In 2004, I bought this GMC Router Table for $113. I figured if it was a piece of junk, it was well worth it for the table, fence and accessories. It is now 2016 and the motor finally gave out. It has served me well, but had issues. The table made up for it's under-powered motor with high RPMs. Needless to say, there is a tendency of burning wood at high RPMs, so I adjusted by lowering the speed and taking many shallow passes to achieve full cut depth. Twelve years later the motor has finally given up, so I began a couple of days ago looking for replacement parts which I could not find. I decided to make a removable mounting plate/insert for one of my routers and convert it into a new motor for my router table.
You should be able to accomplish this with minimal tools and materials. It just so happens that 1/2" Maple Ply fits in the opening perfectly when the 8 leveling/adjustment screws for leveling the mounting plate are backed all the way down. The ply was left over from making dresser drawers so I only needed to purchase three 5/16" bolts and washers totaling less than $1. Your own router will dictate what you need.
Step 1: Strip Table Down and Create New Mounting Plate/Insert
Remove the Speed Control / On/Off Switch unit. Remove the Motor Mounting Plate and the screws that mount the Motor/Lift Assembly to the Mounting Plate. Recess all eight Height Adjustment Screws to achieve the full depth of the recessed area. The depth is just under 1/2" which works out well, because 1/2" plywood is slightly undersized.
Select your material you will use to mount your router. Use the stripped down Mounting Plate as a template for your new material. Rip and cross-cut your new material to size, trace rounded corners and alignment notch and mark the four holes for mounting the plate/insert to the table. Make a large "X" from corner to corner to find the center of your new insert/mount. Next, cut your material to shape and drill out the plate to table mounting holes.
Remove the base of your router. The one I am using is a Ryobi router which happens to be a few years older than the router table and is still running strong. Use the screw holes that mount your router's removable base to align over the center "X" that you drew to find center on your new plate/insert. The larger holes shown on my base go into three 5/16" threaded holes in the aluminum base under the removable plastic base. I marked these to drill through for the mounting of my router. Since there were only three holes, I mis-drilled and had to flip the board over to get the reverse since the router is mounting on the underside. I filled the mistake with a piece of 3/8" dowel. Drill holes slightly over-sized for your mounting screws or bolts for ease of alignment.
Step 2: Drill Mounting Holes. Counter Bore for Flush Fasteners.
Begin by drilling the mounting holes for your router slightly oversized for ease of aligning the fasteners. I had to counter bore for the washers and head depth on the bolts. You will need to adjust for the type of fasteners you use. At the center of the "X" you found earlier, drill an opening slightly larger than the largest router bit you intend to use. Once that is done, you can either reuse your old table inserts, or create your own removable inserts. I used the old ones and laid one of them upside down to trace the outline. You will have to cut a shallow dado the depth of the insert to have your inserts sit flush with the table. Set the depth of your router bit to the thickness of your removable insert. Score the trace line with a razor. When routing a groove, the surface fibers tend to lift and will obscure your pencil line with fuzzy wood fibers. When the router bit reaches your razor-scored line, the fuzzy fibers will disappear and you will know you have cut to your traced line making a tight fit for your insert. If you are using a spiral upcut bit, make sure the bit is tight inside the collet. They have a tendency to creep down and increase the depth of cut. If you look at the fourth picture, you can see where this happened. I wandered a little bit with the router as well. If you are reusing the old inserts, you will have to remove the tab that extends down and holds the spring in place for a flush fit with the table surface.
Step 3: Mount Plate/Insert to Router. Mount Router in Table.
You are almost ready to use your new router table. Place your router upside down. Place the new mounting plate/insert over the base of your router, align the hole to the router mounting holes and insert and secure your mounting fasteners (picture 1). Picture 2 is the back of my router with the switch that locks the shaft of the router for loosening and tightening the collet around the router bits. Picture three faces forward so I can turn the router on and adjust and lock the depth of the bit. Picture 4, the router is ready to be inserted. Picture 5 shows where the four mounting plate/insert screws insert to mount to the router table. All I have to do is remove four screws in the corners, and three 5/16" bolts and I can easily use as a handheld router, or easily convert back to a router table. Pictures 6 and 7 show that all the original table accessories like the fence and feather boards can be reused.