Axminster Tools do spare bits for the Parf system but bare in mind that they use a guide for bit for increased accuracy.From videos, the parf guide uses a 'special' 20mm bit - to keep a clean hole, entry and exit. Seems to work too.
Has anyone found such a bit on sale anywhere in the UK please?
I have produced a number of these Parf tables using Valchromat from Sydenham Plywoos and panels. The will cut a whole sheet to the size for you and they are super accurate. and they supply any offcuts which is really useful.
Good Luck
Lampost 46