I cann't get a exact idea about this. Have searched and read all the threads with "kerf" and "kerfing".

Plywood will be 3/4" ACX, cut in 16" strips and laid either perpendicular or 45 degrees to the flooring. Flooring is 3/4" quartered red oak, nice long pieces mostly. Planning to staple with 1.5" staples from a new Bostitch MIII.

Concrete to be leveled in advance to the best of my ability (most hateful part of this project!)

I plan to put one kerf down the middle of the 16", so 8" on each side.

But what about cross cuts? At every 8", that would be 11 cuts per sheet.

Think I can get by with every 12 or 16?

I do plan to build a jig to allow me to position rapidly to make multiple cuts, and I may even buy a second saw, so that one saw will be set to kerf and the other set to cut all the way through. Logically, I will make the cross cuts across a full 4 foot sheet and then make the rip cuts lengthwise thereafter.

Thanks again guys......

You do not need to kerf your plywood subfloor strips lengthwise. Kerfs should be 1/2 the thickness (in your case, 3/8") Kerf every 12" or so using a skil saw. This doesn't need to be perfect, just free hand it and estimate the 12". All you're doing is relieving the plywood so it will lay flat. Check out this article from NOFMA. There's a picture of kerfed plywood in there.
https://www.nofma.org/Portals/0/Publica ... 010_04.pdf

Nice -- I had read that article once, but didn't recall the spacing that they recomended for kerfs. Of course, in the section where they are talking about kerfing, they also allude that this helps give glue something to stick too. Question then arrises, whether their kerfing recomendation is intended for glued down subfloor, as opposed to floated.

In any case, I may still kerf it once legthwise, and I will probably build a jig to make the process fast. 12" OC for the horizontal kerfs seems adaquate, unless someone else cares to chime in.

As to the need for exactness, as opposed to free hand kerfing, I can say only this -- I have done some kerfing in other circumstances (building curved forms) and I can say that slight curves in the kerf defeat the geometry and vastly reduce the amound of flex that wood can achieve. Imagine a curved kerf and imagine what happens when it tries to bend --- some areas have to move more than others. Anyhow, I know the kerfing is for stress relief and as such perhaps it doesn't matter. But if I can make the exact and true, so much the better!!