TCH A.L : Aluminum twin cutter heads for rough and fine boring operations. Diameter range 500-800mm.
  Designationd mind maxD1DaSSkgGICATGIREMgiic
  TCH A.L500 500.00600.00494.0060.00060 8.7004652437 0
  TCH A.L600 600.00700.00594.0060.00060 8.3404652438 0
  TCH A.L700 700.00800.00694.0060.00060 8.3404652439 0

Aluminum body, with steel serrated seats.
The "O" position on the counterweight balances the BHF boring head for D=200 mm boring diameter position. For every 10 mm change in boring diameter, move the counterweight by 1 measurement mark.
Please verify