Universal Pen turning Bushing

thingiverse

Well, mostly universal. The hole fits snugly on standard mandrels at 7mm, then increases incrementally to 8mm, 9mm, 10mm, 11mm, and finally reaches 12mm before topping out at 13mm. So the largest blank that can be accommodated is precisely 12mm. The bushing serves as a useful reference point to gauge your final size against the incremental steps, but ultimately relies on precision tools like calipers for accurate measurements.