Well let’s get this thing going. The object is to make a rectangular hole in the middle of a board. Two boards actually; one for the top mortise and one for the bottom. Start by getting the measurement of the diameter of your router base. We need to make the jig wide enough so the base doesn’t bump into the hinges. As you will see later, you can mortise the hinges into the jig to make a flat surface, however, this would take time and risk the two boards being slightly out of alignment which will throw off the final result. Just seems easier to make it wide enough for the base. You’ll see what I mean.
I made mine 4” wide. You will need four pieces identical in size. I use 1/2” plywood which is strong enough for the router yet shallow enough for the bit to reach the mortise. (Note: pictured here is 3/4” ply which I used before discovering that the bit would not reach the bottom of the mortise).
Use a scrap piece to dial in the blade height. Here I’m using a 5/8” guide bushing so the blade needs to be raised just 5/16”.
Check the chart on the previous blog or the specs that come with the hinges to determine the exact length of the hole. To center the hole use a fence to register each side and make matching cuts the distance from the edge that is required to form the outsides of the hole. Then plow out the middle of each cut.
Now is a good time to clean up the cuts and mark centerlines. Be careful not to remove too much material as you’ve invested a lot of time already to get a precision mortise. You can fine tune the opening later. Next glue up the matching pairs making sure the pieces are flat and the sides are flush.
You want to end up with parts that look like these.
This gripping tale to be continued…
-- tim hill www.newcalshop.com