Problem solved simple and easy. I got some 10.9 steel bolts. This stuff is hard but turns like a dream with carbide metal inserts I have.
I start with 8mm bolts(0.315").
![](https://i.ibb.co/DLmk9fC/IMG-20220828-140457-3.jpg)
After one pass, I,m down to 5mm (0.197")
![](https://i.ibb.co/Ycq9mzr/IMG-20220828-140811-2.jpg)
Second pass I am down to 3,4mm (0.134")
![](https://i.ibb.co/Wsbq5Xp/IMG-20220828-141141.jpg)
After that, I nibble the shaft down to 2,9mm(0.114") and the head to 3.9mm (0.154"). I can cut cleanly shavings down to 0,025m (0.0001"). Have to use a magnifier to watch the cutting.
![](https://i.ibb.co/hmc03fc/IMG-20220828-141757.jpg)
Threading in the lathe with the tailstock fixture.
![](https://i.ibb.co/SNrCDG4/IMG-20220828-142111.jpg)
Finished screw.
![](https://i.ibb.co/RPQYvZm/IMG-20220828-143119.jpg)
Best regards
Rolf