Free plans to build a X cross support dining table from Ana-White.com
8 - 2x6 @ 83 1/2" (tabletop boards) - measurement shown in diagram is wrong
2 - 2x6 @ 44" (breadboard ends) - CUT TO FIT!!!
3 - 2x4 @ 38" (long point to long point, ends cut at 30 degrees off square, ends are NOT parallel)
4 - 2x4 @ 35 1/2" (long point to long point, ends cut at 30 degrees off square, ends are NOT parallel)
4 - 2x4 @ 33" (long point to long point, ends cut at 30 degrees off square, ends are NOT parallel)
8 - 2x4 @ 20 1/4"
2 - 1x4 @ 36"
1 - 2x4 @ 64"
1 - 2x4 or 2x2 @ 68 5/8" (long point to short point, both ends cut PARALLEL at 20 degrees off square)
2 - 2x4 or 2x2 @ 34" (longest point measurement, both ends cut INWARD from measurement, one at 50 degrees off square and one at 20 degrees off square)
Please read through the entire plan and all comments before beginning this project. It is also advisable to review the Getting Started Section. Take all necessary precautions to build safely and smartly. Work on a clean level surface, free of imperfections or debris. Always use straight boards. Check for square after each step. Always predrill holes before attaching with screws. Use glue with finish nails for a stronger hold. Wipe excess glue off bare wood for stained projects, as dried glue will not take stain. Be safe, have fun, and ask for help if you need it. Good luck!
Build your tabletop first with 1 1/2" pocket holes and 2 1/2" pocket hole screws. A trick I do is build the tabletop without breadboard ends first. Then I take a circular saw (using a clamped board as a guide) and run it down the end edges to make sure all my boards are exactly the same length. Then I measure and cut the breadboard end to fit and attach it.
For a smoother tabletop, try using tongue and groove for the tabletop boards.
If your saw doesn't do 50 degree miters, what you can do is just use 2x2s at an angle cut (you can make angle cuts with a circular saw to just about any degree), cutting two 2x2s the full length and overlappping them, crossing in the middle. Then you can go back and fill in the spaces with 2x2s if you want.