I didn't want to pay for the actual Stewmac binding guide so I more or less stole it >:)

Here is the actual thing if you want a much better one.

Hardware

• M3 x 5mm                              (1x)
• M3 x 15mm                             (1x)
• M3 Nut                                    (2x)   –  a nylock nut would also probably work
• M3 Washer                             (1x)    –  I used a fibre PCB washer for this
• M3 x 5mm Heat set inserts  (2x)   –  6mm long would also probably work

Printing

Print the main body standing upright with a brim. 0.2mm layer height with 3-4 walls for strength, no support.

The moving bit should be printed on its side, with support enabled and 100% infill or lots of walls. This also needs to be quite strong.

I would recommend using a still filament for both parts as you don't really want it to flex. Mainly probably don't use PETG. I used PLA and that seemed strong enough.

Assembly

1. Install the inserts
2. The 15mm screw goes in the hole on the moving bit and is captured by the two nuts jammed together. This is a bit annoying to do but can be done with some small pliers or forceps. If you have reusable loctite then you should put some on this screw. I didn't have any so I had to make do with dental floss and super glue.
3.  The 5mm gets the washer and goes through the slot on the moving bit. Make sure this is reasonably tight, but not so tight the plastic bends when adjusting the depth of cut. also, USE LOCTITE. This screw will disappear otherwise.

How to use

The 15mm screw adjusts the depth of cut and the height can be adjusted by moving the bit in the collet and by turning the whole guide on the Dremel. 

You should set the Dremel to ~2750 RPM. That seemed to work for me

Also, the router bit can be found in one of those sets of cheap Dremel router bit sets on eBay or Aliexpress.

Cut height limit is about 8mm. Cut depth limit is 3mm (I think). 

NOTE

This thing worked surprisingly well (as you can see) but please make sure you do a few tests before cutting anything important, check for loose screws, etc. Oh and don't push it into the wood too hard when cutting the binding channel, it does not like that at all. This part will need a few passes to get to full depth.

The attachment thread is ¾ - 12 UN 0.75" if you need to know.