The zero play guide bar system is a huge benefit for anyone making and using jigs in a climate where conventional wood guide bars will expand and contract. I will use this with my table saw miter slot but you may find it useful with your band saw or router table.
Microjig has devised a nice solution https://www.microjig.com/products/zeroplay
I relied upon the users manual to inform my design and hardware choices.
This current model has adjustability to fit slots from 0.688-0.774in (17.5-19.7mm)
STL UNITS ARE IN INCHES
Each guide piece is 8.94" (227mm) long. One guide set will fit diagonally on a 200mm x 200mm build plate.
There are two configurations for this design. One uses heat-set inserts, one uses a little bit longer fasteners into low-profile hex nuts.
--- For Assembling the bars for heat-set insert configuration ---
2 - top_V2_in.stl prints
2 - base_in.stl print
12 - 8-32 thread size, 0.185" installed length heat-set inserts for plastics (mcmaster: https://www.mcmaster.com/#93365a140/=1c5hk4f)
6 - 8-32 thread 3/16" long button head hex drive screws (mcmaster https://www.mcmaster.com/#91306a264/=1c5hkqt)
--- For Assembling the bars for hex nut configuration ---
2 - top_V2_nuts_in.stl prints
2 - base_nuts_in.stl print
12 - 8-32 thread size Narrow Hex Nut
6 - 8-32 thread 1/4" long button head hex drive screw
--- For Assembling the METRIC bars for heat-set insert configuration ---
12 - M4 heat set inserts (https://www.mcmaster.com/#94180a351/=1cjbptu)
6 - M4 x 0.7mm thread - 5mm long button head hex drive screws (https://www.mcmaster.com/#91239a136/=1cjbqk5)
2 - base_metric_mm.STL (STL UNITS IN MILLIMETERS)
2 - top_V2_metric_mm.STL (STL UNITS IN MILLIMETERS)
--- For attaching the bars to your specific jig ---
6 - 8-32 thread 1/2" long* pan head screw (mcmaster https://www.mcmaster.com/#91735a194/=1c5hman)
6 - #10 flat washer (mcmaster https://www.mcmaster.com/#92141a011/=1c5hmtj)
To adjust, you will need a 3/32" allen wrench
Follow the user guide (linked above) for the setup/installation. I did NOT create a stop piece for setup, as you can easily use a clamp and scrap materials to the same effect.
After printed parts were removed from printer, I used some sandpaper to touch-up the long faces of my prints (there was a little deformation around the knit line). I also suggest that you flatten the bottom face after installing the inserts as material will swell around the holes on the underside.
*This length with change depending on how thick the base plate of your jig is or how deep you're counterboring into that material.
I built my jigs with the heat-set inserts, but the request was made for a hex nut version. The footprint of a conventional hex nut takes up a lot of room and affects the wall thickness between parts. I opted for a "narrow" low-profile nut and a little longer fastener for maximum thread engagement. You'll notice that there are subtle variations in feature thickness between the configurations, make sure you print the right combination!
Threaded inserts installed and assembly fasteners shown.
My simple approach for preventing the base part from sliding forward as fitment between the rail occurs.
A closer view of the interaction between the clamped rail and the part. As you can see, there's a small piece of wood making contact with JUST the base part. The top piece should be able to move freely.
Fully adjusted in the slot.
I added my first set to a hastily-built sled I was ready to throw out. I had to knock off the old plywood guides and sand the bottom flat in those areas. That allowed me to get the replacement 3D printed guides close. I drilled oversized holes so I could realign things when I was tightening everything down from above.
The #8-32 screws I found to use weren't very long so I had to counterbore the holes pretty deep to be able to engage with the insert threads. I could only access two of the three holes for each guide so I figure it's a worst case scenario.
As you can see, the slop in the through holes allowed me to realign the jig quite well! I would still prefer to use these guides on a new-construction sled/jig but I'm glad to know it works so well with old-work.