Save yourself some dollars and make splines out of hardboard [Masonite]. It's cheap, cuts easily [wear a mask - it's dusty], and is more than adequate for the job. The main function of the splines is to keep the boards in alignment. If the ends of the boards will show, i.e., no breadboard ends, make sure you stop the grooves at least one inch before where the finished end will be. If you decide on a breadboard end, don't glue it on. Lateral expansion of the field boards will tear it apart. That's a subject for another thread. Save the expensive Gorilla Glue for a project where you really need that much performance. Titebond-II is more than enough for this table. Spend a little money on a carbide slot cutter bit with a 1/4 inch thick cutter [the same thickness as the hardboard]. Take the router out of the table - this job will come out better if the router is handheld, because if the boards have any curve, and if you run them across the table with the convex side up, the bit will not stay centered on thickness of the stock. Spend some time - a lot of time - arranging the boards before making any grooves. A lot of people talk about alternating the growth rings, but I think it is even more important to orient the grain. Look at the edge of each board to see which way the grain slopes up to the face. If you keep all of the grain sloping the same way it will be much easier to plane the top after glue up. To prove this to yourself, clamp two scrap boards side-by-side with alternate grain slopes, and plane the face over the joint. One face will plane smoothly and the other will tear out. Guess how I learned this. Once the boards are laid out, mark all of the faces with chalk, and make a big chalk triangle to help with re-assembly. Make sure that you rout each board with the face up, towards the router, so that any variation in board thickness will fall on the underside of the tabletop. Go easy on the glue. I small bead of squeeze-out confirms the proper amount. Practice on scrap. If you use black pipe clamps, keep them away from the wood and the glue. Waxed paper works well. Clamp up the assembly dry before you reach for the glue. You don't want to find out that you don't have enough of the right sized clamps while your glue is setting up. I'd recommend clamping long scraps along the faces to keep the assembly from curving. Put waxed paper under them so they don't become part of the table. Scraping off as much of the glue bead as you can reach when it gets tacky - about 20-30 minutes after clamping, will save you some work later. Take your time, especially with planning. The table might be aound for centuries. Enjoy. Tom