Reply by Dzhaughn

I am a beginner. Here is a crazy idea that occurred to me to do this parallell “rip” in 2 passes. I think it uses only standard, usual operations. Any objections?

(1) Ensure one side of the board is straight, joint if necessary.
(2) Set router table fence to desired width
(3) With straight bit, rout a dado 1/4” deep, parallell to the jointed edge. This is not a through cut, just a dado 4” from and paralell to the jointed edge.
(4) use a jig saw or hand saw to crudely cut through the middle of the dado
(5) use a flush trim bit to trim off excess, referencing the remaining wall of the dado. (No fence on this step.)

Any safety concerns about this procedure?

Next, with the hope of smaller off-cuts, reverse steps 3 and 4? That is, trim the board to roughly parallel + and extra 1/8”, then rout a rabbet referencing the jointed edge against the fence. (Still not a through cut.) Then flush trim. Is that different? Why?

Apart from safety: Downsides: a bit tedious, maybe uses a lot of router bits as opposed to saw blades. Upsides: Clean cuts, repeatable operation, no extra tools required, easy enough to build your own router table. If it works, it would reduce the investment and shop space to do good quality repeatable parallel rips.