Origin/Rega VTA adjuster?

I also leave the washer off.

I don't use the toothed washer myself. As long as the nut holds okay you're fine without it.

Don't overtighten the nut BTW. Hand tight or a pinch more is plenty. I agree it's pretty unwieldy.

Thanks for your response Twl,I have done the filing with the sander from a bicycle kit and that seems o.k.How do I set the nut and washer under the plinth? It feels a bit wieldy,can I leave the washer off?

You must file the hole open to allow the adjuster to turn easily, but to not be a "sloppy" fit. I filed mine a little at a time with a round file, and kept trying the fit of the adjuster as I went along, so that I didn't file away too much from the armhole. It should only require a small amount of increase in the diameter of the hole, and you can probably do it in about 5 minutes.