In article ,
GarageWoodworks wrote:
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.

You might want to look at the commercial offerings from Rollon Corp.
www.rollon.com/USA/rollon.htm

I haven't purchased anything from them, but have had discussions with
sales and engineering abut some of their _big_ stuff (multi-ton loads).
I found them _most_ helpful, even when dealing with an application that
was _way_ outside the scope of what they normally deal with. And this
was research _only_ for an admitted one-off project.

Their "mono-rail" has accuracy of +/- 0.1mm in the 'normal' precision units.
+0.000/-0.04mm in the really high-precision ones. lengths for single
sections, up to roughly 4 meters.

lots of other alternatives, too, if you need something telescoping.
Catalog data includes the data to figure out how much play there will be
in your application. Assuming you can build to the precis ion of their
gear.