If it is to be your main nether surface above the joists, I wouldn't go less than 1/2". In fact, I use medium grade 1/2" ply, the kind used for sheeting under a roof. However, many will insist that 5/8 and 3/4" are their prefered thickness. What matters is that it doesn't delaminate easily, isn't badly warped, and that you support the 1/2" stuff with joists of some kind on 12-14" centers.
Crandell
As I get closer to entering the stage where I put on the decking for the benchwork frame, i have found that I do not want to use what I originally planned. I was going to use the extruded pink foam, but after the recent posting about it, I decided to go a different way. I am now leaning to plywood or OBS board. What do you members recommend? Also 1/4" or 1/2" thickness?
Thanks