Horizontal Mortiser -- Tool

The Horizontal Mortiser collection contains OpenSCAD and .stl files used to build a woodshop tool to create mortises for floating tenons.  The full complement of files are now in place (January 6, 2023).   The tool and its use are illustrated in the YouTube video: 

A complete tool comprises the prints listed below.  They are described starting at the router and moving through to the assembly that holds the workpiece.  I made all of mine using PLA.  I think PETG might be a better choice, but marginally so, and I didn't feel the additional strength justified the expense of stocking PETG.  If you have PETG, then I recommend using it.  In my own prints I accepted the default infill (15-20%) and numbers of layers.  I may have to increase these parameters if parts fail down the line.

Router Braces:  Braces clamp the cylindrical core of the router into a square footprint.  They are shown in dark blue in the photo and video.  Two are required.  I recommend the 5-inch (125mm) versions for stability but 4-inch (100mm) versions are also available.  With 5-inch braces left-right travel is up to 2-inches (50mm).  A 4-inch brace at the front allows up to 3-inches (75mm) of travel.  In my own setup I use 5 inches at the back and 4 inches at the front.  You will need two braces, either two 5-inch, two 4-inch, or one each of a 5 and a 4.

My router has a 69mm diameter.  If your router has a different diameter, use the OpenSCAD source to adjust it.  I included instructions as comments in the source.

Frame:  The red frame guides the left-right travel of the router.  It holds machine bolts on both sides for the adjustment of travel, and thus the length of the mortise.

Truck:  The truck sits under the router attached to the underside of the router's plywood base.  In the video it makes a brief cameo as a green print.  It has the 8mm cylinders that fit and glide in the tracks, and are therefore components of forward-backward motion of the router.

Tracks:  The tool shown has two side-tracks and one corner-track.  Using all three lets the router come at the workpiece from the side or end, each with three positions.  You could use only one side-track if you wanted to address the workpiece from only one face (either the end or side) and from only one position.

Pucks:  Moving over to the area that holds the workpiece, it starts with three black cylinders (pucks) screwed into a Baltic birch plywood base criss-crossed with dovetails suited to holding MatchFit clamps made by Microjig.  Two pucks at a time mate with two holes in the base of the ramp, and thus set the orientation of the dark blue ramp and yellow platform.

Ramp:   The dark blue ramp has a gently rising run of sawteeth that mate with a similarly angled run of sawteeth of the platform.  Together they adjust the height of the workpiece so that the router can address the centre of the mortise.

Platform:  The yellow platform can be positioned along the ramp and thereby adjust the height of the workpiece.  It has slots for ¼-20 (approx M6) nuts for the attachment of either of two fences.  Nuts placed into the slots are below grade so that the workpiece lies flat in the platform.

Platform Fences:  Either of two fences attach to the platform rimming the side or the end-and-side with 1/8th inch (3mm) rails proud of the platform surface.  The L-shaped (end-and-side) fence is for mortises into the ends of workpieces, whereas the side fence is for long workpieces when mortises are to be placed along the edge some distance from the workpiece end.  The fences are useful when making mortises into multiple identical workpieces.

Matchfit Grid 8x8:  Added a few months later, this is a 3D printed replacement for the grid into which Matchfit Clamps would be inserted.  Originally I presumed woodworkers would make their own by routing long dovetails into a plywood or solid wood base.  But since the grid is a straightforward print, here it is.  At this writing the grid has not been tested, so one concern is whether the layer lines have sufficient adhesion to hold clamps without separating.  I recommend consulting tips on enhancing layer adhesion before printing.  A shop-built grid would need 3 pucks; this 3D printed version has pucks integrated in its design.