Endbore Jig
I've tried a number of ways to drill holes in the end of cross panels (e.g. pic a and b) and ended up designing my own jig . The second image gives another perspective of the jig.
The body is 3/4" architectural channel milled so that the channel is 19.5mm to fit over the typical 19.4mm melamine panel. The channel is drilled with 1/2" holes 32mm apart. The holes accept special bushings that come with any desired inside diameter. These are high quality bushings used in metalworking applications. They have ridges around the perimeter as well as a clamp ring to hold them in place. The MDF stop blocks are located with 5mm sleeves and clamed in place with M4 pan head screws into the sleeves.
The smaller jig is set up with stops at 22.5mm for drilling nailer and toe kick rails (19mm X panels and system holes as construction holes). Depending on what I am making I use 5, 7, and 8mm end holes. With this jig it is easy to swap bushings for the job at hand.
I like the channel idea but it is not real flexible if using melamine and plywood as melamine is a bit over 3/4" and plywood is under. Its not very elegant but you can add masking tape to the inside of the channel to narrow the opening. One thought is to use angle stock, instead of channel, with the bushings centered 9.5mm from the inside corner of the L.
