Pocket Routing with 3D-Printed Template and Matchfit Clamps - 2023-12-24 - Entry 42

My dad wanted to route some USB thumb drive-sized pockets into the backs of his wooden LED clocks and asked me if I had a quick way to do that. I did not, but I do, now.

The main takeaway is that I seem to be standardizing on using a 5/16″ router bit with a 7/16″ bushing for everything, using 3D printed templates 1/8″ or thicker that I attach to the workpiece using either [Matchfit] clamps or #6 screws.

Equipment:

Router: Bosch 1617 that Heather gave me for Christmas years ago
Bushing: Bosch RA1128 bushing set (I excluseively use the 7/16″ OD one)
Bit: 5/16″ up-spiral bit with 1/2″ shank
3D printer and filament of your choice (I use an AnyCubic Kobra Max and Overture PLA)
Matchfit clamps

Files:

OpenSCAD design for the template (which can be used to make an approximately 1″×3″ pocket), and for an insert (which can be set inside the to make a slightly smaller, 72mm×20mm pocket)
STL files for the template and the insert

Technique: Similar to thet for routing my monitor mounts. Pocket is cut with a 5/16″ router bit in a 7/16″ bushing, using a template specifically designed for said bit and bushing with Matchfit dovetail slots in the back so that it can be clamped to the workpiece (and maybe also the workbench) without the clamps obstructing the top surface of the template, where the router needs to rest.

The jig, clamped with Matchfit clamps to a table, with the to-be-routed workpiece sandwiched in-between

The exact difference in radius between the router bit and the bushing is theoretically 1/16″, but to give a bit of wiggle room, the above designs use a 2mm offset (i.e. the hole in the template is 1″+4mm × 3″+4mm). In the OpenSCAD designs this is called template_counterbore_r_offset. The extra ~0.8mm of wiggle room was mostly for routing slots the exact width of the bit, so not really applicable for routing these thumb drive pockets.

For cases where I can attach the template to the workpiece using screws or where the template and/or workpiece are large enough to clamp together and still have room between the clamps for the router to do its work, I make 1/8″ thick templates, since that is about how far the bushing sticks out the bottom of the router.

In the future, I think I will design the main body of the jig with a large 'standard sized' opening in the middle, with the assumption that inserts will be used. That way I can save PLA by re-using the bulk of the thing, and having to print only a new insert per pocket shape.