Precision ground, quenched, and tempered.
All popular heavy-duty chucks manufactured by Schunk, Forkardt, Röhm, and SMW (with sharp serrations).
Forkardt: NH 400-500; NHF 400-500
Schunk: TH/THF 380-500, HSL 400
SMW: HFKS 400, HFK 400-500
Socket head screws DIN 912 - 12.9!
Other T-nuts available ex works.