With the reprapped x-axis ends you have a captured nut and lock-down bolt to hold the x-rods in place. In my wooden rep-strap design I abandoned this as too complex to incorporate in wood. Instead, I've come up with the following simple approach to secure the rods.
A small brass screw, fitted to a pilot hole which glances the stainless rod holds it in place very firmly. The tapered nature of the screw means that it pushes more on the rod as it advances into the wood.
Thanks for viewing, feel free to add comments or ask questions. I'm also contactable via PM (personal message) on the RepRap Forum (forums.reprap.org) under username "NumberSix".