In article bb46c83c-741f-4882-91e4-c4bac1735529@
26g2000yqv.googlegroups.com, says...

I'm still struggling with my X,Y tables for my H-mortiser. I've tried
full extension drawer guides and they had way too much vertical
slop. I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. Four bushings total inserted into two separate equal
lengths of wood. The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.

You might find it helpful to take a look at the "linear motion" section
of vxb bearings: http://www.vxb.com/page/bearings/CTGY/LM. They've
got a wide range of options for not too horrible prices.