I had a member ask me about a mortising jig I made for my router. Posting pics in a PM seems cumbersome, so I decided to respond here and that way others can see it and perhaps glean some ideas. The text below is in respons to John's original questions:
I use a double flute straight bit with no bearing, though an upspiral carbide bit would be better. I plunge at each end of the mortise and then make multiple passes to cut the remainder of the mortise. There is no need for any kind of bearing bit since the router rides on the jig and is confined by the side rails and the stop blocks I install (screw or clamp) for the particular mortise being cut.
I have taken pictures of it disassembled (not, I was using the base with a strip of wood screwed to it to clamp to the stock, so disregard that piece.
The jig consists of the following:
1. the base made of hardboard which has hardwood rails to keep the router centered, and a slot for the bit. I also screw or clamp stop blocks to this part of the jig.
2. The parallelogram is simply two pieces of hard board drilled on center which then mounts to the base with short bolts/nuts. Then there are the hardwood strips attached at the outer ends of the hardboard. This is what centers the jig on the stock being morticed. I made this before I had a drill press so I had to shim it with tape. Drilling all pieces exactly the same and centered is key to making this work properly. (I need to make a new one)
Simply clamp the hardwood strips to the stock, put stop blocks in place and you have centered mortices. I also draw a line on the base which aligns with one end of the mortice to make set-up quick.
Let me know if there is anything that isn't clear.
Jake
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