Use this jig to mill boards too wide to run through your thickness planer.
It’s an unavoidable fact of woodworking life that the wonderfully figured board you want to use is just too wide to fit on your jointer. Or perhaps you need to flatten the surface on that end grain cutting board that you have just glued up (don’t even think of trying this on a jointer). Build this versatile router based surfacing jig and you’ll be able to dress any surface you may come across. This jig is large enough to accommodate material up to 26″ wide and almost three feet long, but you can scale it to suit the sizes of stock you will most likely be using. The material is clamped to the bed of the table and then the router runs back and forth over the surface between the two outside rails. Two sets of rails provide additional clearance to accommodate thicker stock. Adding a couple of extra rail extensions to increase the height will allow you to mill even thicker material.
The Router Base
Begin by preparing a router base plate (A) to fit the router you will be using. The measurements given here fit the Freud FT1700VCE router, freud.ca, that I have dedicated to this jig; adjust your measurements accordingly to fit your router. When sizing the base plate, be sure to provide enough space for the handles and any other protrusions to clear the carriage beams when it is plunged to full depth. To hold the router captive and provide positive guidance I used a Freud 58-100 four-wing slot cutter to rout a shallow groove that allowed the polycarbonate sheet to slide into the T-track. Remove the sub base from your router and use it to mark out the screw holes to mount the new base to the router; you may need longer screws.
Begin by cutting the base (B) to size. It won’t be needed until later, but cutting it now allows you to use it as a work surface as you proceed. To provide the maximum strength without any wood movement concerns, the two carriage beams (C) that support the router guides are made up of three laminations of ¾” Baltic birch plywood. Cut the blanks for the beam and glue it up. When the glue has set, trim the beams to width and cut them to length. Set up a dado set on the table saw and configure it to cut a groove for the T-track sections; the sections should fit snugly without movement but should not be forced into the dado. Use a drill press to drill clearance holes in the T-track for the shank of the #6 hinge screws and then use a larger drill bit to countersink the head below the surface of the track. Cut the dados and mount the track on the two beams; space the screws every two inches on the guide track to support the weight of the router. The stop block track on top of the beam only requires five screws.
Cut the two carriage ends (D) to size. Use a doweling jig to drill a pair of dowel holes at both ends of each carriage beam and the corresponding holes in the carriage ends. Use the dado set to plough a dado on the outside surface of the ends between the two dowel holes for the UHMW guides. Cut the gussets (E) for the top of the carriage. Assemble the carriage on the base and cut a couple of sacrificial spacers to fit across the interior of each end of the carriage. True up the carriage to be sure the router base plate slides back and forth easily. If it binds, make the grooves ever so slightly wider; do not make them deeper. Using T-bolts, fasten the gussets in place using the ends of the stop block track to keep the carriage square and rigid. Drill and counterbore a hole for a ¼-20 large head bolt through the carriage end and beam, then drill an intersecting hole for a cross dowel and use these to pull the ends together.
The router carriage slides back and forth on the T- tracks; the two different track heights provide additional thickness capacity while the UHMW guides make the whole carriage slide easily on the aluminum track. Begin with a 24″ piece of UHMW (leevalley.com) item #46J90.16, and use the Freud slot cutter to run a groove to accommodate the UMHW in the track opening. Use a set of calipers to ensure the material left exactly matches the opening in the track. Move to the table saw and use a blade with flat topped raker teeth to nibble away at the remaining material until the profile matches the inside profile of the track. Raise the blade slightly and make a pass on both sides of the material and check the width of the remaining stock. Repeat this until you have the desired dimension.
With the profile cut on the UHMW, rip the guide strip from the material and cut it into 5″ lengths. Drill a pilot hole through a leftover piece of track and then slide the UHMW guides into the track and use the hole in the guide track to center a bit on the UHMW and drill a couple of screw clearance holes through it. Follow this up with a countersink bit to allow the head of the screw to sit below the surface. Set the guides into the dados on the carriage ends and screw them in place. Drill a hole in the center of the dado for the locking T-bolt.
The Main Table
There are two methods to hold down the material as it is being surfaced. The first is to use toggle clamps affixed to a beam suspended between the two side rails. While this works well, the board must be longer than the surfaced area to accommodate the areas under the beams rendered inaccessible to the router. To eliminate this problem, construct the side clamping hold-downs. Rout three sets of grooves across the width of the milling table to accommodate ¼” T-bolts. Drill corresponding holes into a piece of oak for the clamp bar (F) and counterbore the top side to allow the head of the nut to sit flush with the surface of the oak. Drill a series of holes across the width of the clamp bar and insert T-nuts into the side facing the center of the jig. Using a bench grinder, grind a point on the end of a series of long ¼-20 bolts and thread them into the holes. If you can’t find long bolts, cut some ready rod and double nut one end.
To complete the main table, cut the plywood sides (G) and the solid wood backer (H) and laminate them together. Trim them to size and then plough the dados for the three pieces of T-track. Drill and countersink the holes in the track and then mount them in the dados. Confirm the amount of material you will need to remove from the sides to match the width of the base and use a thickness planer for this. Mount the sides to the table base using wood screws; use the carriage as a spacer and some clamps to be sure the sides are the correct distance apart for smooth operation.
Using the Jig
To flatten the surface of a rough board, place it on the milling table and snug the clamping bar up to the material. Use the pointed bolts on either side to firmly clamp the board down. Install a bottom-cleaning bit in the router and move the router back and forth along the width of the stock while progressing from one end of the board to the other.
Because the object is to hold the piece firmly in place for surfacing, material will not slide through the jig very effectively. By making a sacrificial bottom out of a piece of laminate covered MDF, this jig can easily be converted into a fluting jig or used to run any manner of mouldings. Using the stop blocks it can also be used to rout dados, through and stopped, in both sides of a bookshelf.