the fairly stout tap wedges them in, the nut stops them coming loose.
Well I always thought this but the ones I got from the LBS were soft and kept developing play until there was hardly any head visible. In the end I changed one side and gave the other a good bash and its been OK since. Except that I was then told I'd probably damaged me balls Ouch!
The ones I have for Holly are pre-filed. I only have one pair as I couldn't afford any spares Hopefully with a NOS TDC axle and original Nicklin chainset, then it'll work better than the cheap Indian copies I got from Cycles of Yesteryear.
Going to give it a bash (literally) tonight. I know that they have to point in opposite directions, but I thought there was a specific way they should go in. Is that correct? Nut up or down on the downstroke. I can't remember which