I made a new (router) dado jig this morning. My old one was made in haste for a bookcase project. It worked fine, especially once I made it (more easily) adjustable, but it's not long enough for a project I have in mind.
To adjust the dado width, I used threaded (female) inserts and star knobs. The last time I used those inserts I had a devil of a time getting them into the wood. Some people here suggested cutting the head off a 1/4-20 bolt, chucking it into a drill, and threading a pair of nuts onto it as a back stop.
That sounded like a good idea, and I was just about to cut the head off a bolt when another idea struck me. I threaded the insert onto the knob itself, all the way to the body of the knob. Then I turned the insert into the wood by hand with the knob. When the knob touched the wood, I backed the knob out of the insert.
To my surprise, it really was flush with the wood, but I turned it in another half-turn with a screwdriver anyway. In retrospect, I could have eliminated that step by putting a washer (one whose outer diameter was smaller than the insert) onto the knob threads before putting on the insert.
It's probably not a better method than the one suggested here if you're doing a lot of them, but it worked fine.