Real vs dimensional sizes

[dearchap]

Ok so I bought the bedswing timber frame plan from timberframehq. All the timbers used are dimensional 6x6 and 4x6. I recently ordered and picked up some fresh sawn 4x6 and 6x6s timbers from PA. However these seem to be "proper" 6"x6" and 4"x6" instead of 3.5x5.5 and 5.5x5.5. I was assuming the sawmill would provide dimensional lumber. My question is what should I just make the swing as per plans but update the tenon shoulders appropriately and keep the same tenon lengths, widths ?

[Magicman]

Dimensional is a sort of non-definite term.  Store bought dimensional or full size dimensional?  Both are dimensional but different dimensions depending upon who is defining.

This conversation has come up many times and I always verify and be sure that my customer and I are referring to the same dimensions. 

[NewYankeeSawmill]

Good advice @Magicman , I always do a meet-n-greet w/ the customer @ the site to look at the logs together and make sure all points are cleared up and agreed upon.
I would just update the plans to accommodate the thicker lumber @dearchap . It will be stronger and definitely unique. Not store-bought lumber. I actually try to use that as a marketing point when selling my mobile service ("Do you want 2x4's that are 2" x 4"?")

[Ianab]

My question is what should I just make the swing as per plans but update the tenon shoulders appropriately and keep the same tenon lengths, widths ?

Yup, just tweak the joints to work. The tenon will be the same strength, even if the wood is 1/2" larger. 

As you have fresh sawed lumber, it will shrink as it dries (maybe by 5%(?), then wood is usually planed down to a standard size. So that 5.5" beam actually came off the saw at 6". 

Building this sort of thing with green wood is fine, as both your mortise and tenon shrink about the same, and the joints should actually tighten up over time. The various timber framing techniques have been worked out over the years to take this drying and shrinking into account.