[Bill Baker]

 I need to source the inserts for control knobs. You know, the metal or nylon push-in insert that has a set screw for tightening onto a volume or source selector shaft. Looking for 1/4" ID. Anyone know where I can get these?

[JoshK]

Not sure exactly.  You might be able to get it from the usual electronic sources like digikey, mouser, allied, etc.  Or you can buy some really cheap knobs off this dude and pull the inserts out of them.

ebay store

[Bill Baker]

 Thanks Josh but none of the suppliers you mentioned have such an animal. As far as using inserts from cheaper knobs, I have done this but I need a lot of them and it would need to source them rather than purchase knobs and take them apart.
 Somebody has to know where to aquire these

[jules]

Find an engineer to make some for you. I've had them made in brass, 1/4" ID, 5/8" OD with an appropriate set screw and the cost was very reasonable. The quality of anything you buy is usually just ok but if you have 'em made to your own specs they'll probably be much better.

jules