisted, and they were left out in the sun. (Not my idea) I don't know how I got away with it, new sawyer I guess. I can't seem to cut any oak without turning every cut, and that is cuttin 1x boards. I definately prefer pine for staying straight.


Dave

I used one sweet gum timber in my house, with no problems. Just did it to be contrary. Had cut it previously for a crosstie but never took it to sell, and it sat outside in the sun for 6 months w/o bowing or twisting, so I used it for a 6x8 jack rafter. Could be mistaken by the casual observer for oak or hickory. Beech and hickory are two other woods that sometmes get a bad rap for timber framing, but I have had success with them too.