Plastic scanning beads at amazon-dot-com!

[gary]

That's what I am hoping Graham, if not, then it should be good enough to build a more accurate one - not an uncommon approach in CNC community apparently.

Just made a hub for the bead disk out of MDF! would you believe? just to test the g-code before wasting expensive metal, and it fits perfectly, the disk runs perfectly true now to see if beads are located correctly.

[Klaas Robers]

I think that aluminium paint is more dense than black paint. However when the black paint is really black there is no need for it.

Try the black part in the sun, look through the disc directly into the sun and observe if you see any sunlight. If not this is Ok. Black paint is in most cases made black by small particle of carbon, burned coal or wood, I don't know the english word for it. But that might dissipate the EM radiation well, as we make also resistors of this material.