I'm fairly sure the 1580 series 4" chucks are Imperial – if so the pitch of the teeth should be 5.08mm – that is the distance from the front edge of one tooth to the front edge of the following one, i.e. the total width of one tooth and the gap next to it. The height of the slot in the side of these jaws is 4.85mm.

The metric P-B 100mm jaws have a pitch of 6mm and a 7mm high slot.


If your chuck is Imperial, I think soft jaws type EJC will fit – for replacement hard jaws you could try try P/nos. 2580 10603 (inside), and 2580 10602 (outside). Both of these are now obsolete. I'm not absolutely certain these will fit, but it might give you something to go on. If you want to do further internet legwork, I found the dimensional / part no. information from pdf spec. sheets from Rotagrip and Thame Workholding's websites…
Edited By DiogenesII on 26/06/2021 19:20:02